How stopping movement affects working memory

University Of California, San Diego, La Jolla CA

Investigators

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Abstract

DESCRIPTION (provided by applicant): We all experience the sort of situation where, during a conversation, we are interrupted by a salient external signal (a 'novel'), e.g. a breaking window. We quickly orient to the novel, and then find that our train of thought, or more specifically our working memory (WM), has been interrupted. This proposal tests the theory that one reason for this WM decrement is because the salient stimulus activates the brain's motor stopping network, and this network has global effects on currently active motor and non-motor cortical contents. Based on our published and preliminary data we advance for the following neural systems model: a) novels act as stop signals, generating a rapid motor stop via the brain's global stopping network, b) this network is implemented via the subthalamic nucleus (STN) of the basal ganglia, c) activation of the STN leads to a widespread pulse of suppression on thalamocortical drive, d) as all motor and non-motor representations (including WM) are partly sustained by thalamocortical drive, there is a temporary interruption which manifests as a WM decrement. Validating this model has far-reaching significance for better understanding the relationship between stopping and WM in cognitive psychology; for better understanding the relation between the 'over-stopped' state in PD and cognitive inflexibility, and for advancing a new theory of distractibility, relevant for psychiatry. We test the model in PD patients and in healthy volunteers. In PD patients we will examine how stopping affects WM while we simultaneously record local field potentials from implanted STN electrodes and scalp EEG from the frontal cortex. We expect that stopping-induced activity in the STN will correspond with reductions in the cortical marker for WM, thus linking the putative global STN stop signal with a decrement in WM. In healthy volunteers we will use Transcranial Magnetic Stimulation of motor cortex as a surrogate probe of the global STN stop signal. We expect that the degree of global motor suppression measured by this method will correspond with the decrement in WM induced by stop signal as well as novels.