Conditioning pp 663-676 | Cite as

A Neural Analog of Conditioning: Modifications of Pyramidal Tract Response

  • L. L. Voronin
  • V. A. Markevich
Part of the Advances in Behavioral Biology book series (ABBI, volume 26)


Two basic explanations of conditioning at neurophysiological levels are known (see Kandel 1976; Voronin, 1976, 1980a with references). The first one postulates changes in synaptic efficacy and the second one presumes modifications in neuronal postsynaptic properties (membrane threshold, endogeneous pacemaker and the like). We shall refer to these two classes of hypotheses as “synaptic” and “membrane” hypotheses, correspondingly. Most theorists favour synaptic hypotheses, although it has been strongly supported only for the most simple type of learning — i.e. habituation of defensive reflex in invertebrates (Kandel, 1976; Zucker, 1972). In conditioning experiments Woody et al. (1970) and Woody and Engel (1971) found that thresholds for direct electrical stimulation in motor areas projecting to the target muscle of the conditioned response (CR) were lower in conditioned than in naive animals. These data were not supported for other types of CRs (Kotlyar et al., 1979). Nevertheless some measurements, especially those of Woody and Black-Cleworth (1973), with intracellular recordings may be interpreted as an indication of a decrease in membrane thresholds as a postsynaptic mechanism underlying the elaboration of the CR. Long lasting postsynaptic resistance shifts of cortical neurons have been found in. experiments (Woody et al., 1978) which imitated some features of conditioning procedures and might be termed “cellular analogs” of CRs (see Kandel, 1976). On the other hand, changes in amplitude of excitatory postsynaptic potentials (EPSP) have been found in motor cortical neurons in our experiments (Voronin and Kozhedub, 1971; Voronin, 1976, 1980a) and by other authors (Baranyi and Feher, 1978) on cellular analogs of CRs. Moreover, short latency EPSPs were found to appear in neurons of sensorimotor cortex after elaboration of a behavioral CR — a so called “local conditioned startle response” (Voronin and Ioffe, 1974; Voronin, 1976, 1980a). These data have been considered as the experimental support of the idea that an increase in the efficacy of excitatory synapses underlies behavioral conditioning.


Conditional Stimulus Conditional Stimulus Presentation Direct Cortical Stimulation Additional Wave Pairing Procedure 
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Copyright information

© Springer Science+Business Media New York 1982

Authors and Affiliations

  • L. L. Voronin
    • 1
    • 2
  • V. A. Markevich
    • 1
    • 2
  1. 1.Brain InstituteAcademy of Medical SciencesMoscowUSSR
  2. 2.Institute of Higher Nervous Activity and NeurophysiologyAcademy of SciencesMoscowUSSR

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