Cortex - Articles in Press

Reduced attentional capacity, but normal processing speed and shifting of attention in developmental dyslexia: Evidence from a serial task - Corrected Proof

Cristina Romani, Effie Tsouknida, Anna M. di Betta, Andrew Olson — 2010-07-26

Abstract: We report the performance of a group of adult dyslexics and matched controls in an array-matching task where two strings of either consonants or symbols are presented side by side and have to be judged to be the same or different. The arrays may differ either in the order or identity of two adjacent characters. This task does not require naming – which has been argued to be the cause of dyslexics’ difficulty in processing visual arrays – but, instead, has a strong serial component as demonstrated by the fact that, in both groups, Reaction times (RTs) increase monotonically with position of a mismatch. The dyslexics are clearly impaired in all conditions and performance in the identity conditions predicts performance across orthographic tasks even after age, performance IQ and phonology are partialled out. Moreover, the shapes of serial position curves are revealing of the underlying impairment. In the dyslexics, RTs increase with position at the same rate as in the controls (lines are parallel) ruling out reduced processing speed or difficulties in shifting attention. Instead, error rates show a catastrophic increase for positions which are either searched later or more subject to interference. These results are consistent with a reduction in the attentional capacity needed in a serial task to bind together identity and positional information. This capacity is best seen as a reduction in the number of spotlights into which attention can be split to process information at different locations rather than as a more generic reduction of resources which would also affect processing the details of single objects.

Newborn brain event-related potentials revealing atypical processing of sound frequency and the subsequent association with later literacy skills in children with familial dyslexia - Corrected Proof

2010-07-26

Abstract: The role played by an auditory-processing deficit in dyslexia has been debated for several decades. In a longitudinal study using brain event-related potentials (ERPs) we investigated 1) whether dyslexic children with familial risk background would show atypical pitch processing from birth and 2) how these newborn ERPs later relate to these same children’s pre-reading cognitive skills and literacy outcomes. Auditory ERPs were measured at birth for tones varying in pitch and presented in an oddball paradigm (1100Hz, 12%, and 1000Hz, 88%). The brain responses of the typically reading control group children (TRC group, N=25) showed clear differentiation between the frequencies, while those of the group of reading disability with familial risk (RDFR, 8 children) and the group of typical readers with familial risk (TRFR, 14 children) did not differentiate between the tones. The ERPs of the latter two groups differed from those of the TRC group. However, the two risk groups also showed a differential hemispheric ERP pattern. Furthermore, newborn ERPs reflecting passive change detection were associated with phonological skills and letter knowledge prior to school age and with phoneme duration perception, reading speed (RS) and spelling accuracy in the 2nd grade of school. The early obligatory response was associated with more general pre-school language skills, as well as with RS and reading accuracy (RA). Results suggest that a proportion of dyslexic readers with familial risk background are affected by atypical auditory processing. This is already present at birth and also relates to pre-reading phonological processing and speech perception. These early differences in auditory processing could later affect phonological representations and reading development. However, atypical auditory processing is unlikely to suffice as a sole explanation for dyslexia but rather as one risk factor, dependent on the genetic profile of the child.

Variability in the word-reading performance of dyslexic readers: Effects of letter length, phoneme length and digraph presence - Corrected Proof

Eva Marinus, Peter F. de Jong — 2010-07-26

Abstract: The marked word-length effect in dyslexic children suggests the use of a letter-by-letter reading strategy. Such a strategy should make it more difficult to infer the sound of digraphs. Our main aim was to disentangle length and digraph-presence effects in word and pseudoword reading. In addition, we examined differences in intra-individual variability between dyslexic and normal readers. Word and pseudoword naming tasks were administered to 24 dyslexic readers individually matched to chronological-age and reading-age controls. As expected, dyslexic and younger children displayed stronger length effects. In contrast to our expectations, the dyslexic and younger children were faster in reading (pseudo)words with a digraph than in reading (pseudo)word of similar letter length but without a digraph. Normal readers were equally fast on both types of (pseudo)words. However, considering phoneme-length effects, digraph presence caused an additional delay in all reading groups, but only for pseudowords. In addition, this effect was stronger for the dyslexic and younger readers. Finally, dyslexic readers’ intra-individual variability in reading was larger than the variability in both groups of normal readers. Proportionally, the largest difference in variability with the normal readers was found on the short words.

A dual-route perspective on poor reading in a regular orthography: An fMRI study - Corrected Proof

2010-07-22

Abstract: This study examined functional brain abnormalities in dyslexic German readers who – due to the regularity of German in the reading direction – do not exhibit the reading accuracy problem of English dyslexic readers, but suffer primarily from a reading speed problem. The in-scanner task required phonological lexical decisions (i.e., Does xxx sound like an existing word?) and presented familiar and unfamiliar letter strings of existing phonological words (e.g., Taxi-Taksi) together with nonwords (e.g., Tazi). Dyslexic readers exhibited the same response latency pattern (words

Cognition and the cerebellum - Corrected Proof

Sergio Della Sala — 2010-07-12

A recent special issue of Cortex (issue 7, 2010) encompassed a collection of papers tackling the “enigma” () of the relationship between the cerebellum and cognition. This included two reviews on the role played by the cerebellum in associative learning () and in language (). The eight Research Reports were on the development of human cerebellum (), on its topographical organisation (), on general neuropsychological profile () associated with cerebellar lesions or on cerebellar activations during the performance of executive or working memory tasks (). The three further papers dealt with the effects of cerebellar malformations or tumors on children’s development ().

What do brain lesions tell us about theories of embodied semantics and the human mirror neuron system? - Corrected Proof

Analia L. Arévalo, Juliana V. Baldo, Nina F. Dronkers — 2010-07-12

Abstract: Recent work has been mixed with respect to the notion of embodied semantics, which suggests that processing linguistic stimuli referring to motor-related concepts recruits the same sensorimotor regions of cortex involved in the execution and observation of motor acts or the objects associated with those acts. In this study, we asked whether lesions to key sensorimotor regions would preferentially impact the comprehension of stimuli associated with the use of the hand, mouth or foot. Twenty-seven patients with left-hemisphere strokes and 10 age- and education-matched controls were presented with pictures and words representing objects and actions typically associated with the use of the hand, mouth, foot or no body part at all (i.e., neutral). Picture/sound pairs were presented simultaneously, and participants were required to press a space bar only when the item pairs matched (i.e., congruent trials). We conducted two different analyses: 1) we compared task performance of patients with and without lesions in several key areas previously implicated in the putative human mirror neuron system (i.e., Brodmann areas 4/6, 1/2/3, 21 and 44/45), and 2) we conducted Voxel-based Lesion-Symptom Mapping analyses (VLSM; ) to identify additional regions associated with the processing of effector-related versus neutral stimuli. Processing of effector-related stimuli was associated with several regions across the left hemisphere, and not solely with premotor/motor or somatosensory regions. We also did not find support for a somatotopically-organized distribution of effector-specific regions. We suggest that, rather than following the strict interpretation of homuncular somatotopy for embodied semantics, these findings support theories proposing the presence of a greater motor-language network which is associated with, but not restricted to, the network responsible for action execution and observation.

Argentina’s early contributions to the understanding of frontotemporal lobar degeneration - Corrected Proof

2010-06-28

Abstract: Over a 100 years have passed since Pick’s description of what is now termed frontotemporal lobar degeneration (FTLD). FTLD is a topic of intense current research interest yet some relevant contributions by non-English speaking authors have received little attention, which makes the history of FTLD research incomplete. In the hopes of filling some of the gaps in the history of FTLD research, the present article introduces fundamental work carried out in Argentina during the first half of the 20th century by Christfried Jakob and Braulio A. Moyano. Jakob’s neurophilosophy, as well as his empirical descriptions on dementia and theoretic insights into the role of the frontal lobes are highlighted. Moyano’s works on frontotemporal dementia (FTD), specifically concerning language deficits and the concept of focal pathology in Alzheimer disease presenting with progressive aphasia are introduced. These early contributions are examined in the light of the current knowledge on FTLD, highlighting some of the authors’ early original contributions, as well as their misconceptions. These authors remain largely unknown despite the fact that their contributions were fundamental in kindling interest in behavioral neurology in Latin America, which continues to this day.

