Prehension is the act of reaching towards, grasping, and manipulating an object with one's hand. It is an extraordinarily complex behaviour that requires the assimilation and processing of information from multiple sensory modalities, and generation of precise, but flexible actions to achieve desired outcomes. At the neocortical level, this behaviour is controlled by functional network interactions between several parietal and frontal regions. The experiments composing this thesis contribute to ongoing research investigating how these regions interact with one another during the planning, execution, and reprogramming of prehension behaviour. Here, these interactions are studied in both the healthy brain, and following an injury resulting from stroke. First, functional interactions between the ventral premotor cortex (PMv) and the primary motor cortex (Ml) were investigated during a naturalistic prehension task. Results suggest that PMv can exert either a facilitatory or inhibitory influence over Ml corticospinal output depending on whether the action must be reprogrammed. In a follow-up experiment, we used a novel approach with transcranial magnetic stimulation (TMS) to induce plasticity in the PMv-Ml pathway. The observed effect was consistent with Hebbian-based associative plasticity induction, and showed different forms of expression when measured either at rest or during the performance of a prehension task. Finally, we conducted a longitudinal training study in a group of chronic stroke patients suffering from severe hand plegia, in which they used prehension- related motor imagery to control a mechanical hand orthosis through a brain- computer interface. While most patients did show significant improvements in task performance during training, these improvements varied across the group. We attempted to explain this inter-patient variability by relating performance to graph theoretical measures of functional and structural network architecture. These results highlighted specific ipsilesional and contralesional parietofrontal regions and related white-matter connections that appear to have a crucial role in BCl training task performance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:558211 |
| Date | January 2011 |
| Creators | Buch, Ethan R. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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