Digital Commons Network^™

The Impact Of Emotional Sounds On Arousal And Task Performance, Brian Wu

Electronic Thesis and Dissertation Repository

In times of emotional arousal, it is hypothesized that neural processes are triggered to “heighten” our senses to better respond to threatening stimuli. Some studies have tested this by exposing participants to emotional sounds to determine their impacts on visual acuity but have found mixed results. Previous studies have not investigated interactions between arousal induced by emotional sounds and visual acuity. Participants (N = 42) performed an orientation detection task while presented in silence or with sounds that varied in valence. Results displayed comparable accuracy across conditions but significantly faster response times during the presentation of negative sounds on the …

Towards Understanding And Improving Speech Processing, Sonia Yasmin

Electronic Thesis and Dissertation Repository

This dissertation explores mechanisms for understanding and improving speech processing. First, I used EEG to investigate the acoustic and semantic processing of continuous naturalistic speech masked by multi-talker babble. I found that different features of the same speech signal are reflected in different aspects of the neural tracking response, which are themselves differentially affected by noise. These findings point to a complex relationship between speech intelligibility and neural speech encoding.

Next, I systematically reviewed the current advancements in speech enhancement technologies. I find that speech enhancement algorithms are limited in their generalizability to speech-noise (i.e., babble). I demonstrate that, for …

Frontoparietal Circuitry Underlying Saccade Control In The Common Marmoset, Janahan Selvanayagam

Electronic Thesis and Dissertation Repository

Our visual world is full of far more stimuli than can be processed simultaneously. Yet we are able to efficiently extract behaviourally relevant information from a scene, primarily by performing rapid saccadic eye movements. These processes are under the control the frontoparietal network, two critical nodes of which are: the lateral intraparietal area (LIP) and the frontal eye fields (FEF). Extensive research in the macaque has causally implicated these areas in visual attention and oculomotor control. However, the organization of the activity of single neurons in these areas across cortical layers remains poorly understood as these regions are deep within …

Neural Responses To Magnetic Orientation Information In Songbirds, Madeleine Ir Brodbeck

Electronic Thesis and Dissertation Repository

Effective navigation and orientation is essential for animals to survive. The study of migratory birds provides insights into these processes, particularly through mechanisms like the geomagnetic compass, which uses Earth's magnetic field for directional information. A brain region in songbirds relevant to this is cluster N, known for its potential role in processing geomagnetic information. Notably, cluster N appears exclusive to nocturnally migratory birds, being active solely at night, and lesion studies reveal that an intact cluster N is necessary for geomagnetic compass orientation. However, given the scarcity of empirical data concerning cluster N, substantial questions persist regarding its function. …

Selective Recruitment Of Cerebellum In Cognition, Ladan Shahshahani

Electronic Thesis and Dissertation Repository

Previous studies of cerebellar function in humans have shown that it is activated by a myriad of tasks ranging from motor learning and language to working memory and more. These studies have prompted a deviation from the traditional view of the cerebellum as a purely motor structure. However, the precise contribution of the cerebellum to these tasks remains ambiguous.

A prevalent assumption in fMRI studies is interpreting BOLD activation as evidence of the cerebellum's involvement in specific tasks. However, this interpretation is potentially misleading, especially considering that the BOLD signal predominantly represents cerebellar input, with output activity largely absent. Consequently, …

White Matter Connectome Associations With Reading Functions In Children, Chenglin Lou

Electronic Thesis and Dissertation Repository

This thesis investigated associations between the white matter connectome and reading in children with a wide range of reading abilities. It is well established that the connectome supports the interplay among brain regions and connections within an integrated system. In this dissertation, I examine the hypothesis that it could therefore represent multiple mapping processes among reading components and further explain variations in reading performance. Such associations between the organization of the connectome and reading skills have not been well explored. This thesis aimed to address this issue by considering both the relationship between connectome measures and standardized reading performance out …

Fraction Magnitude Understanding Across Learning Formats: An Fmri Study, Chloe A. Henry