Frontal lobe damage impairs process and content in semantic memory: Evidence from category-specific effects in progressive non-fluent aphasia - Corrected Proof

Jamie Reilly, Amy D. Rodriguez, Jonathan E. Peelle, Murray Grossman — 2010-06-24

Abstract: Portions of left inferior frontal cortex have been linked to semantic memory both in terms of the content of conceptual representation (e.g., motor aspects in an embodied semantics framework) and the cognitive processes used to access these representations (e.g., response selection). Progressive non-fluent aphasia (PNFA) is a neurodegenerative condition characterized by progressive atrophy of left inferior frontal cortex. PNFA can, therefore, provide a lesion model for examining the impact of frontal lobe damage on semantic processing and content. In the current study we examined picture naming in a cohort of PNFA patients across a variety of semantic categories. An embodied approach to semantic memory holds that sensorimotor features such as self-initiated action may assume differential importance for the representation of manufactured artifacts (e.g., naming hand tools). Embodiment theories might therefore predict that patients with frontal damage would be differentially impaired on manufactured artifacts relative to natural kinds, and this prediction was borne out. We also examined patterns of naming errors across a wide range of semantic categories and found that naming error distributions were heterogeneous. Although PNFA patients performed worse overall on naming manufactured artifacts, there was no reliable relationship between anomia and manipulability across semantic categories. These results add to a growing body of research arguing against a purely sensorimotor account of semantic memory, suggesting instead a more nuanced balance of process and content in how the brain represents conceptual knowledge.

SACNA logo - Corrected Proof

Sergio Della Sala — 2010-06-21

This issue cover depicts the logo of the South African Clinical Neuropsychological Association (SACNA): http://www.sacna.co.za/. I trust you agree that it is intriguing and creative. It has been designed by Digby Ormond-Brown, a Neuropsychologist member of the SACNA, who is also an artist.

Cognitive correlates of the spontaneous out-of-body experience (OBE) in the psychologically normal population: Evidence for an increased role of temporal-lobe instability, body-distortion processing, and impairments in own-body transformations - Corrected Proof

Jason J. Braithwaite, Dana Samson, Ian Apperly, Emma Broglia, Johan Hulleman — 2010-06-18

Abstract: Recent findings from studies of epileptic patients and schizotypes have suggested that disruptions in multi-sensory integration processes may underlie a predisposition to report out-of-body experiences (OBEs: ). It has been argued that these disruptions lead to a breakdown in own-body processing and embodiment. Here we present two studies which provide the first investigation of predisposition to OBEs in the normal population as measured primarily by the recently devised Cardiff anomalous perception scale (CAPS; ). The Launay–Slade Hallucination scale (LSHS) was also employed to provide a measure of general hallucination proneness. In Study 1, 63 University students participated in the study, 17 of whom (26%) claimed to have experienced at least one OBE in their lifetime. OBEers reported significantly more perceptually anomalies (elevated CAPS scores) but these were primarily associated with specific measures of temporal-lobe instability and body-distortion processing. Study 2 demonstrated that OBEers and those scoring high on measures of temporal-lobe instability/body-distortion processing were significantly impaired, relative to controls, at a task requiring mental own-body transformations (OBTs) (). These results extend the findings from epileptic patient studies to the psychologically normal population and are consistent with there being a disruption in temporal-lobe and body-based processing underlying OBE-type experiences.

Surround modulation of neuronal responses in V1 is as stable over time as responses to direct stimulation of receptive fields - Corrected Proof

Sergiu P. Paşca, Wolf Singer, Danko Nikolić — 2010-06-17

Abstract: In the primary visual cortex (V1) the modulation of neuronal responses by surround stimuli displays considerable variability. At present, it is not known whether this variability across neurons is due to temporal instability or to neuron-specific differences. We explored this question in the cat visual cortex by making multi-channel recordings while repeatedly presenting surround gratings of collinear and orthogonal orientation to the centre stimulus for a period of 96h. Our results indicate that surround modulation is temporally stable to about the same degree as the responses evoked by the centre stimuli. The results support the notion that the mechanisms of surround modulation exhibit a high degree of stability and play an important role in the modulation of cortical responses.

A new selective developmental deficit: Impaired object recognition with normal face recognition - Corrected Proof

Laura Germine, Nathan Cashdollar, Emrah Düzel, Bradley Duchaine — 2010-06-14

Abstract: Introduction: Studies of developmental deficits in face recognition, or developmental prosopagnosia, have shown that individuals who have not suffered brain damage can show face recognition impairments coupled with normal object recognition (). However, no developmental cases with the opposite dissociation – normal face recognition with impaired object recognition – have been reported. The existence of a case of non-face developmental visual agnosia would indicate that the development of normal face recognition mechanisms does not rely on the development of normal object recognition mechanisms.Methods: To see whether a developmental variant of non-face visual object agnosia exists, we conducted a series of web-based object and face recognition tests to screen for individuals showing object recognition memory impairments but not face recognition impairments. Through this screening process, we identified AW, an otherwise normal 19-year-old female, who was then tested in the lab on face and object recognition tests.Results: AW’s performance was impaired in within-class visual recognition memory across six different visual categories (guns, horses, scenes, tools, doors, and cars). In contrast, she scored normally on seven tests of face recognition, tests of memory for two other object categories (houses and glasses), and tests of recall memory for visual shapes. Testing confirmed that her impairment was not related to a general deficit in lower-level perception, object perception, basic-level recognition, or memory.Discussion: AW’s results provide the first neuropsychological evidence that recognition memory for non-face visual object categories can be selectively impaired in individuals without brain damage or other memory impairment. These results indicate that the development of recognition memory for faces does not depend on intact object recognition memory and provide further evidence for category-specific dissociations in visual recognition.

Constructional ability in two- versus three-dimensions: Relationship to spatial vision and locus of cerebrovascular lesion - Corrected Proof

Daniel X. Capruso, Kerry deS. Hamsher — 2010-06-14

Abstract: Introduction: Clinical evaluation and research on constructional ability have come to rely almost exclusively on two-dimensional tasks such as graphomotor copying or mosaic Block Design (BD). A return to the inclusion of a third dimension in constructional tests may increase the spatial demands of the task, and improve understanding of the relationship between visual perception and constructional ability in patients with cerebral disease.Method: Subjects were patients (n=43) with focal or multifocal cerebrovascular lesions as determined by CT or MRI. Tests of temporal orientation, verbal intelligence, language, object vision and spatial vision were used to determine which factors were predictive of performance on two-dimensional BD and Three-Dimensional Block Construction (3-DBC) tasks.Results: Stepwise linear regression indicated that spatial vision predicted BD performance, and was even more strongly predictive of 3-DBC. Other cognitive domains did not account for significant additional variance in performance of either BD or 3-DBC. Bilateral cerebral lesions produced more severe deficits on BD than did unilateral cerebral lesions. The presence of a posterior cerebral lesion was the significant factor in producing deficits in 3-DBC.Conclusions: The spatial aspect of a constructional task is enhanced when the patient is required to assemble an object in all three dimensions of space. In the typical patient with cerebrovascular disease, constructional deficits typically occur in the context of a wider syndrome of deficits in spatial vision.

Examining the effects of inversion on lateralisation for processing facial emotion - Corrected Proof

Victoria J. Bourne — 2010-06-11

Abstract: There is an increasing amount of evidence which suggests that each hemisphere is differently specialised for processing facial stimuli, with the right hemisphere specialised for the processing of configural information and the left hemisphere specialised for the processing of featural information. While there is evidence for this distinction from studies of face recognition, it has not been shown in studies of lateralisation for processing facial emotion. In this study the chimeric faces test was used with faces expressing anger, disgust, fear, happiness, sadness or surprise, presented in either an upright or an inverted orientation. When presented upright, a significant right hemisphere bias was found for all six emotions. However, when inverted, a significant left hemisphere bias was found for the processing of happiness and surprise, but not for the processing of negative emotions (although the analysis was approaching significance for anger). These findings support the hypothesis that each hemisphere is differently specialised for processing facial emotion, but contradicts previous work that examined the effects of inversion on chimeric face stimuli.

