Context maintenance, an aspect of cognitive control, is the internal representation and utilization of task-relevant information that helps achieve task goals. Alterations in context maintenance may be responsible for the cognitive difficulties seen in people with obsessive-compulsive disorder (OCD). We used two tasks designed to measure context maintenance: a) the cued-Stroop, a single-trial version of Golden’s Stroop test that varies the cue for each trial (color-naming or word-reading), and b) the AX-CPT task, a continuous performance task that has participants respond to an “A” only when followed by an “X,” with all other non-target trials labeled as AY, BX, and BY (and “Y” and “B” representing all non-X and non-A letters, respectively). Participants included 31 people with OCD and 30 psychiatrically-healthy controls that completed a neuropsychological test battery, self-report questionnaires measuring mood and symptom severity, and the computerized cued-Stroop and AX-CPT tasks. There was a 1s or 5s delay between the cue and probe for both tasks so as to vary the duration of context maintenance. We conducted a 2 (Group) x 2 (Delay) x 3 (Trial Type) repeated measures ANOVA for the cued-Stroop and a 2 (Group) x 2 (Delay) x 4 (Trial Type) repeated measures ANOVA for the AX-CPT. Dependent measures included median reaction times (RT) and mean error rates (ER). Both groups showed a congruency effect for the cued-Stroop, with slower RTs and greater ERs for the incongruent trials than the neutral and congruent trials, as well as lower ERs for BY trials compared to BX and AY trials of the AX-CPT task. There were no significant differences in RTs or ERs between groups for delay or condition for the cued-Stroop (ps > .45) or for the AX-CPT (ps > .07). The present study shows that people with OCD did not show deficits in context maintenance in two separate tasks. Limitations include low power, higher functioning participants with OCD, and the presence of comorbid depression and anxiety in some participants with OCD.

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<p>During task-switching, if we occasionally encounter stimuli that cue more than one task (i.e. bivalent stimuli), response slowing is observed on all univalent trials within that block, even when no features overlap with the bivalent stimuli. This observation is known as the bivalency effect. Here, I show that the bivalency effect reflects a form of top-down cognitive control that is not easily explained by most current models of control in the literature. The research presented within my thesis reveals that the bivalency effect reflects an adjustment in cognitive control that is highly dependent on past experience with response conflict (chapters 4 and 5), violations of expectancy (chapter 3 and 5), and recent inhibition (chapters 3, 4, and 5). Furthermore, the processes in response to these factors are likely captured by the dorsal anterior cingulate cortex (dACC) and the temporal parietal junction (TPJ) (chapters 2 and 5), reflecting responses to inhibitory demands, and extra visual feature extraction after encountering bivalent stimuli, respectively. These findings provide support for a recent cognitive control model that suggests that the role of the ACC is to track current and recent changes in the environment in order to optimize future performance by predicting changes in cognitive demand (Sheth et al., 2012).</p> / Doctor of Philosophy (PhD)

<p>Recent research on cognitive control has focused on the learning consequences of high selective attention demands in selective attention tasks. The current study extends these ideas by examining the influence of selective attention demands on remembering. In Experiment 1, participants read aloud the red word in a pair of red and green interleaved words. Half of the items were congruent (the interleaved words were the same), and the other half were incongruent (the interleaved words were different). Following the study phase, participants completed a recognition memory test with a remember/know classification. A mirror effect was observed in the recognition memory data, with better memory for incongruent than for congruent items. In Experiment 2, context was only partially reinstated at test, and again better memory for incongruent compared to congruent items was observed. However, the processes supporting recognition decisions varied depending on context reinstatement, with only full context reinstatement resulting in differences in recollection for congruent and incongruent items. These results demonstrate that selective attention process demands associated with incongruent items affect episodic learning.</p> / Master of Science (MSc)

