The name is absent

54 The Rice Institute Pamphlet

three different purposes: (1) to specify more precisely the
actual cortical points of stimulation and their effects, (2) to
examine more closely the sensory and motor processes re-
lated to electrical stimulation, and (3) to determine the ef-
fects on behavior resulting from the surgical excision of corti-
cal tissue.

(1) Attempts to specify more precisely the cortical points
of stimulation and their effects ran into two kinds of diffi-
culties. First, repeated stimulation of the same location for a
particular patient did not always elicit the same response.
Depending on other conditions, not all well understood, the
stimulation of a point which had resulted in a particular^- re-
sponse might yield the opposite response, a response appro-
priate to an adjacent area, a combination of several responses,
or no response at all. Second, although the topographical
mappings from patient to patient showed the same general
order, the cortical location and the amount of tissue involved
varied widely. For surgical purposes it was necessary to re-
plot the effects of electrical stimulation for each patient
(Penfield & Rasmussen, 1950). Not only were the responses
to stimulation variable, but the tissues themselves varied
greatly. Detailed histological studies of the cortex measuring
surface, volume, thickness, number of neurons, and density,
among other characteristics, reveal such variability between
specimens that statistical analyses are coming to be accepted
as necessary procedures (Lashley & Clark, 1946; Sholl, 1956).
Lashley (Jeffress, 1951) found that animals grossly indistin-
guishable in behavior might have brains which differed by
100 per cent in the average size of cells in certain sections of
the frontal lobes or by 50 per cent in the number of nerve
cells in the temporal lobes; certain cells present in one brain
might be absent in the other. Lashley concluded that “the
anatomic variability is so great as to preclude . .. any theory

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