Right posterior cortical functions in a tumour patient series - Corrected Proof

Tim Shallice, Alessandro Mussoni, Serena D’Agostino, Miran Skrap — 2010-06-10

Abstract: It is standardly believed that the localisation of cognitive function by means of impairments arising from cortical tumour is not possible as the functional defects that result are mild and unspecific. These assumptions were not supported in an investigation of four processes generally sensitive to right posterior cortical lesions, when patients with parieto-occipital lesions were compared with prefrontal ones. In three of the tests loading on the individual processes – Reaching Accuracy, Star Cancellation, Fragmented Letters and Cube Analysis – parieto-occipital impairments were found in the basic groups analysis and this was so in the right-hemisphere group. More critically, in these tests Lesion Behaviour Mapping showed the critical lesion site for the tests to have relatively little overlap with those of the other tests, indicating that the cognitive effects were not widespread and diffuse. In addition, in three of the tests the critical lesion sites fitted localisations arrived from other procedures. Patients with high-grade tumours performed considerably worse than those with low-grade tumours in only two of the tests (Star Cancellation, Cube Analysis) particularly in the right parieto-occipital group. In three (Reaching Accuracy, Star Cancellation, Cube Analysis) there was a deterioration with the operation specifically in the low-grade tumour patients. It is suggested that a tumour patient series may provide converging evidence for the localisation of a function initially obtained by some other procedure.

Are left fronto-temporal brain areas a prerequisite for normal music-syntactic processing? - Corrected Proof

Daniela Sammler, Stefan Koelsch, Angela D. Friederici — 2010-06-07

Abstract: An increasing number of neuroimaging studies in music cognition research suggest that “language areas” are involved in the processing of musical syntax, but none of these studies clarified whether these areas are a prerequisite for normal syntax processing in music. The present electrophysiological experiment tested whether patients with lesions in Broca’s area (N=6) or in the left anterior temporal lobe (N=7) exhibit deficits in the processing of structure in music compared to matched healthy controls (N=13). A chord sequence paradigm was applied, and the amplitude and scalp topography of the Early Right Anterior Negativity (ERAN) was examined, an electrophysiological marker of musical syntax processing that correlates with activity in Broca’s area and its right hemisphere homotope. Left inferior frontal gyrus (IFG) (but not anterior superior temporal gyrus – aSTG) patients with lesions older than 4 years showed an ERAN with abnormal scalp distribution, and subtle behavioural deficits in detecting music-syntactic irregularities. In one IFG patient tested 7 months post-stroke, the ERAN was extinguished and the behavioural performance remained at chance level. These combined results suggest that the left IFG, known to be crucial for syntax processing in language, plays also a functional role in the processing of musical syntax. Hence, the present findings are consistent with the notion that Broca’s area supports the processing of syntax in a rather domain-general way.

Limb apraxia in corticobasal syndrome - Corrected Proof

Vessela Stamenova, Eric A. Roy, Sandra E. Black — 2010-06-07

Abstract: Corticobasal syndrome (CBS) is a progressive neurodegenerative disorder with asymmetric presentation and course characterized by degeneration of basal ganglia and cortical structures. Limb apraxia is a commonly observed deficit in CBS. Few studies have examined comprehensively the nature of deficits in limb apraxia. The goal of our study was to investigate the severity of deficits in various conceptual and gesture production task modalities. CBS patients were divided in two groups based on the side of brain that was initially affected by the disease. Ten patients with right hemisphere presentation (RHP) and seven with left hemisphere presentation (LHP) were included. The results showed that while selective conceptual tasks deficits were present in both groups, the overall picture suggests preserved conceptual representations of tools and actions in CBS patients with either LHP or RHP. Both groups were impaired relative to controls on gesture production tasks. Performance on transitive gestures was more severely affected in both groups than intransitive gestures. Imitation was more severely affected than pantomime, suggesting deficits in visuomotor transformations. The addition of verbal cuing during concurrent imitation affected only the LHP patients, rendering them more impaired relative to controls in their imitation with verbal cuing as opposed to their imitation only performance. Imitation of non-representational gestures was least accurate and intransitive gestures were most accurate. Patients were more severely impaired relative to controls when holding the object and when they were shown pictures of tools to pantomime.

Is evaluation of humorous stimuli associated with frontal cortex morphology? A pilot study using facial micro-movement analysis and MRI - Corrected Proof

2010-06-01

Abstract: Humour involves the ability to detect incongruous ideas violating social rules and norms. Accordingly, humour requires a complex array of cognitive skills for which intact frontal lobe functioning is critical. Here, we sought to examine the association of facial expression during an emotion inducing experiment with frontal cortex morphology in healthy subjects.Thirty-one healthy male subjects (mean age: 30.8±8.9 years; all right-handers) watching a humorous movie (“Mr. Bean”) were investigated. Markers fixed at certain points of the face emitting high-frequency ultrasonic signals allowed direct measurement of facial movements with high spatial–temporal resolution. Magnetic resonance images of the frontal cortex were obtained with a 1.5-T Magnetom using a coronar T2- and protondensity-weighted Dual-Echo-Sequence and a 3D-magnetization-prepared rapid gradient echo (MPRAGE) sequence. Volumetric analysis was performed using BRAINS.Frontal cortex volume was partly associated with slower speed of “laughing” movements of the eyes (“genuine” or Duchenne smile). Specifically, grey matter volume was associated with longer emotional reaction time ipsilaterally, even when controlled for age and daily alcohol intake.These results lend support to the hypothesis that superior cognitive evaluation of humorous stimuli – mediated by larger prefrontal grey and white matter volume – leads to a measurable reduction of speed of emotional expressivity in normal adults.

A hierarchy for relational reasoning in the prefrontal cortex - Corrected Proof

Daniel C. Krawczyk, M. Michelle McClelland, Colin M. Donovan — 2010-06-01

Abstract: The human brain possesses a unique capacity to reason about abstract relationships among items in our environment. The neural organization of reasoning abilities has remained elusive. Two approaches toward investigating human reasoning have involved studying visuo-spatial reasoning abilities and studying analogical reasoning. These approaches have both revealed anterior prefrontal cortex (PFC) involvement, but no prior studies have jointly investigated these two forms of reasoning to understand any potential convergence of activation within the PFC. Using fMRI, we tested the extent to which these two forms of reasoning (visuo-spatial and analogical) overlap in PFC activation. We conducted a visuo-spatial reasoning task that required processing multiple changes across three abstract pictures. This task activated a progressively anterior series of PFC regions when multiple relations had to be integrated. We also conducted a four-term analogy task in a stage-wise manner and compared results from this task to semantic and perceptual control conditions that did not require integrating relations across the problems. We found greater activation for analogical reasoning in the series of PFC regions that were sequentially involved in the visuo-spatial reasoning task. These findings indicate that stages of neural processing overlap for different domains within human reasoning. The pattern of differences across the analogy task suggests a hierarchical organization for relational reasoning across domains in which posterior frontal cortex is active across concrete reasoning tasks, while progressively more anterior regions are recruited to process increasingly abstract representations in reasoning.

Harvey Cushing’s contributions to motor mapping: 1902–1912 - Corrected Proof

2010-05-31

Abstract: This review examined Dr. Harvey Cushing’s cases in the surgical records of Johns Hopkins Hospital, from 1896 to 1912. 41 patients who underwent cortical stimulation for intra-operative motor mapping were selected for further analysis. We demonstrate that Cushing used cortical stimulation to define primary motor and sensory cortices in the treatment of tumors, trauma, and epilepsy, within adult and pediatric populations. In addition, he performed stimulation of sub-cortical white matter during 4 of these surgeries, setting the stage for contemporary use of this technique in improving post-operative outcomes. This review of Cushing’s early intra-operative motor mapping illuminates his contributions, and clarifies his influence on the evolution of cortical mapping from an experimental technique to a staple of contemporary neurosurgery.