Electronic Thesis and Dissertation Repository

Knowledge of fraction magnitudes are an important, but notoriously difficult mathematical concept to master. Behavioural work has begun to explore and compare the instructional tools used for fraction learning. However, how fraction instructional tools are processed in the brain remains an underexplored question. Therefore, in the present thesis, we used functional brain MRI methodology to examine the neural activity of adult participants while completing a fraction verification task using the number line and area model, two common methods of fraction learning. We found that both models commonly recruited fronto-parietal activity, the neural regions typically implicated in number processing. However, we …

Investigating The Roles Of The Dorsal And Ventral Striatum In Humor Comprehension And Appreciation Throughout Health, Aging, And Parkinson’S Disease, Maggie Prenger

Electronic Thesis and Dissertation Repository

Humor processing is thought to involve two distinct components. The first, humor comprehension, involves detecting and resolving incongruities that are present within a humorous stimulus. This is related to cognitive processes such as ambiguity resolution, response inhibition, working memory, and cognitive flexibility, functions that are mediated in part by the dorsal portion of the striatum (DS). Humor appreciation, on the other hand, refers to the subjective amusement and mirth that one experiences in response to a joke. This is related to reward processing, which implicates the ventral portion of the striatum (VS). Across three separate studies, we investigated the involvement …

The Modulation Of Lfp Characteristics In The Freely Moving Common Marmoset, William Jm Assis

Electronic Thesis and Dissertation Repository

The hippocampus is a neural structure critical for navigation. Neurons in this region, along with others, create a functional network which generates large-amplitude modulations known as local field potential (LFP) activity. Prior LFP research has predominantly used rodent animal models, however recent studies have shown that frequencies associated with navigation in other mammals do not correlate to those of the rodent. We hypothesized that LFP characteristics in the common marmoset are modulated by the speed and axis of travel of the animal. Two marmosets were placed in a free moving 3-dimensional environment where movement and neurological activity were recorded. Results …

Disentangling The Role Of Parvalbumin-Expressing Interneurons In Stimulus-Response Learning And Cognitive Flexibility, Harleen Rai

Electronic Thesis and Dissertation Repository

Habits enable animals to efficiently navigate their surroundings while tending to more cognitively demanding environmental factors. One mechanism underlying habit is known as stimulus-response (S-R) learning, which takes place in the dorsolateral striatum (DLS). However, there is limited knowledge regarding the complex striatal microcircuits involved in S-R learning and cognitive flexibility. Recently, attention has turned toward the GABAergic Parvalbumin-expressing (PV) interneurons that can modulate striatal outputs. Here, we utilized chemogenetic techniques and touchscreen cognitive assessments to analyze the influence of PV neurons on S-R learning in mice. When PV neurons were inhibited, during the acquisition of a S-R and cognitive …

Category Learning Dlpfc Single-Dissociation By Fnirs, Tim Qiu

Electronic Thesis and Dissertation Repository

It remains an open question whether modern neuroimaging clearly dissociates the Explicit system that learns by encoding rules, and the Implicit system that learns by encoding information-integration boundaries. Further, there are nearly no applications of fNIRS as a modality in studying category learning. We conduct two behavioural experiments to validate a carefully controlled categorization task intended to dissociate Explicit and Implicit systems. Then we apply fNIRS neuroimaging within-subjects to localize a neuroanatomical dissociation. We localized two effects to R DLPFC (1) a simple single-dissociation of higher activity in RB categorization, and (2) a negative relationship between overall task performance and …

Shedding Light On Hearing In Coma: Investigating The Applicability Of Functional Near-Infrared Spectroscopy For Assessing Auditory Function And Aiding Prognosis In Patients With Acute Disorders Of Consciousness, Reza Moulavi Ardakani

Electronic Thesis and Dissertation Repository

There is a critical need for a bedside neuroimaging tool to aid in the prediction of functional recovery outcomes for patients with acute disorders of consciousness (DoC) in the early days following severe brain injury. Current neurobehavioral examinations and prognosis tools have limitations in predicting good outcomes, leading to potential mistreatment or premature withdrawal of life support. Functional near-infrared spectroscopy (fNIRS) is a viable candidate for such purposes due to its portability and cost-effectiveness. Auditory processing, viewed as a multi-level and multifaceted brain function, could provide a sensitive and specific marker of residual cognitive function in unresponsive patients. This study …

