Research Unit in Cognitive Neurosciences
UNESCOG investigates the organisation and functioning of the language and cognitive system while taking its biological substrate into account.Experimental psychologists, neuropsychologists and electrophysiologists work on both normal and brain-damaged individuals in the following domains: audio-visual interactions, auditory and visual attention, speech perception and recognition, reading disturbances, cognitive consequences of schooling, literacy and ageing, organisation of the semantic system, retrieval of information from memory (in particular episodic and prospective), re-education of working memory, impairments of executive functions and of social representations due to brain lesion. Besides experimental approaches from cognitive psychology and neuropsyclology, UNESCOG's researchers employ methods of neuropsychological patient examination and of cerebral imagery (recording of evoked potentials and of hemodynamic changes).
Does working memory mediate hemispheric differences in number processing ?
How numbers are cognitively represented in our brain?Consensus exists that this representation is spatially rather than linguistic. However, what kind of spatial coordinates are involved is subject to debate. The dominant view is that numbers are represented along a visuo-spatial 'mental number line' but other theories suggest that numbers are represented verbal-spatially. According to the literature on spatial processing, hemispheric dominance exists for these different types of spatial processing. Within the present research project we put forward the hypothesis that working memory load mediates hemispheric differences in number processing. We predict that hemispheric differences in number processing task will be observed only if a working memory load is applied. This interaction between different number processing tasks and different types of working memory load will be investigated using different methodologies such as a behavioral approach, neuro-imaging and neuropsychological research.
Interactions between numbers and space
A tight correspondence has been postulated between the representations of number and space. Evidence for this correspondence is provided by a number of different observations. Some people, when they think of numbers, have vivid spatial imaginations of these numbers (e.g. linearly organized, often in three dimensions). Other evidence for the correspondence between numbers and space is provided by the distance effect: the larger the numerical distance between two numbers, the more easily they are discriminated. A related observation is made in the SNARC effect: people respond faster with the left hand side to relatively small numbers and with the right hand side to large numbers. This observation shows that the number representation is spatially oriented from left to right. Finally, patients with left neglect, following a right hemisphere lesion, fail to report, orient to, or verbally describe stimuli in the contralesional left hemispace. When these patients are asked to bisect a visually presented physical line, the line is typically bisected towards the ipsilesional, not neglected hemispace. Similar observations were made with numerical intervals where a significant displacement towards large numbers, corresponding to the right side of the mental number line, was observed. The goal of the present project is to keep exploring those different phenomenons.