Differences in active versus passive short-term memory acquisition for smooth pursuit eye movements revealed by event-related fMRI

Actively following, as opposed to passively observing, a predictable target motion results in a shorter latency and higher initial eye velocity of anticipatory smooth pursuit (Burke and Barnes, 2008). To investigate if this behavioural advantage to following the target is also observed in brain activity, 11 subjects participated in both behavioural and fMRI imaging (3T, Philips) experiments with the objective of determining differences in functional activation between active pursuit and passive observation of predictable target motion. We used a novel paradigm in which two sequentially presented motion stimuli were segregated by a variable delay (2, 4 and 6s). Subjects were instructed, via a coloured cue, to either follow both presentations of the target (Go-Go: green cue) or passively view the first target presentation and follow the second (NoGo-Go: pink cue). In the Go-Go and NoGo-Go conditions the target presentations in the pair were matched in both timing and velocity (i.e. the 1st presentation was predictive of the 2nd presentation). In an additional randomized condition a green cue with a cross indicated that the subject must follow both presentations; however, in this random condition the presentations differed in both timing and velocity. The pre-processed normalized fMRI results were segregated into 3 sections before a haemodynamic model was applied: (i) first target presentation, (ii) delay and (iii) second target presentation. We reveal significant differential activation in active versus passive tasks in all 3 sections, with significant differences in the delay period in posterior parietal, frontal/supplementary eye fields, and medial temporal brain regions. The results indicate clear task-related differences in how the brain processes and holds predictive target information during active and passive pursuit. Burke, M. R., & Barnes, G. R. (2008). Anticipatory eye movements evoked after active following versus passive observation of a predictable motion stimulus. Brain Research, 1245, 74–81. This work was supported by funding from the Medical Research Council and a Translational Imaging Grant from the University of Manchester.