Todd Handy


Relevant Thesis-Based Degree Programs


Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Cognition and motion: the relationship between cognitive function, physical activity, and gait dynamics in young adults (2020)

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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The spatial and temporal dynamics of self-relevance of attention for objects (2017)

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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The neurocognitive consequences of the wandering mind : a mechanistic account of sensory-motor decoupling (2014)

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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Imaired attentional processing as a risk factor for falls in older adults (2013)

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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Attentional and cognitive consequences of migraine visual cortical hyperexcitability (2012)

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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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Out-of-home mobility : a measure of daily cognition in young adults (2023)

Work in gerontology has established an important relationship between cognition and mobility, in that maintaining mobility is reliant on maintaining the integrity of executive cognitive functions. While young adults do not exhibit cognitive decline as do older adults, they can experience momentary fluctuations in cognitive abilities via daily cognitive failures or errors, compounded by variations in mood states. Studying cognition, mood and mobility in an integrated fashion would be beneficial for broadening our understanding of daily cognition, yet these relationships are rarely studied in young adults. The aim of this work is to examine how fluctuations in daily cognition as well as mood impact out-of-home mobility in young adults, to see whether such relationships extend across the life span. We passively collected global positioning system (GPS) data from undergraduate and graduate student participants (N = 173) for two weeks; they filled out baseline measures of cognition and mood in-lab, as well as daily questionnaires on their phones, assessing cognition, mood, and daily activity patterns (place visits, transportation use, environments visited). Spearman correlations showed that at the two-week aggregate level, greater daily cognition and baseline executive functioning were associated with less time spent at home, but these measures did not provide predictive value in regression models. Greater daily positive mood was predictive of greater distances travelled, but we did not find support for cognition impacting distances travelled. Taken together, these mixed findings suggest that mobility is not as readily impacted by fluctuations in cognitive and mood states in young, healthy adults, as is seen in older adults or clinical populations. Future work should focus on extending existing theoretical frameworks to young adults and assessing what other factors may be of relevance.

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Examining physical activity mode and intensity on cognitive functioning in young adults (2018)

The effect of physical activity (PA) on cognition has long been recognized. However, despite a well-documented PA-cognition association in older adults and children, the effect of PA on cognitive functioning in young adults remains unclear. Further complicating the PA-cognition association is that as research in this field has expanded, different methodologies, interventions, and cognitive assessments have led to a diversity of findings and inconsistent results. Diversity in the protocol of PA-cognition studies has made direct comparison of results challenging because of the numerous known variables that moderate the PA-cognition relationship. Additionally, the intermediate period between the near and long-term timescales, particularly in this population, is an under-investigated area of research. Unfortunately, this unattended timeframe may prove vital in understanding why results are not systematically convergent. In this study we examine the PA-cognition relationship in young adults over seven-days while accounting for other covariates known to moderate the PA-cognition association. The aim of this work is to address how some of the variance in findings is related to PA mode and intensity, and to consider how interplay between age, sex, physical fitness, and sleep alter those relationships. In addition, we examine two broad aspects of cognitive function, attention and working memory, in order to compare directly the effect of PA on cognitive performance. Statistical analysis showed that PA plays an important role in a subset of cognitive processes, with a pronounced PA-cognition relationship at these intermediate periods. Additionally, we demonstrate that PA modes and intensities differentially effected cognitive processes, such that particular combinations of mode and intensity benefitted cognition processes selectively. Further, we have confirmed the importance of sex as an influential predictor of cognitive performance. Despite assessing theoretically similar cognitive processes, it is evident from the differential findings that the neurophysiological effects of PA may achieve neurocognitive gains selectively. Generally, these results suggest that PA is predictive of cognitive performance on attentional tasks, but little evidence supports gains in working memory in young adults at intermediate timescales.

