which for strong feedback over many paths has an approximate magnitude . Since, however, both Tin and TB are proportional to the
gain k, we have a transmission modulus that is practically independent of k.
Fluctuations of gain in the M feedback paths tend to cancel out if they occur
at random about a stable mean value and the summating unit is thus more
accurate than one operating without feedback.More complex circuits giving what has been called 'detail filtering' and
'maximum amplitude filtering' have also been described (Taylor, 1959), and
the main problems for the future appear to centre on the classification of types
of circuit and quantitative analysis of their properties. Eventually it may be
possible to draw accurate signal flow diagrams from observation of the nervous
system but at present we can only make hypothetical diagrams that do not
conflict with any observations of anatomy and neurophysiology for the region
considered.
REFERENCES
| BURNS B. DELISLE ( 1954). The production of after bursts in isolated unanaesthetized cerebral cortex. J. Physiol 125, 427-446. | |
| COLE K. S. ( 1955). Automatic computation of nerve-excitation. National Bureau of Standards Report No. 4238, 1-39. | |
| ECCLES J. C. ( 1953). The Neurophysiological at Basis of Mind. Oxford. p. 132. | |
| HODGKIN A. L. ( 1948). The local electric changes associated with repetitive action in a non-modullated axon. J. Physiol. 107, 163-181. | |
| HODGKIN A. L. & HUXLEY A. F. ( 1952). A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. 177, 500-544. | |
| MASON S. J. ( 1953). Feedback Theory--some properties of signal flow graphs. Proc. I.R.E. 41, 1144. | |
| MCINTYRE A. K. ( 1956). Multiple firing at central synapses. Nature, Lond. 178, 302-304. | |
| TAYLOR W. K. ( 1955). Electrical simulation of some nervous system functional activities. Information Theory, Ed. Cherry C. Butterworth. 314-328. | |
| TAYLOR W. K. ( 1959). Pattern recognition by means of automatic analogue apparatus. Proc. Inst. Electrical Engs.106B., No. 26. 198-209. | |
| UTTLEY A. M. ( 1954). The classification of signals in the nervous system. E.E.G. Clin. Neurophysiol. 6, 479-494. |
EXPLANATION OF PLATES
| Plate 1. For explanation, see text. | |
| Plate 2. Voltage waveforms at points in the neuron and synapse analogues. | |
| Plate 3. Responses of the circuit shown in Fig. 5. |
-168-
Questia, a part of Gale, Cengage Learning. www.questia.com
Publication information:
Book title: Models and Analogues in Biology.
Contributors: Society for Experimental Biology - OrganizationName.
Publisher: Academic Press.
Place of publication: New York.
Publication year: 1960.
Page number: 168.
This material is protected by copyright and, with the exception of fair use, may not be further copied, distributed or transmitted in any form or by any means.
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