The influence of anatomical locus of lesion and of gender-related familiarity factors in category-specific semantic disorders for animals, fruits and vegetables: A review of single-case studies - Corrected Proof

Guido Gainotti — 2010-05-18

Abstract: According to a recent study conducted on patients with posterior cerebral artery (PCA) infarcts (), a prevalent impairment of fruit and vegetable knowledge might be due to damage of the left fusiform gyrus, whereas the representation of animals might be disrupted by anterior temporal lesions. To check the influence of gender and anatomical factors in a larger number of patients, a review was made of all the single-case studies of patients who satisfied the following criteria: (a) a prevalent or selective defect in the representation of animals or fruit and vegetable knowledge; (b) the presence of detailed anatomical data, allowing to evaluate if there is a clear distinction between lesions provoking a prevalent defect for animals and for fruits and vegetables. Results showed that both similarities and differences exist between patients showing a selective impairment for animals and for fruits and vegetables. Important lesions of the mesial and inferior areas of the temporal lobes are, indeed, often observed in patients with every kind of category-specific semantic disorder for living entities, but aetiological, anatomical and gender-related familiarity factors determine the prevalent impairment of animals or of fruits and vegetables in these patients. A prevalent impairment of fruits and vegetables is usually observed in men showing a lesion in the territory of the left PCA, encroaching upon the occipital and the infero-mesial aspects of the left temporal lobe, whereas a prevalent impairment of animals is often found in women showing a bilateral lesion of the anterior temporal cortices. The anatomical differences are interpreted in terms of the ‘sensori-motor model of semantic knowledge’, whereas the gender-related asymmetries are considered as due to social roles related familiarity factors.

An oculomotor and computational study of a patient with diagonistic dyspraxia - Corrected Proof

2010-05-11

Abstract: Diagonistic dyspraxia (DD) is a behavioural disorder encountered in split-brain subjects in which the left arm acts against the subject’s will, deliberately counteracting what the right arm does. We report here an oculomotor and computational study of a patient with a long lasting form of DD. A first series of oculomotor paradigms revealed marked and unprecedented saccade impairments. We used a computational model in order to provide information about the impaired decision-making process: the analysis of saccade latencies revealed that variations of decision times were explained by adjustments of response criterion. This result and paradoxical impairments observed in additional oculomotor paradigms allowed to propose that this adjustment of the criterion level resulted from the co-existence of counteracting oculomotor programs, consistent with the existence of antagonist programs in homotopic cortical areas. In the intact brain, trans-hemispheric inhibition would allow suppression of these counter programs. Depending on the topography of the disconnected areas, various motor and/or behavioural impairments would arise in split-brain subjects. In motor systems, such conflict would result in increased criteria for desired movement execution (oculomotor system) or in simultaneous execution of counteracting movements (skeletal motor system). At higher cognitive levels, it may result in conflict of intentions.

Vocal response times to real and imagined stimuli in spatial neglect: A group study and single-case report - Corrected Proof

2010-05-10

Abstract: The relationships between spatial neglect for perceptual objects and representational for imagined items are difficult to explore because of several methodological problems, including the dearth of comparable tests for real and imagined scenes. We asked 19 patients with right brain damage and 12 healthy controls to say whether an auditorily presented French geographical location was left or right of Paris, and recorded their vocal response times. Afterwards, participants performed a similar test with visually presented items. Although several patients had asymmetries of performance on the perceptual version of the test, only one patient was more accurate for right-sided than for left-sided imagined stimuli, thus showing evidence for imaginal neglect. However, this patient performed normally on place description and on mental number line bisection, perhaps as a consequence of different strategies he employed for these tasks. Overall, our results confirm previous evidence showing that imaginal neglect is less frequent than, and often occurs in association with, perceptual neglect. Imaginal neglect may result from the contribution of deficits partly distinct from those implicated in perceptual neglect, such as impaired endogenous orienting of attention or deficits of spatial working memory.

Cerebral hemodynamic lateralization during memory tasks as assessed by functional transcranial Doppler (fTCD) sonography: Effects of gender and healthy aging - Corrected Proof

2010-05-10

Abstract: Introduction: Previous neuropsychological, lesional and functional imaging studies deal with the lateralization of memory processes, suggesting that they could be determined by the stage of processing (encoding vs retrieval) or by content (verbal vs non-verbal stimuli). The aims of the present study were: 1) to investigate if tasks that can be carried out using different strategies depending on the verbalizability of the material induce a lateralization of the mean cerebral blood flow velocity (mCBFV) in the middle cerebral arteries (MCAs), as monitored by a functional transcranial Doppler (fTCD); 2) to evaluate if these patterns of cerebral activation differ in relation to age, gender and task performance.Methods: Using TCD bilateral monitoring, we recorded mCBFV variations in 35 male and 35 female healthy, right-handed volunteers, classified as “young” (age range 21–40 years, n=35) or “old”(age range 41–60 years, n=35), performing four different cognitive tasks: encoding and recognition of Geometric Figures (GF), encoding and recall of Object Localization (OL) on a picture, encoding of a verbal Room Description (RD) and Arithmetic Skill (AS).Results: We found a significant right lateralization for the OL recall phase, and a significant left lateralization for RD and AS. When we took into consideration gender, age and performance, there was a strong effect of age on both OL encoding and recall phase, with significant right lateralization in young volunteers not seen in the older ones. No difference in gender was detected. We found a gender×performance interaction for RD, with poor performance females showing significant left lateralization.Conclusions: According to our findings, hemispheric lateralization during memory encoding is material specific in both men and women, depending on the verbalizability of the material. mCBFV right lateralization during scene encoding and recall appears lost in older people, suggesting that healthy elderly could take advantage of mixed verbal and non-verbal strategies.

Detection of pitch violations depends upon the familiarity of intonational contour of sentences - Corrected Proof

Lucia Colombo, Chizuru Deguchi, Magali Boureux, Michela Sarlo, Mireille Besson — 2010-05-07

Abstract: Introduction: Former studies have shown that a pitch change in utterances in speech was detected accurately in both native (French) and unfamiliar (Portuguese) language and produced an early negativity and a late positivity in the event-related brain potentials (ERPs), more clearly marked in the native language (). The present study used the same design to further investigate the influence of the familiarity of the language context on pitch perception with Italian participants. The aim was to examine the effects of pitch change in the native (Italian) and foreign (French) languages, and in meaningless sentences preserving the intonational contour of the mother tongue (jabberwocky).Method: Weak and strong pitch changes incongruous with the preceding context were compared to a control congruous condition. Participants had to decide as fast and as accurately as possible if they perceived a pitch change. Both behavioral (accuracy and reaction times – RTs) and ERP measures were analyzed.Results: Results showed optimal accuracy and faster RTs in Italian, followed by jabberwocky, and then French. The same trend was present in ERP data, with an early negativity over temporal sites and a late positivity over parietal sites. These effects developed earlier and were more pronounced for the strong incongruity in Italian and in jabberwocky than in French.Conclusions: The similarity of results for Italian (congruous) and jabberwocky sentences on one hand, and the difference of results for French sentences, on the other hand, show that familiarity with intonational contour of utterances/speech provided essential cues to perform the task.

