SEGREGATION OF NEURAL CIRCUITS INVOLVED IN SPATIAL LEARNING IN REACHING AND NAVIGATIONAL SPACE

Recent behavioral and neuropsychological studies suggest that visuo-spatial memory for reaching and navigational space is dissociated. In the present fMRI study, we investigated the hypothesis that learning spatial sequences in reaching and navigational space is processed by partially segregated neural systems. To this aim, we adapted the Corsi Block Tapping Test (CBT) and the Walking Corsi Test (WalCT); the latter is a modification of the CBT in which subjects observe and reproduce spatial sequences by walking in a room instead of tapping wooden blocks on a table. Subjects were scanned while learning supra-span sequences of spa- tial locations through observation of video clips in which an actor tapped the blocks within reaching space (CBT) or walked on tiles placed on a carpet (WalCT). A large cerebral net- work spanning from visual occipital to parietal to frontal areas was activated during learning of both the CBT and the WalCT sequences. Within this network right lingual gyrus, calcarine sulcus and dorsolateral prefrontal cortex were specifically associated to learning in naviga- tional space, whereas left inferior temporal gyrus, lingual and fusiform gyrus and middle oc- cipital gyrus were associated to learning sequences in reaching space. These results support the idea of a partial segregation between neural circuits for reaching and navigational space not only in the domain of perception and action planning but also in spatial learning and long- term memory.