418 A. L. TOWE 



In nearly every instance where activity in two units has been recorded 

 simultaneously via the same electrode (implying that the two units are close to 

 one another), one unit has shown the occlusive type of interaction while the 

 other has shown the active inhibitory type. Mountcastle and Powell (1959) 

 have reported a related response to tactual stimulation. Figure 6 illustrates 

 this phenomenon, showing a very short inhibitory interaction. It is evident, 

 therefore, that a topographical map of excitatory fields and inhibitory 

 "surrounds" for the units in a small patch of cortex would appear as a jumble 

 of fields. Closely spaced neurons in the cortex can "look back" to the same 

 stimulus input through different input populations, some elements of which 

 are excitatory and some inhibitory. 



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Amassian, V. E. (1953) Evoked single cortical unit activity in the somatic sensory areas. 

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Kennedy, T. T. and Towe, A. L. (1958) Response of somatosensory cortical units to 

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Morse, R. W. and Towe, A. L. (1959) Summation within the somatosensory system. 

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Mountcastle, V. B. and Povv'ELL, T. P. S. (1959) Neural mechanisms subserving cutaneous 

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Towe, A. L. and Amassian, V. E. (1958) Patterns of activity in single cortical units fol- 

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