Animals learning

The tests generally involve some form of maze but the simplest is the passive avoidance test. In this the animal learns that in a certain environment it will be punished with an electric shock for some particular action, like stepping onto a special part of the floor of the test chamber. The test of memory is how long the rat avoids (remains passive to) making the movement that will initiate the shock. Of course, drugs that reduce the animal s anxiety also modify the response. Using a maze in its simplest T shape, the animal is placed at the base of the vertical arm and a food reward at the end of one of the horizontal arms. Clearly the animal has to learn which arm contains the reward. Memory is assessed by the time taken for a food-deprived animal to reach the reward and the number of false arm entries. This simple system can be made more complex by introducing many more arms and branches but the principle is the same. 

Whitney G., Alpem M. and Dizinno G. (1974). Female odors evoke ultrasounds from male mice. Anim Learn Behav 2, 13-18. 

Mackintosh, N. The Psychology of Animal Learning. Academic Press, New York, 1974. 

Johnston, R. E. (1975) Sexual excitation function of hamster vaginal secretion. Anim. Learn. Behav. 3, 161-6. 

Schellinck, H.M., Slotnick, B.M. and Brown, R.E. (1997) Odors of individuality originating from the major histocompatibility complex are masked by diet cues in the urine of rats. Anim. Learn. Behav. 25, 193-199. 

Burghardt, G. M., Wilcoxon, H. C., and Czaplicki, J. A. (1973). Conditioning in garter snakes aversion to palatable prey induced by delayed illness. Animal Learning and Behavior 1,317-320. 

Galef, B. G., Kennett, D. J., and Stein, M. (1985). Demonstrator influence on observer diet preference effects of simple exposure and the presence of a demonstrator. Animal Learning and Behavior 13,25-30. 

Denny P, Justice MJ (2000) Mouse as the measure of man Trends Genet 16 283-287 Dickinson A (1980) Contemporary animal learning theory. Cambridge University Press, Cambridge... 

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In this category of models the animal learns a performance, typically to abstain from a behavior that it would normally display according to its natural and current tendency. For example, in the so-called Vogel test a partly water-deprived and thirsty rat learns that, during a signaled period, every lick at the water spout will be followed by a mild electric foot-shock. This sequence induces anxiety and an untreated (control) animal will abstain from drinking. However, animals pretreated with anxiolytic drugs will overcome their inhibition and tolerate at least some of the shocks and drink even when punished. 

Ainslie, George, and Richard J. Hermstein. 1981. "Preference Reversal and Delayed Reinforcement." Animal Learning and Behavior 9 476-82. 

Dickinson, Anthony. 1980. Contemporary Animal Learning Theory. New York Cambridge University Press. 

Ainslie, G. and Herrnstein, R. J. (1981) Preference reversal and delayed reinforcement , Animal Learning Behavior 9,476-82. 

Exactly how consequences can reinforce motivation without being part of it is somewhat mysterious, but the fact is that they can. Animal behavior is not animated by conscious intentions, but it is certainly guided by consequences. In fact, almost all that is known about reinforcement comes from the study of animal learning and adaptation - the rest is mainly extrapolation and speculation. 

The categories of methods used in behavioral toxicology fall into two principal classes, stimulus-oriented behavior, and internally generated behavior. The former includes two types of conditioned behavior operant conditioning, in which animals are trained to perform a task in order to obtain a reward or to avoid a punishment, and classical conditioning, in which an animal learns to associate a conditioning stimulus with a reflex action. Stimulus-oriented behavior also involves unconditioned responses in which the animal s response to a particular stimulus is recorded. 

Experimental procedure whereby an animal learns to receive brief, low intensity electrical stimuli to subcortical regions of the brain that elicit a reward. 

Another modification is to include probe trials, where no escape platform is present (Czech et al. 2000). The retention measure is the time spent in the maze quadrant associated with the escape platform. An animal which remembers the location of the platform will spend more time in that quadrant of the maze. An essential requirement is that the probe trial remains short, say 1 minute, to avoid the animal learning that the platform is no longer present. If new learning can be thus avoided, probe trials provide the most sensitive index of the animal s retention of the position of the platform, unconfounded by random elements (the animal finding the platform by chance). 

Brown, M. F., and Moore, J. A. (1997). In the dark II spatial choice when access to extrinsic spatial cues is eliminated. Animal Learning and Behavior, 25, 335-346. 

Cheng, K. (1994). The determination of direction in landmark-based spatial search in pigeons a further test of the vector sum model. Animal Learning and... 

Dickinson A (1994) Instrumental conditioning. In MacKintosh N (Ed.), Animal Learning and Cognition, pp. 45-79. Academic Press, San Diego. 

Dickinson A, Balleine B (1994) Motivational control of goal directed action. Anim Learn Behav 22 1-18. 

Falk JL (1977) The origin and function of adjunctive behavior. Anim Learn Behav 5 325-335. 

Another way of demonstrating the rewarding effects of drugs in animals is the conditioned place preference paradigm, in which an animal learns to approach an environment in which it has previously received a rewarding stimulus. Rats had a positive THC place preference after doses as low as 1 mg/kg (41). 

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