Life Sciences Commons^™

The Effects Of Concurrent Cognitive Load On The Processing Of Clear And Degraded Speech, Harrison Ritz

Electronic Thesis and Dissertation Repository

A previous study has found that perceiving degraded speech requires attention, with compromised behavioral and neurological measures of speech processing for degraded speech, but not clear speech, when participants are distracted (Wild et al., 2012b). We extended these findings by examining behavioral and neural correlates of speech perception under different levels of cognitive load using multiple object tracking. We also investigated the role of attention in perceiving degraded speech that was as intelligible as clear speech, in order to separate perceptual outcomes (i.e., intelligibility) from the requisite processing demands. We found that the speech perception system is heterogeneous in its …

Pharmacogenetics Of Non-Motor Symptoms In Parkinson's Disease, Brian Robertson

Electronic Thesis and Dissertation Repository

Memory deficits are recognized in Parkinson’s disease (PD). The nature of these memory deficits is unclear because few studies have both isolated memory encoding and retrieval processes while testing patients on and off their dopamine replacement medication. Previous work suggests encoding depends upon regions innervated by the ventral tegmental area, which is relatively spared in PD, while retrieval depends upon dorsal striatum, which is dopamine deficient even early in PD. We investigated the impact of a dopamine transporter (DAT1), a dopamine reuptake protein, polymorphism (a 40-base-pair variable repeat affecting expression) on encoding and retrieval in healthy, elderly controls as well …

The Role Of Forebrain Cholinergic Signalling In Regulating Hippocampal Function And Neuropathology, Mohammed Al-Onaizi

Electronic Thesis and Dissertation Repository

Cholinergic dysfunction has been associated with cognitive abnormalities in a variety of neurodegenerative and neuropsychiatric disorders, including Alzheimer’s Disease (AD). Cumulative use of drugs with anticholinergic activity is associated with increased risk for dementia and AD. Also, cholinergic function has been implicated in predicting the development of key neuropathological hallmarks seen in AD. However, the relationship between cholinergic dysfunction and conservation of cognitive ability as well as neuronal cell maintenance is not fully understood. Here, we tested how information processing and distinct molecular mechanisms associated with AD are regulated by cholinergic tone in genetically-modified mice in which cholinergic transmission was …

The Neural And Cognitive Basis Of Cumulative Lifetime Familiarity Assessment, Devin Duke

Electronic Thesis and Dissertation Repository

Perirhinal cortex (PrC) has been implicated as a brain region in the medial temporal lobes (MTL) that critically contributes to familiarity-based recognition memory, a process that allows for recognition to occur independently of contextual recollection. Informed by neurophysiological research in non-human primates, fMRI, as well as behavioural work in humans, the current thesis research tests the novel hypothesis that PrC cortex functioning also underlies the ability to assess cumulative lifetime familiarity with object concepts that are characterized by a lifetime of experiences. In Chapter 2, a patient (NB) with a left anterior temporal lobe (ATL) lesion that included PrC as …

Classifying Music Perception And Imagination Using Eeg, Avital Sternin

Electronic Thesis and Dissertation Repository

This study explored whether we could accurately classify perceived and imagined musical stimuli from EEG data. Successful EEG-based classification of what an individual is imagining could pave the way for novel communication techniques, such as brain-computer interfaces. We recorded EEG with a 64-channel BioSemi system while participants heard or imagined different musical stimuli. Using principal components analysis, we identified components common to both the perception and imagination conditions however, the time courses of the components did not allow for stimuli classification. We then applied deep learning techniques using a convolutional neural network. This technique enabled us to classify perception of …

Cannabinoid Cb1 Transmission In The Mesolimbic Reward Pathway, Tasha Ahmad

Electronic Thesis and Dissertation Repository

Cannabinoid CB1 receptor (CB1R) transmission within the mesocorticolimbic system plays an important role in forming associative memories, and processing both positive and negative experiences. Opiates generally produce potent rewarding effects and previous evidence suggests that CB1 transmission may modulate the neural reward circuitry involved in opiate reward processing. The ventral tegmental area (VTA), medial prefrontal cortex (mPFC), basolateral amygdala (BLA), and Nucleus Accumbens (NA) are all implicated in opiate-reward processing, contain high levels of CB1 receptors, and are all modulated by dopamine (DA). Although, CB1 transmission within these areas has been heavily implicated in associative memory and learning, the potential …

Exploring And Training Spatial Reasoning Via Eye Movements: Implications On Performance, Victoria A. Roach

Electronic Thesis and Dissertation Repository

This dissertation sought to determine if eye movements could serve as an indicator of success in spatial reasoning, and if eye movements associated with successful completion could be applied to strategically improve spatial reasoning.

