Jerzy Konorski (1903?1973) exerted a vital influence on the development of physiological psychology and neurobiology. Konorski and his friend and collaborator, Stefan Miller, distinguished instrumental conditioned reflexes as a separate type of acquired behavior, different from classical (Pavlovian) conditioned reflexes. In a series of pioneering studies Konorski demonstrated basic differences between the two types of conditioned reflexes. After the Second World War, he reinterpreted the results of research on conditioned reflexes on the basis of the mechanisms of Sherringtonian neurophysiology and introduced the term plasticity of the nervous system. His work, 'Conditioned reflexes and neuron organization', published in 1948, signaled Konorski's place as one of the founders of contemporary neuroscience. He contributed significantly to the understanding of complex interactions of various classes of behaviors: innate and acquired, those driven by opposite motivations, and those elicited by cues signaling different contingencies. In his book ' 'Integrative activity of the brain' (1967), Konorski analyzed the brain as a complex system directing the functioning of the organism as a whole.
A strong tendency not to return to the previously shocked compartment of a shuttle box was proposed as the main factor retarding two-way avoidance learning (1). It has been shown that the fly-away, rapid escape from an electrified grid, a species-specific defensive reaction of the rat, was observed at the very beginning of avoidance training. Subsequently latencies of the escape response increased, reflecting the conflict situation (2). Here, the modulatory role of a darkness (D) stimulus on the fly-away escape response is studied. Three groups each of 25 experimentally naive male rats were trained under unsignalled escape (Esc), signalled escape (Esc_D), or avoidance (Av_D) procedures. Only shock was presented in Esc, compound shock and darkness in Esc_D, and darkness preceded for 5 s and then accompanied shock in Av_D. The nominal 1.6-mA scrambled pulsed DC shock (50 Hz pulse rate) on the grid floor could be terminated (escaped) by running to the opposite compartment or prevented (avoided) by the same response during the signal-shock interval. The first escape latency was shortest in the Esc_D and longest in Av_D groups (P<0.05, Kolmogorov-Smirnov test; Fig. 1A). Simultaneous presentation of D and shock, presumably enhanced the fly-away escape response because of the higher energizing role of a compound. In contrast, the initial presentation of D in the delayed CS-US contingency may elicit an orienting reflex which interferes with the fly-away reaction. The gradual dissipation of group differences with continued presentation of the stimuli (Fig. 1B) supports this conclusion. During the first 10 trials there were no reliable changes in escape latencies in groups Esc_D or Esc. In contrast, curvilinear changes were revealed in group Av_D: the escape latency on trial 1 was longer than on trials 2, 5, and 6, whereas the escape latency on trials 5 and 6 were shorter than on each of trials 8, 9, and 10 (Kolmogorov-Smirnov test, Ps<0.05). The mean frequency of avoidance responses during these trials was small (0.024/trial). An even earlier increase in escape latency using the avoidance procedure was found with a more salient warning signal (3). Thus, differing from these escape procedures, the avoidance procedure induced the lengthening of escape latencies as early as the first 10 trials of training.
The changes of intertrial response (ITR) rate along the intertrial interval duration were examined in 30 rats trained in two way avoidance. The lowest ITR rate was observed just after a cross through response terminating a trial. Rats trained with a warning signal of darkness showed over all higher ITR rates and shorter periods of post trial reduction of ITR rate than rats trained with a more salient noise warning signal. The period of post trial low ITR rate lengthened in consecutive sessions indicating the gradual development of a safety state.
Two groups of 15 rats each were trained in a shuttle box to escape foot-shock either unsignalled or presented in compound with a visual cue: darkness. The visual cue presented in shock compartment amplifies the behavioral tendency actually prevailing in the response repertory of the rat. During the 1st session the compound enhanced the species-specific flight resulting in shortening of the rat?s escape latency. Thereafter, during subsequent sessions, darkness exaggerated resistance to enter the other compartment, thus escape latencies were longer under compounded than under unsignalled procedure. The darkness cue reduces the intertrial response rate relative to the unsignalled group. This latter finding supports the discrimination model of the effect, since the compound helps the animals to discriminate the illuminated ?safe? period between trials from the aversive shock period. Our data seem to suggest that the darkness presented synchronously with escapable grid-shock acquires aversive properties.
In separate groups of rat forward and backward procedures for classicla defensive conditioning were superimposed on on-going bar pressing for food.The forward conditioned stimulus elicited suppression of bar presses, indicating acquisition of fear.The backward stimulus paired with identical shock elicited behaviour typical for rats in a condition of safety and caused an increase of bar press rate.Enhancement of bar presses acquired in the cource of bacward conditioning was stable, immune to influences from unsignalled shocks presented in the same experimental context, and resistant to extinction when all shocks were discontinued.Properties of the employed variety of the backward conditioning procedure are discussed.QWhen a brief shock overshadowed the onset of a backward stimulus, the remaining portion of the stimulus became a signal of safety.