Saccade latency bias toward temporal hemifield: evidence for role of retinotectal tract in mediating reflexive saccades

Publication date: Available online 31 January 2018 Source:Neuropsychologia Author(s): Kristin Koller, Robert D. Rafal The superior colliculus (SC) plays a critical role in mediating reflexive eye movements. Under optimal conditions, for example including a temporal ‘gap’ of 200 ms after fixation offset and prior to target onset, it is possible to isolate a population of ‘express’ saccades with very short latencies between (80 − 120 ms). Ablation of the SC abolishes express saccades in monkeys. However, it remains to be established whether express saccade generation is dependent upon visual afferents transmitting direct retinal projections to SC via the retinotectal tract (RTT). In nineteen healthy human participants, we used a gap paradigm to investigate whether express saccades demonstrate shorter latencies to targets in the temporal hemifield, a marker for RTT function. A population of predominantly reflexive saccades (with latencies between 70 − 150 ms) was isolated in which latencies toward temporal hemifield targets were shown to be shorter than toward nasal hemifield targets. The advantages for reflexive saccades toward temporal hemifield targets suggest that visual efferents from the retina to the superior colliculus contribute to generating reflexively triggered saccades.

Source: Neuropsychologia - February 1, 2018 Category: Neurology Source Type: research