Life Sciences Commons^™

The Sensory Properties Of The Fast Visuomotor System, Rebecca Kozak

Electronic Thesis and Dissertation Repository

The brain has a remarkable capacity to rapidly transform vision into action, which allows us to initiate reaches towards targets within fractions of a second. Despite being fundamental to our interaction with a dynamic environment, these fast visuomotor transformations and their underlying neural substrates are poorly understood. This gap in the literature is further exacerbated by the unreliable presence of rapid visuomotor responses on the upper limb, likely due to the use of less optimal stimuli and paradigms. My thesis explores the stimulus properties which best evoke short latency reaction times and electromyographic responses during visually guided reaching, their application …

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 …

Assessment Of Intrinsic Hand Neuromuscular Physiology, Philemon Tsang

Electronic Thesis and Dissertation Repository

Alterations to the peripheral nervous system and neuromuscular physiology may impact hand function in a typical or clinical population, such as individuals with ulnar neuropathy. The mechanisms that influence these positive and negative changes are still not well understood. The three studies within my thesis aim to validate the reliability of decomposition-based quantitative electromyography (DQEMG) measurements and explore the changes in intrinsic hand neuromuscular physiology in a typical aging population and individuals recovering from a surgical intervention for severe ulnar neuropathy.

The purpose of the first study was to determine the test-retest reliability of near-fibre (NF) jiggle, a measure of …

Spatial And State-Dependent Effects Of Transcranial Magnetic Stimulation Of Prefrontal Cortex In Non-Human Primates, Chao Gu

Electronic Thesis and Dissertation Repository

The indirect effects of transcranial magnetic stimulation (TMS) within a distributed neural network are still largely unknown. Here we propose to use the non-human primate (NHP) oculomotor system as an animal model for investigating the effects of TMS. Across three animals, single pulses of TMS to the prefrontal cortex (PFC), including the frontal eye fields (FEF), reliably evoked a contralateral head turning synergy, similar to what is seen following intracortical microstimulation. Furthermore, double pulses of TMS paired with the memory-guided saccade paradigm only evoked neck muscle activity preceding contralateral saccades, showing similar state-dependency as previously observed in human TMS studies. …