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The influence of acetaminophen on task related attention (2018)

The attenuating effects of acetaminophen on neuroaffective and neurocognitive processing, bear striking similarity to those of event-related processing observed during periods of off- task thoughts. The current study was designed to investigate whether acetaminophen impacts or alters normal patterns of neurocognitive disengagement with events in the external environment during off-task attentional states. In a placebo-controlled, between-groups design, participants performed a sustained attention to response task (SART) while event- related potentials (ERPs) to target events were recorded. At random intervals participants were queried for their attentional reports at the time of stoppage – either “on-task” or “off- task”. The frequency of off-task attentional reports and the ERPs generated by target events immediately preceding these subjective reports were assessed. Behaviourally, the frequency of off-task attentional reports was comparable between groups. Electrophysiologically, there were two findings of note. First, there was an overall main effect of attentional state on the amplitude of the P300 ERP component elicited target events, such that the mean amplitude was significantly attenuated during off-task vs. on-task attentional states in both the acetaminophen and placebo groups. Second, the amplitude of the LPP ERP component elicited by target events showed a significant decrease in amplitude during off-task attentional states that was specific to the acetaminophen group. Take together, my findings suggest that acetaminophen impacts neurocognitive disengagement during off-task attentional states, but not by increasing the attenuation of more basic stimulus categorization processes as indexed by the P300 ERP component, but rather, by catalyzing the attenuation of deeper, more contemplative stimulus evaluations, as indexed by the LPP ERP component.

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An unforgeettable apple: Attention and memory for forbidden objects (2013)

Are we humans drawn to the forbidden? From jumbo-sized soft drinks to illicit substances, the influence of prohibited ownership on subsequent demand has made this question a pressing one. We know that objects we ourselves own have a heightened psychological saliency, relative to comparable objects that are owned by others, but do these kinds of effects extend from self-owned to "forbidden" objects? To address this question I developed a modified version of the Turk shopping paradigm in which “purchased” items were assigned to various recipients. Participants sorted everyday objects labeled as self-owned, other-owned, and either forbidden to oneself (Experiment 1) or forbidden to everyone (Experiment 2). Subsequent surprise recognition memory tests revealed forbidden objects with high (Experiment 1) but not low self-relevance (Experiment 2) were recognized as well as self-owned objects and better than other-owned objects. In a third and final experiment I used event-related potentials (ERPs) to determine whether self-owned and self-forbidden objects, which showed a common memory advantage, are in fact treated the same at a neurocognitive-affective level. I found that both object types were associated with enhanced cognitive analysis, relative to other-owned objects, as measured by the P300 ERP component. However, I also found that self-forbidden objects uniquely triggered an enhanced response preceding the P300, in an ERP component (the N2) sensitive to more rapid, affect-related processing. Our findings thus suggest that while self-forbidden objects share a common cognitive signature with self-owned objects, they are unique in being identified more quickly at a neurocognitive level.

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The effects of music playing on cognitive task performance (2011)

Numerous music cognition studies have demonstrated the cognitive benefits of both long-term and short-term musical training. Whereas a great number of these studies deal with the short-term benefits for the music listener or the longer term benefits for the novice or accomplished musician, our study examines the short-term effects of music playing for the advanced performer. For our pretest-posttest design, we recruited advanced classically/score-based trained pianists. The participants started by completing a creative exercise (alternative uses task) or detail-oriented exercise (proofreading task). They then performed a piano piece for ten minutes. The performances were followed by completion of the second cognitive task (whichever task they were not given in the pretest condition). No significant pretest-posttest differences in creativity were reported. However, we found that participants performed significantly worse in the posttest detail-oriented task. Our results suggest that performance in tasks involving attention to detail—specifically, a proofreading task involving the visual detection of errors — may be hindered immediately following a short period of score-based music playing when the piece is already familiar to the performer.

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Slow fluctuations in attentional control of sensory cortex (2010)

Top-down control of visual sensory cortex has long been tied to the orienting of visual spatial attention on a rapid, moment-to-moment basis. Here we examined whether sensory responses in visual cortex are also modulated by natural and comparatively slower fluctuations in whether or not one is paying attention to the task at hand. Participants performed a simple visual discrimination task at fixation as the event-related potentials (ERPs) to task-irrelevant probes in the upper visual periphery were recorded. At random intervals, participants were stopped and asked to report on their attentional state at the time of stoppage––either "on-task" or "off-task." ERPs to the probes immediately preceding these subjective reports were then examined as a function of whether attention was in an "on-task" vs. "off-task" state. We found that sensory-evoked responses to the probes were significantly attenuated during "off-task" relative to "on- task" states, as measured by the visual P1 ERP component. In two additional experiments we replicated this effect while (1) finding that "off-task" sensory attenuation extends to the auditory domain, as measured by the auditory N1 ERP component, and (2) eliminating state-dependent shifts in general arousal as a possible explanation for the effects. Collectively, our findings suggest that sensory gain control in cortex is yoked to the natural ebb and flow in how much attention we pay to the current task over time.

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