What Are the Functions of the Superior Colliculus and Its Involvement in Neurologic Disorders?

The superior colliculus (SC) is an evolutionary conserved sensorimotor structure that is specialized for detecting, localizing, and orienting toward environmental events and has a critical role in orienting motor responses, visuospatial attention, and perceptual decision-making.1-8 The SC consists of a superficial layer that receives visual inputs and intermediate and deep motor layers that initiate saccades and other orienting movements toward the contralateral hemispace. Modern molecular and genetic methods combined with behavioral assessments have provided further understanding of the cell types, circuits, and functions of the SC (reviewed in ref. 9,10). The SC is affected by α-synuclein and tau neuropathology in Lewy body dementia (LBD),11 shows abnormal responses to visual stimuli in Parkinson disease (PD),12,13 may contribute to impaired saccades in progressive supranuclear palsy (PSP),14 and may be involved in the pathophysiology of cervical dystonia.15,16 This brief review will focus on recent concepts on the functional organization and connectivity of the SC that are relevant to understand the pathophysiology of these and other neurologic disorders.