Role of the Parabigeminal Nucleus in Visuomotor Behavior
Cui, He
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Permalink
https://hdl.handle.net/2142/82496
Description
Title
Role of the Parabigeminal Nucleus in Visuomotor Behavior
Author(s)
Cui, He
Issue Date
2003
Doctoral Committee Chair(s)
Malpeli, Joseph G.
Department of Study
Neuroscience
Discipline
Neuroscience
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Neuroscience
Language
eng
Abstract
The parabigeminal nucleus (PBN) is a small satellite of the superior colliculus, located on the edge of the midbrain. To identify activity related to visuomotor behavior, we recorded from PBN cells in cats trained to fixate moving and stationary targets. Cats tracked moving targets primarily with small catch-up saccades, and for target speeds of 2--6 deg/s, they did so with sufficient accuracy to keep targets within 2.5 deg of the visual axis most of the time. During intersaccade intervals of such close-order tracking, PBN cells fired at rates related to retinal position error (RPE), the distance between the current fixation and the saccade target. Each was characterized by a preferred direction of RPE. Most commonly, activity rose rapidly with increasing RPE, peaked at a small RPE within the area centralis, and dropped off gradually with increasing target distance. For some cells, the range over which activity was monotonically related to RPE was considerably larger, but since the PBN was not systematically sampled, the maximum range of RPE encoded is presently unknown. During saccades, activity began to change at about peak saccade velocity, and then rapidly reached a level appropriate to the RPE achieved at saccade end. Most response fields were large, and stationary saccade targets presented anywhere within them evoked brisk responses that terminated abruptly upon saccade offset. Spontaneous saccades in the dark had little effect on PBN activity. PBN activity is not solely sensory---it appears to be affected by attention. In contrast to the superficial SC, PBN shows strong response selectively to potential saccade targets, but not to behaviorally-irrelevant stimuli. A briefly flashed target triggers a prolonged response if animals pay attention and prepare to make saccade toward it. PBN cells also respond to anticipated targets during close-order tracking when the moving target is briefly invisible. These data suggest that the PBN is an integral part of a midbrain circuit generating location information for saccade target.
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