Modality-specific reactive and predictive responses in the human superior colliculus.

Inspired by recent theoretical work emphasizing predictive neural processing, we tested whether a midbrain structure for multimodal sensory integration-the superior colliculus-would show predictive responses to both visual and somatosensory stimulation. A multi-stage experimental design allowed us to test predictive activity in the human superior colliculus while 7-Tesla functional magnetic resonance imaging (fMRI) allowed us to map its sensory response across superior colliculus layers (N = 80). As expected from non-human animal work, visual and somatosensory stimulation elicited distinct depth-dependent responses. We also observed a predictive response: these same modality-specific and depth-dependent effects occurred during task periods preceding direct stimulation, when sensorimotor input was identical between visual and somatosensory conditions. Further analyses rule out cross-trial carryover and show corresponding effects in the thalamic sensory nuclei. Here our results confirm that, in humans, the superior colliculus is sensitive to both visual and somatosensory input, and they demonstrate that it carries predictive signals for upcoming sensory events.