Horton, Chris Ian2020-09-292020-09-292019https://hdl.handle.net/1794/2576034 pagesStopping ongoing actions is a fundamental aspect of behavior. A pathway from the basal ganglia to the thalamus is hypothesized to be important for stopping and uses the inhibitory neurotransmitter gamma amino-butyric acid (GABA). The primary motor cortex (M1) is also a critical node in the pathway to the muscles, and M1 GABA may also serve an important function in stopping. In this study, we examined the relationship between stopping behavior and GABA levels in the thalamus and M1 over two experiments in a group of 29 participants. We measured Go reaction time and stopping speed with simple and choice behavioral stop-signal tasks and measured GABA content with magnetic resonance spectroscopy. We found no relationships between stopping performance and GABA content within either brain region. However, there was a negative correlation between GABA content in both the thalamus and primary motor cortex and reaction time in the choice task, with higher GABA levels associating with faster reaction times. These results suggest that there may be more dependence on brain GABAergic mechanisms for a choice task than a simple task.en-USHuman PhysiologyGABAMRSStoppingThalamusPrimary Motor CortexThesis/Dissertation