In this study, the neural correlates associated with target encoding during visually guided and memory guided reaching were examined. Participants performed aiming movements using a stylus on a graphics tablet with visual stimuli projected onto a mirror positioned above the aiming surface. For the experimental protocol, individuals were provided with a 100% predictive cue followed by a brief preview of a target. The cue was indicative of the events that would occur after the preview of the target. Specifically, the delay period between the offset of the target preview and the imperative stimulus to move (i.e., 2s or 5s delay), and also whether the target would reappear when the imperative stimulus was presented (i.e., FV or NV). Event related brain potentials (ERP) associated with target encoding (i.e., target preview period) were averaged and compared across vision and delay conditions. Kinematic analyses were also used to examine the behavioural manifestations of the reaches. Results from the ERP analysis during target encoding revealed differences of brain activity based upon expected availability of vision; these differences occurred at time-points consistent with motor plan formation and updating (i.e. N2-P3, Kourtis et al 2012). At later epochs, there was a further modulation of activity based upon the expected delay condition, independent of visual condition. Corresponding behavioural results were in-line with previous memory guided reaching experiments. In all, the expected conditions under which a movement will be made significantly influences the manner of target encoding.
Meeting abstract presented at VSS 2013