Letter | Published:

Evoked Single Cortical Unit Activity in the Primary Cortical Receiving Areas

Naturevolume 169page971 (1952) | Download Citation



Amassian and Thomas are somewhat bold in implying that the complexities of the cortex can be reduced to no more than these simple and consistent patterns of response. Apart from their use of paralytic drugs, the main difference between our techniques lies in the size of electrodes used; mine were “of less than 5 µ diameter” and the action potentials of many millivolts amplitude were recorded only from electrodes of about 1 µ tip diameter. It is probable that electrodes of 4–12 µ tip diameter record distinct action potentials only from particularly large cells, which tend to be well separated, and this may be responsible for the simple and consistent responses obtained. Regarding the reproducibility of small electrode recordings, I have found that in a long series the number of action potentials evoked by a stimulus may vary widely; but there is a fairly constant latency at any one locus for the first appearance of action potentials belonging to a given group.

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  1. Department of Anatomy, University College, Gower Street, London, W.C.1

    • B. G. CRAGG


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