Is Acceleration Used for Ocular Pursuit and Spatial Estimation during Prediction Motion?

Here we examined ocular pursuit and spatial estimation in a linear prediction motion task that emphasized extrapolation of occluded accelerative object motion. Results from the ocular response up to occlusion showed that there was evidence in the eye position, velocity and acceleration data that participants were attempting to pursue the moving object in accord with the veridical motion properties. They then attempted to maintain ocular pursuit of the randomly-ordered accelerative object motion during occlusion but this was not ideal, and resulted in undershoot of eye position and velocity at the moment of object reappearance. In spatial estimation there was a general bias, with participants less likely to report object reappearance being behind than ahead of the expected position. In addition, participants’ spatial estimation did not take into account the effects of object acceleration. Logistic regression indicated that spatial estimation was best predicted for the majority of participants by the difference between actual object reappearance position and an extrapolation based on pre-occlusion velocity. In combination, and in light of previous work, we interpret these findings as showing that eye movements are scaled in accord with the effects of object acceleration but do not directly specify information for accurate spatial estimation in prediction motion

Bribing the eye: expected reward modulates smooth pursuit eye movements

Introduction: Reward expectancies can have profound effects on behavioral choices: primates select the target that is associated with the highest expected reward or value. Previous studies on smooth pursuit eye movements, the eyes’ main response to visual motion, showed that eye velocity dynamically reflects selection in favor of targets with higher expected reward. The current study examined whether reward also modulates basic kinematics of human smooth pursuit: does expecting a higher reward make us track moving objects better? Methods: We recorded eye position in 22 untrained human observers who were instructed to accurately track a small spot of light, moving at constant speed across a computer monitor; luminance contrast of the spot was either high (exp1) or low (exp2). Expected reward was manipulated by using pictures of Canadian 5 or 25 cent coins as cues (presented for 1000 ms preceding stimulus motion) indicating a low or high-reward trial, respectively. The ratio of low- to high-reward trials was 4:1; reward cues were equal in size and luminance. Observers were told that for each high-reward trial 25 cents would be added to their remuneration as a reward for accurate tracking. A control condition without reward cues served as a baseline. Results: We found consistent effects of reward expectation on smooth pursuit in both experiments. In high-reward trials, pursuit was initiated faster (higher acceleration and velocity) and maintained with better accuracy (gain) and lower velocity error. High reward also resulted in smoother pursuit responses with fewer and smaller catch-up saccades. Conclusion: We found adaptive improvements of smooth pursuit as a result of high reward expectation across the entire pursuit response. Reward may increase neuronal sensitivity, thereby boosting the system’s capability of processing visual motion information for pursuit

Effects of reward on the accuracy and dynamics of smooth pursuit eye movements

Reward modulates behavioral choices and biases goal-oriented behavior, such as eye or hand movements, toward locations or stimuli associated with higher rewards. We investigated reward effects on the accuracy and timing of smooth pursuit eye movements in 4 experiments. Eye movements were recorded in participants tracking a moving visual target on a computer monitor. Before target motion onset, a monetary reward cue indicated whether participants could earn money by tracking accurately, or whether the trial was unrewarded (Experiments 1 and 2, n = 11 each). Reward significantly improved eye-movement accuracy across different levels of task difficulty. Improvements were seen even in the earliest phase of the eye movement, within 70 ms of tracking onset, indicating that reward impacts visual-motor processing at an early level. We obtained similar findings when reward was not precued but explicitly associated with the pursuit target (Experiment 3, n = 16); critically, these results were not driven by stimulus prevalence or other factors such as preparation or motivation. Numerical cues (Experiment 4, n = 9) were not effective