| Over the last decade, functional magnetic resonance imaging (fMRI) has become a major tool for studying the human brain non-invasively. More recently, this technique has been applied to investigations of the non-human primate brain, which is the most widely studied animal model for human neocortical organization and function. The major aim of the work presented in this thesis was to investigate the large-scale functional organization of cortical visual areas in the macaque, with an emphasis on the temporal cortex, using fMRI techniques. This aim was pursued via four lines of experiments. First, a method for scanning awake and behaving monkeys was established. All devices, such as the apparatus for restraining the monkey's head and the reward system, had to be constructed from MR-compatible materials that did not interfere with the signal acquisition. Due to the horizontal bore of our scanner, the animal had to be restrained in a horizontal position and specifically trained to perform behavioral tasks in a noisy and extremely confined environment. Second, we tested the feasibility of using fMRI to investigate the system-wide recovery of neural function following cortical lesions. An animal with a striate cortex lesion was scanned during a free-viewing experiment, allowing us to assess the extent of the lesion non-invasively, as well as its effect on the BOLD signal in adjacent regions. Third, several experiments were performed to map the early visual cortex using awake monkey fMRI. These experiments served to verify the methodology and to relate the organization of retinotopic areas to that of more anterior object-selective areas. Fourth, several experiments were performed aimed at examining the organization of the temporal cortex. fMRI studies have suggested that the human ventral temporal cortex contains a small number of areas selective for certain categories such as faces and bodies. Single-cell studies have reported the existence of face-, hand- and body-responsive cells non-uniformly distributed throughout the temporal cortex of the macaque. Our results show several overlapping face- and body part-selective regions throughout the temporal cortex. Differences in selectivity and laterality amongst the areas suggest that they may be involved in different aspects of perceptual processing. |