Spatial frequency-specific effects on the attentional bias: Evidence for two attentional systems - Corrected Proof

Vaughan V.W. Singh, Boge Stojanoski, Ada Le, Matthias Niemeier — 2010-05-06

Abstract: Using a gratingscales task as a sensitive measure of the attentional bias, we have recently observed a new form of frequency-specific cross-over; people showed left-biased preferences when comparing the high spatial frequency (HiSF) components of the task and rightward biases when comparing low spatial frequencies (LoSFs). Here we investigated which mechanisms underlie the cross-over. (1) We found that leftward and rightward biases were positively correlated, suggesting that the same set of mechanisms are involved in both versions of the task. (2) When we cued attention to the left or right side we found transient effects on gratingscales biases that were symmetrical for the LoSF condition but asymmetrical for the HiSF condition. This indicates that the HiSF condition itself biased stimulus-driven attention more to the left side than the LoSF condition. (3) When we lowered the contrast of the HiSF or the LoSF stimulus components, specifically the latter case made HiSF and LoSF conditions more different. This suggests that HiSF and LoSF conditions differ because HiSF components are more salient and more likely stir stimulus-driven attention. Our data are consistent with the idea that the attentional bias results from right-dominant control mechanisms of stimulus-driven attention potentially interacting with voluntary control mechanisms.

Cross-modal interactions between human faces and voices involved in person recognition - Corrected Proof

2010-05-05

Abstract: Faces and voices are key features of human recognition but the way the brain links them together is still unknown. In this study, we measured brain activity using functional magnetic resonance imaging (fMRI) while participants were recognizing previously learned static faces, voices and voice–static face associations. Using a subtraction method between bimodal and unimodal conditions, we observed that voice–face associations activated both unimodal visual and auditory areas, and specific multimodal regions located in the left angular gyrus and the right hippocampus. Moreover, a functional connectivity analysis confirmed the connectivity of the right hippocampus with the unimodal areas. These findings demonstrate that binding faces and voices rely on a cerebral network sustaining different aspects of integration such as sensory inputs processing, attention and memory.

Face and object imagery in congenital prosopagnosia: A case series - Corrected Proof

Jeremy J. Tree, Jaimie Wilkie — 2010-04-30

Abstract: It has been reported that congenital prosopagnosics may have a general imagery deficit or an imagery deficit specific to faces. However, much of this evidence is based on self-report questionnaires, rather than experimentally based testing (). This study tested face and non-face based imagery in a case series of congenital prosopagnosics, utilising both questionnaire based and forced choice accuracy measures. Our findings indicate that all the prosopagnosics showed impaired face based imagery, which contrasted with normal performance on imagery of objects and colours – a pattern that is consistent with reports of acquired prosopagnosia (). Given all our experimentally based testing indicated face imagery impairments, despite no such problems being seen on self-report questionnaires, we would argue that testing based only on the latter must be interpreted with some caution. Overall, we would advocate that our findings demonstrate a category specific visual imagery impairment in congenital prosopagnosia, such that general imagery skill can be intact in such cases.

Dyslexia and practice in the attentional blink: Evidence of slower task learning in dyslexia - Corrected Proof

Nicholas A. Badcock, John H. Hogben, Janet F. Fletcher — 2010-04-21

Abstract: In this paper we provide an extension to our previous investigation into dyslexia and the attentional blink (AB) (). The AB is a phenomenon of temporal attention whereby there is a performance cost in reporting a second target when it appears within 500msec of a first target. We examined performance differences between the first and second 90 trials in a single AB session in a group of adult readers as well as in 6 blocks of 30 trials for T1 only. Overall, there was a significant improvement across the session but most critically, this improvement was greater in magnitude and slower in the phonological dyslexic observers than in control observers. Therefore, group differences were related to rate of improvement. In line with a recent review of the literature, it is suggested that the overall performance difference between the groups relates to general performance factors and not the AB per se. Whether extended practice would entirely attenuate the group difference remains to be seen but it is suggested that the general performance difference relates to development of successful coordination of visual and temporal uncertainties in the distracter and target stimuli.

Who actually read Exner? Returning to the source of the frontal “writing centre” hypothesis - Corrected Proof

Franck-Emmanuel Roux, Louisa Draper, Barbara Köpke, Jean-François Démonet — 2010-04-14

Abstract: We have translated the most famous text of Sigmund Exner (1846–1926), which relates to the existence of a localised “writing centre” in the brain. We discuss its relevance to modern studies and understanding of writing and agraphia. In Exner’s most famous text, he hypothesised about the eponymous “Exner’s Area”, a discrete area within the brain that was located in the left middle frontal gyrus, which was dedicated to the function of writing. This text in German, included in a book published in 1881 “Untersuchungen über die Lokalisation der Functionen in der Grosshirnrinde des Menschen” (Studies on the localisation of functions in the cerebral cortex of humans), lent itself to passionate debates during the following decades on the possibility of finding a specific writing centre in left middle frontal gyrus. Modern authors still refer back to the evidence cited in this seminal text. However, over the 281 pages of Exner’s book, only a few chapters dealt with agraphia. Only four of the 167 case reports in the book explicitly mention agraphia. Although Exner describes the anatomical details of these lesions (from autopsies), no patient had pure agraphia, and only one case had an isolated lesion of the posterior part of the middle frontal gyrus. The small number of patients, the absence of pure agraphia symptoms, and the variation in the anatomy of these lesions are the main reasons why Exner’s hypothesis of a writing centre in left middle frontal gyrus has been continually debated until now. More than the seminal publication of Sigmund Exner on agraphia, we think that the diffusion of his hypothesis was partly due to the influence that Exner and his family had within the scientific community at the turn of the 20th century.

Unusual amnesia in a patient with VGKC-Ab limbic encephalitis: A case study - Corrected Proof

Luke D. Kartsounis, Rajith de Silva — 2010-04-01

Abstract: We describe the case of a patient with confirmed voltage-gated potassium channel antibody-associated encephalitis (VGKC-Ab). MRI studies revealed bilateral hyper-intensity in the hippocampi, with their volumes preserved. At presentation, the patient's anterograde and retrograde memory skills were found to be impaired and he showed fluctuation in his ability to recall familiar information. Following treatment with immunotherapy, his condition improved considerably and, in a series of follow up assessments, he performed satisfactorily (i.e., within the average range or above) on formal tests of memory, as well as on a range of other cognitive tests, including tests of executive function. By contrast, in the context of contemporaneous unstructured interviews, he showed a strong tendency to confabulate. We argue that the reported case broadens the phenomenology of VGKC-Ab limbic encephalitis and raises important theoretical questions about the aetiology of this patient's most unusual memory disorder.

Understanding deficits in empathy after traumatic brain injury: The role of affective responsivity - Corrected Proof

2010-03-24

Abstract: People with traumatic brain injury (TBI) often find social situations challenging because they can no longer respond to the emotional state of the people they are with. Many also lack emotional empathy in their social interactions. But are these problems related? The present study addressed this question by examining psychophysiological indices of emotional responding, including facial electromyography (EMG) and skin conductance during exposure to happy and angry facial expressions, in addition to self-rated emotional empathy in 21 adults with severe TBI and 22 control participants. In comparison to control participants, those in the TBI group displayed a reduction in the ability to empathize emotionally, and showed reduced physiological responding to the emotional expression of anger. By contrast, the control group spontaneously mimicked the emotional expressions they were exposed to, regardless of affective valence, and also demonstrated higher skin conductance responsivity to angry faces. The data further suggested that a loss of emotional empathy plays a role in the emotional response deficits to angry facial expressions following TBI. The results have implications for understanding the impaired social functioning and poor quality of interpersonal relationships commonly seen as a consequence of TBI.

