This thesis is a cross-disciplinary project, drawing on the techniques of behavioural ecology to reconstruct aspects of the socioecology of the early hominids. The modelling approach advocated in this project is an attempt to move towards the conceptual modelling approach forwarded by Tooby & DeVore (1986), moving away from referential and phylogenetic primate models to reconstruct hominid social behaviour. The project contributes to one current aim in palaeoanthropology; to develop a theoretical framework with which to reconstruct the behaviour of extinct taxa. The raw data for these models come from comparative analyses of behavioural ecology of extant primates. The fundamental basis of systems models of socioecology, is that the relationship between the environment and behaviour is characterised. The choice of environmental parameters has proved to be crucial, therefore I have characterised the key environmental variables that affect animals both directly (e.g. thermoregulatory stress), and indirectly (e.g. via habitat productivity). The quantitative relationships found in this chapter will serve as useful constants for further models. I first present a re-analysis of the systems models of baboons, refining previous models by R. Dunbar. The statistical techniques underlying these linear program models was further supported by the stability of the models when new data were included. Long-term climate data that were accurately sited were found to produce the most predictive equations. The results of the reanalysis of the baboon models gave support to their extension to another taxa. I then extend the range of the time-budget based models to the chimpanzees. The initial focus on chimpanzees is not solely because they are phylogenetic analogues. The emphasis of the models is that they are habitat specific. Relationships between behaviour and environment are used to develop functional equations to explore an animals flexibility of response to varying environmental conditions. Predictions could be made about: maximum ecologically tolerable group size, territory size, diet and extent of geographic range. The geographic distribution of chimpanzees predicted by the model was found to match very closely the current distribution. The models of chimpanzee, baboon and gelada socioecology were then compared. Dietary differences between the taxa accounted for their ecological niche separation. The models of extant primate systems models developed in this thesis provide a firm foundation for extending the models to extinct taxa. Preliminary models are presented, extending these analyses to the extinct australopithecines to forward the development of a conceptual model for the early hominids.

No description available.

No description available.

This work characterized the ability of mice to respond for conditioned reinforcement, a phenomenon that can be used to investigate neural substrates of incentive learning. In both C57Bl/6 and CD1 mice, a reward-associated stimulus acted as a conditioned reinforcer (CR). Responding was stable over multiple test days, enhanced in CD1 mice by the dopamine transporter (DAT) blocker methylphenidate, and was extinguished when responding no longer produced the CR. However, transgenic C57Bl/6 mice overexpressing DAT, which decreased striatal dopamine by 40% responded normally for CR. Therefore, these results suggest that mice can be used to study brain mechanisms of incentive motivation. However, the choice of mouse strain in this paradigm is important as outbred CD1 mice appeared more susceptible to a DAT blocker compared to the inbred C57Bl/6 strain. These results also suggest that selective responding for a CR remains intact in a chronically hypodopaminergic state.

This work characterized the ability of mice to respond for conditioned reinforcement, a phenomenon that can be used to investigate neural substrates of incentive learning. In both C57Bl/6 and CD1 mice, a reward-associated stimulus acted as a conditioned reinforcer (CR). Responding was stable over multiple test days, enhanced in CD1 mice by the dopamine transporter (DAT) blocker methylphenidate, and was extinguished when responding no longer produced the CR. However, transgenic C57Bl/6 mice overexpressing DAT, which decreased striatal dopamine by 40% responded normally for CR. Therefore, these results suggest that mice can be used to study brain mechanisms of incentive motivation. However, the choice of mouse strain in this paradigm is important as outbred CD1 mice appeared more susceptible to a DAT blocker compared to the inbred C57Bl/6 strain. These results also suggest that selective responding for a CR remains intact in a chronically hypodopaminergic state.

Fine motor control of the hand relies on intact somatosensory integration and feedback. Impaired hand movements are observed in patient groups where touch perception and processing within the primary somatosensory cortex (SI) is abnormal. A repetitive transcranial magnetic stimulation paradigm called continuous theta-burst stimulation (cTBS) can be used to induce physiological changes to the underlying cortex. The effect of cTBS on tactile perception is unknown. This Master’s research thesis examined the effect of cTBS over SI on tactile discrimination on the hand in healthy humans. Specifically, the goal of this thesis was to reveal the modulatory effects of cTBS on tactile temporal and spatial psychophysical measures on the hand. In separate experiments, temporal discrimination threshold (TDT) and the spatial measure of amplitude discrimination were measured from the right hand before and for up to 35 minutes following cTBS over left SI. Compared to pre cTBS values, TDT was elevated immediately following cTBS (3-6 minutes) and at later intervals (11-18 minutes). Spatial tactile perception was also measured through amplitude discrimination over the same time course and compared to pre cTBS values thresholds were impaired for up to 18 minutes. These experiments reveal that cTBS over SI impairs tactile acuity on the contralateral hand. The effects last for up to 18 minutes and subsequent measures return to pre cTBS levels. This work is important in identifying means to modulate SI cortical excitability and has potential for clinical application in patient groups with altered somatosensory processing.

No description available.

No description available.

No description available.

No description available.