The congruency sequence effect literature is inconsistent when it comes to the issue of the boundaries of this phenomenon. Some have argued that control is implemented at the level of a stimulus dimension while other have claimed that control operates across dimensions and tasks. Flexible control boundaries defined by task sets might explain the inconsistent findings. Response set manipulations have been shown to influence control boundaries. Unitary response sets can produce cross-dimension congruency sequence effects but applying separate response sets to a task can lead to the absence of the congruency sequence effect on dimension switch trials. This thesis is concerned with the extension of these findings. The study applied response set manipulations to a paradigm (Stroop Trajectory Task) that has exhibited robust crossdimension congruency sequence effects. In addition, the influence of switching routine on congruency sequence effects was tested. It was expected that separate response sets for different stimulus dimensions would eliminate the congruency sequence effect on switch trials. Switching routine was anticipated to act as a weaker boundary marker but nevertheless it was expected that systematic switching routines should have at least attenuated the congruency sequence effect on switch trials. Contrary to expectations it was found that the congruency sequence effect was present in switch trials across all conditions.

Humans frequently encounter cognitive conflict situations, such as the need to ignore distractions or make a decision with multiple options. Cognitive control over attention and behavior in conflict situations is a basic executive functioning skill vital for goal-oriented behaviors. Musicians spend many hours exercising cognitive control while ignoring distractions, focusing on specific sounds, and avoiding incorrect movements. Therefore, musicians are a useful population to examine the effects of long-term experience on cognitive control. The current study used independent component analysis, time-frequency analysis, and ERP analysis on electrophysiological data to identify neocortical activity and timescales of cognitive control during an auditory Simon Task. Musicians showed no cognitive control advantage over non-musicians. Consistent with previous research, we found short-term compatibility sequence effects as well as longer-term effects of base rate (proportion of compatible trials) in response time Simon effect data. Sequence effects and a base rate x compatibility interaction also emerged for some ERP and ERSP components, including frontal theta in the ERSPs. We then used predictive models to test whether changes in the Simon effect across base rates were due to changing numbers of each sequence type that necessarily accompany base rate manipulations. Results indicate that sequence effects account for 17% of the reaction time cognitive control shift associated with proportion compatible manipulations. The base rate manipulation affected behavior and neural correlates above and beyond sequence effects. / Lisa Chinn

A series of experiments investigated the relationship between locus coeruleus-norepinephrine (LC-NE) function and striatal dopamine (DA) tone and the flexibility of stability of cognitive control. Across 4 experiments, participants completed an attention shifting task, in which they had to periodically switch the focus of their attention while avoiding distraction. In 3 of the 4 experiments, participants’ eyes were tracked to collect eye blink rate and pupil size, indices of striatal dopamine and LC-NE function respectively. A second aim of this project was to determine whether DA- and NE-linked variability in cognitive control was predictive of more ecologically valid real-world behaviors. To this end, participants in Experiment 4 also completed an additional lab session, in which they performed an internet search task, designed to be similar to what a student might experience in their everyday life. Participants then completed 2 weeks of follow-up questionnaires to provide a self-report of their daily experience of distractibility and flexibility. We hypothesized that observable indices of flexibility and distractibility during the internet search task would mediate the relationship between attention task performance and real-world experiences. Results indicated that EBR is related to attentional flexibility; however the specific shape of the effect was inconsistent across studies, with one showing a linear effect on the ability to update the attentional set, and the other showing a quadratic effect. There were large, consistent main effects of both tonic and phasic pupil measures on attention task performance, with longer latencies, larger phasic responses, and larger baseline pupil sizes all tending to predict slower responding and a higher error rate. There was no clear pattern of pupil effects across conditions, however, and so it is not clear whether pupil-linked changes in task performance are related to specific effects on cognitive control processes, or rather a more general arousing effect on performance. Finally, there were also no clear links suggesting that observable behaviors on our internet search task could be used to bridge between attention task performance and real-world behavior.

