No description available.

No description available.

No description available.

No description available.

The whole-cell patch-clamp technique was established in the laboratory in order to investigate the modulation of excitatory amino acid-mediated synaptic transmission in the rat hippocampal slice. Following the successful development of the technique the basic properties of excitatory amino acid-mediated synaptic transmission in the CA3-CA1 pathway were studied. Stimulation of the SCCFs (Schaffer collateral-commissural fibres) under conditions in which the inhibitory transmission was blocked resulted in a compound EPSC (excitatory postsynaptic current) mediated by AMPA (-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartic acid) receptors. Application of a brief high-frequency stimulus to the SCCFs resulted in a long-lasting potentiation of the EPSC. Various compounds were applied to the slice to establish whether tetanus-induced potentiation could be mimicked pharmacologically. No potentiation was observed with perfusion of the ionotropic glutamate-receptor agonists L-glutamate, NMDA or AMPA, the latter two producing a transient depression of the EPSC. Following this a series of experiments were performed that investigated the consequences of mGluR (metabotropic glutamate receptor) activation. Perfusion with the selective agonist 1S,3R-ACPD ((1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid) resulted in a small depression of both the compound EPSC and the isolated NMDA receptor-mediated EPSC. In the presence of AA (arachidonic acid (10M)), 1S,3R-ACPD produced a slight potentiation of the response that was not blocked by the NMDA receptor antagonist D-AP5 (D-(-)-2-amino-5-phosphonopentanoic acid). The co-application of 1S,3R-ACPD and NMDA also produced a slight enhancement of the EPSC, as did AA when applied alone. These findings are consistent with an involvement of mGluRs in the induction of LTP, when activated in the presence of AA.

No description available.

The aim of this thesis is to examine where in the human brain sensory and affective processing of taste takes place. Two patient studies and two neuroimaging studies were performed. Taste intensity perception was evaluated in patients with unilateral resection from the AMTL, and in healthy control subjects. The results from two independent experiments indicate that AMTL removal leads to taste intensity perception changes, including decreases in the accuracy of judging actual concentrations of taste solutions, and increases in the perceived intensities of an aversive bitter taste. It is possible that the latter result reflects a potentiation of the aversiveness of bitter as opposed to, or in addition to a change in intensity perception of taste intensity alone. / To define more precisely the regions of the insula/operculum and orbitofrontal cortex (OFC) {putative primary and secondary gustatory regions (PGA and SGA, respectively)} that are activated by gustatory stimulation in humans, standardized Talairach coordinates from all available studies were compiled and plotted onto an averaged MRI image. As in non-human primates, it is likely that the human PGA is represented in several regions within the middle to anterior insula, and in frontal and parietal opercula. The precise location of the human SGA is less clear, but is likely within the caudal region of the OFC. / In the final study, successive [15O]H2O PET scans were performed on volunteers as they ate chocolate to beyond satiety. Thus, the sensory stimulus was held constant while its reward value was manipulated by feeding. As predicted, modulation was observed in both the primary and secondary gustatory regions, corresponding to the regions identified in the previous study. This finding suggests overlapping representation of sensory and affective processing of taste in humans. Additionally, different groups of structures were selectively recruited depending on whether subjects were eating chocolate when they were highly motivated to eat or highly motivated not to eat. / In summary, the work contained within this thesis suggests that sensory and affective processing of taste occurs in the AMTL, PGA, and SGA. Such an interaction marks a departure from classical theories of sensory organization based upon studies performed largely in the visual modality.

No description available.

The clinical utility of electrodermal response measures as a predictor of outcome from traumatic vegetative state was investigated. Electrodermal potential data were obtained from five subjects in acute vegetative state at 1 to 3 months post-trauma (Acute group), five subjects in persistent vegetative state at more than 1 year post-trauma (PVS group), five subjects who were more than 1 year post-trauma and had recovered from vegetative state (RVS group), and 10 normal subjects (Control group). Measures included startle response amplitude, baseline lability, habituation and orientation to tones, responses to famous faces and written commands, and total number of skin potential responses. In addition, subjects in the Acute group were reassessed with respect to clinical outcome at 6 months post-trauma. Results revealed significant group differences between the Control group and each of the brain-injured groups in startle response amplitude, baseline lability, and total number of responses. The RVS group had significantly larger startle response amplitudes than the PVS group. Some subjects in the PVS group and all subjects in the Acute group exhibited no startle response on one or more days of testing. Significant group differences also were found for habituation and orientation. Habituation was present in 80% of the Control and RVS subjects, 20% of the Acute subjects and 0% of the PVS subjects, and orientation was present in 80% of the Control subjects, 20% of the Acute and RVS subjects and 0% of the PVS subjects. Group variance in startle response amplitude, baseline lability and total number of responses was significantly greater in the Control group compared with the brain-injured subject groups. In the Acute group, a larger startle response amplitude, greater baseline lability, a greater total number of electrodermal responses, and habituation and orientation were associated with a positive outcome at 6 months post-trauma. These results indicate electrodermal responsiveness is generally reduced following traumatic brain injury, even in subjects with a relatively good recovery from vegetative state. Greater electrodermal activity in early vegetative state may be associated with better potential for recovery.

No description available.