Selecting and inhibiting responses: Common cognitive and neural substrates?

Abstract

Despite the brain receiving a constant influx of sensory information in ever-changing environments, humans are nonetheless able to flexibly guide their behaviour in accordance with higher goals and plans. The cognitive system achieves this by implementing executive control processes that monitor, regulate and alter the settings of lower level cognitive processes that are involved in analyzing incoming sensory information and executing motor plans. At the core of goal-directed behaviour are the abilities to select appropriate responses and inhibit planned actions in response to changes in the environment or internal states. While there have been considerable advancements made in understanding the behavioural and neural substrates of response selection and response inhibition, we currently know relatively little about the relationship and possible interplay between these two key cognitive operations. The experiments in this thesis investigate the behavioural and neural overlap in response selection and response inhibition processes by identifying the latent structure that underpins performance in a wide range of action control tasks, exploring the causal role of a brain region that has been implicated in both processes, and by inspecting the degree to which response selection training transfers to other response selection and inhibitory control tasks.Study 1 describes a behavioural study that employed an individual differences approach to investigate the underlying relationships across a battery of common response selection tasks (as measured by the psychological refractory period paradigm (PRP), single response selection task, and attentional blink (AB) task), and response inhibition tasks (as measured by the stop-signal task (SST), Go-Nogo tasks, Stroop, and Flanker task). In order to avoid task impurity and construct validity problems that can seriously undermine the utility of correlational and exploratory factor analytic studies, I used confirmatory factor analysis to statistically extract only what is common about the tasks.Using this approach, I found that response inhibition and response selection were separable, with SST and Go-Nogo task performance related to response inhibition, and the PRP, Stroop, Single Response Selection, and AB tasks related to response selection.These findings suggest that response selection and response inhibition reflect two distinct cognitive operations.As neurocognitive work has implicated the superior medial frontal cortex (SMFC) in both response selection and the proactive modulation of response tendencies when stopping is occasionally required (inhibitory response selection control), it suggests that the neural substrates for these two cognitive operations overlap in this brain region. In Response selection performance is typically compromised due to the processing limitations associated with cognitive control and decision-making when completing two tasks together relative to when completing the component tasks in isolation. While these multitasking performance decr...