Exploring the neural network underlying task-relevancy influences on movement-related gating

• Main Author: Brown, Katlyn Elizabeth
• Language: English
• Published: University of British Columbia 2013
• Online Access: http://hdl.handle.net/2429/44747

Movement-related gating is influenced by task-relevancy manipulations, such that increased sensory information ascends to the cortex when information is relevant, but does not when it is irrelevant (1). Regardless of relevancy, during movement smaller cortical somatosensory responses are produced as compared to those evoked by similar stimulation at rest (1). These task-relevancy effects have specifically been documented during movement of the lower limb (1). Task-relevancy effects have been hypothesized to be controlled by the prefrontal cortex (PFC) based on this region's known role in selective attention, as well as filtering of distracting information at later stages of somatosensory processing (2). The purpose of the current study was first to verify task-relevancy influences on movement-related gating in the upper limb, and second to test the contribution of the PFC to these relevancy effects. Eleven healthy participants received median nerve stimulation at the left wrist during three conditions: rest, task-irrelevant movement, and task-relevant movement. The cortical responses to these median nerve stimulations were measured in the form of somatosensory evoked potentials (SEPs). Each of these three conditions was collected on a baseline day and on two separate days following either continuous theta burst (cTBS), which has a net inhibitory effect on cortical excitability, over the contralateral primary somatosensory cortex (S1) or the right dorsolateral prefrontal cortex (DLPFC). Results demonstrated a significant interaction effect between the stimulation site and the condition, with post-hoc tests revealing that following cTBS over S1 or DLPFC, relevancy based modulation of SEP amplitude was abolished. These results indicate that both S1 and DLPFC are integral to individual ability to facilitate relevant sensory information in order to complete a motor task.