Abstract
Background: Recent monkey studies suggest that the spatial location of reward cues influences saccadic programming, even when reward is not contingent on the location of the target and the saccade. This has been interpreted as an effect of reward operating through modulating attention in cortical areas involved in saccade generation.
Objective: We examined human saccades to determine a) if reward and penalty differed in their effects, b) if these effects were greater in more cognitively demanding saccades, and c) if the contingency of financial consequences on stimulus location had spatially selective effects.
Methods: Human subjects made prosaccades or antisaccades after motivational cues indicating if correct responses would be rewarded, incorrect ones penalized, or neither. In non-contingent sessions, financial consequences applied regardless of stimulus location, while in contingent sessions, they occurred only when the stimulus or response was at the same location as the motivational cue.
Results: Financial motivation generally resulted in shorter latencies. This effect was similar for prosaccades and antisaccades, and greater for reward than for penalty. Motivation also improved antisaccade accuracy. However, while non-contingent sessions showed an inhibition-of-return-like effect for the location of the motivational cue, this did not differ between reward, penalty or neutral trials. When financial consequences were contingent on location, locations without financial consequences lost the benefits in reaction time and accuracy seen in non-contingent trials, while the locations with financial consequences maintained these benefits but did not show further gains in performance.
Conclusions: Reward is more efficient than penalty in enhancing saccadic performance and this is similar for both automatic prosaccades and cognitively demanding antisaccades. With motivation, the saccadic system can not only enhance responses to multiple locations simultaneously, but also optimize movements only to locations where financial consequences apply, and not to those where they do not.
LL was supported by an MSFHR post-doctoral fellowship, This work was supported by CIHR operating grant MOP-81270.