Using the line images of Shepard and Metzler, an electronic test of mental rotations ability (EMRT) was designed. Two versions of the test were created, allowing for both a timed (6 seconds per question) and untimed testing environment. Four experiments were designed and completed to relate mental rotation ability (MRA) scores from the EMRT, to patterns in chrononumeric and visual salience data. In each experiment, participants …

Seasonality Of The Stress Response In House Sparrows (Passer Domesticus)., Michael R. Hasstedt

Electronic Thesis and Dissertation Repository

Seasonal changes in plasma corticosterone (CORT) levels indicate that birds modify their stress response through the year. Although this has been well documented, the method by which birds achieve this seasonality is not well understood. In this study I used house sparrows to determine if changes in glucocorticoid receptor (GR) immunoreactivity in several stress-related brain nuclei showed seasonal variation. The house sparrowsshowed seasonal variation in their stress response with baseline CORT levels being highest during the breeding season and lowest during winter. There was also significant change in plasma CORT post-dexamethasone during breeding, but not during other times of the …

Laminar Fmri In Auditory Cortex At 7t, Jacob Jl Matthews

Electronic Thesis and Dissertation Repository

Auditory cortex is involved in the perception, attention, memory and imagery of sounds. Neuroimaging has been a rich source of information on which cortical areas are recruited for different tasks. However, a more detailed understanding has been confined to animal studies using invasive imaging modalities, and high-resolution functional descriptions of auditory cortex, including columnar/laminar specific activity, topographical organization within layers, and the way these representations transfer between processing structures remain poorly understood in humans. We present 7T fMRI as a non-invasive tool for high-resolution functional imaging of human auditory cortex on the laminar scale. We describe MATLAB tools for optimizing …

Determining Attention Deficits In Mouse Models Of Alzheimer’S Disease Using Touchscreen Systems, Talal Masood

Electronic Thesis and Dissertation Repository

Behavioural testing in mouse models of Alzheimer’s disease (AD) suffers from lack of standardization and reproducibility issues between laboratories. In order to solve this, a touchscreen system has been developed for mice based on the CANTAB. There are several cognitive dysfunctions that occur due to AD, including deficits in attention that can be tested using the touchscreens. In this study, we tested two mouse models of familial AD (5xFAD and 3xTG) with mutations that lead to an accelerated rate of amyloidosis. Both male and female mice were tested at two separate locations in order to test for the reproducibility of …

Contribution Of The Dorsolateral Prefrontal Cortex To Attentional And Mnemonic Processes In Visual Search, Brandon Belbeck

Electronic Thesis and Dissertation Repository

A key characteristic of selective visual attention is that it may be deployed on the basis of our knowledge or goals of the task at hand. Here, we used cryogenic deactivation to investigate the contribution of the dorsolateral PFC to cognitive flexibility and working memory, as well as their relation to the deployment of attention. Macaque monkeys performed visual search tasks requiring them to foveate a target in an array of stimuli. These included a feature search, a constant-target conjunction search, a variable-target search and variable-target with delay search task, with each being more cognitively demanding than the last. Bilateral …

A Kinematic Analysis Of Visual And Haptic Contributions To Precision Grasping In A Patient With Visual Form Agnosia And In Normally-Sighted Populations, Robert Whitwell

Electronic Thesis and Dissertation Repository

Skilled arm and hand movments designed to obtain and manipulate objects (prehension) is one of the defining features of primates. According to the two visual system hypothesis (TVSH) vision can be parsed into two systems: (1) the ventral ‘stream’ of the occipital and inferotemporal cortex which services visual perception and other cognitive functions and (2) the ‘dorsal stream’ of the occipital and posterior parietal cortex which services skilled, goal-directed actions such as prehension. A cornerstone of the TVSH is the ‘perception-action’ dissociation observed in patient DF who suffers from visual form agnosia following bilateral damage to her ventral stream. DF …

Category-Specific Item Recognition And The Medial Temporal Lobe, Christopher B. Martin

