fMRI Study of the Cerebal Bases of the Spatialization Process in Working Memory

The present neuroimaging study investigates cerebral and behavioral markers of spatialization. Spatialization in memory corresponds to a mental representation of successive items from left to right in Westerners. A simple task to detect spatialization consists in presenting a series of stimuli sequentially. All stimuli are centered on the screen, so there is no spatial information during the task. After the presentation of the sequence, there is a recognition phase in which the participant is requested to take a decision as to whether a memory probe belongs to the sequence maintained in memory. The decision is made by pressing a key with the left or the right hand, depending on the instruction. The main measure is the difference in response times between the two hands. The standard spatialization effect in working memory in Westerners is that left-key responses are faster when retrieving the first items of the sequence whereas later items elicit faster right-key responses. To date, the factors that can influence this spatialization process in working memory as well as the brain structures involved remain largely unknown. Participants need to complete three experimental conditions associated with fMRI recording of brain activity. In task A (Visual Spatial), participants will see the sequences presented from left to right; in task B (Visual No Spatial), participants will see sequences of items presented in the middle of the screen; and in task C (Auditory), the sequences will be presented in an auditory format. When comparing tasks, A and B, we will be able to investigate if seeing information from left to right (spatialization is provided through the spatial coordinates of the items) is comparable to spatializing information from left to right (spatialization is not provided, all items have the same spatial coordinates). The comparison between task B and C will allow us to investigate the effect of seeing items (spatialization is not provided, all items have the same spatial coordinates) versus hearing them (spatialization is not provided and items have no spatial coordinates).