Sustained dynamics of saccadic inhibition and adaptive oculomotor responses during continuous exploration

Abstract

In natural environments, stimuli often recur across time and space, requiring the visual system to remain sensitive to novelty while managing predictability. A central question in systems neuroscience is how motor systems adapt to repeated sensory events without compromising responsiveness. We investigated this adaptive capacity using saccadic inhibition (SI)—a reflexive suppression of eye movements triggered by sudden visual transients—as a probe of oculomotor dynamics during naturalistic viewing. Human participants (17 females, 4 males) freely explored visual arrays while brief gaze-contingent flashes appeared five times at random intervals, either foveally or parafoveally. SI reliably occurred ∼120 ms post-flash across repetitions and locations, indicating robust sensory-driven inhibition. However, the rebound phase—reflecting saccade reprogramming—showed a progressive decline. In a second experiment (14 females, 5 males), only the first or the fifth flash was visible on each trial. In this case, neither inhibition nor rebound was altered, suggesting that the rebound decline is driven by repeated sensory stimulation rather than exploration time. This dissociation reveals selective habituation of motor re-engagement mechanisms, while reflexive inhibitory gating remains stable. We propose that inhibition is mediated by circuitry that transiently suppresses saccade initiation and resists habituation. By contrast, the weakening rebound reflects a separate, habituation-prone route that reduces saccade generation to irrelevant events. Functionally, this imbalance implies a recalibration within the saccade generator, preserving inhibitory capacity while constraining motor output. Our findings uncover a distinct form of oculomotor habituation and demonstrate how SI reveals dynamic decoupling of sensory input and motor output under repeated stimulation. Significance Statement The ability to interrupt and resume eye movements in response to environmental changes is fundamental to visual exploration. We investigated how this process unfolds across repeated visual transients in naturalistic conditions. Our findings show that saccadic inhibition remains stable across time, whereas the subsequent rebound phase habituates. This dissociation suggests that distinct processes mediate reflexive interruption and motor recovery habituation. Our data indicate that dynamic modulation of motor gating circuits is a mechanism for optimizing oculomotor behavior. These results deepen our understanding of visual-motor coordination, provide insight about the constraints governing the underlying system circuitry, and may inform clinical tools for assessing sensorimotor adaptability in health and disease.