Role of the Frontal Eye Field, Superior Colliculus, and Basal Ganglia in Flexible Saccade Behavior
Abstract
A distributed network of cortical and subcortical brain regions mediates the control of voluntary behavior, but it is unclear how this complex system may flexibly shift between different behavioral events. This thesis describes the neurophysiological changes in several key nuclei across the brain during flexible behavior, using saccadic eye movements in rhesus macaque monkeys. We examined five nuclei critical for saccade initiation and modulation: the frontal eye field (FEF) in the cerebral cortex, the subthalamic nucleus (STN), caudate nucleus (CD), and substantia nigra pars reticulata (SNr) in the basal ganglia (BG), and the superior colliculus (SC) in the midbrain. The first study tested whether a ‘threshold’ theory of how neuronal activity cues saccade initiation is consistent with the flexible control of behavior. The theory suggests there is a fixed level of FEF and SC neuronal activation at which saccades are initiated. Our results provide strong evidence against a fixed saccade threshold in either structure during flexible behavior, and indicate that threshold variability might depend on the level of inhibitory signals applied to the FEF or SC. The next two studies investigated the BG network as a likely candidate to modulate a saccade initiation mechanism, based on strong inhibitory output signals from the BG to the FEF and SC. We investigated the STN and CD (BG input), and the SNr (BG oculomotor output) to examine changes across the BG network. This revealed robust task-contingent shifts in BG signaling (Chapter 3), which uniquely impacted saccade initiation according to behavioral condition (Chapters 3 and 4). The thesis concludes with a published short review of the mechanistic effects of BG deep brain stimulation (Chapter 5), and a general discussion including proof of concept saccade behavioral changes in an MPTP-induced Parkinsonian model (Chapter 6). The studies presented here demonstrate that the conditions for saccade initiation by the FEF and SC vary according to behavioral condition, while simultaneously, large-scale task dependent shifts occur in BG signaling consistent with the observed modulation of FEF and SC activity. Taken together, these describe a mechanistic framework by which the cortico-BG loop may contribute to the flexible control of behavior.
URI for this record
http://hdl.handle.net/1974/15291Collections
Request an alternative format
If you require this document in an alternate, accessible format, please contact the Queen's Adaptive Technology CentreRelated items
Showing items related by title, author, creator and subject.
-
The effect of anti-saccade training on cognitive function in healthy adults and Parkinson's disease patients
Elsaeid, BasmaOur novel study investigated how the anti-saccade training can influence cognitive capabilities of healthy and Parkinson’s disease participants. The rationale is that the anti-saccade task requires top-down control and ... -
Microsaccades in Parkinson's disease
McInnis, Hailey (2014-01-10)Individuals with Parkinson’s disease (PD) display deficits in voluntary saccade generation but improved automatic, visually-triggered saccade performance. This can be tested using prosaccades, saccades to visual stimuli, ... -
Cardiovascular correlates of arousal and their relationship to saccadic behavior
Dibrov, Alexander (2014-11-11)Understanding the effect of subject arousal on saccadic behavior can shed light on the mechanisms by which arousal influences executive and oculomotor systems. Increased vagal activity is a key component of the parasympathetic ...