Electronic Thesis and Dissertation Repository

Much neuropsychological and neuroimaging research has been focused on the contributions of different medial temporal lobe (MTL) structures to recognition memory. The majority of these studies have linked perirhinal cortex (PrC) to item recognition, whereas the hippocampus and parahippocampal cortex (PhC) have primarily been associated with the recollection of contextual detail pertaining to a specific prior stimulus encounter. Here, I report results from three fMRI studies that examined the neural correlates of item recognition with a specific focus on the relationship between such signals and category-specific effects in the MTL. In Chapter 2, I reveal that category-specific representations in both …

The Relationship Between Dairy Product Consumption And Cognitive Performance In A Group Of Community-Dwelling Healthy Older Adults, Mariam R. Ismail

Electronic Thesis and Dissertation Repository

Dietary intake is one of the modifiable factors that may affect older adults’ cognitive function in their later years. Very little research has considered the potential role of dairy products on cognitive function. The aim of the present study was twofold: first, to investigate whether there is a difference in cognitive performance between older adults who consumed the recommended amount of dairy products (3 servings per day) and individuals who consumed less than the recommended amount (1 or 2 servings per day); second, to examine whether there is an association between the nutrients contained in the dairy products and cognitive …

Neural Correlates Of Spontaneous Bold Fluctuations: A Simultaneous Lfp-Fmri Investigation In The Non-Human Primate, Masoomeh Hashemi

Electronic Thesis and Dissertation Repository

Resting-state functional magnetic resonance imaging (rs-fMRI) is widely used to explore functional connectivity (FC) between brain regions across neurological and psychiatric diseases. However, the neural basis of spontaneous low frequency blood-oxygen level dependent (BOLD) fluctuations is poorly understood.

Here, we acquired rs-fMRI data in macaque monkeys together with simultaneous recordings of local field potentials (LFPs) in prefrontal cortex area 9/46d. We first evaluated the correlation between LFPs (1-100 Hz) and BOLD signals and found unique frequency power correlates of positive and negative FC. Anti-correlation of high and low power envelopes indicated that ongoing cross-frequency interactions are a neural correlate of …

Characterizing Persistent Developmental Dyscalculia: A Cognitive Neuroscience Approach, Stephanie D. Bugden

Electronic Thesis and Dissertation Repository

Developmental dyscalculia (DD) is a specific learning disorder of calculation abilities. In the present thesis I report a series behavioural and functional neuroimaging studies to further elucidate the core numerical deficits underlying DD. I recruited a sample of children with DD who demonstrated persistent impairments in arithmetic. In Chapter 2, to validate the selection criteria, I compared the performance of children with and without persistent DD on a test of numerical magnitude processing. The data showed that only children with persistent DD presented with deficits in numerical magnitude processing, while those with inconsistent DD perform at the level of age-matched …

Mindfulness Meditation Versus Eeg-Alpha Neurofeedback: The Role Of Eeg-Alpha Enhancement In Attentional Control, Theodore Chow

Electronic Thesis and Dissertation Repository

This thesis directly compared two active interventions known to enhance the EEG-Alpha rhythm, mindfulness meditation (MM) with EEG-Alpha enhancement neurofeedback (NFB), relative to a non-active Sham-NFB control. Seventy-three university students were randomized to one of the three 15-minute single-session interventions. Participants were subsequently compared on their ability to enhance EEG-Alpha amplitude as well as regarding Stroop behavioural performance, EEG event-related potentials, and EEG-Alpha event-related desynchronization (ERD) as markers of attentional control. Participants randomized to MM, NFB, and Sham did not differ in their ability to modulate the EEG-Alpha rhythm post-intervention. However, enhancements in EEG-Alpha amplitude were seen within the MM …

Investigating The Primate Prefrontal Cortex Correlates Of Cognitive Deficits In The Ketamine Model Of Schizophrenia, Kevin J. Skoblenick

Electronic Thesis and Dissertation Repository

The World Health Organization has classified schizophrenia as one of the five leading causes of disability worldwide. Afflicting almost 1% of the world’s population, the disease’s greatest impact stems from its reduction in patients’ cognitive faculties. In order to better study these impairments, a pharmacological model has been developed using the NMDA antagonist, ketamine. This disease model successfully recreates the cognitive dysfunction of schizophrenia, allowing researchers to search for associated electrophysiological changes.

