Once you feel it, you see it: insula and sensory-motor contribution to visual awareness for fearful bodies in parietal neglect

The interplay between the neural mechanisms of visual awareness and those involved in emotion processing and the mapping of related somatic changes remains unclear. To address this issue we studied one patient with visual extinction following right parietal damage, in a combined behavioral, psychophysiological and neuroimaging experiment. Patient M.P. was presented with neutral and fearful bodily expressions, either unilaterally in the left (LVF) or right visual field (RVF), or in both visual fields simultaneously. Fearful expressions presented in the left visual field simultaneously with neutral bodies in the RVF were detected more often than left-side neutral bodies. Signal detection analysis showed that the preferential access of fearful bodies to visual awareness is related to higher perceptual sensitivity for these stimuli during attentional competition. Pupil dilation, which indexes autonomic arousal, increased for fearful more than for neutral bodies. Moreover, dilation for extinguished fearful bodies was bigger than for consciously perceived fearful bodies. This decoupling between (increased) arousal and (lack of) conscious visual experience argues against a direct relationship between visual awareness of emotional signals and peripheral changes. Neuroimaging results showed that fearful bodies activated the left amygdala and extrastriate cortex when consciously perceived as well as when extinguished. Critically, however, conscious perception of fearful bodies was uniquely associated with activity in the anterior insula, somatosensory, motor and premotor cortex (PMC), and the cerebellum. This suggests that the integration between peripheral arousal and the moment-to-moment mapping at the central neural level of these bodily changes is critical for the conscious visual experience of emotional signals.