. Brain mechanisms and learning, a symposium. Psychophysiology; Learning, Psychology of. J. C. ECCLES 343 synaptic terminals and account for at least part of the depressed synaptic efficacy. It is important, therefore, to attempt by other procedures to produce a profound diminution of the discharge of impulses from the annulospiral endings of the muscle spnidles belonging to the muscles under test. Several experimental procedures, either alone or in suitable combination, have been tried (Westerman, unpublished). For example, tenotomy or splinting the limbs in plaster should considerably reduce
. Brain mechanisms and learning, a symposium. Psychophysiology; Learning, Psychology of. J. C. ECCLES 343 synaptic terminals and account for at least part of the depressed synaptic efficacy. It is important, therefore, to attempt by other procedures to produce a profound diminution of the discharge of impulses from the annulospiral endings of the muscle spnidles belonging to the muscles under test. Several experimental procedures, either alone or in suitable combination, have been tried (Westerman, unpublished). For example, tenotomy or splinting the limbs in plaster should considerably reduce the activation of the stretch receptors of a muscle, although it must be realized that annulospiral endings arc extremely sensitive to mechanical stimuli and certainly could not be silenced by these procedures (Matthews,. Min Fig. 4 Min Plots of the time courses of post-tetanic potentiations of EPSPs produced by a conditioning tetanus of lo seconds at 400 c/s, as indicated by the hatched coknnns. Specimen records are shown in Fig. 3. In Fig. 4 A the heights of the EPSPs are plotted relative to the control height, open circles being for the operatively severed pathway (FDL) and filled circles for the control pathway (FHL). Fig. 4B as for Fig. 4A, but for maxinuim slopes of the rising phases of the EPSPs. Note that in Fig. 4A the time scale is greatly shortened after 3 minutes (reproduced from Eccles, Krnjevic and Miledi (1959), with permission 01 the Jonnuil of Physiology). 1933; Hunt and Kuffler, 1951; Kobayashi, Oshima and Tasaki, 1952; Granit, 1955). In attempting further to reduce their discharge, the appro- priate ventral roots have been severed so as to suppress the activation of muscle spindles by impulses in the gamma efferent fibres (Leksell, 1945; Kuffler, Hunt and Quilliam, 195 i; Hunt, 1951; Granit, I955)- I11 all these experiments, controls were provided by the symmetrical reflex paths of the other limb, where a suitable dummy operation had been performed; and, in
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