In this project I examined the behavioural and neurophysiological effects of ketamine on non-human primates performing the anti-saccade task. Success in this task requires a degree of cognitive …

Revisiting Working Memory: Are Domain, Process And Global Models Mutually Exclusive, Nested Or Orthogonal?, Jeffrey P. Wong

Electronic Thesis and Dissertation Repository

Working memory (WM) is a cognitive function whereby task-relevant information is actively maintained and manipulated in mind for goal-directed behaviour. Three competing models, here dubbed the global, domain and process models, have attempted to explain its neural underpinnings. Despite extensive research however, no consensus has been reached. Here, we use two new WM paradigms to demonstrate that all three models are partially correct. In the first experiment, our results show that selected frontoparietal regions (MD), from the global model, are largely stimulus-independent. However, more posterior and caudal frontoparietal regions show stimulus-dependent activations as described by the domain model. In the …

When Faces "Feel" Familiar: The Role Of Affective Signals In Face Recognition, Lauren E. Dunphy

Electronic Thesis and Dissertation Repository

Previous research has suggested that there may be an increase in positive affect and autonomic arousal in response to seeing a familiar face. These studies rarely distinguish between faces for which there is only a “feeling” of familiarity, and faces for which this feeling is accompanied by the retrieval of semantic knowledge about the individual. In the current study we aimed to make that distinction. Participants made recognition judgments on famous and non-famous faces while galvanic skin responses (GSR), zygomatic muscle activity, and heart rate (HR) were recorded. We found increases in GSR (autonomic arousal), and zygomatic muscle activity (positive …

Reaching For The Light: The Prioritization Of Conspicuous Visual Stimuli For Reflexive Target-Directed Reaching, Daniel K. Wood

Electronic Thesis and Dissertation Repository

The degree to which something stands out against the background of its environment communicates important information. The phenomenon of camouflage is a testament of the degree to which visual salience and probability of survival tend to overlap. Salient stimuli often elicit fast, reflexive movements in order to catch prey or avoid a predator. The overarching goal of the work presented in this thesis is to investigate how the physical salience of visual stimuli influence the programming and execution of reaching movements. I approached this question by recording kinematics and muscle responses during reaching movements. Broadly, this thesis investigates the effect …

Contribution Of Trpm2 To Memory Loss In An Alzheimer's Mouse Model, Megan M. Chen

Electronic Thesis and Dissertation Repository

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the progressive deterioration of memory and other intellectual abilities. Accumulation of amyloid-β (Aβ) peptide, the major contributor to the senile plaques central to AD, is thought to mediate neurotoxicity by inducing oxidative stress and calcium dysregulation. Transient Receptor Potential Melastatin type 2 (TRPM2) is a calcium permeable, non-selective cation channel activated under oxidative stress and ultimately induces cell death. The APPSWE/PSEN1ΔE9 double transgenic mouse model carries the human APPswe (Swedish mutations K594N/M595L) and PS1 mutations with a deletion in exon 9 (PS1-dE9), and is one of the most commonly used AD …

Taking Tone Into Account: Cognitive Neuroscientific Investigations Of Mandarin Chinese Spoken Word Processing, Jeffrey G. Malins

Electronic Thesis and Dissertation Repository

To date, theories of how humans recognize spoken words have yet to account for tonal languages such as Mandarin Chinese. One reason for this is that we know relatively little about how native speakers of tonal languages process spoken words in the brain. This dissertation addresses this problem by examining Mandarin spoken word processing in both adult native speakers and typically developing children. In adults, functional magnetic resonance imaging (fMRI) was used to assess the extent to which the brain regions involved in processing tonal information are distinct from those involved in vowel processing (Chapter 2), while event related potentials …

Neural Circuits Involved In Mental Arithmetic: Evidence From Customized Arithmetic Training, Christian Battista

Electronic Thesis and Dissertation Repository

An arithmetic training study was conducted using a novel paradigm known as Customized Arithmetic Training (CAT). Using the CAT system, self-reports obtained from the participants were used to generate individually tailored problem sets. These problem sets balanced strategy use such that each participant started with an equal amount of problems solved by fact retrieval (e.g., 2 + 2 = 4) and an equal amount of problems solved by procedural calculation (e.g., 34 + 37). Following the training period, participants solved trained and untrained problems from their customized arithmetic sets while undergoing an fMRI scan, after which they again provided self-reported …

