The current study utilized a priming paradigm in conjunction with a visual halffield presentation to determine if the right hemisphere contributes to pragmatic processing. Primes included conversational dialogues that either performed a speech act or did not. The targets identified the speech act and were presented to one of the two visual fields (lvf-RH or rvf-LH). It was hypothesized that the right visual field-left hemisphere (rvf-LH) would be more accurate and faster at identifying targets regardless of the script type that preceded it and the left visual field-right hemisphere (lvf-RH) would be significantly more accurate and faster at identifying targets when preceded by a script that performed the identified speech act. Results indicated that the lvf-RH was more accurate and faster at identifying a target regardless of the type of script that preceded it, while the rvf-LH was differentially affected by the type of script. / Department of Psychological Science

The pedunculopontine tegmental nucleus (PPTg) lies within the pontomesencephalon and contains cholinergic and non-cholinergic neurones. It has extensive afferent and efferent connections throughout the brain. Early research suggested a role for the PPTg in the mediation of locomotor activity, and it was believed to form the major substrate of the electrophysiologically identified mesencephalic locomotor region (rviLR). Studies using selective excitotoxic lesions of the PPTg demonstrated that it has no role in the mediation of spontaneous or nucleus accumbens-induced (NAcc) locomotion. However evidence has suggested that the cuneiform nucleus (CNF) and not the PPTg is the main locus of the .MLR. The effects of bilateral ibotenate CNF lesions on spontaneous and amphetamine-induced locomotion stimulated from the NAcc were therefore investigated. CNF lesions had no effect on either type of locomotor activity. Bilateral ibotenate lesions of the PPTg have been shown to influence the expression of orofacial stereotypies following administration of systemic amphetamine. Oral stereotypies can be elicited reliably by direct stimulation of the ventrolateral caudate-putamen (VLCP). This thesis sought to clarify the role of the PPTg in the mediation of oral stereotypies, by combining bilateral ibotenate lesions of the PPTg with direct microinjection of amphetamine into the VLCP. Lesions of the PPTg caused a shift in the dose response curve to amphetamine resulting in an increase in the incidence and intensity of oro facial stereotypies at lower doses. Thus the PPTg appears to have inhibitory control over the expression of orofacial behaviors. It is hypothesised that while neither the PPTg nor the CNF have a role in the mediation of locomotor activity per se they may provide an integrative functional role, which influences motor outflow. The role of the CNF in the transmission of nociception and a role for the PPTg in the mediation of striatal outflow is discussed.

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The objective of this investigation was to determine whether lesions to the region of the mammillary bodies of rats impair performance on various learning and memory tasks. It was demonstrated that such lesions are sufficient to impair performance on tasks that require memory for spatial information. Deficits were found in both working and reference memory paradigms, with more severe impairments in the former. Ability to discriminate spatial location was not affected when delay was minimal, but retention was progressively impaired as delay was increased. A dissociation in the effect of the lesions on performance of analogous spatial and nonspatial tasks was observed. The lesions did not impair the learning of a visual discrimination/reversal, or a conditioned taste aversion. It is concluded that lesions to the region of the mammillary bodies have a selective effect on spatial learning and memory. The relevance of these findings to Korsakoff's psychosis is discussed.

This doctoral work consists of several studies that investigated the relationship between language lateralization and structural asymmetries found in auditory and language-related regions of the human brain. Language lateralization was determined via the intracarotid Sodium Amytal procedure in epilepsy patients. In study 1, three groups of patients were investigated: a left speech group (LSG); a right speech group (RSG); and a bilateral speech group (BSG). Two auditory cortex regions: Heschl's gyrus (HG) and the planum temporale (PT) were labelled on the magnetic resonance imaging scan of each subject. Additionally, an automatic voxel-based morphometry (VBM) analysis was performed. The overall findings suggested that the structural asymmetries found in the auditory regions did not clearly and directly relate to language lateralization. The VBM analysis, however, revealed a grey matter concentration difference in the region of Broca's area favoring the left hemisphere (LH) in the LSG, and the right hemisphere (RH) in the RSG. That structural difference did relate to language lateralization and was further investigated in studies 2 and 3. Previously collected positron emission tomography data were examined in these two studies. Three regions of interest (ROI) analyses and one group average analysis were performed. Activation related to various speech tasks was examined. The ROI analyses revealed a significant activation difference favoring the LH for two targeted speech-task subtractions but only for the LSG. The group analysis, in contrast, revealed that the LSG showed a functional asymmetry favoring the LH, and that the RSG showed a functional asymmetry favoring the RH. Overall, the present results provided only partial evidence for a relationship existing between structural asymmetry in Broca's area and language lateralization. The structural asymmetries found in HG and the PT, in contrast, did not clearly and directly relate to language

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