Executive functions underlie our ability to control our behavior according to our goals. One element of executive function is top-down inhibitory control. Over the last funding periods we have distinguished two kinds of inhibitory control ? reactive and proactive. Reactive inhibitory control can have broad effects and is driven by stop signals. It is apparently implemented by prefrontal connections to the basal ganglia, which we suppose blocks thalamic drive to cortex. By contrast, proactive inhibitory control is set up in advance of any response and is apparently implemented by sensorimotor cortex, also with downstream effects on basal ganglia and thalamus. Here we leverage our knowledge of these reactive and proactive inhibitory systems to ask how we keep unwanted thoughts out of mind and what mental strategies can be used to reduce pain.
Aim 1 tests whether prefrontally-driven reactive inhibitory control prevents thought intrusions. We use the so-called Think/NoThink paradigm in which, on NoThink trials, people have to try to prevent the intrusion of an unwanted memory. We have shown this relates to increased prefrontal beta band power. We do simultaneous EEG/fMRI to localize the prefrontal node that best corresponds with the requirement to Not Think, and we then use fMRI- guided repetitive Transcranial Magnetic Stimulation (TMS) to create a ?virtual lesion? of that prefrontal node to test its causal role in preventing intrusions of thought.
Aim 2 moves away from reactive inhibitory control to test how proactive inhibitory control reduces subjective pain. We inculcate a proactive inhibitory state (which corresponds to increased sensorimotor beta power) and we then test if, during this state, a nociceptive pain stimulus is rated as less painful subjectively. We then do repetitive TMS to create a ?virtual lesion? of M1 (and circuitry) to test the causal role of sensorimotor beta oscillations in a ?suppressive? state pertinent to reducing pain ratings.
Aim 3 tests whether inculcating a proactive suppression state can prevent thought intrusions. We will do this by embedding the Think/NoThink requirement in task-states characterized by increased beta oscillations. These states are generated either endogenously by the subject given a cue or by the use of beta band entrainment with rTMS.
Human brain systems for stopping action have been well-studied. This proposal leverages the extant knowledge in this area to test how people are able to stop inappropriate thoughts/memories from coming to mind, and also how they can ?dampen? their wider action system in a way that prevents motor and sensory provocations, including pain.
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