Lukowiak K, Colebrook E
Neuroscience Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
J Physiol (Paris). 1988;83(3):198-206.
Classical conditioning of the gill withdrawal reflex can be demonstrated in two different in vitro Aplysia preparations. The data obtained show that as conditioning of the gill withdrawal reflex proceeds there are changes in synaptic efficacy at the central sensory-motor neurone synapse. These changes in synaptic efficacy, however, are not necessary nor are they sufficient for the observed changes in gill reflex behaviour. Changes must be occurring at other loci within the nervous system to mediate the associative learning. We hypothesized, based on data obtained from one type of in vitro preparation, that changes occur in the ability of the motor neurone to elicit a gill withdrawal response as a result of classical conditioning training. In order to test this hypothesis we depolarized an identified gill motor neurone before and after classical conditioning and found that the motor neurone's ability to elicit a gill movement was facilitated following classical conditioning training. In control preparations that received an explicitly unpaired stimulus paradigm (which does not lead to classical conditioning of the reflex) there was a decrease in the efficacy of a gill motor neurone to elicit a gill withdrawal response. There are a number of possible sites within the integrated central (CNS) and peripheral (PNS) nervous systems where changes could occur to bring about the alterations in motor neurone efficacy. Our results suggest that changes in neuronal activity which underlie learning occur at multiple sites within the nervous system and that a complete understanding of the mechanisms of associative learning can only be obtained when all of these sites are taken into account.
鳃收缩反射的经典条件作用可以在两种不同的海兔离体标本中得到证明。所获得的数据表明，随着鳃收缩反射条件作用的进行，中枢感觉 - 运动神经元突触处的突触效能会发生变化。然而，这些突触效能的变化对于观察到的鳃反射行为的改变既非必要条件，也不充分。神经系统内的其他位点必定也发生了变化，以介导这种联想学习。基于从一种离体标本获得的数据，我们推测，由于经典条件作用训练，运动神经元引发鳃收缩反应的能力会发生变化。为了验证这一假设，我们在经典条件作用前后对一个已识别的鳃运动神经元进行去极化处理，发现经过经典条件作用训练后，该运动神经元引发鳃运动的能力得到了增强。在接受明确非配对刺激范式（不会导致反射的经典条件作用）的对照标本中，鳃运动神经元引发鳃收缩反应的效能有所降低。在整合后的中枢神经系统（CNS）和外周神经系统（PNS）内，有许多可能发生变化的位点，这些变化可能导致运动神经元效能的改变。我们的结果表明，作为学习基础的神经元活动变化发生在神经系统内的多个位点，只有考虑到所有这些位点，才能全面理解联想学习的机制。
