Segmentational grouping in music listening refers to the organisation of individual tones into tone groups that tend to be processed and subsequently recalled as perceptual units or chunks. Grouping of tones via this process tends to occur at natural breaks in structure of a tone sequence, so that relatively larger changes in pitch, amplitude or timing are perceived as boundaries which cue the segmentational grouping process. Segmentational grouping processes have been examined using behavioural research techniques; yet neurophysiological processes underlying the grouping process have received little attention, and are poorly understood. This study aimed to identify brain regions involved in the segmentational grouping process as cued by rhythmic information. Participants performed two auditory tasks while brain electrical activity responses were monitored using Steady-State Probe Topography (SSPT). Behavioural responses evoked in a task probing individuals' use of lengthened-duration tones to organise memory for pitch sequences indicated that longer-duration tones were used as cues to organise working memory representations of the musical patterns. Examination of dynamic SSPT responses during the encoding phase of a probe recognition task indicated that greater use of rhythmic cues to organise working memory representations was associated with activation of a network of left hemisphere frontal, temporal and parietal regions. During the lengthened tone, activation of left central and vertex regions and progressive activation of left temporal and temporoparietal regions were linked with use of the deviant status of the lengthened tone to update temporal expectations for the sequence. Excitatory responses observed in left posterior frontal and temporal regions to a tone following the lengthened tone were proposed to reflect temporal allocation of attention to this point in time, whereas sustained excitatory activation of left temporal, and temporoparietal regions reflected the role of these regions in supporting representations of the tone events in working memory. Finally, late inhibitory responses to the tone following the lengthened tone in left frontal, temporal, temporoparietal, and parietal regions were linked with the manipulation and closure of the working memory trace in association with the grouping process. Together, these findings support the activation of a network of left frontal, temporal and parietal regions underlying rhythmic grouping of pitch sequences.

People engage in a constant and reflexive process of categorizing others according to their race, gender, age or other salient social category. Decades of research have shown that social categorization often elicits stereotypes, prejudice, and discrimination. Social perception is complicated by the fact that people have multiple social identities and self-categorization with these identities can shift from one situation to another, coloring perceptions and evaluations of the self and others. This dissertation provides evidence that self-categorization with a novel group can override ostensible stable and pervasive racial biases in memory and evaluation and examines the neural substrates that mediate these processes. Experiment 1 shows that self-categorization with a novel mixed-race group elicited liking for ingroup members, regardless of race. This preference for ingroup members was mediated by the orbitofrontal cortex – a region of the brain linked to subjective valuation. Participants in novel groups also had greater fusiform and amygdala activity to novel ingroup members, suggesting that these regions are sensitive to the current self-categorization rather than features associated with race. Experiment 2 shows that preferences for ingroup members are evoked rapidly and spontaneously, regardless of race, indicating that ingroup bias can override automatic racial bias. Experiment 3 provides evidence that preferences for ingroup members are driven by ingroup bias rather than outgroup derogation. Experiment 4 shows that self-categorization increases memory for ingroup members eliminating the own-race memory bias. Experiment 5 provides direct evidence that fusiform activity to ingroup members is associated with superior memory for ingroup members. This study also shows greater amygdala activity to Black than White faces who are unaffiliated with either the ingroup or outgroup, suggesting that social categorization is flexible, shifting from group membership to race within a given social context. These five experiments illustrate that social perception and evaluation are sensitive to the current self-categorization – however minimal – and characterized by ingroup bias. This research also offers a relatively simple approach for erasing several pervasive racial biases. This multi-level approach extends several theories of intergroup perception and evaluation by making explicit links between self-categorization, neural processes, and social perception and evaluation.

The term working memory (WM) refers to a set of cognitive processes that allows for the temporary storage and manipulation of information. Neural correlates of the N- back task, a well-established WM measure used in neuroimaging, have been studied extensively in adults but less so in developmental populations. This thesis determines the effect of age on brain activations that mediate cognitive processes for remembering non- verbal/visual stimuli. Block-design fMRI was used to record activity in 84 subjects (6-35 years) during a visual-patterns 0- and 1-back task. Regions activated during the 1-back condition were largely common to all age groups, with adults displaying the largest extent of activations. Children and adolescents showed similar 0-back activations (distinct from 1-back) while adults engaged an analogous 1-back activation pattern during 0-back, suggesting that brain mechanisms underlying memory and attentional processes required for this task in children and adolescents are not yet mature and that strategy usage is still developing.

The term working memory (WM) refers to a set of cognitive processes that allows for the temporary storage and manipulation of information. Neural correlates of the N- back task, a well-established WM measure used in neuroimaging, have been studied extensively in adults but less so in developmental populations. This thesis determines the effect of age on brain activations that mediate cognitive processes for remembering non- verbal/visual stimuli. Block-design fMRI was used to record activity in 84 subjects (6-35 years) during a visual-patterns 0- and 1-back task. Regions activated during the 1-back condition were largely common to all age groups, with adults displaying the largest extent of activations. Children and adolescents showed similar 0-back activations (distinct from 1-back) while adults engaged an analogous 1-back activation pattern during 0-back, suggesting that brain mechanisms underlying memory and attentional processes required for this task in children and adolescents are not yet mature and that strategy usage is still developing.

People engage in a constant and reflexive process of categorizing others according to their race, gender, age or other salient social category. Decades of research have shown that social categorization often elicits stereotypes, prejudice, and discrimination. Social perception is complicated by the fact that people have multiple social identities and self-categorization with these identities can shift from one situation to another, coloring perceptions and evaluations of the self and others. This dissertation provides evidence that self-categorization with a novel group can override ostensible stable and pervasive racial biases in memory and evaluation and examines the neural substrates that mediate these processes. Experiment 1 shows that self-categorization with a novel mixed-race group elicited liking for ingroup members, regardless of race. This preference for ingroup members was mediated by the orbitofrontal cortex – a region of the brain linked to subjective valuation. Participants in novel groups also had greater fusiform and amygdala activity to novel ingroup members, suggesting that these regions are sensitive to the current self-categorization rather than features associated with race. Experiment 2 shows that preferences for ingroup members are evoked rapidly and spontaneously, regardless of race, indicating that ingroup bias can override automatic racial bias. Experiment 3 provides evidence that preferences for ingroup members are driven by ingroup bias rather than outgroup derogation. Experiment 4 shows that self-categorization increases memory for ingroup members eliminating the own-race memory bias. Experiment 5 provides direct evidence that fusiform activity to ingroup members is associated with superior memory for ingroup members. This study also shows greater amygdala activity to Black than White faces who are unaffiliated with either the ingroup or outgroup, suggesting that social categorization is flexible, shifting from group membership to race within a given social context. These five experiments illustrate that social perception and evaluation are sensitive to the current self-categorization – however minimal – and characterized by ingroup bias. This research also offers a relatively simple approach for erasing several pervasive racial biases. This multi-level approach extends several theories of intergroup perception and evaluation by making explicit links between self-categorization, neural processes, and social perception and evaluation.

The processing of information within the visual system is limited by several cognitive and neural bottlenecks. One critical bottleneck occurs in visual working memory (VWM), as the amount of information that can be maintained on-line is limited to three to four items. While numerous theories have addressed this limited capacity of VWM, it is unclear how processing bottlenecks in the initial selection and perception of visual information affect the number or precision of representations that can be maintained in VWM. The purpose of this dissertation was to examine whether early competition for resources within the visual system limits the number or precision of representation that can be maintained in VWM. To establish whether competitive interactions affect VWM, Chapters 1 – 4 tested whether performance on VWM tasks was related to the distance between memory items. The results of these experiments reveal that when objects are presented close together in space, VWM performance is impaired relative to when those same objects are presented further apart. Using a three-component model of continuous responses in a recall task, Chapters 3 – 4 demonstrated that the distance between objects primarily affects the precision of responses, and increases the number of non-target errors. Chapter 5 extended these findings to distractors, demonstrating that multiple distractors affect the precision and accuracy of VWM responses. Chapters 6 – 7 tested how attentional selection can bias memory representations, revealing that objects that are given high attentional priority were reported with greater precision. Finally, Chapters 8 and 9 examined bias-signals as a potential source of individual differences in VWM performance, revealing that high-performers have more precise representations of sub-capacity representations than low-performers. Together, these results reveal that VWM performance is limited by competition for representation within the visual system, and that attention plays a critical role in resolving competition and consequently, determining the contents of VWM.

The past 40 years have seen an enormous amount of research aimed at investigating human reasoning and decision-making abilities. This research has led to an extended debate about the extent to which humans meet the standards of normative theories of rationality. Recently, it has been proposed that dual-process theories, which posit that there are two distinct types of cognitive systems, offer a way to resolve this debate over human rationality. I will propose that the two systems of dual-process theories are best understood as investigative kinds. I will then examine recent empirical research from the cognitive neuroscience of decision-making that lends empirical support to the theoretical claims of dual-process theorists. I will lastly argue that dual-process theories not only offer an explanation for much of the conflicting data seen in decision-making and reasoning research, but that they ultimately offer reason to be optimistic about the prospects of human rationality.

