84 research outputs found
Effort-related functions of nucleus accumbens dopamine and associated forebrain circuits
Background
Over the last several years, it has become apparent that there are critical problems with the hypothesis that brain dopamine (DA) systems, particularly in the nucleus accumbens, directly mediate the rewarding or primary motivational characteristics of natural stimuli such as food. Hypotheses related to DA function are undergoing a substantial restructuring, such that the classic emphasis on hedonia and primary reward is giving way to diverse lines of research that focus on aspects of instrumental learning, reward prediction, incentive motivation, and behavioral activation.
Objective
The present review discusses dopaminergic involvement in behavioral activation and, in particular, emphasizes the effort-related functions of nucleus accumbens DA and associated forebrain circuitry.
Results
The effects of accumbens DA depletions on food-seeking behavior are critically dependent upon the work requirements of the task. Lever pressing schedules that have minimal work requirements are largely unaffected by accumbens DA depletions, whereas reinforcement schedules that have high work (e.g., ratio) requirements are substantially impaired by accumbens DA depletions. Moreover, interference with accumbens DA transmission exerts a powerful influence over effort-related decision making. Rats with accumbens DA depletions reallocate their instrumental behavior away from food-reinforced tasks that have high response requirements, and instead, these rats select a less-effortful type of food-seeking behavior.
Conclusions
Along with prefrontal cortex and the amygdala, nucleus accumbens is a component of the brain circuitry regulating effort-related functions. Studies of the brain systems regulating effort-based processes may have implications for understanding drug abuse, as well as energy-related disorders such as psychomotor slowing, fatigue, or anergia in depression
Propofol, more than halothane, depresses electroencephalographic activation resulting from electrical stimulation in reticular formation
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Description and evaluation of a remote camera and triggering system to monitor carnivores
Remotely triggered cameras have been used in many ecological studies, but most are relatively inexpensive one-time-only systems or expensive infrared systems. We describe the setup and wiring technique for a moderately priced, multiple-photo camera system. Two study areas, California and Vermont, were used to assess usefulness of the camera system. Although some target carnivore species were photographed regularly, visitation rates of other carnivores were low, due either to low population densities or camera shyness. Cameras generally worked well under all conditions, but the pressure-plate triggering devices sometimes became inoperable during heavy rains. Other camera activation systems may reveal additional uses for this remote camera system
Fluctuations in density functional theory: random metallic alloys and itinerant paramagnets
Epitaxial Growths and Surface Science Techniques Applied to the Case of Ni Overlayers on Single Crystal Fe(001)
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