Assessment of Behavioral and Neural Dynamics of Proactive Control Through Transcranial Focused Ultrasound Neuromodulation and Electroencephalography

The ability to control movements is critical for interacting with the environment. Movements can be controlled in an anticipatory manner (proactive) or as a late-corrective action (reactive). Proactive control uses contextual information to prepare possible actions based on the predicted nature of the following event before it occurs. This dissertation research explores proactive control behavior and underlying neural dynamics in healthy humans. The first experiment investigated the effect of timing in proactive control by manipulating the duration between contextual information presentation and an associated event requiring a response in the AX-version of the continuous performance task (AX-CPT). It was found that a shorter interstimulus interval promoted predominant proactive control. Having optimized the task to promote proactive control, the next experiment focused on establishing the contingent negative variation (CNV) observed in electroencephalography (EEG) as a neural correlate of proactive control. In experiment 2, two response pattern variations of AX-CPT with consistent, contextual conditioning were administered in a within-subject design. The CNV amplitude was shown to correlate with proactively prepared anticipatory responses. Current fMRI and EEG source analysis literature report the middle cingulate cortex (MCC) activation in the anticipatory response phase during proactive control simultaneous with the CNV. However, the functional role of MCC in proactive control is still debated. In experiment 3, participants performed AX-CPT while a neural site in MCC, p24’, was stimulated with low-intensity transcranial-focused ultrasound (tFUS) simultaneous with EEG. The CNV exhibited a reduced amplitude and more response errors in tFUS versus no-tFUS trials in the deterministic context of AX-CPT, indicating disrupted proactive control. We conclude that MCC is associated with proactive control based on the modulation of CNV, which encodes contextually dependent anticipatory responses.