A series of experiments examined both the phenomenological nature and centrality of Cognitive Control in common cognitive paradigms. This was done primarily by employing manipulations of Congruency Proportion (CP), which are thought to modulate key aspects of Cognitive Control. Experiment 1 leads this investigation by examining the degree to which participants are consciously aware of the influence of CP in the Simon task. Here, it was observed that participants’ subjective reports of the proportion of congruent trials did not predict their actual CP effects, suggesting a non-conscious locus of CP effects. Experiments 2 and 3 followed up these preliminary findings by assessing the degree to which CP effects differentially modulate the application of Cognitive Control in two variants of the size congruity paradigm (Numerical Judgement and Physical Judgement). Here, I found that manipulations of CP significantly impacted the Numerical Judgement task, but not the Physical Judgement task, and thus seriously challenge the notion of a central and unitary Cognitive Control module. In Experiment 4, I assessed the systematic variation (via correlations) of effects from the size congruity paradigm and the Stroop task across blocks of trials at different levels of CP. In addition, I examined the degree to which the effects of CP were related to common self report measures of Cognitive Control (the Need for Cognition scale and Cognitive Failures Questionnaire). The pattern of within-task and between-task reliabilities was examined to elucidate the degree to which there is a common central control component that governs behaviour in all tasks. There was surprisingly little to no relation among the CP effects observed in these three tasks. In addition, neither participants’ engagement with the task (as indexed by theNeed for Cognition Scale), nor their propensity to have attentional slips (as indexed by the Cognitive Failures Questionnaire) predicted their performance in any way. Taken together, this set of experiments has seriously undermined the received view that CP effects arise from a central and unitary form of conscious control. These results are discussed in terms of contemporary theories of Cognitive Control.

A series of experiments examined both the phenomenological nature and centrality of Cognitive Control in common cognitive paradigms. This was done primarily by employing manipulations of Congruency Proportion (CP), which are thought to modulate key aspects of Cognitive Control. Experiment 1 leads this investigation by examining the degree to which participants are consciously aware of the influence of CP in the Simon task. Here, it was observed that participants’ subjective reports of the proportion of congruent trials did not predict their actual CP effects, suggesting a non-conscious locus of CP effects. Experiments 2 and 3 followed up these preliminary findings by assessing the degree to which CP effects differentially modulate the application of Cognitive Control in two variants of the size congruity paradigm (Numerical Judgement and Physical Judgement). Here, I found that manipulations of CP significantly impacted the Numerical Judgement task, but not the Physical Judgement task, and thus seriously challenge the notion of a central and unitary Cognitive Control module. In Experiment 4, I assessed the systematic variation (via correlations) of effects from the size congruity paradigm and the Stroop task across blocks of trials at different levels of CP. In addition, I examined the degree to which the effects of CP were related to common self report measures of Cognitive Control (the Need for Cognition scale and Cognitive Failures Questionnaire). The pattern of within-task and between-task reliabilities was examined to elucidate the degree to which there is a common central control component that governs behaviour in all tasks. There was surprisingly little to no relation among the CP effects observed in these three tasks. In addition, neither participants’ engagement with the task (as indexed by theNeed for Cognition Scale), nor their propensity to have attentional slips (as indexed by the Cognitive Failures Questionnaire) predicted their performance in any way. Taken together, this set of experiments has seriously undermined the received view that CP effects arise from a central and unitary form of conscious control. These results are discussed in terms of contemporary theories of Cognitive Control.

