Behavioral and neural short-latency and long-latency conditioned responses in the cat

Abstract

Differentiation of associative short-latency, orienting ("alpha") and long-latency, delayed ("true") conditioned responses was attempted in cats in which both behavioral responses (specific head movements to the conditioned stimulus (CS) and to the unconditioned stimulus (UCS)) and neural evoked responses, mainly from the hippocampus, were simultaneously recorded. The time-amplitude characteristics and the latency of these responses were used as criteria. The experimental design comprised two groups which received paired conditioning (CC) and randomly unpaired stimulus control (CO) treatments in a balanced order. This design permitted the study of habituation, sensitization, associative learning, as well as the mutual interaction of these treatments (preexposure effects). The results showed that both nonassociative habituation and sensitization, and associative short-latency and long-latency learning could be demonstrated in these groups at behavioral and neural response levels, and that the order of treatments either facilitated (the CC-CO group) or retarded (the CO-CC group) subsequent paired learning. The results also indicated some specific interaction of the CS and UCS during paired learning. The UCS is proposed as having some modifying effect on the time-amplitude characteristics of the response to the CS during the interstimulus interval (ISI). The theoretical part of the thesis attempts to relate recent empirical findings in different areas of neurobiological research to traditional concepts of the theory of learning and conditioning. Sensitization is suggested as playing an important role in both nonassociative and associative learning and is also considered to represent a probable explanation for the nature of instrumental responses and learning. Deliberate elicitation of the short-latency behavioral response (a directed head movement to the left) and the differentiable characteristics (latency and topography) of the unconditioned response in the present studies together with some preliminary observations of spontaneous head movements occurring during intertrial intervals (ITI) of the paired training sessions lend empirical support to these hypotheses.