ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Filtering by
- All Subjects: Neurosciences
- Creators: Smith, Brian H.
For successful locomotion, animals require visual and somatosensory information. Even though a number of supraspinal centers receive both in varying degrees, processing this information at different levels of the central nervous system, especially their contribution to visuo-motor and sensory-motor integration during locomotion is poorly understood.
This dissertation investigates the patterns of neuronal activity in three areas of the forebrain in the cat performing different locomotor tasks to elucidate involvement of these areas in processing of visual and somatosensory information related to locomotion. In three studies, animals performed two contrasting locomotor tasks in each and the neuronal activities were analyzed.
In the first study, cats walked in either complete darkness or in an illuminated room while the neuronal activity of the motor cortex was recorded. This study revealed that the neuronal discharge patterns in the motor cortex were significantly different between the two illumination conditions. The mean discharge rates, modulation, and other variables were significantly different in 49% of the neurons. This suggests a contextual correlation between the motor cortical activity and being able to see.
In two other studies, the activities of neurons of either the somatosensory cortex (SI) or ventrolateral thalamus (VL) were recorded while cats walked on a flat surface (simple locomotion) or along a horizontal ladder where continuous visual and somatosensory feedback was required (complex locomotion).
We found that the activity of all but one SI cells with receptive fields on the sole peaked before the foot touched the ground: predictably. Other cells showed various patterns of modulation, which differed between simple and complex locomotion. We discuss the predictive and reflective functionality of the SI in cyclical sensory-motor events such as locomotion.
We found that neuronal discharges in the VL were modulated to the stride cycle resembling patterns observed in the cortex that receives direct inputs from the VL. The modulation was stronger during walking on the ladder revealing VL’s contribution to locomotion-related activity of the cortex during precision stepping.
damage, immune system activation, impaired protein function, or aberrant DNA methylation. In the case of DNA methylation, I demonstrate that inhibiting DNA methylation dynamics can impair long-term memory formation, while the nurse-to- forager transition is not altered. These experiments could serve as the bases for and reference groups of studies testing the effects of metal or metalloid toxicity on DNA methylation. Each potential mechanism provides an avenue for investigating how neural function is influenced by the physiological status of non-neural organs. And from an ecological perspective, my results highlight the need for environmental policy to consider sublethal effects in determining safe environmental toxin loads for honey bees and other insect pollinators.