Multimodal representation of visual perception

The posterior parietal cortex is involved in multimodal integration of sensory inputs for creating a stable internal representation of the extrapersonal space. Such representation is used by the neural network as basis to plan and generate motor outputs. Studies performed in our laboratory showed that neurons in area PEc in the parietal cortex, are activated by optic flow stimuli with a tuning for the focus of expansion (FOE) position in space, suggesting a role of this area in heading perception. To assess if heading is encoded in eye- or head-centered coordinates in area PEc, we recorded the extracellular activity of single neurons in two monkeys (M. fascicularis) trained in a reaction time task. To verify whether PEc neurons are able to integrate multimodal signals, such as those related to optic flow selectivity with extraretinal inputs, we varied the spatial position of FOE and target. We tested the retinotopic organization of FOE neuronal selectivity and then we compared the responses to the optic flow stimulus at same retinal FOE offset and different eye position. We also varied the head position in space along the horizontal axis. We show results on eye/head position modulation of neuronal optic flow responses in PEc cells, suggesting that area PEc combines optic flow input with extraretinal signals related to eye and/or head position. These results allow to hypothesise a role of this area in guiding locomotion by computing the transformation from eye-centered to head-centered coordinates.