Eating disorders involve the inability to appropriately regulate a behavioral response to food due to impaired reward sensitivity, affect regulation and cognitive control, resulting in deleterious effects on the individual's physical and mental well-being. In this way eating disorders may be analogous to addictive disorders (e.g. alcoholism). Furthermore, eating and addictive disorders co-occur at very high rates and appear to have similar contributing mechanisms (impaired reward sensitivity, impaired affect regulation and impaired cognitive control). Overvaluation of weight and shape concerns appears to be one unique characteristic of eating disorders, not shared with addiction. The current study examined the relationship between impaired reward sensitivity, impaired affect regulation and impaired cognitive control with addiction vulnerability. Furthermore, weight and shape concerns were examined as a potential moderator of the relationship between addiction vulnerability and binge eating. A total of 1000 undergraduate students completed self-report measures examining the three posited mechanisms for addiction vulnerability and disordered eating. A subset of 101 students (50 binge-eaters and 51 non-binge eaters) also completed behavioral measures of the three posited mechanisms. The results of this study support the proposed model that weight and shape concerns moderate the relationship between addiction vulnerability and binge eating. Results also demonstrated on a behavioral task that individuals who endorsed binge eating were more likely to act impulsively and quit the PASAT-C task faster than control subjects. Furthermore, they demonstrated a greater increase in irritability while completing the task which may have resulted in their desire to quit the task earlier. No differences were found on behavioral measures of reward sensitivity (delay discount task) or cognitive control (stop signal task). Future studies should continue to examine the construct of addiction vulnerability to provide additional validity for the construct as well as examine it in the context of all forms of disordered eating. / Psychology

People’s decisions regarding effort-based tasks such as engaging in physical activity depend on the subjective value of the activity: weighing the costs against the benefits (Chong et al., 2016). Exerting cognitive effort while performing one task negatively biases people's decisions to exert effort on subsequent cognitive tasks, suggesting a shift in their subjective valuation of the task due to mental fatigue (Kool & Botvinick, 2014). Similarly, exerting physical effort negatively biases decisions to further exert effort on a future physical task (Iodice et al., 2017a, Iodice et al., 2017b). The purpose of the present study was to investigate the effect of mental fatigue on people's decisions to engage in an acute bout of exercise and whether the effect of mental fatigue on decision-making was mediated by a benefit-cost analysis. Among those who decided to exercise, the study also aimed to investigate the relationship between mental fatigue and exercise behaviours during a self-selected, self-paced, bout of exercise. Recreationally active participants (N = 55, Mage = 19.04 ± 1.04 years) completed either a 10-minute, high cognitive demand (Stroop) task or low cognitive demand (documentary viewing) task to manipulate levels of mental fatigue. Participants then made a choice between engaging in a 20-minute self-paced moderate-to-vigorous intensity exercise task or a 20-minute non-exercise task. Prior to choosing, participants rated their mental fatigue and their perceived benefits and costs of the exercise task. The cognitive task had a strong effect on mental fatigue (p < .001, Cohen's d = 1.40). The mediation analysis showed no direct effect of mental fatigue on choice; however, there was a significant indirect effect indicating the benefit-cost score mediated the effect of mental fatigue on choice (95% C.I. = -.02 to -.0004). Higher levels of mental fatigue were associated with a lower benefit-cost score (r = -.33, p = .01) which, in turn, was associated with a decreased likelihood of choosing the exercise task (r = .31, p = .02). For those who chose to engage in the exercise task (N = 28), higher levels of mental fatigue were associated with higher ratings of perceived exertion (r = .38, p = .05). Findings provide insight into the effects of mental fatigue on people's exercise behaviours, illustrating a rational decision-making process that is dependent upon the subjective evaluation of the costs and benefits of engaging in physical activity or sedentary alternatives. / Thesis / Master of Science (MSc)

In this dissertation, I have addressed the question of how resting-state EEG markers primarily in the alpha frequency range are linked to general cognitive performance and age. In the three studies presented in the work, I show that alpha power, frequency, and temporal dynamics, have distinct contributions to cognitive control functions in different age groups. Moreover, individual alpha peak frequency as well as the slope of 1/f decay of the PSD shows consistent age-related alterations, while alpha power is linked to structural alterations in the white matter. Our research extends further existing literature by specifying relevant neural networks as well as important methodological considerations that should be taken into account when analysing properties of oscillations.

<p dir="ltr">This work provides a new framework for investigating instances where multitasking and focusing do not need to trade off, but can rather coexist.</p>