The brain is constantly changing. Genetically specified developmental pathways interact with extrinsic factors including illness, injury and learning to shape the brain. This thesis presents two projects on experience dependent plasticity over different timescales. Exerting its effect across years, deafness provides a model of long term crossmodal plasticity. In the first part of this thesis I ask how deafness affects the thalamus. Diffusion weighted imaging was used to segment the thalamus and with probabilistic tractography, thalamo-cortical connections were traced. Microstructural properties of visual and frontal thalamic segmentations, thalamo-cortical tracts throughout the brain, apart from the temporal thalamo-cortical tract were altered. The neuroanatomical sequelae of deafness are evident throughout the brain. Deaf people have enhanced peripheral vision, facilitating a protective orienting mechanism when hearing cannot be relied upon. Widefield population receptive field (pRF) modeling with fMRI was completed to examine the functional and structural properties of primary visual cortex. Deaf participants had enlarged pRF profiles and thinner cortex in peripheral visual regions, again emphasizing plasticity across many years. In the second part I examine plasticity over the course of days. Visuomotor transformations translate visual input to motor actions, and its neural instantiation might change with training. We used a pattern component model on fMRI data to reveal a gradient of visual to motor information from occipital to parietal to motor cortex. Strikingly, we observed motor coding in visual cortex and visual coding in motor cortex. More tentatively, our results suggest that during sensorimotor skill learning there is decreased dependence on visual cortex as motor cortex learns the novel visuomotor mapping. In summary, I show crossmodal processing and plasticity in regions previously considered not to exhibit these properties, both in long- and short-term plasticity. This work emphasizes the contribution that computational neuroimaging can provide to the field of experience dependent plasticity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:654612 |
| Date | January 2015 |
| Creators | Lyness, C. R. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1467245/ |
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