Motor alimentary conditioned reflexes and delayed reactions in dogs following destruction of the caudate nucleus]

The characteristics of formation and achievement of motor conditioned reactions were studied in seventeen dogs before and after the lesion of head or body of the caudate nucleus. It has been shown that the degree of higher nervous activity disturbances depends on the localization of injuries in the nucleus, and on the complexity of the tests used. The caudate nucleus exerts a modulating effect on the parameters of motor conditioned reflexes and takes a direct part in the structure of delayed reflexes. Lesion of the caudate nucleus body is attended with more serious disturbances of higher nervous activity than lesion of its head.     

Renewal and reinstatement of the conditioned but not the unconditioned response following habituation of the unconditioned stimulus

Research on the inhibition of learned fear currently relies almost exclusively on one specific procedure, namely extinction of the conditioned stimulus (CS). Importantly, however, learned fear responses can be reduced by a number of other procedures, including habituation of the unconditioned stimulus (US). We recently demonstrated that reductions in learned fear following US habituation, like CS extinction, were subject to both renewal and reinstatement (Storsve et al., 2010). The present study further investigates the associative and non-associative processes shared between habituation and extinction. Given that habituation is typically context-independent (Mackintosh, 1987), in the present study we directly compared renewal and reinstatement of both a conditioned response (CR; freezing) and an unconditioned response (UR; startle) following habituation. It was found that the reduction in conditioned freezing resulting from habituation was context specific (i.e., a change in context led to a renewal of the conditioned fear response; Experiment 1) and was attenuated when a pre-test shock was given (i.e., reinstatement of conditioned fear was observed; Experiment 2). In contrast, habituation of an unconditioned response elicited by the US (i.e., a startle response) was unaffected by either a change in test context or administration of a pre-test shock. This dissociation in the effects of habituation on learned and unlearned responses is discussed in relation to theories of fear extinction.     

The relationship between the dose of caffeine and the magnitude of conditioned reflex salivation in dogs]

Statistical estimates carried out on a comprehensive experimental material of the archives in the Laboratory of physiology of nervous system types at the Pavlov Institute of Physiology, USSR Academy of Sciences, made it possible to plot average static characteristics of changes in the magnitude of positive conditioned reflexes in dogs, depending on the dose of caffeine. It appeared that conditioned reflexes decreased to some extent after a 0.01 g dose; within the range of 0.05 to 1 g doses, the magnitude of reflexes increased to the maximum; within the range of 0.1 to 0.5 g, their magnitude diminished from the maximum to the normal level, and, finally, a dose of 0.5 g or greater resulted in a drop of the magnitude of the reflexes below the normal level.