Basal ganglia activation localized in MEG using a reward task

The basal ganglia are a crucial component of neural networks underlying reward response and many other behaviors. Magnetoencephalography (MEG) can be used to non-invasively study the spatiotemporal dynamics of activity in neural networks. However, challenges associated with detecting deep sources has caused many to doubt the ability of MEG to detect basal ganglia signals. In this study, we employed a gambling task to assess the feasibility of using MEG to investigate basal ganglia-cortical networks during reward processing. Participants gambled to win or lose 5 or 25 cents and received unexpected high-value rewards of 50 cents at random intervals. We contrasted activity between reward conditions in the beta (15-30 Hz), gamma (30-60 Hz), and high gamma (60-150 Hz) bands. We found differences in oscillatory power in the beta and high gamma bands while contrasting the large reward condition with both the small reward and large loss conditions. Basal ganglia activity was localized to the caudate, putamen, and globus pallidum, while cortical activity appeared primarily in parietal and temporal areas. Our results show robust basal ganglia power differences in response to reward and corroborate animal literature showing beta and high gamma activation in the striatum. This experiment demonstrates that it is possible to study basal ganglia activity using MEG and reveals specific characteristics of the normal reward response that will inform future research.