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J Neurophysiol. 2016 Aug 1;116(2):645-57. doi: 10.1152/jn.00119.2016. Epub 2016 May 11.

Role of expected reward in frontal eye field during natural scene search.

Author information

1
Department of Physical Medicine and Rehabilitation, Northwestern University and Rehabilitation Institute of Chicago, Chicago, Illinois; and j-glaser@u.northwestern.edu.
2
Department of Neurobiology, Northwestern University, Evanston, Illinois.
3
Department of Physical Medicine and Rehabilitation, Northwestern University and Rehabilitation Institute of Chicago, Chicago, Illinois; and.

Abstract

When a saccade is expected to result in a reward, both neural activity in oculomotor areas and the saccade itself (e.g., its vigor and latency) are altered (compared with when no reward is expected). As such, it is unclear whether the correlations of neural activity with reward indicate a representation of reward beyond a movement representation; the modulated neural activity may simply represent the differences in motor output due to expected reward. Here, to distinguish between these possibilities, we trained monkeys to perform a natural scene search task while we recorded from the frontal eye field (FEF). Indeed, when reward was expected (i.e., saccades to the target), FEF neurons showed enhanced responses. Moreover, when monkeys accidentally made eye movements to the target, firing rates were lower than when they purposively moved to the target. Thus, neurons were modulated by expected reward rather than simply the presence of the target. We then fit a model that simultaneously included components related to expected reward and saccade parameters. While expected reward led to shorter latency and higher velocity saccades, these behavioral changes could not fully explain the increased FEF firing rates. Thus, FEF neurons appear to encode motivational factors such as reward expectation, above and beyond the kinematic and behavioral consequences of imminent reward.

KEYWORDS:

electrophysiology; modeling; saccades

PMID:
27169506
PMCID:
PMC4982900
DOI:
10.1152/jn.00119.2016
[Indexed for MEDLINE]
Free PMC Article

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