The role of frontal oculomotor structures in the predictive control of eye movements /

• Main Author: Gagnon, Danny
• Format: Others
• Language: en
• Published: McGill University 2005
• Subjects: Eye > Movements.; Vision.; Neurophysiology.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85909

The role of the FEF/FPA and SEF in oculomotor prediction was investigated using psychophysics, functional MRI (fMRI) and TMS. The separate contribution of advance knowledge of target direction and target timing to predictive saccades, and neural activity in frontal oculomotor structures was first investigated. The greatest proportion of predictive saccades were elicited when subjects had advance knowledge of both target direction and target timing; advance knowledge of target direction increased the proportion of predictive saccades, while advance knowledge of target timing decreased saccade latencies without increasing predictive saccades. Activity was greater in the FEF for all saccade tasks with a predictable component than reflexive saccades. Activity in the FEF was higher in tasks for which saccade latencies were lower. These data suggest that target direction and target timing independently reduce saccade latencies, and that this information converges in the FEF to allow the generation of predictive saccades. In the SEF, activity was greater only in the condition when both target direction and target timing were predictable. This finding may reflect a role of the SEF in oculomotor sequencing rather than in prediction per se. === In order to assess whether the FEF play a general role in oculomotor prediction, and not just in saccades, the role of the FPA in predictive pursuit was evaluated by applying TMS to the FPA and SEF during sinusoidal pursuit. TMS of the FPA modulated eye velocity both at peak target velocity and at the target turnaround. The induced changes in eye velocity occurred with a short latency, that is, before visual signals could travel from the retina to brainstem. This would suggest that TMS of the FPA likely increased the gain of the transformation of predictive signals, rather than visual signals, to motor commands. Stimulation of the SEF increased eye velocity only when applied at the target turnaround. Previous studies have demonstrated that stimulation of SEF increases eye velocity during pursuit initiation. Our finding that this facilitation also occurs at the target turnaround may berelated to similarities between pursuit initiation and the turnaround, including the necessity to rapidly increase eye velocity from zero.