Abstract
Smooth pursuit (SP) and saccadic (SAC) eye movements share the ability to anticipate or predict object motion, which is a fundamental feature of animal behaviour. We have compared predictive and non-predictive SP and SAC responses using temporally and spatially equivalent paradigms, whilst simultaneously monitoring brain activity using fMRI. The visual stimulus comprised a double gap-step-ramp task (SP) and a double gap-step task (SAC) to either predictable (PRD) or randomized (RND) target motion/location. 12 subjects performed eye movement trials in the standard laboratory, prior to a recording session inside the fMRI scanner (1.5T, Philips Intera). Eye movements were monitored using infra-red limbus tracking systems in both the laboratory (Skalar IRIS, CRS Ltd) and scanning environments (MR-eyetracker, CRS Ltd). Laboratory based eye movement data revealed the latency difference between RND and PRD conditions in SP is less pronounced and distinct than in SAC. Performing contrasts on resultant functional brain images for PRD and RND conditions revealed elevated BOLD responses in a network of brain areas including left putamen/insula, left precuneus and left supramarginal gyrus. We additionally found differential activation for dorsolateral prefrontal cortex (BA 45/9) in both the SAC and SP trials. Many areas involved in predictive SP and SAC eye movements reveal an overlap in brain activation, demonstrating that the mechanisms involved in motor prediction may be generated by common circuitry.
This project was funded by the MRC