Object affordance and spatial-compatibility effects in Parkinson's disease - Corrected Proof

Adam Galpin, Steven P. Tipper, Jeremy P.R. Dick, Ellen Poliakoff — 2010-03-02

Abstract: Movement in Parkinson's disease (PD) is strongly influenced by sensory stimuli. Here, we investigated two features of visual stimuli known to affect response times in healthy individuals; the spatial location of an object (the spatial effect) and its action-relevance (the ‘affordance’ effect). found that while PD patients show normal spatial effects, they do not show an additional affordance effect. Here we investigated whether these effects are driven by facilitation or inhibition, and whether the affordance effect emerges over a longer time-course in PD. Participants (24 PD and 24 controls) viewed either a lateralised door handle (affordance condition), a lateralised abstract stimulus (spatial condition), or a centrally presented baseline stimulus (baseline condition), and responded to a colour change in the stimulus occurring after 0msec, 500msec or 1000msec. The colour change indicated whether to respond with the left or right hand, which were either spatially compatible or incompatible with the lateralised stimulus orientation in the affordance and spatial conditions. The baseline condition allowed us to assess whether compatibility effects were driven by facilitation of the compatible response or inhibition of the incompatible response. The results indicate that stimulus orientation elicited faster responses from the nearest hand. For controls, the affordance effect was stronger and driven by facilitation, whilst the spatial condition was driven by inhibition. In contrast, the affordance and spatial-compatibility effects did not differ between conditions in the PD group and both were driven by facilitation. This suggests that the PD group responded as if all stimuli were action-relevant, and may have implications for understanding the cueing of movement in PD.

Prism adaptation does not change the rightward spatial preference bias found with ambiguous stimuli in unilateral neglect - Corrected Proof

Margarita Sarri, Richard Greenwood, Lalit Kalra, Jon Driver — 2010-02-22

Abstract: Previous research has shown that prism adaptation (prism adaptation) can ameliorate several symptoms of spatial neglect after right-hemisphere damage. But the mechanisms behind this remain unclear. Recently we reported that prisms may increase leftward awareness for neglect in a task using chimeric visual objects, despite apparently not affecting awareness in a task using chimeric emotional faces (). Here we explored potential reasons for this apparent discrepancy in outcome, by testing further whether the lack of a prism effect on the chimeric face task task could be explained by: i) the specific category of stimuli used (faces as opposed to objects); ii) the affective nature of the stimuli; and/or iii) the particular task implemented, with the chimeric face task requiring forced-choice judgements of lateral ‘preference’ between pairs of identical, but left/right mirror-reversed chimeric face tasks (as opposed to identification for the chimeric object task). We replicated our previous pattern of no impact of prisms on the emotional chimeric face task here in a new series of patients, while also similarly finding no beneficial impact on another lateral ‘preference’ measure that used non-face non-emotional stimuli, namely greyscale gradients. By contrast, we found the usual beneficial impact of prism adaptation (prism adaptation) on some conventional measures of neglect, and improvements for at least some patients in a different face task, requiring explicit discrimination of the chimeric or non-chimeric nature of face stimuli. The new findings indicate that prism therapy does not alter spatial biases in neglect as revealed by ‘lateral preference tasks’ that have no right or wrong answer (requiring forced-choice judgements on left/right mirror-reversed stimuli), regardless of whether these employ face or non-face stimuli. But our data also show that prism therapy can beneficially modulate some aspects of visual awareness in spatial neglect not only for objects, but also for face stimuli, in some cases.

Line bisection in unilateral homonymous visual field defects - Corrected Proof

Susanne Schuett, Ruth Dauner, Josef Zihl — 2010-02-22

Abstract: The contralesional line bisection error in unilateral homonymous hemianopia is a frequent but neglected clinical phenomenon. Our knowledge about this bisection error is based on small samples of hemianopic patients. Moreover, horizontal line bisection has never been investigated in other unilateral visual field defects. The present study is the first to examine line bisection in a large, representative sample of patients with unilateral homonymous visual field defects. We investigated horizontal line bisection in 129 patients with left- or right-sided homonymous hemianopia (60.5%), upper and lower quadranopia (24.8%), and paracentral scotoma (14.7%), and determined the magnitude and direction of line bisection error. The contralesional horizontal line bisection error was present not only in patients with hemianopia but also in those with upper or lower quadranopia or paracentral scotoma. Neither the type nor the severity of the visual field defect was found to determine the bisection error. Only the side of the field defect seemed to determine the horizontal direction of the bisection error (left-/rightward). The contralesional bisection error is not a specifically “hemianopic” phenomenon. It is frequently associated with any unilateral homonymous visual field defect, i.e., hemianopia, upper/lower quadranopia, paracentral scotoma. Moreover, our results further support the recent finding that the contralesional bisection error is not a direct consequence of the visual field defect. Yet, they also suggest that, although the visual field defect does not seem to be the primary cause of the contralesional bisection error, it may nevertheless contribute to it.

Cerebellar brain volume accounts for variance in cognitive performance in older adults - Corrected Proof

2010-02-18

Abstract: Introduction: Frontal lobe atrophy is implicated in patterns of age-related cognitive decline. However, other brain areas, including the cerebellum, support the work of the frontal lobes and are also sensitive to the effects of ageing. A relationship between cerebellar brain volume and cognitive function in older adults is reported, but no study has separated variance associated with cerebellar gray matter volume and cerebellar white matter volume; and no study has examined whether or not brain volume in the cerebellum is related to cognitive function in older adults after statistical control for frontal lobe volume of gray and white matter.Method: We used voxel based morphometry (VBM) and structural equation modelling (SEM) to analyse relations between general cognitive ability (G) and volume of GM and WM in frontal areas and cerebellum in a sample of 228 older adults (121 males and 107 females).Results: Results indicate that GM volume in the cerebellum predicts G, even when total intracranial volume (TICV) and GM gray and WM volumes in frontal lobes are statistically controlled. However, results differ for males and females, with males showing a stronger relationship between brain volume in the cerebellum and G.Conclusions: Results are discussed in light of neurological models of cognitive ageing and the significance of the cerebellum in models of cognitive functioning.

Phonological–lexical activation: A lexical component or an output buffer? Evidence from aphasic errors - Corrected Proof

Cristina Romani, Claudia Galluzzi, Andrew Olson — 2010-02-17

Abstract: Single word production requires that phoneme activation is maintained while articulatory conversion is taking place. Word serial recall, connected speech and non-word production (repetition and spelling) are all assumed to involve a phonological output buffer. A crucial question is whether the same memory resources are also involved in single word production. We investigate this question by assessing length and positional effects in the single word repetition and reading of six aphasic patients. We expect a damaged buffer to result in error rates per phoneme which increase with word length and in position effects. Although our patients had trouble with phoneme activation (they made mainly errors of phoneme selection), they did not show the effects expected from a buffer impairment. These results show that phoneme activation cannot be automatically equated with a buffer. We hypothesize that the phonemes of existing words are kept active though permanent links to the word node. Thus, the sustained activation needed for their articulation will come from the lexicon and will have different characteristics from the activation needed for the short-term retention of an unbound set of units. We conclude that there is no need and no evidence for a phonological buffer in single word production.

Impaired capacity for autonoetic reliving during autobiographical event recall in mild Alzheimer's disease - Corrected Proof

Muireann Irish, Brian A. Lawlor, Shane M. O'Mara, Robert F. Coen — 2010-02-15

Abstract: The capacity to mentally travel back in time and relive past events via autonoetic consciousness has been shown to be compromised even in the early stages of Alzheimer's disease (AD). To further understand the unravelling of the recollective experience in pathological ageing, we investigated autobiographical memory (ABM) using the Episodic Autobiographical Memory Interview (EAMI) in thirty middle-aged and thirty healthy elderly controls, and twenty patients with mild AD. Of key interest was the recall of contextual details and the behavioural markers predictive of autonoetic reliving. AD patients exhibited significant difficulties in recalling contextual details across all life epochs on the EAMI manifesting in a negative temporal gradient from the Early Adulthood epoch onwards. Overall there was a low incidence of autonoetic consciousness during ABM recall across all participant groups and life epochs when compared with previous studies. AD patients showed a compromised capacity to mentally relive past memories (AD

Cerebral reorganization as a function of linguistic recovery in children: An fMRI study - Corrected Proof

2010-02-08

Abstract: Characterizing and mapping the relationship between neuronal reorganization and functional recovery are essential to the understanding of cerebral plasticity and the dynamic processes which occur following brain damage. The neuronal mechanisms underlying linguistic recovery following left hemisphere (LH) lesions are still unknown. Using functional magnetic resonance imaging (fMRI), we investigated whether the extent of brain lateralization of linguistic functioning in specific regions of interest (ROIs) is correlated with the level of linguistic performance following recovery from acquired childhood aphasia. The study focused on a rare group of children in whom lesions occurred after normal language acquisition, but prior to complete maturation of the brain. During fMRI scanning, rhyming, comprehension and verb generation activation tasks were monitored. The imaging data were evaluated with reference to linguistic performance measured behaviorally during imaging, as well as outside the scanner. Compared with normal controls, we found greater right hemisphere (RH) lateralization in patients. However, correlations with linguistic performance showed that increased proficiency in linguistic tasks was associated with greater lateralization to the LH. These results were replicated in a longitudinal case study of a patient scanned twice, 3 years apart. Additional improvement in linguistic performance of the patient was accompanied by increasing lateralization to the LH in the anterior language region. This, however, was the result of a decreased involvement of the RH. These findings suggest that recovery is a dynamic, ongoing process, which may last for years after onset. The role of each hemisphere in the recovery process may continuously change within the chronic stage.