Adverse experiences have long-term consequences for biological, behavioral, and psychosocial adjustment. Adolescents may be particularly susceptible to these effects due to heightened sensitivity to environmental influences, the protracted development of the prefrontal cortex, and risk for psychopathology. We used a person-centered approach to characterize distinct profiles of adversity in early adolescence, and examined associations with later cognitive control and psychopathology. One hundred and sixty-seven adolescents (53% male) and their primary caregivers participated in a longitudinal study, with approximately one year in between each assessment. At Time 1 (Mage = 14.07 years), we collected reports on seven indicators of adversity: socioeconomic disadvantage, abuse, neglect, household chaos, parent substance use, parent depression, and negative life events. At Times 2, 3, and 4, adolescents' behavioral performance and blood-oxygenation-level-dependent response during a cognitive control task were measured. Two years later, at Time 5, adolescents and their caregiver reported on adolescent internalizing and externalizing symptomatology. Using latent profile analysis, we identified three distinct adversity subgroups: a low risk group, a low socioeconomic status (SES)/high parent substance use (SU) group, and a high risk group. Adolescents in the low SES/high parent SU group had the lowest levels of behavioral cognitive control. Furthermore, the low SES/high parent SU group and the high risk group both had significantly higher levels of psychopathology relative to the low risk group. There were no significant group differences with respect to neural cognitive control, and neither neural nor behavioral cognitive control predicted psychopathology. A cumulative risk approach using a mean score of adversity produced a similar general pattern of results, but obscured the unobserved heterogeneity in adverse experiences. These results highlight the utility of a person-centered approach to the characterization of adversity in adolescence and illustrate distinct developmental consequences for cognitive functioning and psychopathology. We expand upon prior empirical work by demonstrating that the co-occurrence of low SES and parent substance use may place adolescents at increased risk for deficits in behavioral cognitive control, which may be an important target for intervention and prevention efforts. / Doctor of Philosophy / During childhood and adolescence, most individuals are exposed to some form of adversity, such as abuse, neglect, poverty, or parent mental illness. These factors can have long-term effects on brain functioning and mental health. Adolescents may be especially affected by adversity because their brain is in an important stage of development and they are also more sensitive to social and environmental influences. The purpose of this study was to better understand if certain patterns of adversity experiences were associated with adolescents' self-regulation abilities and mental health outcomes. We recruited 167 adolescents and their primary caregivers from the community and asked them to report on adolescents' experiences of adversity at age 13-14. Specifically, we asked about socioeconomic status, abuse, neglect, household chaos, parent substance use, parent depression, and negative life events. Once each year for the next three years, adolescents completed a self-regulation task while they were in a Magnetic Resonance Imaging (MRI) machine. We examined their performance on the task as well as their brain activation. Two years later, at 18-19 years old, adolescents and their caregiver reported on the adolescent's mental health symptoms. Results indicated that there were three groups of adolescents with different combinations of adverse experiences: a low risk group, a low socioeconomic status (SES)/high parent substance use (SU) group, and a high risk group. Adolescents in the low SES/high parent SU group had the worst performance on the self-regulation task. Furthermore, both the low SES/high parent SU group and the high risk group had significantly higher mental health problems relative to the low risk group. There were group differences in terms of brain activation. Finally, neither performance nor brain activation during self-regulation was associated with mental health problems. We also tested these associations by using an average score of adversity, rather than dividing participants into subgroups. When we compared these approaches, the results were generally similar, but the subgroup approach provided more specific information about what types of experiences put adolescents at higher risk for self-regulation and mental health problems. Thus, the subgroup approach may be useful for better understanding the nuanced consequences of adversity. Our findings further show that the co-occurrence of low SES and parent substance use may place adolescents at increased risk for deficits in self-regulation, which may be an important target for intervention and prevention efforts.

In this thesis, I investigated effects of conflict strength and ageing on cognitive control. Conflict strength was manipulated in the Eriksen flanker task using two different approaches: 1. independent variation of flanker and target contrast; 2. manipulation of stimulus onset asynchrony (SOA). Reducing flanker contrast relative to target contrast decreased conflict strength, as shown by a reduction in compatibility effects, when contrast conditions were presented in a randomized fashion but not when they were presented block-wise. An SOA of 100 ms did lead to increased compatibility effects compared to SOAs of 0 ms and 200 ms. Effects of conflict appear to be reflected in the N2 component of the ERP. Although priming played a crucial role in the emergence of the sequential adjustment effect, conflict strength also influenced this effect to a certain degree, supporting the claim that sequential adjustments represent an adaptation of cognitive control. Post-error slowing and error-related ERP components, on the other hand, were not affected by the conflict manipulations, suggesting that errors cannot be explained in terms of conflict processing. Effects of ageing on cognitive control were investigated in a group of middle-aged participants. Although physiological indicators of conflict and error processing were compromised in this age group and overall response times were increased, compatibility, sequential adjustment, and post-error slowing effects were of comparable size as in young adults. These findings suggest that participants could successfully compensate for age-related physiological changes at this early stage of ageing. In conclusion, the research presented in this thesis provided important information to extend our knowledge of factors influencing cognitive control processes.

