Conflict-dependent gain control in area VIP during visual-vestibular self-motion processing

Visual and vestibular signals are continuously integrated to estimate self-motion, yet these sensory cues are often inconsistent under natural conditions. How cortical circuits regulate multisensory interactions under cue conflict while preserving stable heading representations remains poorly understood. Here, we recorded neurons in male macaque ventral intraparietal area (VIP) during passive movement stimulation while systematically varying visual-vestibular heading offsets. VIP neurons exhibited strong conflict-sensitive gain modulation: congruent cues enhanced neuronal responses, whereas increasing cue offsets progressively suppressed response gain. This effect was observed not only in multisensory neurons but also in neurons classified as predominantly visual or vestibular, indicating widespread cross-modal interactions across the population. In contrast, preferred-heading shifts remain modest, suggesting that cue conflict primarily modulated response gain rather than altering heading tuning. Despite substantial suppression at the single-neuron level under large cue offsets, population Fisher information was largely preserved, indicating robust heading discriminability. Further analyses revealed flexible sensory weighting in VIP, with visual and vestibular contributions shifting as cue conflict increased. Finally, a feedforward-gated normalization model substantially improved the characterization of VIP responses by allowing cue conflict to dynamically regulate the effective normalization pool, thereby capturing both multisensory enhancement at small visual-vestibular heading offset and suppression under large cue conflict. Together, these findings show that VIP exhibits conflict-dependent regulation of multisensory gain, preserving robust self-motion representations under sensory conflict. Significance statement Visual and vestibular cues are often misaligned in natural environments, creating a challenge for accurate self-motion perception. We demonstrate that neurons in the macaque ventral intraparietal area (VIP) dynamically adjust multisensory gain according to the degree of visual-vestibular conflict. As the visual-vestibular heading offset increases, neuronal responses are progressively enhanced or suppressed, while population coding of heading direction remains largely preserved. A conflict-sensitive normalization model accounts for these response dynamics and outperforms traditional multisensory integration models, suggesting that VIP implements adaptive gain-control computations to regulate interactions between visual and vestibular signals. These results identify a cortical mechanism that links sensory conflict detection to robust perceptual coding, advancing our understanding of multisensory processing in the brain.