Visual–vestibular interactive responses in the macaque ventral intraparietal area (VIP)

TLDR

Self‑motion detection relies on the interaction of multiple sensory systems for accurate perception and motor response. The study examined how multimodal signals are encoded and interact in the macaque ventral intraparietal area. Visual responses were elicited using large‑field stimuli that simulated forward or backward self‑motion or front‑parallel movement. VIP neurons receive vestibular input that co‑modulates with visual and somatosensory signals; most cells are visually driven, about a third respond to horizontal rotation, vestibular responses track head velocity (sometimes acceleration or position), align codirectionally with visual motion, and somatosensory signals match visual preference, supporting VIP’s role in encoding self‑motion.

Abstract

Abstract Self‐motion detection requires the interaction of a number of sensory systems for correct perceptual interpretation of a given movement and an eventual motor response. Parietal cortical areas are thought to play an important role in this function, and we have thus studied the encoding of multimodal signals and their spatiotemporal interactions in the ventral intraparietal area of macaque monkeys. Thereby, we have identified for the first time the presence of vestibular sensory input to this area and described its interaction with somatosensory and visual signals, via extracellular single‐cell recordings in awake head‐fixed animals. Visual responses were driven by large field stimuli that simulated either backward or forward self‐motion (contraction or expansion stimuli, respectively), or movement in the frontoparallel plane (visual increments moving simultaneously in the same direction). While the dominant sensory modality in most neurons was visual, about one third of all recorded neurons responded to horizontal rotation. These vestibular responses were typically in phase with head velocity, but in some cases they could signal acceleration or even showed integration to position. The associated visual responses were always codirectional with the vestibular on‐direction, i.e. noncomplementary. Somatosensory responses were in register with the visual preferred direction, either in the same or in the opposite direction, thus signalling translation or rotation in the horizontal plane. These results, taken together with data on responses to optic flow stimuli obtained in a parallel study, strongly suggest an involvement of area VIP in the analysis and the encoding of self‐motion.