This study investigated color discrimination as a possible localized function of right or left cerebral hemispheres in humans. Previous studies have shown conflicting results. Studies implicating the left hemisphere have contaminated color discrimination with verbal-symbolic ability. Other studies implicating the right hemisphere emphasized color-matching ability. This study pointed out the importance of response latency as well as accuracy and also the importance of testing the data for meeting the assumptions of the statistical technique utilized. It was concluded that color discrimination is normally a right-hemisphere function in right-handed individuals. Differences in individual ability, although large, were not found to be systematically related to sex or eye dominance, but may be learned individual differences. The study further pointed out the inappropriateness of referring to a major or dominant cerebral hemisphere without stipulating which function is being considered.

Cu,rrent research has suggested that musical stimuli are processed in the right hemisphere except in musicians, in whom there is an increased involvement of the left hemisphere. The present study hypothesized that the more musical training persons receive, the 1 more they will rely on an analytic/left hemispheric processing strategy. The subjects were 10 faculty and 10 student nonmusicians, and 10 faculty and 10 student musicians. All subjects listened to a series of melodies (some recurring and some not) and excerpts (some real and some fake) in one ear and to a different series of melodies in the other ear. The task was to identify recurring vs. nonrecurring melodies and real vs. fake excerpts. For student musicians, there was a_ left ear/right hemispheric advantage for melody recognition, while for student nonmusicians, the situation was the reverse. Neither faculty group showed any ear preference. There were no significant differences for excerpt recognition. Two plausible explanations of the faculty performance were discussed in terms of a maturation factor and a functionally more integrated hemispheric approach to the task .

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Functional MRI is a method of imaging changes in blood oxygenation that accompany neural activity in the brain. A specific area within fMRI studies investigates what the brain is doing when it is not being stimulated. It is postulated that there are distinctly separate regions of the brain that are connected based upon functional relations and that these connected regions synchronously communicate even during rest. Resting state connectivity has become a tool to investigate neurological disorders in humans without specific knowledge of the mechanisms that correlate neural activity with brain metabolism and blood flow. This work attempts to characterize resting state connectivity in the rat brain to establish a model that will help elucidate the relationship between functional connectivity, as measured with fMRI, and brain function. Four analysis techniques, power spectrum estimation, cross correlation analysis, principle component analysis, and independent component analysis, are employed to examine data acquired during a non-stimulation, single-slice, gradient echo EPI sequence in search of functionally connected, spatially distant regions of the rat brain.

Traditional fMRI utilizes blood oxygenation level dependent (BOLD) contrast to map brain activity. BOLD signal is sensitive to the hemodynamic changes associated with brain activity, and gives an indirect measure of brain activity. Low frequency fluctuations (LFFs) have been observed in the BOLD signal even in the absence of any anesthetic agent, and the correlations between the fluctuations from different brain regions has been used to map functional connectivity in the brain. Most studies involving spontaneous fluctuations in the BOLD signal extract connectivity patterns that show relationships between brain areas that are maintained over the length of the scanning session. The research presented in this document investigates the spatiotemporal dynamics of the BOLD fluctuations to identify common spatiotemporal patterns within a scan. First, the presence of a visually detectable spatiotemporal propagation pattern is demonstrated by utilizing single-slice data with high spatial and temporal resolution. The pattern consists of lateral-medial propagation of BOLD signal, demonstrating the presence of time-varying features in spontaneous BOLD fluctuations. Further, a novel pattern finding algorithm is developed for detecting repeated spatiotemporal patterns in BOLD fMRI data. The algorithm is applied to high temporal resolution T2*-weighted multislice images obtained from rats and humans in the absence of any task or stimulation. In rats, the primary pattern consists of waves of high signal intensity, propagating in a lateral-medial direction across the cortex, replicating the results obtained using visual observation. In humans, the most common spatiotemporal pattern consisted of an alteration between activation of areas comprising the "default-mode" (e.g., posterior cingulate and anterior medial prefrontal cortices) and the "task-positive" (e.g., superior parietal and premotor cortices) networks. Signal propagation from focal starting points is also observed. The pattern finding algorithm is shown to be reasonably insensitive to the variation in user-defined parameters, and the results are consistent within and between subjects. This novel approach for probing the spontaneous network activity of the brain has implications for the interpretation of conventional functional connectivity studies, and may increase the amount of information that can be obtained from neuroimaging data.

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A word-generation experiment explored the relative contributions of the left temporal neocortex and the left hippocampal region to verbal recall. Patients with large hippocampal excisions (LTH) were impaired in immediate recall of synonyms, whereas those with small hippocampal excisions (LTh) were not. Both groups were impaired in immediate recall of rhymes, and in delayed recall of both synonyms and rhymes. A nonverbal associative-learning task, where the stimulus-items came from a visual continuum, also resulted in a deficit for the LTH (but not the LTh) group. Patients with right temporal lobectomy performed both tasks normally. On an absolute-judgement task involving the accurate numbering of a set of six individually-presented rectangles, only the groups of patients with large hippocampal excisions were impaired, regardless of side of lesion. These findings support the view that the temporal neocortex is important for gaining access to information in semantic memory, whereas the hippocampal region is essential for the temporary storage of new information beyond the span of immediate memory.