Attention allows us to select important aspects of incoming sensory information while filtering out irrelevant information. It has crucial significance in understanding neurophysiological, emotional and behavioral outcomes. The research reported here focused on one central question: how do attentional manipulations influence various stages of cognition and emotion to result in goal-directed behavior? In six experiments, I used behavioral and functional Magnetic Resonance Imaging (fMRI) measures to investigate the impact of attention on visual recognition, mood and self-regulation. The results showed that attention influences functional connectivity between body-selective visual processing areas in occipito-temporal cortex. Changes in the scope of attention were also found to influence mood and self-regulation. Broadening attentional focus improves mood and self-regulation. Narrowing attentional focus impairs mood and self-regulation. Self-regulation was also aided through the pre-engagement of attentional inhibition. This diverse set of methodologies and experimental paradigms provides converging evidence that attention influences goal-relevant functional connections to facilitate visual processing, promotes fluency of information to result in better mood and prioritizes goal-relevant representations to result in successful self-regulation. / NSERC

<p>Cognitive neuroscience is an interdisciplinary enterprise aimed at explaining cognition and behavior. It appears to be succeeding. What accounts for this apparent explanatory success? According to one prominent philosophical thesis, cognitive neuroscience explains by discovering and describing mechanisms. This "mechanist thesis" is open to at least two interpretations: a strong metaphysical thesis that Carl Craver and David Kaplan defend, and a weaker methodological thesis that William Bechtel defends. I argue that the metaphysical thesis is false and that the methodological thesis is too weak to account for the explanatory promise of cognitive neuroscience. My argument draws support from a representative example of research in this field, namely, the neuroscience of decision-making. The example shows that cognitive neuroscience explains in a variety of ways and that the discovery of mechanisms functions primarily as a way of marshaling evidence in support of the models of cognition that are its principle unit of explanatory significance.</p><p> </p><p>The inadequacy of the mechanist program is symptomatic of an implausible but prominent view of scientific understanding. On this view, scientific understanding consists in an accurate and complete description of certain "objective" explanatory relations, that is, relations that hold independently of facts about human psychology. I trace this view to Carl Hempel's logical empiricist reconceptualization of scientific understanding, which then gets extended in Wesley Salmon's causal-mechanistic approach. I argue that the twin objectivist ideals of accuracy and completeness are neither ends we actually value nor ends we ought to value where scientific understanding is concerned. </p><p>The case against objectivism motivates psychologism about understanding, the view that understanding depends on human psychology. I propose and defend a normative psychologistic framework for investigating the nature of understanding in the mind sciences along three empirically-informed dimensions: 1) What are the ends of understanding? 2) What is the nature of the cognitive strategy that we deploy to achieve those ends; and 3) Under what conditions is our deployment of this strategy effective toward achieving those ends? To articulate and defend this view, I build on the work of Elliot Sober to develop a taxonomy of psychologisms about understanding. Epistemological psychologism, a species of naturalism, is the view that justifying claims about understanding requires appealing to what scientists actually do when they seek understanding. Metaphysical psychologism is the view that the truth-makers for claims about understanding include facts about human psychology. I defend both views against objections.</p> / Dissertation

Behavioral evidence has shown that older adults are less able to overcome proactive interference in memory than young adults. However, it is unclear what underlies this deficit. Imaging studies in the young suggest overcoming interference may require post-retrieval selection, a process thought to be mediated by the left mid-ventrolateral prefrontal cortex (VLPFC). Further, selection may resolve interference by enhancing or suppressing perceptual processing. The present fMRI study investigated whether age-related changes in VLPFC-mediated post-retrieval selection underlie older adults' deficits in overcoming interference in associative memory. Participants were tasked with remembering which associate (face or scene) objects were paired with most recently during study, under conditions of high or low proactive interference. Behavioral results demonstrated that as interference increased, memory performance decreased similarly across groups. Across groups, activity in the left mid-VLPFC also increased with interference. However, right PFC post-retrieval monitoring effects, but not left mid-VLPFC, distinguished successful vs. unsuccessful resolution of interference for both young and older adults, suggesting selection alone may be insufficient for successful resolution of interference. Age-related memory deficits may be related to reduced recruitment of relational processing effects in the dorsolateral and anterior PFC, as well as reduced memory retrieval effects in the hippocampus. Lastly, results showed evidence that selection may modulate perceptual processing of retrieved memory representations. Namely, activity in the parahippocampal place area (PPA) was greater when participants selected scene, versus face, regardless of accuracy. Further, older adults showed reduced effects in the PPA, possibly reflecting reduced differentiation of perceptual processing. Taken together, these results suggest age-related deficits in overcoming proactive interference are not related to post-retrieval selection, but reduced recruitment of PFC-mediated relational processes, coupled with reduced associative memory retrieval.