Investigating the effect of reward on saccadic eye movement parameters in macaque monkeys

One of the most effective factors in control of attention is the amount of reward associated with the target stimulus. The aim of this study was to investigate effects of different reward magnitudes on saccadic eye movement parameters as a behavioral index of attention.

We used two male macaque monkeys in a saccadic behavioral task. Monkeys trained to saccade to a presented stimulus that was associated with low, medium, or high reward magnitudes. For two monleys, latency, peak velocity and accuracy of saccades in two separate groups (fast and slow) in three reward regimes were analyzed using three ways ANOVA and Bonferroni post-hoc tests.

Latency of the saccades to stimuli associated with higher reward magnitude was lower compared to latency of saccades to the stimuli associated with smaller reward magnitudes. The saccades were more accurate when targeting stimuli associated with higher reward magnitudes than targeting low reward stimuli. Changes in the reward associated with the saccadic targets did not consistently affect the saccadic peak velocity.

The reward associated with saccadic target stimuli resulted in a decrease in saccadic reaction times and improvement in accuracy of saccades, with inconsistent effects on saccade velocity. Our observations are consistent with current literature showing value as a main component in guiding attention.
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