Behavioural and electrophysiological changes during avoidance conditioning to light flashes in the rat

Abstract

In freely moving rats with chronically implanted epidural electrodes behaviour, respiration, motion, ECoG, visual evoked potentials (EP) and after-discharges (AD) were recorded during avoidance conditioning to flash series, after preceding short-lasting habituation to the experimental situation and to the CS. The changes in behaviour and in the electrophysiological parameters recorded during our experiments may be arranged in three regularly occurring phases: (a) phase of disturbance, (b) phase of adaptation and (c) phase of well adapted behaviour. The phase of disturbance occurs in the awake, freely moving animal with every essential change in situation. It is characterized by general excitation, acceleration of respiration, large decrease in amplitude of EP, strong desynchronization of ECoG and non-appearance of AD after light flashes. Intensity and duration of these changes are correlated with the intensity of disturbance and the degree of training. This phase is very quickly replaced by the phase of adaptation in which excitation becomes more and more confined, and goal-directed behaviour develops. Now the occurrence of inhibitory phenomena ( e.g. arrest reaction) can be observed. EP reach a maximum, background activity of the ECoG is still desynchronized but has a tendency to decrease in frequency and rise in amplitude, and AD appear. The phase of adaptation gradually changes into the phase of well adapted behaviour, in which the animal displays an unstrained, quiet behaviour. The conditioned motor acts are performed nearly automatically. EP, ECoG and AD are the same as in a quiet undisturbed animal which has a tendency to fall asleep. From all this one can see that the same general laws are fundamental to habituation, conditioning, and extinction, getting their specific characters through special processes corresponding to the specificity of the situation, for instance the special motor activation during the conditioned motor reflex (occurrence of 6–9 c/sec rhythm) or the extremely strong occurrence of inhibitory phenomena during extinction (EP and number and duration of AD are particularly increased).