Abstract
The primate superior colliculus (SC) is a key component of the system controlling voluntary movements of the eyes and head. A longstanding view is that the SC maintains a retinotopic representation of visual space, and issues commands specifying movements referenced to the fovea. While an accurate representation of target position relative to the fovea is crucial to gaze shifts, information about the position of the eyes in their orbits is important to a number of potential SC functions that include determining the relative contributions of eye and head movements to generate gaze movements, integrating multimodal sensory input, and generating sequences of multiple movements. Nevertheless, the existence and potential role for eye position signals in the SC remains controversial.
Highlights
Adding to a growing body of evidence for an eye position role in superior colliculus (SC) function, a recent paper by Groh (2011) makes clever use of microstimulation to demonstrate an effect of orbital position of the eyes on the magnitude of saccades evoked from the monkey SC
While stimulation effects are notoriously difficult to interpret, Groh argues that these results confirm the existence of an eye position signal in the SC, and she further argues that the eye position signals should be incorporated into an accurate model of saccade generation
Two variations of a revised saccade generation model are proposed. Both acknowledge the existence of an eye position signal within the SC, but they differ in three ways: (1) how the putative eye position signal relates to well-characterized saccade vector signals in the same area, (2) whether that signal is enhanced or diminished by electrical stimulation, and (3) how and where that eye position signal is utilized downstream
Summary
Adding to a growing body of evidence for an eye position role in SC function, a recent paper by Groh (2011) makes clever use of microstimulation to demonstrate an effect of orbital position of the eyes on the magnitude of saccades evoked from the monkey SC. Groh’s report is significant because it compares the effects of two different stimulation frequencies, yielding greater insight into possible mechanisms, and provides a theoretical framework to help explain the presence and purpose of an eye position signal in the SC. While stimulation effects are notoriously difficult to interpret, Groh argues that these results confirm the existence of an eye position signal in the SC, and she further argues that the eye position signals should be incorporated into an accurate model of saccade generation.
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