Cortical and Subcortical Contributions to Stop Signal
Response Inhibition: Role of the Subthalamic Nucleus
Adam R. Aron and Russell A. Poldrack
Department of Psychology and Brain Research Institute, University of California, Los Angeles, California 90095
Suppressing an already initiated manual response depends critically on the right inferior frontal cortex (IFC), yet it is unclear how this
inhibitory function is implemented in the motor system. It has been suggested that the subthalamic nucleus (STN), which is a part of the
basal ganglia, may play a role because it is well placed to suppress the "direct" fronto-striatal pathway that is activated by response
initiation. In two experiments, we investigated this hypothesis with functional magnetic resonance imaging and a Stop-signal task.
Subjects responded to Go signals and attempted to inhibit the initiated response to occasional Stop signals. In experiment 1, Going
significantly activated frontal, striatal, pallidal, and motor cortical regions, consistent with the direct pathway, whereas Stopping signif-
imaging confirmed the location of Stopping activation within the vicinity of the STN. We propose that the role of the STN is to suppress
thalamocortical output, thereby blocking Go response execution. These results provide convergent data for a role for the STN in Stop-
signal response inhibition. They also suggest that the speed of Go and Stop processes could relate to the relative activation of different
neural pathways. Future research is required to establish whether Stop-signal inhibition could be implemented via a direct functional
neuroanatomic projection between IFC and STN (a "hyperdirect" pathway).
Key words: striatum; frontal; activation; fMRI; cognitive control; imaging; Parkinson's disease