A P300 Based Cognitive Assessment Battery For Severely Motor-Impaired And Overtly Non-Responsive Patients, Aaron M. Kirschner

Electronic Thesis and Dissertation Repository

Diagnosing disorders of consciousness (DOC) is notoriously difficult, with estimates of misdiagnosis rates as high as 40%. Moreover, recent studies have demonstrated that patients who do not show signs of volitional motor responses can exhibit preserved command following detected by functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Although these patients clearly retain some cognitive abilities, lack of consistent motor responses makes administration of standard neuropsychological tests impossible. Consequently, the extent of their cognitive function is unknown. In the current study, we developed and validated a P300b event related potential (ERP) neuropsychological battery in healthy participants to assess components of …

Toxin-Induced Gustatory Conditioning In Rats: Examining The Effects Of Low Dose Toxins In Food On Rat Feeding Behaviour And Avoidance Conditioning, Amber N. Good

Electronic Thesis and Dissertation Repository

Foraging animals must learn which foods in their environment will maximize their nutritional needs but minimize the amount of ingested toxins. These animals rely on the integration of sensory and gustatory information and post-ingestive feedback from the foods they consume. Gustatory conditioning can be studied by using the conditioned taste avoidance paradigm and the toxin LiCl. This thesis first examined the dose related effects of low levels of LiCl on the ingestion of different palatable sucrose and salt solutions. The present findings support the hypothesis that rats use a behavioural tolerance mechanism to regulate their intake of foods containing low …

The Influence Of Proficiency And Age Of Acquisition On Second Language Processing: An Fmri Study Of Mandarin-English Bilinguals, Emily S. Nichols

Electronic Thesis and Dissertation Repository

Research investigating the neural correlates of second language (L2) processing has usually studied age of acquisition (AoA) and proficiency separately. Presently, we examined both in parallel, treated as continuous variables. We used fMRI to study neural activity for L2 processing in adult native Mandarin speakers who are L2 English speakers. Behavioral measures of language proficiency and AoA were obtained from subjects prior to performing a picture-word matching task during an fMRI scan. Brain activity during L2 English processing was shown to be independently affected by AoA and proficiency; activity in left superior temporal gyrus and right parahippocampal gyrus was modulated …

Flexibly Adapting To Emotional Cues: Examining The Functional And Structural Correlates Of Emotional Reactivity And Emotion Control In Healthy And Depressed Individuals, Steven G. Greening

Electronic Thesis and Dissertation Repository

The ability of emotionally significant stimuli to bias our behaviour is an evolutionarily adaptive phenomenon. However, sometimes emotions become excessive, inappropriate, and even pathological, like in major depressive disorder (MDD). Emotional flexibility includes both the neural processes involved in reacting to, or representing, emotional significance, and those involved in controlling emotional reactivity. MDD represents a potentially distinct form of emotion (in)flexibility, and therefore offers a unique perspective for understanding both the integration of conflicting emotional cues and the neural regions involved in actively controlling emotional systems.

The present investigation of emotional flexibility began by considering the functional neural correlates of …

Exploring The Neural Basis Of Top-Down Guided Action In Macaque Monkeys, Jessica M. Phillips

Electronic Thesis and Dissertation Repository

To thoroughly characterize any brain mechanism requires an appropriate animal model for invasive studies. An invaluable model system used toward a comprehension of cognitive neurophysiology is the macaque monkey. It is important to delineate similarities and limitations for this model in relation to the human brain and cognition. In this thesis, we have thus conducted three experiments to investigate putative generalizations between monkeys and humans regarding the neural processes associated with top-down action control in monkeys.

Our daily behaviour is largely comprised of automatic routine actions. The frequent repetition of certain behaviours in response to particular contexts can give rise …

Fmri Reveals The Neural Correlates Of Real And Pantomimed Tool Use In Humans, Joseph Umberto Paciocco

Electronic Thesis and Dissertation Repository

Although functional magnetic resonance imaging (fMRI) can be used to study the neural mechanisms underlying greatly expanded cognitive functions in humans like tool use, surprisingly little fMRI research has been done on actual tool use. In fact, due to technical constraints, most fMRI studies have used pantomimed actions as a proxy for real use. However, human neuropsychology patients who are impaired at pantomiming often improve when handling a tool suggesting potential neural differences. We used fMRI to record brain activation while 13 right-handed participants performed one of two tasks, real or pantomime tool use with one of two tools, a …