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Spatial navigation is a cognitive skill fundamental to successful interaction with our environment. Normal aging is associated with weaknesses in this skill, with severe deficits in the context of Alzheimer's disease. Identifying mechanisms underlying how the aged brain navigates is important to understanding these age-related weaknesses and potentially strengthening or preserving spatial navigation ability in the aging population. One understudied aspect of spatial navigation is self-motion perception. Important to self-motion perception is optic flow, which is the pattern of visual motion experienced while moving through our environment. Several brain regions are optic flow-sensitive (OF-sensitive), responding more strongly to optic flow than other types of visual motion. The goal of the experiments in this dissertation was to examine the role of visual motion perception and cortical motion area dynamics in spatial navigation in cognitively intact aged adults. Visual path integration tasks were used because they highlight the use of radial and translational optic flow to keep track of one’s position and orientation, respectively. In the first experiment, a positive relationship between radial optic flow sensitivity and visual path integration accuracy that was stronger in aged adults was found. In the second experiment, brain activity was measured using functional magnetic resonance imaging (fMRI) while participants performed visual path integration (VPI) and turn counting (TC) tasks. Stronger activity in the OF-sensitive regions LMT+ and RpVIP during VPI, not TC, was associated with greater VPI accuracy in aged adults. In the third experiment, the functional connectivity between OF-sensitive regions and the rest of the brain during the VPI and TC tasks was measured using fMRI. Stronger average functional connectivity between the OF-sensitive regions LMT+, RMT+, LpVIP, RpVIP, LpV6 and right supramarginal gyrus and posterior cingulate during VPI, not TC, was associated with greater VPI task accuracy in aged adults. The results demonstrate novel relationships between visual path integration accuracy and radial motion perception, the response of OF-sensitive cortical regions during visual navigation, and the interaction strength between OF-sensitive regions and parietal cortex during visual navigation in aged adults. This work expands our knowledge of mechanisms underlying spatial navigation processes in the aged human brain.

A terracotta portrait bust of the Marquis de Lafayette with the signature “houdon an. 1790”, now broken, was given to Boston College by Edward S. Ryan in 1966. The two objectives of this study were: (1) To determine the methods used to create this bust and (2) whether or not it could have been made in the studio of Jean-Antoine Houdon. A materials analysis using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) was performed on five representative samples from different regions of the bust. Three samples were unpolished and two were polished using an argon beam milling technique, completely preserving the heterogeneous samples. It was found that the bust was created by pressing wet clay into piece mold, the waxy surface is not original to the sculpture, and the pink layer is the result of a higher iron particle concentration. It is almost impossible to absolutely determine whether or not Houdon made the bust, due to uncertainties in provenance and the large number of busts made by, and copied from, Houdon. However, it is clear that the materials original to the sculpture correlate with the time Houdon lived and the methods he used.

In this study, we use paintings that canonically and/or visually belong to the Abstract Expressionist movement to study how the brain processes different forms of color and luminance. Subjects viewed 240 unique images in the experiment in a block design. All of the paintings used in the experiment were painted by the artists in color. Half of the 240 images were three styles of painting in their original (saturated) forms, and the other half were desaturated versions of the same paintings. In our analysis, we compared saturated Abstract Expressionist paintings to their desaturated counterparts - both as a group and within the Gesture and Color Field styles. We also compared the desaturated Gesture paintings to their saturated counterparts because many of the Gesture painters created work with little to no color. Through these contrasts, we show that different regions in the brain process color and luminance. Notably, we show that (1) the brain processes color in the Gesture and Color Field paintings differently (2) color is capable of producing significant activation in the amygdala and (3) the color and luminance in the Gesture paintings produce strikingly different patterns of significant activation.