Perceptual objects often comprise of a visual and auditory signature, which arrives simultaneously through distinct sensory channels, and multisensory features are linked by virtue of being attributed to a specific object. The binding of familiar auditory and visual signatures can be referred to as semantic audiovisual (AV) integration because it involves higher level representations of naturalistic multisensory objects. While integration of semantically related multisensory features is behaviorally advantageous, multisensory competition, or situations of sensory dominance of one modality at the expense of another, impairs performance. Multisensory facilitation and competition effects on performance are exacerbated with age. Older adults show a significantly larger performance gain from bimodal presentations compared to unimodal ones. In the present thesis project, magnetoencephalography (MEG) recordings of semantically related bimodal and unimodal stimuli captured the spatiotemporal patterns underlying both multisensory facilitation and competition in young and older adults. We first demonstrate that multisensory processes unfold in multiple stages: first, posterior parietal neurons respond preferentially to bimodal stimuli; secondly, regions in superior temporal and posterior cingulate cortices detect the semantic category of the stimuli; and finally, at later processing stages, orbitofrontal regions process crossmodal conflicts when complex sounds and pictures are semantically incongruent. Older adults, in contrast to young, are more efficient at integrating semantically congruent multisensory information across auditory and visual channels. Moreover, in these multisensory facilitation conditions, increased neural activity in medial fronto-parietal brain regions predicts faster motor performance in response to bimodal stimuli in older compared to younger adults. Finally, by examining the variability of the MEG signal, we also showed that an increase in local entropy with age is also behaviourally adaptive in the older group as it significantly correlates with more stable and more accurate performance in older compared to young adults.

Medulloblastoma is the most common malignant central nervous system (CNS) tumor in childhood. The cranio-spinal radiation (CSR) required to treat this disease results in long-term cognitive and neurologic impairments. Medulloblastoma was recently categorized into four genetic subgroups (WNT, SHH, Group 3, and Group 4). This study examined neuropsychological and intellectual functioning in 91 medulloblastoma patients (41 Group 4; 20 Group 3; 18 SHH; 12 WNT) following treatment, and examined the impact of several medical, treatment and demographic factors on functioning over time. Longitudinal growth curve analyses revealed hydrocephalus most clearly predisposes to poor neuropsychological functioning. Results also indicate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment; however, comparing between subgroups revealed Group 4 performs most poorly, and Group 3 has the best overall intellectual outcome. Lastly, qualitative analyses suggest treatment with a larger CSR dose may contribute to poor intellectual functioning.

Emotions can have important and powerful effects on cognitive processes. The emotional content of stimuli plays a role, as does the perceiver’s emotional response. Of particular interest here was whether subjective reactions (i.e., liking) to novel stimuli are related to subsequent memory performance. Although it is well established that memory influences liking, the present investigation sought to document whether the association is reciprocal, asking if liking influences memory. A series of five experiments examined whether liking is related to recognition memory for novel music excerpts. In the general method, participants listened to a set of music excerpts and rated how much they liked each one. After a delay, they heard the same excerpts plus an equal number of novel excerpts and made recognition judgments, which were then examined in conjunction with liking ratings. Across all five experiments, higher liking ratings were associated with improved recognition performance. This association was evident after a 24-h delay between the exposure and test phases (Experiment 2), when participants made liking ratings after recognition judgments (Experiment 3), when possible confounding effects of similarity and familiarity were held constant (Experiment 4), and when a deeper level of processing was encouraged for all of the excerpts (Experiment 5). The findings implicate the presence of a direct association between liking and recognition. Considered jointly with previous findings, it is now clear that listeners tend to like music that they remember, and to remember music that they like.

The present study tested the hypothesis that distractor-based facilitation of visual search occurs because familiar distractors are processed and rejected in groups. We recorded participants’ eye movements during a visual search task to determine if familiar distractors were associated with an increased average distance between fixations and distractors. The study provided convergent evidence of a strong relation between search efficiency and distractor familiarity, wherein the distance between fixations and distractors increases with the efficiency of search. Further examination of eye movements suggested that the grouping of familiar distractors resulted in an efficient scanning of the search display by increasing the area of the display effectively processed during each fixation and therefore reducing the need to fixate individual distractors.

Six experiments were conducted to examine the factors modulating the size of age differences in recollection. The research presented in the current thesis was guided by the notions of self-initiated processing and environmental support. Older and younger adults’ performance in recollection was measured by Jacoby’s (1990) process dissociation procedure (PDP); the age differences as a function of self-initiated processing demands of the task and the amount of support provided to the participants were assessed by manipulating the encoding (Experiments 2.1, 2.2, and 2.3) and retrieval (Experiments 3.1, 3.2, and 3.3) contexts. Experiments 2.1, 2.2, and 2.3 examined interactions of aging and encoding contexts. Recollection under baseline conditions (i.e. visually presented words) was contrasted with recollection of items encoded under contexts that are assumed to enhance memory. The results showed differential age-related patterns of benefits from encoding conditions: Presenting pictures with words benefited older adults more than younger adults; word generation benefited both groups equally; and presenting sound effects with visual words benefited younger more than older adults. Experiments 3.1, 3.2, and 3.3 investigated age-related changes in retrieval processes and their interactions with retrieval contexts. In each of the three experiments, some of the test lists were constructed so that participants had to recollect specific aspects of the encoding event to differentiate between the to-be-included and to-be-excluded items, whereas other test lists were constructed so that they only had to recollect general aspects. Older adults showed reduced levels of recollection than younger adults for the high-specificity test lists only (Experiment 3.1). Encoding manipulations improved (Experiment 3.2) or reduced (Experiment 3.3) recollection performance but the effects did not interact with test, whereas DA at retrieval (Experiment 3.3) in younger adults partly mimicked aging. In summary, the six experiments showed that older adults have greater difficulties in spontaneously carrying out distinctive and integrative processes at encoding, and in accessing specific information at retrieval compared to their younger counterparts. These age-related changes further interact with the processing demanded or afforded by the encoding and retrieval conditions.

