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J Neurophysiol. 2017 May 1;117(5):1987-2003. doi: 10.1152/jn.00786.2016. Epub 2017 Feb 15.

Temporal dynamics of retinal and extraretinal signals in the FEFsem during smooth pursuit eye movements.

Bakst L1,2, Fleuriet J2,3, Mustari MJ4,2,3,5.

Author information

1
Graduate Program in Neuroscience, University of Washington, Seattle, Washington.
2
Washington National Primate Research Center, University of Washington, Seattle, Washington.
3
Department of Ophthalmology, University of Washington, Seattle, Washington; and.
4
Graduate Program in Neuroscience, University of Washington, Seattle, Washington; mike.mustari@wanprc.org.
5
Department of Biological Structure, University of Washington, Seattle, Washington.

Abstract

Neurons in the smooth eye movement subregion of the frontal eye field (FEFsem) are known to play an important role in voluntary smooth pursuit eye movements. Underlying this function are projections to parietal and prefrontal visual association areas and subcortical structures, all known to play vital but differing roles in the execution of smooth pursuit. Additionally, the FEFsem has been shown to carry a diverse array of signals (e.g., eye velocity, acceleration, gain control). We hypothesized that distinct subpopulations of FEFsem neurons subserve these diverse functions and projections, and that the relative weights of retinal and extraretinal signals could form the basis for categorization of units. To investigate this, we used a step-ramp tracking task with a target blink to determine the relative contributions of retinal and extraretinal signals in individual FEFsem neurons throughout pursuit. We found that the contributions of retinal and extraretinal signals to neuronal activity and behavior change throughout the time course of pursuit. A clustering algorithm revealed three distinct neuronal subpopulations: cluster 1 was defined by a higher sensitivity to eye velocity, acceleration, and retinal image motion; cluster 2 had greater activity during blinks; and cluster 3 had significantly greater eye position sensitivity. We also performed a comparison with a sample of medial superior temporal neurons to assess similarities and differences between the two areas. Our results indicate the utility of simple tests such as the target blink for parsing the complex and multifaceted roles of cortical areas in behavior.NEW & NOTEWORTHY The frontal eye field (FEF) is known to play a critical role in volitional smooth pursuit, carrying a variety of signals that are distributed throughout the brain. This study used a novel application of a target blink task during step ramp tracking to determine, in combination with a clustering algorithm, the relative contributions of retinal and extraretinal signals to FEF activity and the extent to which these contributions could form the basis for a categorization of neurons.

KEYWORDS:

FEF; extraretinal; initiation; smooth pursuit

PMID:
28202571
PMCID:
PMC5411476
DOI:
10.1152/jn.00786.2016
[Indexed for MEDLINE]
Free PMC Article

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