Unification of sentence processing via ear and eye: An fMRI study - Corrected Proof

2010-02-01

Abstract: We present new evidence based on fMRI for the existence and neural architecture of an abstract supramodal language system that can integrate linguistic inputs arising from different modalities such that speech and print each activate a common code. Working with sentence material, our aim was to find out where the putative supramodal system is located and how it responds to comprehension challenges. To probe these questions we examined BOLD activity in experienced readers while they performed a semantic categorization task with matched written or spoken sentences that were either well-formed or contained anomalies of syntactic form or pragmatic content. On whole-brain scans, both anomalies increased net activity over non-anomalous baseline sentences, chiefly at left frontal and temporal regions of heteromodal cortex. The anomaly-sensitive sites correspond approximately to those that previous studies () have found to be sensitive to other differences in sentence complexity (object relative minus subject relative). Regions of interest (ROIs) were defined by peak response to anomaly averaging over modality conditions. Each anomaly-sensitive ROI showed the same pattern of response across sentence types in each modality. Voxel-by-voxel exploration over the whole brain based on a cosine similarity measure of common function confirmed the specificity of supramodal zones.

Asymmetries in motor attention during a cued bimanual reaching task: Left and right handers compared - Corrected Proof

Gavin Buckingham, Julie C. Main, David P. Carey — 2010-01-25

Abstract: Several studies have indicated that right handers have attention biased toward their right hand during bimanual coordination (). To determine if this behavioral asymmetry was linked to cerebral lateralization, we examined this bias in left and right handers by combining a discontinuous double-step reaching task with a Posner-style hand cueing paradigm. Left and right handed participants received a tactile cue (valid on 80% of trials) prior to a bimanual reach to target pairs. Right handers took longer to inhibit their right hand and made more right hand errors, suggesting that their dominant hand was more readily primed to move than their non-dominant hand, likely due to the aforementioned attentional bias. Left handers, however, showed neither of these asymmetries, suggesting that they lack an equivalent dominant hand attentional bias. The findings are discussed in relation to recent unimanual handedness tasks in right and left handers, and the lateralization of systems for speech, language and motor attention.

When the zebra loses its stripes: Semantic priming in early Alzheimer's disease and semantic dementia - Corrected Proof

2010-01-20

Abstract: Patients suffering from Alzheimer's disease (AD) or semantic dementia (SD) both exhibit deficits on explicit tasks of semantic memory. Semantic priming (SP) paradigms provide a very pure and precise implicit measurement of semantic memory impairment, and a previous study of AD () using one such paradigm revealed that AD patients in the initial stages of semantic deterioration presented an abnormally large priming effect (hyperpriming) in a category-coordinate condition, compared with controls. This astonishing phenomenon could stem from the specific loss of distinctive attributes that make it possible to distinguish between semantically close concepts, while attributes shared by different concepts belonging to a given category remain intact. To test this hypothesis and compare the degradation of semantic memory in AD and SD, we devised an SP paradigm in which word pairs had either a category-coordinate or an attribute relationship. In accordance with our hypothesis, we distinguished between shared (duck–feathers) versus distinctive attributes (zebra–stripes) and close (tiger–lion) versus distant (elephant–crocodile) category-coordinate relationships. This paradigm, together with two explicit semantic memory tasks (picture-naming and categorization), was administered to 16 AD and 8 SD patients and 30 elderly control subjects. The AD patients, at the very beginning of semantic deterioration, only displayed impaired SP effects in the distinctive attribute condition, whereas in the SD patients, who had more severe semantic deterioration, we observed an extinction of SP effects in both attribute conditions. In SD patients, we also report hyperpriming effects in both category-coordinate conditions. Our results suggest that semantic memory impairment follows the same course in both AD and SD, affecting distinctive attributes first and then shared ones. In accordance with distributed models of semantic memory, the loss of distinctive attributes leads to a confusion between close concepts and it is this which causes the transient hyperpriming phenomenon.

The role of the left anterior temporal lobe in language processing revisited: Evidence from an individual with ATL resection - Corrected Proof

Yanchao Bi, Tao Wei, Chenxing Wu, Zaizhu Han, Tao Jiang, Alfonso Caramazza — 2010-01-14

Abstract: Various hypotheses about the role of the anterior temporal lobe (ATL) in language processing have been proposed. One hypothesis is that it binds the semantic/conceptual properties of words, functioning as a hub for linking modality-specific conceptual properties of objects. This hypothesis predicts that damage to ATL would give rise to impaired conceptual knowledge of all categories. A related school of hypotheses assumes that the left ATL is critical for lexical retrieval, with different sub-regions potentially important for different categories of items. We examined these hypotheses by studying a case of surgical resection of left ATL due to a low-grade glioma (LGG). Thorough language assessments performed four months after the operation revealed the following profile: the patient showed intact conceptual knowledge for all categories of items tested using both accuracy and response latency measures; he suffered from name retrieval deficits for proper names (people and place names) and artifacts (including tools), but showed no name retrieval difficulties for animate things. This pattern of results challenges both target hypotheses about the role of ATL in language processing tested here.

Patterns of breakdown in spelling in primary progressive aphasia - Corrected Proof

2010-01-11

Abstract: Introduction: The objective of this study is to determine which cognitive processes underlying spelling are most affected in the three variants of primary progressive aphasia (PPA): Logopenic variant primary progressive aphasia (lvPPA), Semantic variant primary progressive aphasia (svPPA), and Nonfluent variant primary progressive aphasia (nfvPPA).Methods: 23 PPA patients were administered The Johns Hopkins Dysgraphia Battery to assess spelling. Subtests evaluate for effects of word frequency, concreteness, word length, grammatical word class, lexicality (words vs pseudowords), and “regularity” by controlling for the other variables. Significant effects of each variable were identified with chi square tests. Responses on all spelling to dictation tests were scored by error type. 16 of the 23 subjects also had a high resolution MRI brain scan to identify areas of atrophy.Results: We identified 4 patterns of spelling that could be explained by damage to one or more cognitive processes underlying spelling. Nine patients (3 unclassifiable, 4 with lvPPA, 2 with svPPA) had dysgraphia explicable by impaired access to lexical representations, with reliance on sublexical phonology-to-orthography conversion (POC). Two patients (with nfvPPA) showed dysgraphia explicable by impaired access to lexical representations and complete disruption of sublexical POC. Seven patients (4 with lvPPA, 1 with svPPA, 2 unclassifiable) showed dysgraphia explicable by impaired access to lexical-semantic representations and/or lexical representations with partially spared sublexical POC mechanisms. Five patients (1 with nfvPPA, 2 with svPPA, 1 with lvPPA, and 1 unclassifiable) showed dysgraphia explicable by impairment of the graphemic buffer.Conclusions: Any cognitive process underlying spelling can be affected in PPA. Predominance of phonologically plausible errors, more accurate spelling of regular words than irregular words, and more accurate spelling of pseudowords than words (indicating spared POC mechanisms) may indicate a low probability of progression to nfvPPA.

