Life Sciences Commons^™

Direct Electrical Stimulation Of Prefrontal Cortex Modulates The Transient Heart Rate Response To Exercise In Conscious Humans, Bartek Kulas

Electronic Thesis and Dissertation Repository

Prefrontal cortical regions play an essential role in generating appropriate cardiovascular adjustments, particularly in cardio-vagally mediated heart rate (HR) responses to active tasks. Functional imaging studies provide correlational evidence that this region coordinates HR responses to exercise, however, direct experimental evidence of prefrontal cortical HR regulation in humans is not available. Seven persons with epilepsy implanted with intracranial electroencephalography (iEEG) completed 2-second isometric handgrip (IHG) contractions at no-stimulation (NO-STIM) or sham-stimulation (SHAM) conditions, and during direct electrical stimulation (STIM) of the orbitofrontal and medial prefrontal cortex. HR responses to IHG during NO-STIM and SHAM increased HR by Δ4.9±2.7 bpm, compared …

Motor Unit Firing Rate Control Of Agonist Skeletal Muscle During Voluntary Isometric And Shortening Contractions With Limb Movement, Eric A. Kirk

Electronic Thesis and Dissertation Repository

Voluntary movements throughout mammalian lifespan require skeletal muscle contractions that are controlled by time- and recruitment-dependent firing rate patterns. Single motor unit (MU) activity reflects the final efferent neural drive to the muscle, yet the underlying neural control of movement at the MU level is not well understood. Using intramuscular electromyography single MU recordings, relationships between voluntary contraction kinematics and MU firing rates were evaluated in vivo, in groups of young and older adult participants.

The purpose of study one was to characterize how MU firing rates are differently scaled among muscles relative to voluntary contraction intensity. Across 12 …

Microstructural Alterations In Grey And White Matter Following Early-Onset Deafness In The Cat, Alessandra Sacco

Electronic Thesis and Dissertation Repository

Following sensory deprivation such as deafness, compensatory plasticity underlies the reorganization of sensory-specific brain areas to process remaining intact modalities. Previous studies have explored microstructural consequences throughout the brain following auditory deprivation, including the effect of deafness on cerebral water diffusion. However, nearly all investigations have studied these neuronal changes in humans rather than animal models. The present study investigates microstructural differences between 19 hearing and 27 early-deaf cats via diffusion tensor imaging (DTI). Diffusivity scalars were compared within 155 grey and 21 white matter regions. Results indicate structural plasticity in various regions throughout the deaf brain in both tissues, …

Tracking The Mechanisms Of Short-Term Motor Adaptation Within The Framework Of A Two-State Model, Susan K. Coltman

Electronic Thesis and Dissertation Repository

The motor system is continuously monitoring our performance, ensuring that our actions are occurring as planned. Sensory prediction errors, which arise from a discrepancy between the expected and actual sensory consequence of a motor command (i.e., a planned action), are assumed to drive sensorimotor adaptation. Sensorimotor adaptation is thought to involve changes in motor output that allow the motor system to regain its former level of performance in perturbed circumstances. We employed experimental paradigms that involved both mechanical and visual perturbations to evoke sensory prediction errors while participants performed planar reaching movements. Movement error activates learning processes in the brain, …

Brain Representations Of Dexterous Hand Control: Investigating The Functional Organization Of Individuated Finger Movements And Somatosensory Integration, Spencer Arbuckle

Electronic Thesis and Dissertation Repository

Using our hands to manipulate objects in our daily life requires both dexterous movements and the integration of somatosensory information across fingers. Although the primary motor (M1) and somatosensory cortices (S1) are critical for these two complementary roles, it is unclear how neural populations in these regions functionally represent these processes. This thesis examined the functional organization of brain representations (the representational geometry) in M1 and S1 for dexterous hand control and somatosensory processing. To that end, representational geometries were estimated from fine-grained brain activity patterns measured with functional MRI (fMRI). Since fMRI measures a blood-based proxy of neural activity, …

Neural Substrates Of Reward, Error, And Effort Processing Underlying Adaptive Motor Behaviour, Dimitrios J. Palidis

Electronic Thesis and Dissertation Repository

Human motor control is highly adaptive to new tasks and changing environments. Motor adaptation relies on multiple dissociable processes that function to increase attainment of reward and to reduce sensory error and physical effort as costs. This thesis tests the hypothesis that fronto-striatal and dopaminergic neural systems contribute to specific aspects of motor adaptation that occur through reinforcement of rewarding actions.

Behavioral tasks were designed to isolate learning in response to feedback conveying information about reward, error, and physical effort. We also measured behavioral effects of savings and anterograde interference, by which memories from previous motor learning can facilitate or …

Spinal Excitability Changes Following Sensory Electrical Stimulation Of The Forearm, Devin K. Box

Electronic Thesis and Dissertation Repository

Sensory electrical stimulation can be used to suppress tremor in Parkinson’s disease. This study investigated the central mechanism underlying this suppression in healthy participants. Reciprocal inhibition (RI) of the wrist flexors before and after a session of sensory electrical stimulation (SES) applied to the antagonistic extensor muscles was assessed using electromyography. It was hypothesized that a 15-minute session of SES, rated by participants as a 3 on a 0-10 pain scale, would produce an increase in RI. Seven of the 18 participants experienced an increase in RI at 0-5 minutes post stimulation, which returned to baseline at 10-15 minutes. The …

Functional Loss Of Cntnap2 In The Rat Leads To Autism-Related Alterations In Behaviour And Auditory Processing, Kaela Elizabeth Scott

Electronic Thesis and Dissertation Repository

The contactin-associated protein-like 2 gene, CNTNAP2, is a highly penetrant gene thought to play a role in the genetic etiology of neurodevelopmental disorders such as autism spectrum disorder (ASD). Despite its link to ASD, the field lacks a complete understanding of the role CNTNAP2 plays in the hallmarks of ASD: repetitive behaviours and abnormalities in social interaction, language, and sensory processing. Therefore, this thesis first examines if a loss-of-function mutation in the CNTNAP2 gene in the rat (SD-Cntnap2^tm1Sage) is sufficient to cause alterations in social interactions, stereotypic behaviour, and sensory processing. Cntnap2 knockout rats showed deficits …

Uncovering Deficits In Auditory Processing And Cognition Following Hearing Loss And Prefrontal Cortex Dysfunction, Krystyna B. Wieczerzak

Electronic Thesis and Dissertation Repository

How the auditory cortex and higher-order cortical regions, e.g., the prefrontal cortex, interact for accurate auditory processing and perception is not fully understood. Furthermore, although hearing loss is correlated with cognitive impairment, and animal studies have shown that loud noise exposure causes hippocampal neuropathology, the effects of noise-induced hearing loss on the medial prefrontal cortex (mPFC) and higher-level cognitive functions have not been well studied. Using electrophysiological and cognitive-behavioural testing in rats, Chapter 2 provides the first evidence of noise-induced plasticity in the mPFC (e.g., loss of functional connectivity with the auditory cortex) and deficits in stimulus-response habit learning. Although …