Postexercise Executive Function And Cortical Hemodynamics During The Different Phases Of The Menstrual Cycle, Priyanka Persaud

Electronic Thesis and Dissertation Repository

Resting cerebral blood flow (CBF) is increased during the luteal (LUT) phase of the menstrual cycle; however, it is unclear whether this change impacts a postexercise executive function (EF) benefit. Female participants (N=16) performed three experimental sessions: a V̇O_2peak task and 20-min single bouts of moderate intensity aerobic exercise (i.e., 80% of lactate threshold) during their follicular (FOL) and luteal (LUT) menstrual cycle phases. A separate group of male participants (N=21) additionally completed a V̇O_2peak test and a 20-min exercise intervention. Middle cerebral artery velocity (MCAv) was measured during exercise via transcranial Doppler ultrasound to estimate CBF and …

Maturation Of Default Mode Network Functional Connectivity Strength In Utero And The Association With Subcortical Macrostructure: Mapping Brain Ontogeny Supporting Early Cognitive Processing, Susana Correa

Electronic Thesis and Dissertation Repository

The third trimester of gestation is scarcely studied despite this being a key window for the development of learning and memory systems. In a prospective cohort study, 30 pregnant women participated in one or two fetal MR imaging sessions between 28- and 39 weeks of gestational age. Activation time courses were extracted from the default mode (DMN), medial temporal lobe (MTL), and thalamocortical (TCN) networks of the fetal brain. Generalized estimating equations were used to examine the association between the DMN-MTL, DMN-TCV connectivity strength, and subcortical volumes. Increased functional connectivity strength between the DMN-MTL networks was negatively associated with smaller …

Perceptual Benefits From Long-Term Exposure To Naturalistic Sound Patterns, Bruno A. Mesquita

Electronic Thesis and Dissertation Repository

Our brains are proficient in learning recurring structures in the environment, in order to optimize perceptual inferences based on relevant information in a stochastic input. Sensory information is multi-dimensional, and the relationship between sound dimensions may be, in itself, a source of information. Many sounds in our environment covary dynamically, and these covariances may be learned, and therefore shape our perception, through exposure to them in our natural environment. In the present study we investigate how natural (long term), and experimental (short term), learning of statistical regularities in sounds may shape our ability to categorize them (Experiment 1) and to …

Postexercise Executive Function Benefits And Cerebral Blood Flow: In The Lab And At Home, Benjamin Tari

Electronic Thesis and Dissertation Repository

A single bout of aerobic exercise improves executive function; however, the mechanism, or mechanisms, supporting this improvement remain unclear. One candidate mechanism is an exercise-mediated increase in cerebral blood flow (CBF) that enhances the efficiency of executive-related frontoparietal networks. To evaluate the link between exercise, CBF and executive function, three separate experiments were conducted. In the first study, separate 10-min sessions of moderate-to-heavy-intensity aerobic exercise, and a hypercapnic environment (i.e., 5% CO₂) were implemented. The hypercapnic condition was included because it increases CBF independent of the metabolic demands of exercise. The second study investigated whether exercise intensity-specific changes …

The Effect Of Active Learning On Viewpoint Dependence For Novel Objects, Cassandra Wallace Bacher

Electronic Thesis and Dissertation Repository

Active learning of novel objects can facilitate subsequent object recognition and discrimination, but the reasons for its beneficial effects remain unclear. One potential explanation is that active learning enables the formation of a more detailed, realistic, or useful neural object representation than does passive learning. The current study addressed the question of whether active vs. passive learning of objects affects viewpoint discrimination. Participants learned novel wire-like objects either actively or passively and then completed a psychophysical task which they discriminated object orientation. This study did not find a significant difference in viewpoint discrimination between actively and passively learned object representations, …

Using Machine Learning To Identify Neural Mechanisms Underlying The Development Of Cognition In Children And Adolescents With Adhd, Brian Pho

