Marc Thioux Position: Post-doc e-mail

Supervisor: Christian Keysers Peer reviewed publications in scientific journals: Thioux M, Stark DE, Klaiman C, Schultz RT.The day of the week when you were born in 700 ms: calendar computation in an Autistic savant. J Exp Psychol Hum Percept Perform. 2006 Oct;32(5):1155-68. Some individuals are able to determine the weekday of a given date in a few seconds (finding for instance that June 12, 1900, was a Tuesday). This ability has fascinated scientists for many years because it is predominantly observed in people with limited intelligence and may appear very early in life. Exceptional visual memory, exceptional concentration abilities, or privileged access to lower levels of information not normally available through introspection have been advanced to explain such phenomena. In the present article, the authors show that a simple cognitive model can explain all aspects of the performance of Donny, a young autistic savant who is possibly the fastest and most accurate calendar prodigy ever described. Copyright 2006 APA. Thioux M, Pesenti M, Costes N, De Volder A, Seron X.Task-independent semantic activation for numbers and animals.Brain Res Cogn Brain Res. 2005 Jul;24(2):284-90. Epub 2005 Mar 29. Semantic processing of numbers and animals was contrasted with PET in two different tasks (comparison and classification) to test the hypothesis that knowledge about numbers is associated with increased activation in the parietal cortices, regardless of the semantic task (i.e. Classification: is seven odd? Comparison: is seven larger than 5?). By contrast, processing animal names was expected to produce activation in inferior temporal areas. Task-independent activation was observed in the left and right intraparietal sulci for number names, whereas task-independent activation of the left inferior temporal gyrus was found for animal names. No significant interaction between the category (numbers or animals) and the semantic task (comparison or classification) was observed. Accordingly, the IPS activation classically observed during numerical processing appears to be related to category-specific semantic knowledge about numbers. Likewise, the activation of the inferior temporal gyrus associated with the processing of animal names is probably related to category-specific knowledge about animals. The results strongly support the hypothesis that different brain regions are important for storing conceptual knowledge about different semantic categories. Rossion B, Bodart JM, Pourtois G, Thioux M, Bol A, Cosnard G, Benoit G, Michel C, De Volder A.Functional imaging of visual semantic processing in the human brain. Previous neuroimaging studies have identified a large network of cortical areas involved in semantic processing in the human brain, which includes left occipito-temporal and inferofrontal areas. Most studies, however, investigated exclusively the associative/functional semantic knowledge by using mainly words and/or language related tasks, and this factor may have contributed to the large left hemisphere superiority found in semantic processing and to the controversial involvement of left prefrontal structures. The present study investigates the neural basis of visual objects knowledge, accessed exclusively through pictorial information. Regional cerebral blood flow (rCBF) was assessed using positron emission tomography (PET) during 3 conditions in right-handed normal volunteers: resting with eyes closed, retrieval of semantic information related to visual properties of objects (real size), and visual categorization based on physical properties of the image. Confirming previous experiments and neuropsychological findings, most activations were found in left occipito-temporal areas during retrieval of visual semantic knowledge. The absence of any activation in the left prefrontal inferior cortex for visual semantic processing confirms recent observations which suggest that this region would not be involved in retrieval of visual semantic knowledge from living entities. Rather, such knowledge about visual properties of objects, situated closely to cortical regions mediating perception of the visual attributes, can be retrieved directly from these regions when visual images are used as entry level stimuli. Pesenti M, Thioux M, Seron X, De Volder A.Neuroanatomical substrates of arabic number processing, numerical comparison, and simple addition: a PET study. Positron emission tomography was used to localize the cerebral networks specifically involved in three basic numerical processes: arabic numeral processing, numerical magnitude comparison, and retrieval of simple addition facts. Relative cerebral blood flow changes were measured while normal volunteers were resting with eyes closed, making physical judgment on nonnumerical characters or arabic digits, comparing, or adding the same digits. Processing arabic digits bilaterally produced a large nonspecific activation of occipito-parietal areas, as well as a specific activation of the right anterior insula. Comparison and simple addition fact retrieval revealed a fronto-parietal network involving mainly the left intraparietal sulcus, the superior parietal lobule and the precentral gyrus. Comparison also activated, but to a lesser extent, the right superior parietal lobe, whereas addition also activated the orbito-frontal areas and the anterior insula in the right hemisphere. Implications for current anatomo-functional models of numerical cognition are drawn. Pesenti M, Thioux M, Samson D, Bruyer R, Seron X.Number processing and calculation in a case of visual agnosia. We describe the performance of a brain-damaged subject who suffered from visual agnosia leading to major difficulties in generating and exploiting visual representations from long-term memory. His performance in a physical judgement task in which he was required to answer questions about the visual shapes of Arabic numerals reflected his agnosic problems. However, he showed no impairment in usual number processing and calculation tasks. This case shows that, despite some commonalities in number and object processing, actual numerical processes are not affected by visual agnosia and can be preserved even when fine visual processes are impaired.