Submission 416
GABAergic Modulation of Microsaccades in Sustained Fixation and Free Viewing
SymposiumTalk-04
Presented by: Philine Baumert
Modulation of gamma-aminobutyric-acid (GABA) A receptor activity via benzodiazepine administration has been consistently found to reduce saccadic peak velocity. While microsaccades are considered part of the fixational eye movement repertoire, their underlying neurophysiology has been hypothesised to resemble that of large saccades. Whether changes to GABAergic receptor activity affect microsaccades in the same way they do large saccades has not yet been investigated in humans. This study’s aim was to examine whether the established effect of benzodiazepine administration on saccadic peak velocity could be observed in microsaccades. It was further explored whether this might be task-dependent. Thirty healthy adults were administered either 1mg lorazepam or placebo in a randomised, double-blind, within-subjects design. As microsaccades have been shown to vary in purpose and frequency in a highly task-dependent manner, they were assessed in a sustained fixation task as well as a free viewing task. Lorazepam in comparison to placebo led to a decrease in microsaccadic peak velocity in both tasks. It additionally increased microsaccadic frequency and amplitude during sustained fixation but not during free viewing. Overall, our findings confirm the sublime sensitivity of saccadic peak velocity to modulation of GABA A receptor activity via benzodiazepine administration. Notably, this is the first study to expand this finding to microsaccades. Implications for the neurophysiology of microsaccades as well as for their task-dependent purposes are discussed.