Impaired acquisition of a mirror-reading skill in Alzheimer's disease - Corrected Proof

Sarah Merbah, Eric Salmon, Thierry Meulemans — 2010-01-11

Abstract: Several studies using the mirror-reading paradigm have shown that procedural learning and repetition priming may be preserved in the early stages of Alzheimer's disease (AD) (e.g., ). According to the classical interpretation, improved reading time for repeated words is sustained by a repetition priming effect, while procedural learning is demonstrated when this improvement is also observed for new words. Following , the hypothesis tested in the present study was that improved reading of new words could also be due to a repetition priming effect rather than to the acquisition of a mirror-reading skill. Indeed, because the same letters are presented throughout the task, a repetition priming effect for the letters could suffice to explain the improvement in performance. To test this hypothesis, we administered to 30 healthy young and elderly subjects and to 30 AD patients a new mirror-reading task in two phases: an acquisition phase comprising pseudo-words constructed with one part of the alphabet, and a test phase in which both pseudo-words constructed with the same part of the alphabet and pseudo-words constructed with another part of the alphabet were presented. If the new pseudo-words composed with repeated letters were read faster, it would reflect a repetition priming effect; if pseudo-words composed of ‘new’ letters were read faster, it would reflect a procedural learning effect. The results show comparable repetition priming effects in AD patients and in healthy elderly subjects, whereas only healthy subjects showed a procedural learning effect. These results suggest, contrary to previous studies, that the learning of a new perceptual skill may not always be preserved in AD.

Neural response to the behaviorally relevant absence of anticipated outcomes and the presentation of potentially harmful stimuli: A human fMRI study - Corrected Proof

Louis Nahum, Stéphane R. Simon, David Sander, François Lazeyras, Armin Schnider — 2010-01-11

Abstract: Adaptive behavior requires the ability to react to potentially harmful stimuli, characterized by high negative inherent emotional salience (iES) (e.g., spiders, snakes), and to the unexpected non-occurrence of anticipated events. When presented simultaneously, threatening stimuli and unexpected absence of anticipated outcomes induce distinct electrocortical responses in different time periods. In this study, we used fMRI to test whether processing of the absence of anticipated outcomes (prediction errors) was anatomically dissociated from the processing of iES or whether iES simply modulated activity of areas processing the non-occurrence of anticipated outcomes. Participants saw two alternating pairs of faces and indicated for each pair which one would have a declared target stimulus on its nose. Depending on the condition, the target stimulus was either a spider (high iES stimulus) or a disk (low iES stimulus). The target stimulus switched to the other face after several consecutive correct responses, with the switch being indicated by the appearance of the alternative stimulus (disk when the spider was the declared target; spider when the disk was the declared target). We found that the spider induced stronger activation in visual areas than the disk. By contrast, the absence of anticipated outcomes specifically activated the orbitofrontal cortex (OFC), irrespective of the iES of the outcome stimulus. The findings support a generic role of the OFC in outcome monitoring.

The cerebellum and dyslexia - Corrected Proof

Catherine J. Stoodley, John F. Stein — 2010-01-08

Abstract: It has been proposed that cerebellar dysfunction is an underlying cause of developmental dyslexia, which is diagnosed when there is an unexpected discrepancy between a child's reading ability and his or her cognitive skills. Traditionally, the cerebellum is thought to be involved in motor control, although in the last 15 years mounting evidence suggests a cerebellar role in higher-level cognitive processes. Clinical, neuroimaging, and behavioral studies have all supported a role for the cerebellum in dyslexia. Clinical studies document acquired language and reading difficulties in patients with cerebellar damage or degeneration. Both structural and functional imaging studies suggest that the cerebella of dyslexic individuals differ both morphologically and functionally from good readers. In particular, the posterolateral right cerebellar hemisphere (that connects with the left cerebral cortex) is both smaller in size and shows differential activation patterns in some dyslexic individuals. Behavioral studies of “cerebellar” tasks have assessed balance and motor skills, eye-movement control, classical conditioning, and implicit learning in dyslexic participants. Results indicate that at least a subset of dyslexic children and adults performed poorly on these tasks. In some cases, dyslexics' performance correlated with literacy skills and/or the degree of discrepancy between cognitive and literacy skills. However, despite these findings, it remains unlikely that cerebellar dysfunction is the main cause of dyslexia. There are many negative results, only a few clinical reports of acquired dyslexia resulting from cerebellar damage, and questionable specificity of cerebellar involvement in dyslexia, as several other neurodevelopmental disorders show associated cerebellar abnormalities. That said, it is likely that the cerebellum is part of the distributed neural circuitry that is impaired in developmental dyslexia. Future studies should aim to understand this role better in the context of cerebellar regional anatomy and the connections between the cerebellum and the cortical and sub-cortical regions involved in reading.

Extensive video-game experience alters cortical networks for complex visuomotor transformations - Corrected Proof

Joshua A. Granek, Diana J. Gorbet, Lauren E. Sergio — 2010-01-08

Abstract: Using event-related functional magnetic resonance imaging (fMRI), we examined the effect of video-game experience on the neural control of increasingly complex visuomotor tasks. Previously, skilled individuals have demonstrated the use of a more efficient movement control brain network, including the prefrontal, premotor, primary sensorimotor and parietal cortices. Our results extend and generalize this finding by documenting additional prefrontal cortex activity in experienced video gamers planning for complex eye-hand coordination tasks that are distinct from actual video-game play. These changes in activation between non-gamers and extensive gamers are putatively related to the increased online control and spatial attention required for complex visually guided reaching. These data suggest that the basic cortical network for processing complex visually guided reaching is altered by extensive video-game play.

Phantom limb after stroke: An underreported phenomenon - Corrected Proof

Daniel Antoniello, Benzi M. Kluger, Daniel H. Sahlein, Kenneth M. Heilman — 2009-11-16

Abstract: The presence of a phantom limb (PL) resulting from a cerebral lesion has been reported to be a rare event. No prior study, however, has systematically investigated the prevalence of this syndrome in a group of post-stroke individuals. Fifty post-stroke individuals were examined with structured interview/questionnaire to establish the presence and perceptual characteristics of PLs. We document the presence of phantom experiences in over half of these individuals (n=27). We provide details of these phantom experiences and further characterize these symptoms in terms of temporal qualities, posture, kinesthesia, and associated features. Twenty-two participants reported postural phantoms, which were perceived as illusions of limb position that commonly manifested while lying in bed at night – a time when visual input is removed from multi-sensory integration. Fourteen participants reported kinesthetic phantoms, with illusory movements ranging from simple single joint sensations to complex goal-directed phantom movements. A striking syndrome of near total volitional control of phantom movements was reported in four participants who had immobile plegic hands. Reduplicative phantom percepts were reported by only one participant. Similarly, phantom pain was present in only one individual – the sole participant with a pre-stroke limb amputation. The results suggest that stroke results in phantom experiences more commonly than previously described in the literature. We speculate that subtotal deafferance or defective motor efference after stroke may manifest intermittently as a PL.

Two qualitatively different impairments in making rotation operations - Corrected Proof

Tania Buiatti, Alessandro Mussoni, Alessio Toraldo, Miran Skrap, Tim Shallice — 2009-11-16

Abstract: It is widely recognized that mental rotation is a cognitive process which engages a distributed cortical network including the frontal, premotor and parietal regions. Like other visual-spatial transformations it could require operations on both metric and categorical spatial representations. Previous reports have implicated respectively the right hemisphere being involved in the metric processing and the left hemisphere in the categorical processing. By using a modified version of the , we attempted to establish the cortical regions relevant for the categorical and metric aspects of mental rotation transformations. Two groups of patients were found to be impaired in our study, namely the left prefrontal and the right parietal. In particular, whereas the right parietal group made poor use of categorical information, the left prefrontal patients showed a broader mental rotation impairment with a significant number of metric errors. The results are discussed in terms of the model of about the possible mental transformation impairments following brain lesions.