Aging and Ventral-Visual Dedifferentiation of Perceptual Representations
Age-related ventral-visual activity has been characterized by dedifferentiation of brain responses to different categories of visual stimuli such as faces and houses that typically elicit highly specialized responses in specific regions of young adult brains. Cross-category ventral visual dedifferentiation may arise because of reduced neuronal selectivity for different types of visual stimuli with aging. The main focus of this thesis is to show that reduced neuronal selectivity is present even for stimuli within a single category, faces, in older adults, that relates to less distinctive representations as well as age-related changes in behavior. In Experiment 1, I use the functional magnetic resonance adaptation paradigm (fMR-A) to reveal greater adaptation in older compared to young adults when processing pairs of faces that are moderately different, thereby showing reduced neuronal selectivity in older adults' fusiform face area (FFA) that is related to less distinctive face representations with aging. In Experiment 2, I show that changes in attention affect FFA selectivity much more in older adults than young, implicating the importance of more directed attention for maintaining a minimum amount of selectivity in older adults. In Experiments 3 and 4, I additionally show age-related dedifferentiation to faces and houses in East Asians demonstrating dissociable effects of biological aging and differences in external experiences on ventral visual function across different populations. This series of studies jointly provide strong evidence for an age-related decrease in representational distinctiveness that stems from a biological neuronal reduction in selectivity that is linked to behavioral differences in older adults.
Biology, Neuroscience, Psychology, Psychobiology, Psychology, Cognitive
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign