The ability to inhibit a planned but inappropriate response, and switch to executing a goal-relevant motor response, is critically important for the regulation of motor behaviors. Inhibition and switching could be mediated by various control mechanisms. Proactive control uses contextual information (cues) to plan the response for the target stimulus (probe) based on the expectation of a response inhibition or switching stimulus combination. Previous work has reported the involvement of several brain areas associated with proactive inhibition and switching, e.g., dorsolateral prefrontal cortex, anterior cingulate cortex, inferior frontal junction, and pre-supplementary motor area. However, how these areas interact and their functional role in different types of cognitive control is still debated. An AX-version of the continuous performance task (AX-CPT) was used to examine proactive inhibition and switching of motor actions. In a typical AX-CPT trial, a contextual cue stimulus is presented, followed by a probe stimulus after a specific inter-stimulus interval. As part of a trial sequence, if a target cue and target probe are presented, a target response is to be provided when the probe is observed. Otherwise, a non-target response is to be provided for all other stimuli. A behavioral switching AX-CPT experiment (48 subjects) was conducted to explore the parameters that induce a proactive shift in the motor response. Participants who performed the AX-CPT task with relatively shorter interstimulus interval predominantly and consistently exhibited proactive control behavior. A follow-up pilot study (3 subjects) of response inhibition versus response switching AX-CPT was performed using 256-channel high-density electroencephalography (HD-EEG). HD-EEG was used to identify the time course of cortical activation in brain areas associated with response inhibition. It was observed that one out of three participants used a proactive strategy for response switching based on probe response error and probe response reaction time. Instantaneous amplitude spatial maps obtained from HD-EEG revealed cortical activity corresponding to conflict between proactively-prepared incorrect responses and reactively-corrected goal-relevant responses after the probe was presented.

Prospective memory refers to the ability to form and carry out an intention. Prospective memory can be further divided into the subcategories of episodic and habitual prospective memory, which differ in their task demands and electrophysiological components. The focus of the present study is on habitual prospective memory, which is the ability to routinize and consistently fulfill intentions that occur repeatedly. This skill is especially useful for populations with impaired executive functioning and/or memory deficits, such as those with acquired brain injuries. The purpose of this study is to analyze the performance of an undergraduate population on a habitual prospective memory task in order to create a baseline model for comparison with a clinical population. Evidence of habitization to the prospective memory component of the task was discovered, as demonstrated by speeded ongoing-task response times and reduced interference to prospective memory cues. Ongoing task accuracy and prospective memory cue detection were very high, while commission errors were very few, demonstrating ease of the task for neurotypical populations. We speculate that people with acquired brain injuries will not show as significant of a quickening of response times, nor such accurate performance on prospective memory cue trials or the commission error phase.