Abstract
Past studies have shown that reward contingency is critical for sensorimotor learning, and reward expectation speeds up saccades in animals. Whether monetary reward speeds up saccades in human remains unknown. Here we addressed this issue by employing a conditional saccade task, in which human subjects performed a series of non-reflexive, visually-guided horizontal saccades. The subjects were (or were not) financially compensated for making a saccade in response to a centrally-displayed visual congruent (or incongruent) stimulus. Reward modulation of saccadic velocities was quantified independently of the amplitude-velocity coupling. We found that reward expectation significantly sped up voluntary saccades up to 30°/s, and the reward modulation was consistent across tests. These findings suggest that monetary reward speeds up saccades in human in a fashion analogous to how juice reward sped up saccades in monkeys. We further noticed that the idiosyncratic nasal-temporal velocity asymmetry was highly consistent regardless of test order, and its magnitude was not correlated with the magnitude of reward modulation. This suggests that reward modulation and the intrinsic velocity asymmetry may be governed by separate mechanisms that regulate saccade generation.
Highlights
Reward contingency is essential for behavior modification and learning
We found that the magnitude of reward modulation was not correlated with the magnitude of the velocity asymmetry
The present study investigated the effect of monetary reward on the velocities of non-reflexive, visually-guided saccades
Summary
Reward contingency is essential for behavior modification and learning. Many studies have documented that reward signals are processed through the network associated with dopamine neurons (Schultz et al, 1997; Hikosaka et al, 2000; Schultz, 2006; Kobayashi and Schultz, 2008; Bromberg-Martin and Hikosaka, 2009; Basso and Sommer, 2011; Glimcher, 2011). Two recent non-human primate studies have provided independent psychophysical evidence showing that reward expectation sped up saccades (Takikawa et al, 2002; Chen et al, 2013) In these studies, the animals were operant conditioned to perform a series of unrewarded and rewarded saccades either in the same block of trials (Takikawa et al, 2002) or within the same trial (Chen et al, 2013). The animals were operant conditioned to perform a series of unrewarded and rewarded saccades either in the same block of trials (Takikawa et al, 2002) or within the same trial (Chen et al, 2013) The findings of these studies unequivocally indicate that saccadic velocity was a movement variable directly modulated by reward expectation, and not a by product of changes in saccadic amplitude. Such control resulted in speeding up or slowing down saccades via the circuitries of saccadic generation (Sparks, 2002; Hikosaka et al, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
