SELECTING AND INHIBITING RESPONSES: COMMON COGNITIVE AND NEURAL SUBSTRATES? Angela Dawn Bender Bachelor of Psychological Science (Hons I) A thesis submitted for the degree of Doctor of Philosophy The University of Queensland in 2017 School of Psychology 1 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 2 Study 2, I used transcranial direct current stimulation (tDCS) to investigate this hypothesis. In Experiment 1, using the same behavioural paradigm and tDCS protocol that causally demonstrated left posterior lateral prefrontal cortex involvement in response selection and training processes (Filmer et al., 2013a), I found that anodal (excitatory) and cathodal (inhibitory) tDCS of SMFC did not modify response selection and training processes relative to sham stimulation. However, when introducing an inhibitory context to the paradigm where occasional response inhibition was required (Experiments 2 and 3), I found that cathodal stimulation of the SMFC modulated response selection by increasing reaction times in the context of proactive response inhibition. Collectively, these results suggest a context-dependent role of the SMFC in response selection and response inhibition and further indicate that task set can influence the interaction between the brain and behaviour. 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 decrements can be improved with training, it is currently not known whether training-related benefits can transfer to new tasks. In Study 3, I tested whether training on a dual-task can benefit performance on other tasks that are theoretically related to the trained construct. Given reports that training on video action games that requires continuous, dynamic multitasking in a demanding environment can lead to positive transfer effects on aspects of cognition, I asked a group of participants to train on a combined dynamic, continuous visuomotor tracking task and perceptual discrimination task, while an active control group practiced the two component tasks in isolation. Performance on the practiced tasks and on a battery of tests measuring response selection (PRP, Single Response Selection Task, and AB), inhibition (SST, Go- Nogo task, and Stroop) and spatial attention (Flanker) was examined pre- and post- training. Consistent with the dual-task training literature, multitasking training resulted in substantial, task-specific gains in multitasking, but this benefit did not transfer to other untrained tasks. These results suggest that training on a fast paced visuomotor tracking and discrimination task results in task-specific benefits but this benefit does not extend to untrained tasks that are theoretically related to the trained construct. Taken together, the studies reported in this thesis offer novel insights into our understanding of the cognitive and neural substrates of response selection and response inhibition. These findings have implications for current theoretical accounts of response 3 selection and response inhibition processes and contribute to models of how the executive control of action should be operationalized. 4 Declaration by Author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my research higher degree candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. 5 Publications during candidature Peer-reviewed publications Bender, A. D., Filmer, H. L., Garner, K. G., Naughtin, C. K., & Dux, P. E. (2016). On the relationship between response selection and response inhibition: an individual differences approach. Attention Perception & Psychophysics, DOI 10.3758/s13414-016-1 158-8 Bender, A. D., Filmer, H. L., & Dux, P. E. (in press). Transcranial direct current stimulation of pre-supplementary motor area disrupts response selection during proactive response inhibition. NeuroImage. Conference Abstracts: Bender, A. D., Filmer, H. L., & Dux, P. E. (2016). tDCS of pre-SMA area disrupts response selection during proactive response inhibition. OPAM, Boston, November 2016. Bender, A. D., Filmer, H. L., & Dux, P. E. (2015). Can cognitive control improve with training? The Centre for Perception and Cognitive Neuroscience Annual Retreat, Caloundra, December 2015 Bender, A. D., Filmer, H. L., & Dux, P. E. (2015). tDCS of pre-SMA area disrupts response selection during proactive response inhibition. Australasian Cognitive Neuroscience Society, Auckland, New Zealand, November 2015. Publications included in this thesis This thesis contains three empirical studies (Studies 1-3) that have been published or submitted to peer-review journals. The empirical studies are contextualized with a General Introduction and a General Discussion. Contributions for each of the relevant articles are listed below. 6 Bender, A. D., Filmer, H. L., Garner, K. G., Naughtin, C. K., & Dux, P. E. (in press). On the relationship between response selection and response inhibition: an individual differences approach. Attention Perception & Psychophysics, DOI 10.3758/s13414- 016-1158-8. Incorporated in Study 1. Contributor Statement of contribution Angela D. Bender Conceptualized & designed experiments (50%) Data collection, analysis & interpretation (70%) Wrote the paper (50%) Hannah L. Filmer Conceptualized & designed experiments