Electronic Thesis and Dissertation Repository

Childhood and adolescence are marked by improvements to cognition and by the emergence of neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD). What neural mechanisms are associated with cognitive development in ADHD? In this study, I applied machine learning models to functional connectivity profiles to identify patterns of network connectivity that predict various cognitive abilities in a group of participants ages 6 to 16 with ADHD. The models successfully predicted IQ, visual spatial, verbal comprehension, and fluid reasoning in children ages 6 to 11, but not adolescents. Furthermore, the models identified connections with the default mode, memory retrieval, and …

The Express Sensorimotor Response Selects Visual Features Based On Instruction, David Youhanna Mekhaiel

Electronic Thesis and Dissertation Repository

In time-sensitive situations, orienting reflexes allow us to move rapidly in response to stimuli. The express sensorimotor response (ESR) is an orienting reflex presenting as a brief burst of muscle recruitment. Previous studies have identified commonalities between ESRs and express saccades, another orienting reflex.

In this study, we investigate if ESRs share in a characteristic of express saccades: preference for faces. In separate blocks, participants were instructed to reach toward one of two simultaneously appearing targets: a face and another image. Muscle activity in the pectoralis major muscle of the reaching arm was recorded using skin surface EMGs.

We …

Human Neuroimaging Reveals That Agency In A Video Game Boosts Functional Connectivity Within And Between Networks, Emily J. Davidson

Electronic Thesis and Dissertation Repository

In naturalistic settings, brains continuously interface with a dynamic and interactive external environment. The inclusion of such an environment in an fMRI study is difficult, given the practical constraints imposed by the machine itself. This study sought to test whether the ecological validity of fMRI could be enhanced by testing a new paradigm that incorporated a dynamic and interactive virtual environment (DIVE). To determine the viability of this paradigm, functional connectivity was assessed during a DIVE condition and compared to functional connectivity patterns acquired in conditions with equally dynamic stimuli but that lacked interactivity with the environment. This study found …

The Effect Of Propionic Acid On The Habituation To Social And Non-Social Odour Cues In Adult Male Rats, Cashmeira-Dove P. Tyson

Electronic Thesis and Dissertation Repository

The enteric bacterial metabolite, propionic acid (PPA), elicits physiological and behavioural changes in rodents reminiscent of autism spectrum disorder (ASD). This includes abnormal sensory processing and social behaviour. ASD may contribute to social deficits through impaired habituation; therefore, the present study examined the effects of intraperitoneal PPA on the habituation to social and non-social odours. Adult male rats were injected daily with PPA or the vehicle control, and for 3 days, habituated to a conspecific odour or vanilla extract for 10 minutes. On day 4, rats were exposed to a novel conspecific odour or almond extract for 10 minutes to …

Examining The Relationships Between Socio-Cognitive Factors And Neural Synchrony During Movie Watching Across Development, Kathleen M. Lyons

Electronic Thesis and Dissertation Repository

While different cognitive abilities mature, the conscious experiences of children likely become richer and more elaborate. A challenge in investigating relationships between cognitive development and real-world experiences is having measures that assess naturalistic processing. Movie watching offers a solution, since following the plot of a film requires cognitive processes that are similar to real-world experiences. When different adults watch the same film, their brain activity begins to align (known as neural synchrony). The strength of this alignment has been shown to reflect the degree to which different individuals are having a similar experience of the movie. While this phenomenon has …

Role Of The Default-Mode Network During Narrative Integration In Major Depressive Disorder, Darren Ri-Sheng Liang

Electronic Thesis and Dissertation Repository

How brain activity is synchronized across individuals during narrative comprehension has previously been characterized by functional magnetic resonance imaging (fMRI) in healthy and patient populations. To our knowledge, there has been limited investigation as to how it is affected by major depressive disorder (MDD). We addressed this issue with fMRI through examination of inter-subject synchronization in the default mode network (DMN), brain structures which have previously been implicated in MDD pathology. Twenty-two patients with MDD and 20 matched control participants listened to Intact versus Scrambled versions of an auditory narrative; these experimental conditions differed in the degree of temporal integration …

The Effects Of Transcranial Direct Current Stimulation On Beat Perception And Motor Performance, Marina Emerick

