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PubMedDate not supplied

Species-specific defense reactions and avoidance learning. An evaluative review.

Bolles (1970) proposed a theory of avoidance learning, the species-specific defense reaction (SSDR) hypothesis, which emphasized innate constraints on the response repertoire of rats in aversive situations and minimized the role of reinforcement in avoidance learning. The present paper describes Bolles' (1970, 1971, 1972, 1975, 1978) development of SSDR theory and reviews the empirical tests of its assumptions and predictions. It is concluded that the SSDRs described by Bolles, along with some others, are highly probable in aversive situations but that the response repertoire is not limited to them. Further, there is strong evidence for reinforcement effects in the establishment and maintenance of at least some avoidance responses.

Aggression↗
PubMed2003

Frontal-striatal circuit functions: context, sequence, and consequence.

The exact role of the basal ganglia in both the motor and non-motor domains has proven elusive since it is virtually impossible to refer to its function in isolation of cortical, and especially frontal cortical circuits. The result is that we often speak of frontal-striatal circuits and functions but this still leaves us in the dark when trying to specify basal ganglia information processing. A critical review of the data from both basic science and clinical studies suggests that we should break down processing along a temporal continuum, including the domains of context, sequential information processing, and feedback or reinforcement (i.e., the consequences of action). This analysis would cut across other theoretical constructs, such as attention, central executive, memory, and learning functions, traditionally employed in the neuropsychological literature. Under specified behavioral constraint, the basal ganglia can then be seen to be involved in fundamental aspects of attentional control (often covert), in the guidance of the early stages of learning (especially reinforcement-based, but also encoding strategies in explicit paradigms), and in the associative binding of reward to cue salience and response sequences via dopaminergic mechanisms. Parkinson's disease is considered to offer only a limited view of basal ganglia function due to partial striatal depletion of dopamine and the potential involvement of other structures and transmitters in its pathology. It is hoped that the present formulation will suggest new heuristic research strategies for basal ganglia research, permitting a closer link to be established between neurophysiological, functional imaging and neuropsychological paradigms.

Basal Ganglia↗
PubMed1963

Effects of pentobarbital on fixed-ratio reinforcement.

Certain doses of pentobarbital consistently increased the rate of pecking engendered by a fixed-ratio schedule of 30 responses in a group of 13 pigeons, and still higher doses produced decrements in rate of responding. For individual subjects, the dose-effect functions were qualitatively similar, but differed with respect to the doses producing the maximum increase and subsequent decrease in rate. In general, the maximum occurred at lower doses and the decrement was greater at the highest dose in the birds with the highest control rates. It was also possible to distinguish between the effects of pentobarbital and several other drugs on the behavior maintained by FR 30. The results indicate that changes in rate of responding on FR 30 after drug administration are dose-dependent, drug-specific effects.

Animals↗
PubMed1986

Adult and embryonic frontal cortex transplants after frontal cortex ablation enhance recovery on a reinforced alternation task.

Damage to the medial frontal cortex in rats results in a learning deficit on a reinforced alternation task. The rate of recovery from this deficit was accelerated by transplantation of either adult or embryonic frontal cortex, provided that a delay was introduced between injury and transplantation. The rates of recovery for both delayed embryonic and adult transplants did not differ from the undamaged group. In contrast, transplants of embryonic frontal cortex immediately after ablation did not accelerate the rate of recovery. The accelerated rate of behavioral recovery on the reinforced alternation task appeared to correlate with transplant survival.

Acetylcholinesterase↗
PubMed2000

Memory systems in the brain.

The operation of different brain systems involved in different types of memory is described. One is a system in the primate orbitofrontal cortex and amygdala involved in representing rewards and punishers, and in learning stimulus-reinforcer associations. This system is involved in emotion and motivation. A second system in the temporal cortical visual areas is involved in learning invariant representations of objects. A third system in the hippocampus is implicated in episodic memory and in spatial function. Fourth, brain systems in the frontal and temporal cortices involved in short term memory are described. The approach taken provides insight into the neuronal operations that take place in each of these brain systems, and has the aim of leading to quantitative biologically plausible neuronal network models of how each of these memory systems actually operates.

Animals↗
PubMed2005

Noradrenaline involvement in the memory-enhancing effects of exposure to a complex rhythm stimulus following discriminated passive avoidance training in the young chick.

Previous research in our laboratory has demonstrated a significant memory-enhancing effect of exposure to a complex rhythm stimulus following weakly-reinforced passive avoidance learning in chicks. The aim of this study was to explore whether noradrenaline mediates this process. Chicks were trained on a strongly-reinforced single-trial passive avoidance task involving discrimination between two coloured beads. Intracerebral administration of the protein synthesis blocker, anisomycin, revealed that a phase of memory formation sensitive to arousal levels was extended by approximately 35 min following exposure to the complex rhythm stimulus. Administration of 2,4-dinitrophenol showed that this extension occurred during phase B of intermediate-term memory. Finally, a higher dose of the beta-adrenergic receptor antagonist, propranolol, was required to inhibit long-term memory in the presence of the auditory stimulus than in its absence. These findings suggest that the memory-enhancing effects of the complex rhythm stimulus may be mediated by noradrenaline, possibly via an increase in physiological arousal.

2,4-Dinitrophenol↗
PubMed2006

Selective enhancement of associative learning by microstimulation of the anterior caudate.

Primates have the remarkable ability to rapidly adjust or modify associations between visual cues and specific motor responses. Whereas little is known as to how such adjustments in behavioral policy are implemented, recent learning models suggest that the anterior striatum is optimally positioned to have a role in this process. We recorded from single units and delivered microstimulation in the striatum of rhesus monkeys performing an associative learning task. Caudate activity during reinforcement was closely correlated with the rate of learning and peaked during the steepest portion of the learning curve when new associations were being acquired. Moreover, delivering microstimulation in the caudate during the reinforcement period significantly increased the rate of learning without altering the monkeys' ultimate performance. These findings suggest that the caudate is responsible for implementing selective adjustments to the 'associative weights' between sensory cues and motor responses during learning, thus enhancing the likelihood of selecting profitable actions.

Animals↗
PubMed1963

Transfer across drives of the discriminative effect of a Pavlovian conditioned stimulus.

Previous results suggest that a stimulus paired in Pavlovian fashion with reward should exert some discriminative control over an unrelated operant response acquired under a different drive-reward system. In the following experiment, a stimulus was first paired with food reinforcement for a hungry rat. Subsequently, the animal learned to lever-press for water reinforcements when thirsty but not hungry. Finally, the control over lever-pressing of the food-paired stimulus was tested by presenting it at various times during extinction of the lever-pressing response. All animals in the experiment showed the expected effect; each emitted more lever-presses during periods of the food-paired stimulus than during alternate control periods.

Animals↗