Todd Handy

Researchers have delved into mind-wandering (MW) in the last decade to shed light on its significance in understanding and treating human psychopathology. MW offers a unique avenue to examine the cognitive dynamics crucial to the inception and progression of thoughts. This dissertation investigates how attentional states interact with processing affect and incidental emotional information. Chapter 1 reviews the literature to uncover how MW research in ADHD and depression can contribute to a broader understanding of MW mechanisms. This exploration revealed implications such as the role of executive control processes, distinguishing intentional from unintentional MW, and different frameworks to interpret MW. The mechanism-based term Perceptually Decoupled Cognitions (PDCs) is introduced to consolidate various MW-related phenomena. Chapter 2 showed that inattentional PDCs may be distinguished into MW, repetitive negative thinking (RNT), and introspective thinking. Notably, the link between MW and negative mood is at least partially explained by RNT. Chapter 3 delved into in-the-moment task inattention and its immediate impact on emotional processing.Additionally, it explored how everyday tendencies toward PDCs influence task inattention and the processing of incidental emotional stimuli. The results showed that a selective sensitivity to angry faces and its corresponding conservative response bias persists despite being in off-task states. In the concluding chapter, the implications of the above findings are discussed through a novel theoretical model grounded in affect regulation and metacognitive control. This model posits that unintentional PDCs are driven by a fundamental affective system that guides environmental navigation but may not always be adaptive. Meanwhile, intentional PDCs are influenced by a higher-level metacognitive system aligned with personal goals and values. This research provides insights into the intricate interactions among cognition, affect, and attentional states, illuminating the complex dynamics of the human mind in diverse contexts.

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Physical activity (PA) levels have been declining worldwide, despite the physical health benefits of increased PA having been known and messaged for decades. One possible reason for this is that physical health improvements are too long term, and it may be more effective to promote short-term benefits instead. PA has been shown to improve cognitive function over relatively short timescales and promoting these cognitive benefits may be a better approach for increasing PA levels in the population. What remains unclear is how certain moderators can affect the PA-cognition relationship, and how we can better measure PA in real-world environments. Over three studies, my dissertation aims to examine the effect of moderators like PA intensity and PA time window, as well as develop a novel methodology for measuring low-intensity physical activities, like walking, in outdoor settings. In the first study, I found that PA measured over the week prior to cognitive testing is not predictive of cognitive function, and that this does not depend on PA intensity. In the second study, I found that PA measured over the day prior to testing is associated with improved cognitive performance. In the third study, I examined the bidirectional nature of this relationship, and found that changes in cognition can have a marked impact on outdoor walking behaviour, and that these changes in gait dynamics can be detected using a smartphone-based measurement technique. Overall, my research shows that while PA does appear to be associated with cognitive function, the effects are quite small and dependent on factors like when the PA is measured relative to cognitive testing. In terms of PA promotion, more research needs to be conducted on the limits of this relationship before we can draw any definitive conclusions about the cognitive benefits of PA, as small statistically significant effects don’t necessarily translate to useful practical benefits in the real world.

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Ownership is a powerful mechanism for influencing attention. Objects that are owned by the self receive more attention and are more likely to be remembered than equivalent objects that are owned by another person. The most common explanation for this ownership effect is self- referencing/self-relevance: the act of associating an object with the self such that it is personally relevant to the self. What remained unknown is how the ownership-attention relationship functions when the scope of the self is expanded to include the influences of the body and the continuity (or lack thereof) of self-relevance over time. Over three studies, my dissertation aims to contextualize the attentional effects of ownership within these broader dimensions. In the first study, I found that the presence of the body could moderate the classic effect of ownership but that this moderation depends on the body’s ability to directly manipulate the contents of its environment. In the second study, I found that ownership might operate as a form of affective salience, altering attentional prioritization and, in turn, temporal perception. In the third study, I found that objects that cease to be self-owned still receive greater attentional resources than objects that are not initially self-owned, suggesting that the effects of self-relevance are robust to subsequent changes in ownership. My research demonstrates that the effects of ownership on attention may rely on multiple aspects of self, including embodiment and motivational significance. Importantly, one critical element that emerges from these studies is that of an active or agentic self that is distinguishable from more object-based aspects of self. Collectively, these findings suggest that a deeper understanding of ownership effects on attention necessitates a deeper understanding of the self.

