Neural Networks Proceedings of the -School on Neural Networks - June
Sciences may be nowadays grouped into three classes, having as their subjects of study respectively Matter, Life and Intelligence. That "Intelligence" may be studied in a quantitative manner is a discovery of our age, not less significant in many ways tha
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Edited by E. R. Caianiello With 80 Figures
Springer-Verlag New York Inc. 1968
ISBN 978-3-642-87598-4 ISBN 978-3-642-87596-0 DOI 10.1007/978-3-642-87596-0
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Fig. 3. Classification of neurones in primary auditory cortex according to the stimuli to which they would respond, respectively: visual only; no stimuli at al1; to some kind of sound, subdivided into neurones responding only to complex sounds and not to tones, and neurones responding to both
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Fig. 4a-e. Auditory cortex. Examples of neuronal response to tones. Each record displays the neural spike discharge (upper trace) and the stimulating tone (thickening on lower trace). a Sustained excitation. b Sustained inhibition. c, d, e: Transient responses to onset, termination, and onset and termination of tone, respectively. Time bars: 0.5 sec
Upper and Lower Levels of the Auditory System
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at any time was a function of many factors, including the frequency, intensity and repetition rate of the tone, and other factors as yet undefined. Many cells exhibited a labllity of response, that is, they failed to give consistent responses under apparently identical conditions. This last property is as distressing for the experimenter as it must be important for normal cortical function. In spite of these factors, it is generally possible to classify neurones by the response which they give under most stimulus conditions. It is interesting that in contrast to neurones in the cochlear nucleus, about half of the cortical cells were silent in the absence of stimulation. Furthermore, the response of a cortical neurone was not necessarily a monotonic function of intensity; in many cases high intensity stimulation at a given frequency was inhibitory, whereas, low intensity stimulation at the same frequency was excitatory. Dynamic stimuli, in this case modulation of frequency, produced in most cortical cells, very vigorous and consistent responses. In fact, there was a significant propor-
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Hg. 5a and b. Auditory cortex. Neurone activated by modulated tone but not by any steady tone. a No response to tone of 2.5 Kc/s. (Tone indicated by thickening of lower line.) Time scale as (b). b Vigorous though intermittent response to a tone of the same frequency and
intensity as that of (a), hut whose frequency was modulated sHghdy (± 2.5%) at a rate of 10 cIs. Envelope of lower Hne represents excursions of frequency tion of cells (10%) which would only respond to pure tones if the frequency was changing. Fig. 5 shows the responses of such a neurone. No steady tone was effective in exciting the cell (a), whereas it responded periodically (with int
