Nausea reshapes visual exploration and pupillary responses to affective images
Perception is a continuous, active, and dynamic process of inference shaped by current goals, past experience, and hard biological constraints. The physiological state of the body is arguably the most fundamental one. Continuous inference about interoceptive states colors perception with emotions, which in turn affect basic perceptual and attentional processes. How, then, do we really look at the world when experiencing malaise? Here we leverage Galvanic Vestibular Stimulation (GVS) – a non-invasive brain stimulation technique that induces mild dizziness, motion sickness, and nausea – in conjunction with high-resolution eye tracking, pupillometry, and computational modelling. We demonstrate that mild vestibular perturbations disrupt the coupling between gaze and informative low-level visual features. Crucially, however, this effect depends on individual susceptibility and on stimulus valence. Particularly susceptible participants experiencing stronger nausea increase their reliance on visually salient features, and particularly so for threatening (negatively valenced) images. Pupillometry reveals larger tonic pupil size in these participants, consistent with heightened arousal, as well as disrupted phasic responses to affective pictures. Altogether, these results unveil the continuous and dynamic interplay between interoceptive and exteroceptive processes, showing that how we perceive the environment fundamentally resonates with how we feel. Significance statement Feeling unwell – whether from illness or motion – is a universal experience. Bodily signals profoundly shape cognition, emotion, and decision-making. We therefore asked how nausea changes visual exploration of the environment. We electrically stimulated the vestibular system of healthy volunteers to induce dizziness and nausea, while monitoring gaze during free viewing of affective images. The stronger the nausea, the more visual exploration was guided by objectively salient visual features, especially for highly arousing images. Pupillometry revealed larger pupils, consistent with heightened arousal, and disrupted pupillary responses to affective pictures, showing less room for affective processing and increased cognitive control. We conclude that nausea may dull perception, while strengthening its grip on physical reality. Highlights GVS caused variable degrees of dizziness and nausea GVS led to spatial biases in visual exploration which were, however, further dependent on image valence and content During GVS eye fixations landed, on average, at locations that were less salient based on their mere physical properties, provided participants did not experience strong interoceptive perturbations Highly susceptible participants showed the opposite pattern: their fixations landed on visually more salient and informative locations, especially for negative images Participants who felt stronger effects, including nausea, also showed the largest increase in tonic pupil size; concurrently, the signature phasic dilation associated with negative emotions was disrupted Oculomotor behavior and perception adjust dynamically to ongoing interoceptive processes; GVS can be an effective tool to study this dialogue, provided that inter-individual differences are accounted for