The blind sight of emotion: Behavioral and EEG responses to facial expressions in the blind visual field.

The perception of emotional facial expressions has been shown to rely on interactions between high-level social-perceptual regions and early visual cortices. While reentrant signals from the posterior superior temporal sulcus (pSTS) to V1/V2 have been causally implicated in emotion perception, less is known about how such mechanisms operate in individuals with acquired visual field deficits. In this study, we investigated residual emotion perception in a group of patients with chronic hemianopia resulting from post-chiasmatic lesions. Patients performed a two-alternative forced choice task (2AFC), discriminating happy and fearful facial expressions presented briefly and masked, either in the intact or blind visual field. Behavioral performance was assessed in terms of accuracy, response times, and perceptual sensitivity (d′). Patients showed above-chance discrimination of emotional expressions even when stimuli were presented in their blind field, despite a reduction in performance compared to the intact field. This effect was observed consistently across participants and emotional categories, suggesting the presence of spared affective processing outside of visual awareness. EEG recordings were acquired to investigate the temporal unfolding of residual affective processing, and ERP analyses revealed emotion-related modulations, even when stimuli were presented in the blind field. These findings seem to indicate that emotional stimuli may be processed through alternative visual pathways that bypass the primary visual cortex, possibly involving subcortical structures such as the superior colliculus, pulvinar, and amygdala. This study might offer new insights into distributed visual processing and could inform future neuromodulatory interventions aimed at enhancing residual vision.