Parallel programming of saccades in the macaque frontal eye field: Are sequential motor plans coactivated?

Basu, D and Murthy, A (2020) Parallel programming of saccades in the macaque frontal eye field: Are sequential motor plans coactivated? In: Journal of Neurophysiology, 123 (1). pp. 107-119.

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Abstract

We use sequences of saccadic eye movements to continually explore our visual environments. Previous behavioral studies have established that saccades in a sequence may be programmed in parallel by the oculomotor system. In this study, we tested the neural correlates of parallel programming of saccade sequences in the frontal eye field (FEF), using single-unit electrophysiological recordings from macaques performing a sequential saccade task. It is known that FEF visual neurons instantiate target selection whereas FEF movement neurons undertake saccade preparation, where the activity corresponding to a saccade vector gradually ramps up. The question of whether FEF movement neurons are involved in concurrent processing of saccade plans is as yet unresolved. In the present study, we show that, when a peripheral target is foveated after a sequence of two saccades, presaccadic activity of FEF movement neurons for the second saccade can be activated while the first is still underway. Moreover, the onset of movement activity varied parametrically with the behaviorally measured time available for parallel programming. Although at central fixation coactivated FEF movement activity may vectorially encode the retinotopic location of the second target with respect to the fixation point or the remapped location of the second target, with respect to the first our evidence suggests the possibility of early encoding of the remapped second saccade vector. Taken together, the results indicate that movement neurons, although located terminally in the FEF visual-motor spectrum, can accomplish concurrent processing of multiple saccade plans, leading to rapid execution of saccade sequences. NEW & NOTEWORTHY The execution of purposeful sequences underlies much of goal-directed behavior. How different brain areas accomplish sequencing is poorly understood. Using a modified double-step task to generate a rapid sequence of two saccades, we demonstrate that downstream movement neurons in the frontal eye field (FEF), a prefrontal oculomotor area, allow for coactivation of the first and second movement plans that constitute the sequence. These results provide fundamental insights into the neural control of action sequencing. Copyright © 2020 the American Physiological Society

Item Type:	Journal Article
Publication:	Journal of Neurophysiology
Publisher:	American Physiological Society
Additional Information:	The copyright for this article belongs to American Physiological Society.
Keywords:	animal experiment; article; controlled study; electrophysiological procedures; frontal eye field; Macaca; nerve cell; nonhuman; oculomotor system; saccadic eye movement; animal; animal behavior; electrophysiology; female; frontal lobe; Macaca radiata; male; motor activity; physiology; rhesus monkey; saccadic eye movement; sequence learning, Animals; Behavior, Animal; Electrophysiological Phenomena; Female; Frontal Lobe; Macaca mulatta; Macaca radiata; Male; Motor Activity; Neurons; Saccades; Serial Learning
Department/Centre:	Division of Biological Sciences > Centre for Neuroscience
Date Deposited:	08 Feb 2023 08:40
Last Modified:	08 Feb 2023 08:40
URI:	https://eprints.iisc.ac.in/id/eprint/80056

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