Optic flow neurons in area PEc integrate eye and head position signals.

Neurons in area PEc, a visual area located in the superior parietal lobule, are activated by optic flow stimuli. An important issue is whether PEc neurons are able to integrate multimodal signals, such as those related to optic flow selectivity with those about eye and head position. The aim of this study was to assess if angle of gaze and/or head rotation modify the spatial representation of the focus of expansion (FOE), varying FOE, fixation point and head position in space. We found that the rotation of head modulated the firing activity of PEc optic flow neurons. The head position also changed the angle of gaze effect on the PEc neuronal activity. All recorded neurons showed a main interaction effect between head and eye position upon the selectivity for optic flow stimuli. These results seem to suggest that PEc optic flow neurons use different reference frames depending on the position of the eye and/or the head in space emphasizing a possible contribution of this area in guiding locomotion by integrating multiple extraretinal inputs.