The influence of form on motion signal processing in the ventral intraparietal area of macaque monkeys

The visual system relies on both motion and form signals to perceive the direction of self-motion, yet the coordination mechanisms between these two elements in this process remain elusive. In the current study, we employed heading perception as a model to delve into the interaction characteristics between form and motion signals. We recorded the responses of neurons in the ventral intraparietal area (VIP), an area with strong heading selectivity, to motion-only, form-only, and combined stimuli of simulated self-motion. Intriguingly, VIP neurons responded to form-only cues defined by Glass patterns, although they exhibited no tuning selectivity. In combined condition, introducing a small offset between form and motion cues significantly enhanced neuronal sensitivity to motion cues. However, with a larger offset, the enhancement effect on sensitivity became comparatively smaller. Moreover, we observed that the influence of form cues on neuronal response to motion cues is more pronounced in the later stage (1–2 s) of stimulation, with a relatively smaller effect in the early stage (0–1 s). This suggests a dynamic interaction between motion and form cues over time for heading perception. In summary, our study uncovered that in area VIP, form information plays a role in constructing accurate self-motion perception. This adds valuable insights into the complex dynamics of how the brain integrates motion and form cues for the perception of one's own movements.