The dual mechanism of cognitive control framework (DMC) describes cognitive control via two strategies: proactive and reactive. Individuals using a proactive strategy, focus on actively maintaining goal-relevant information in memory, whereas reactive individuals store goal-relevant information and retrieve it when cues are present. Reimer and colleagues (2015, 2017) added cue-probe location shifts to the typical AX-CPT, as well as, a virtual-reality environment version of the AX-CPT. Through this, they found that the effect of location shifts vary depending on whether a proactive or reactive mode of control is utilized. Thus, the aim of the present study was to test whether the effect of location shifts on cognitive control depends on type of control strategy used. Two versions of the AX-CPT were used: shift alone and shift with no-go trials. The shift alone AX-CPT examined the influence of location shifts in proactively-biased young adults. The shift with no-go trials AX-CPT examined the influence of location shifts with a manipulation that is known to induce a reactive control strategy (Gonthier et al., 2016). It was hypothesized that cue-probe location shifts would have a differential effect on mode of control. Results demonstrated that type of AX-CPT given, cue-probe location, and type of trial presented individually influenced participant performance. There was also an interaction between AX-CPT type and trial type that provides evidence for a successful manipulation of mode of control. The hypothesized interaction between all variables, however, was not found. Possible limitations of the present study, as well as, future direction were discussed.

The concept of a unitary cognitive control system has increasingly come under question. Numerous paradigms have emerged that aim to dissect cognitive control into its constituent processes, including task-switching paradigms that require alternation between multiple tasks. A switch in task is associated with increased reaction time (RT) as compared to a repeat in task, which is proposed to at least partially reflect processes associated with reconfiguration of the currently active task-set. Previous event-related brain potential studies show a differential positivity emerging prior to a switch in task that appears to reflect anticipatory task-set reconfiguration. Six experiments were conducted that investigated the behavioural and ERP correlates of task-switching, and in particular, the cognitive control processes involved in anticipatory task-set reconfiguration. Experiment 1 dissociated the effects of passive dissipation of task-set interference from anticipatory task-set reconfiguration. In Experiment 2, it was further verified that the switch-related differential positivity reflects processes associated with anticipatory task-set reconfiguration, particularly initiation of the new task-set. A simplified paradigm was developed in Experiment 3 that maximised engagement in anticipatory task-set reconfiguration, reducing mean RT switch cost. Experiment 4 demonstrated that the RT switch cost and differential positivity in cueing paradigms are associated with task-set reconfiguration rather than a cue repetition benefit. Consistent with previous brain imaging studies, Experiment 5 revealed that anticipatory task-set reconfiguration is associated with increased activation in the prefrontal cortex and parietal lobe. These findings show that task-set reconfiguration processes are activated when switching between tasks and that this consists of multiple components including the active utilisation of cognitive control processes in anticipatory task-set reconfiguration. Task-switching paradigms are thus a useful tool for investigating control processes in healthy populations and as Experiment 6 demonstrates, in clinical populations that have deficits in control processes, such as patients with schizophrenia. / PhD Doctorate

Discrepant findings on whether children with autism display response inhibition deficits may be partially due to the wide variety of behavioral tasks used to assess inhibition. A more useful way of understanding early cognitive/attentional processes that influence response inhibition may be to look at neurophysiological measures. Specifically, the event related potential N2, a measurement of cognitive control or the effortful decision to inhibit a prepotent behavioral response, may be useful in understanding the discrepancy in response inhibition. In the current study we measured the N2 as high-functioning autistic children and age, IQ-matched control children performed a modified Flanker task. We further examined the associations between N2 amplitude and latency and variations in social communication within the HFA sample. Behavioral and electrophysiological data from a modified Flanker task were collected from 27 HFA (1 female) and 24 typically developing controls (1 female) ranging in age from 8- to 16-years. Symptom severity was measured using the ASSQ, ADI, and SCQ. Regarding behavioral performance, HFA children committed more errors than control children when controlling for age and verbal IQ. Electrophysiological performance indicated marginal group differences in N2 amplitude when controlling for age. Typical age-related decline in N2 amplitude was observed in the control group but not in the HFA group. There were no significant group differences found for N2 latency. In addition, greater N2 amplitude was correlated with lower scores on the SCQ for the HFA children. Behavioral performance does not conclude that the HFA children show deficits in inhibition, but deficits regarding impulsivity. Electrophysiological data suggest developmental change in N2 amplitude differentiates the HFA and control groups. Finally, the relationship between larger N2 amplitude and lower scores on the SCQ, within the HFA children, indicate that social communication deficits are less when greater cognitive effort is utilized.