Electronic Thesis and Dissertation Repository

Humans have an intrinsic tendency to move to music. However, our understanding of the neural mechanisms underlying the music-movement connection remains limited, and most studies have used correlational methods. Here, we used transcranial direct current stimulation (tDCS) to causally investigate the role of four motor brain regions involved in movement timing and beat perception: the supplementary motor area (SMA), left and right premotor cortices (PMC), and cerebellum. Subjects were randomly assigned to a brain region to be stimulated and received anodal, cathodal, or sham stimulation on three different days while they reproduced rhythmic sequences. The sequences had either a strong …

Resistance Training Improves White Matter Structural Connectivity In Older Adults At-Risk For Cognitive Decline, Ryu Lien

Undergraduate Student Research Internships Conference

Diabetes is a global health concern that impacts 415 million people worldwide. Individuals who are at-risk for diabetes (characterized by high blood glucose and/or being overweight) have white matter atrophy, decreased cognitive function, and an increased risk of Alzheimer’s disease (AD). Recently, resistance training (RT) has been shown to lower white matter atrophy and white matter lesion volume. However, investigating changes in white matter tracts is complex, hence previous findings remain inconclusive. Diffusion tensor imaging (DTI) serves as a highly sensitive tool that enables visualization and characterization of white matter tracts and has the potential to combat this complexity. The …

Human Claustrum Activation During Pain, Zoravar S. Sidhu, David A. Seminowicz, Brent W. Stewart

Undergraduate Student Research Internships Conference

Chronic pain is one of the principal causes of disability in the world. Many if not all of us deal with or know of someone who deals with chronic pain. Interestingly, it appears that a mysterious part of the brain known as the claustrum has a hand in chronic pain. Although little is known about the actual function of the claustrum, it is hypothesized to synchronize cortical networks during tasks which have a cognitive load.

Recent literature has indicated that during chronic pain conditions, neural network recruitment is modified. In addition, an analysis of an existing fMRI data set determined …

Assessing The Impact Of Lipopolysaccharide On Learning And Memory In Rats, Anahat Luthra

Undergraduate Student Research Internships Conference

The immune system and the central nervous system (CNS) have a bi-direction relationship, modulating one another.⁴ Proinflammatory cytokines released from CNS immune cells have an impact on cognitive processes such as learning and memory.¹ Liposaccharide (LPS), a cell wall component of Gram-negative bacteria, which is used to activate proinflammatory cytokine release has been found to impact learning and memory processes, such as in the anticipatory nausea paradigm (ANP).² Anticipatory nausea and vomiting is that which may occur before a chemotherapy treatment session begins in a patient who has had chemotherapy before. It is caused by triggers like …

Functional Neuroimaging Techniques To Examine Falls And Cognition In Older Adults: A Systematic Review, Tia M. Seleem, Raphael Gabiazon

Undergraduate Student Research Internships Conference

Falls in older adults have been attributed to impaired cognition. There is potential for neuroimaging techniques to understand the biological components that are involved in the cognitive processes pertaining to falls. Therefore, the purpose of this systematic review was to analyze how functional neuroimaging can be used to examine the relationship between falls and cognition among older adults. The following five electronic databases were selected to identify peer-reviewed articles in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: 1) Medline (via OVID), 2) PsycINFO (via OVID), 3) CINAHL (via EBSCO), 4) EMBASE (via OVID), and 5) Pubmed. …

Using A Musical Beat To Influence Linguistic Statistical Learning, Aspen Leung

Undergraduate Student Research Internships Conference

The similarities between music and language continue to provide research questions in the area of psychology. Despite the large amount of research on this area of knowledge, there are still many existing questions in regards to the processing of musical and linguistic stimuli. Statistical learning involves the ability to extract statistical regularities from a stimulus and continues to be studied in both domains due to the similar hierarchical structure of music and language. Recently, neural entrainment (the synchronization of neural oscillations with the rhythm of an external stimulus) has been studied as a mechanism of statistical learning. Music has been …

The Ommaba Project, Katsiaryna Buchko

Undergraduate Student Research Internships Conference

The Open Multimodal Music and Auditory Brain Archive (OMMABA) is the first multimodal (behavioural, EEG, and neuroimaging) database characterizing normal human auditory processing. My project aims to shed light on the importance of this collaborative project that is transforming the field of auditory cognitive neuroscience.