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One unique characteristic of humans is our ability to mind wander – a state in which we engage in thoughts that are not directly tied to sensations from our surrounding environment. The Executive Function Model of mind wandering proposed the decoupling of our executive resources from the external environment is what facilitates the maintenance of these internal trains of thoughts. Accordingly, my dissertation aims to characterize how our neurocognitive processing of external stimuli waxes and wanes as our minds wander away from the task-at-hand. I present three sets of studies in this dissertation, each examining one specific aspect of neurocognitive engagement with the external environment, namely affective processing, behavioral performance monitoring, and attentional processing. Consistent with the Executive Function Model, my research indicates all three types of neurocognitive processing were attenuated during mind wandering episodes. This suggests mind wandering appears to disengage executive resources from our environment and direct them to inner streams of thoughts via this wide-ranging neurocognitive attenuation. One exception to this global pattern of attenuation of external processing is the detection of external stimuli that deviates from our expectations. Taken together, these observations suggest our ability to transiently decouple our thoughts from the external environment is integral to normal human neurocognitive functioning. A deeper understanding of this phenomenon may therefore inform strategies for regulating this mental experience so as to maximize their utility, and minimize their detrimental effects on our daily functioning and well-being.

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Falls are a leading health care issue in our rapidly aging society. While impaired cognitive functioning has previously been linked to falls, my dissertation aims to understand the specific relationship between attentional processing and falls/falls risk. My dissertation is comprised of four separate studies, each examining a specific facet of attention and its corresponding association with falls. The specific domains of attention that I examine include: 1. Visual-spatial attention in the context of task-irrelevant peripheral stimuli; 2. Dual-task ability under cognitive load using a virtual reality system intended to simulate real-world experiences; 3. Time spent engaged in task-unrelated thoughts (i.e., mind-wandering); and 4. The neural correlates that subserve selective attention and executive control. Using multi-modal measures, including event-related potentials, functional magnetic resonance imaging, and behavioural performance, my research examines how each area of attention is impaired as a function of falls history and/or physiological falls risk. Based on the attentional resource model, my research converges on the notion that falls risk is associated with a reduction in the level of available attentional resources, in addition to an impaired ability to appropriately allocate resources to the primary task. Importantly, such deficits in attentional processing may contribute to postural instability, given that the control of balance and posture require a greater proportion of cognitive resources with age. Taken together, these findings have critical implications for developing novel intervention strategies aimed towards improving quality of life and independence among older adults.

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People with migraine have hyperexcitable visual cortical response to normal visual inputs between attacks. Given that our attentional and perceptual processing can be influenced by our sensory experience, we might expect migraine visual cortical hyperexcitability to have a forward cascade of effects on cognitive processing. With this in mind, this dissertation explored the functional consequences of migraine hyperexcitable visual cortices on attentional and cognitive processing between headache attacks. To begin with, given that top-down attentional control signals can affect excitability of sensory response in visual cortex, Chapter 2 assessed if this normal modulation is affected in migraineurs. Using a probabilistic spatial orienting task while measuring ERPs to attended vs. unattended foveal and parafoveal stimuli, Chapter 2 revealed that migraineurs manifest heightened sensory responses of to-be-ignored visual stimuli. Next, Chapter 3 examined the behavioral impact of hyperexcitability of migraine visual cortex in terms of its effect on bottom-up attentional processing, in this case reflexive attentional orienting. Using three behavioral spatial attention paradigms, this chapter provided evidence of heightened reflexive visual-spatial orienting specific to sudden-onset peripheral events. Lastly, Chapter 4 assessed post-spatial-selection consequences of visual cortical hyperexcitability in migraineurs. Participants viewed unfamiliar commercial logos in the context of a target identification task while brain responses were recorded via ERPs. Following this task, participants individually identified those logos that they most liked or disliked. The results of this chapter suggested that migraineurs were not only evaluating environmental stimuli more than controls over time, but also not adequately hedonically categorizing it for quick allocation of attention. Collectively, the research presented in this dissertation suggests that migraineurs have anomalies specifically pointing to increased allocation of attention to extraneous environmental stimuli. The final concluding chapter briefly recaps each research chapter and then critically examines the impact of these findings in the context of four outstanding questions exposed by this research. Specifically, are top-down attentional control signals in migraineurs intact? How might anomalies found in this dissertation be a result of or independent from known sensory cortical abnormalities? How do the findings fit with the migraineur experience? Finally, what are the real-world clinical implications for migraineurs?

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