Year: 2019
Type: dissertation
Study design: Observational Study
Abstract: The brain adapts to structural and functional changes that naturally occur over the latter half of the human lifespan, enabling people to maintain cognitive function. However, the nature of these changes has not yet been fully characterized. The present dissertation examines the extent to which aging is associated with changes in the recruitment of oscillatory activity within hippocampal and neocortical regions to support relational memory performance on a short delay visuospatial memory task. Structural magnetic resonance imaging and magnetoencephalography were used to characterize potential age-related changes in hippocampal volume, oscillatory activity, and subsequent memory performance, and the relationships among them. Sixteen younger and 16 older adults were sequentially presented with three objects during a study phase. Following a short delay, the objects were re-presented simultaneously, and participants had to determine whether the spatial relations among the objects had been maintained. Older and younger adults showed similar task accuracy, and older adults had preserved hippocampal volumes, but had longer response latencies relative to younger adults. Age-group differences in oscillatory activity were observed during the pre-stimulus, study, and test phase. Younger adults had higher theta (~5Hz) and lower beta (~20Hz) than older adults during pre-stimulus. Younger adults also uniquely showed theta power increases in medial temporal and frontal medial regions during the study and test phase that predicted higher task accuracy, whereas older adults showed widespread alpha (~10Hz) and beta power decreases during the study and test phase, which predicted longer response latencies during the test phase. Taken together with the literature reviewed in this dissertation, these findings begin to provide a better understanding of how different oscillatory mechanisms may support the maintenance of cognitive abilities across the lifespan. Specifically, the hippocampal theta power increases in younger adults may reflect relational memory processes, whereas the neocortical alpha and beta power decreases in older adults may reflect a sensory reactivation and attention-based process operating on holistic low-resolution representations.
Source: TSpace (University of Toronto)
Author: Renante Rondina
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2963166790