Linking the Superior Colliculus to Pupil Modulation

Pupil size is becoming a popular index in basic and clinical investigation because it is modulated by various sensory, cognitive, and affective processes. Recent research has shown similar modulations by bottom-up saliency, top-down cognitive, and arousal processes between saccade and pupillary responses. The superior colliculus (SC), a midbrain structure causally linked to eye movements and attention, is implicated in underlying these pupil modulations because SC responses are modulated similarly by these processes. The SC receives multisensory, cognitive, and arousal inputs from multiple cortical and subcortical areas such as the frontal eye field and locus coeruleus and projects directly to the premotor brainstem circuit to initiate the orienting response, which includes pupillary responses. It is likely that multisensory, cognitive, and arousal signals, known to be integrated into the SC, can drive coordinated saccade and pupillary responses.