Nine experiments were conducted to explore pitch-time integration in music. In Experiments 1-6, listeners heard a musical context followed by probe events that varied in pitch class and temporal position. When evaluating the goodness-of-fit of the probe (Experiment 1), listeners’ ratings showed more influence of pitch class than of temporal position. The tonal and metric hierarchies contributed additively to ratings. Listeners again rated goodness-of-fit in Experiment 2, but with instructions to ignore pitch. Temporal position dominated ratings, but an effect of pitch consistent with the tonal hierarchy remained. Again, these two factors contributed additively. A speeded classification task in Experiments 3 and 4 revealed asymmetric interference. When making a temporal judgment (Experiment 3), listeners exhibited a response bias consistent with the tonal hierarchy, but the metric hierarchy did not affect their pitch judgments (Experiment 4). Experiments 5 and 6 ruled out alternative explanations based on the presence of pitch classes and temporal positions in the context, unequal numbers of pitch classes and temporal positions in the probe events, and differential difficulty of pitch versus temporal classification. Experiments 7-9 examined the factors that modulate the effect of temporal variation on pitch judgments. In Experiment 7, a standard tone was followed by a tonal context and then a comparison tone. Participants judged whether the comparison tone was in the key of the context or whether it was higher or lower than the standard tone. For both tasks, the comparison tone occurred early, on time, or late with respect to temporal expectancies established by the context. Temporal variation did not affect accuracy in either task. Experiment 8 used the pitch height comparison task, and had either a tonal or an atonal context. Temporal variation affected accuracy only for atonal contexts. Experiment 9 replicated these results and controlled for potential confounds. The findings imply that the tonal contexts found in typical Western music bias attention toward pitch, increasing the salience of this dimension at the expense of time. Pitch salience likely arises from long-term exposure to the statistical properties of Western music and is not linked to the relative discriminability of pitch and time.

The Uses of Objects Task is a widely used assessment of creative performance, but it relies on subjective scoring methods for evaluation. A new version of the task was devised using Latent Semantic Analysis (LSA), a computational tool used to measure semantic distance. 135 participants provided as many creative uses for as they could for 20 separate objects. Responses were analyzed for strategy use, category switching, variety, and originality of responses, as well as subjective measure of creativity by independent raters. The LSA originality measure was more reliable than the subjective measure, and values averaged over participants correlated with both subjective evaluations and self-assessment of creativity. The score appeared to successfully isolate the creativity of the people themselves, rather than the potential creativity afforded by a given object.

Cognitive impairment affects approximately half of multiple sclerosis (MS) patients. The Multiple Sclerosis Neuropsychological Questionnaire (MSNQ) has previously demonstrated validity for detecting cognitive impairment in MS, and is quick and easy to complete. The objective was to validate an internet version of the MSNQ. The following were completed at home over the internet for 82 MS patients: (a) patient self-report version of the MSNQ (P-MSNQ), (b) informant version of the MSNQ (I-MSNQ), and (c) Centre for Epidemiological Studies Depression Scale (CES-D). Thereafter, patients completed in-office neuropsychological testing using the Brief Repeatable Battery of Neuropsychological Tests (BRB-N). Both the P-MSNQ and I-MSNQ were highly correlated with depression. The best-cut off score on the I-MSNQ was a 26, which gave a sensitivity of 72% and 60% for detecting cognitive impairment on the BRB-N. Given the modest sensitivity and specificity values, the MSNQ is not recommended for neuropsychological screening purposes over the internet.

Impaired social interaction is one of the hallmarks of autism spectrum disorders (ASDs). Emotional faces are arguably the most critical visual emotional stimuli and the ability to perceive, recognize, and interpret emotions is central to social interaction and communication as well as healthy development. There is however, a paucity of studies devoted to neural and cognitive mechanisms underlying emotional face processing in adolescents with ASD. Through an implicit emotional face processing task completed in the MEG, we examined spatiotemporal differences in neural activation during angry and happy emotional face processing. Results suggest atypical frontal involvement in ASD adolescents during angry and happy face processing. In particular, orbitofrontal activation in participants with ASD was found to be delayed but greater in amplitude, relative to controls.

The objective of this research was to investigate the extent to which context contributes to the learning and recognition of episodic auditory-verbal memories (EAM). By combining the Hebb repetition paradigm (HRP) and continuous recognition paradigm (CRP), I capitalized on the advantages of both while manipulating the context in which EAM were retrieved. Through repetition, participants learned sequences of pseudowords in which word order and speaker were varied. A recognition test of either a pseudoword (Experiment I) or the speaker of a pseudoword (Experiment II) revealed temporal and sensory context effects. Results showed that the encoding manipulation did not impact short-term memory but did have an effect on long-term learning. This research helped to clarify the role of context in EAM in both short- and long-term memory, as well as added to the current literature of HRP and CRP. Future directions are discussed.