Saccadic Latencies in Progressive Supranuclear Palsy

The study objective is to assess saccadic latencies (reaction time) in Progressive Supranuclear Palsy (PSP). Saccadic latency to novel stimuli is typically 180-200 msec. With a gap paradigm (introduction of a temporal gap between extinguishing the fixation target and saccade target appearance), some individuals generate express saccades (ES) with shorter latencies (85-130 msec). The superior colliculus (SC) rostral pole plays a role in fixation release and, thus, in ES generation. In monkeys, SC lesions eliminate ES. Given SC involvement in PSP, we hypothesized that latencies will be longer in PSP patients and ES less frequent than in healthy individuals.