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ELECTROPHYSIOLOGICAL
THEORY
51
from the thalamic rhythms (Jasper,
1949).
They appear to regulate thc
basal electrical activity of the brain (Walter,
1953).
These findings are most coherently interpreted if they can be sup-
posed to indicate the anterior hypothalamus as the subcortical sub-
strate of the delta rhythms, and
as
the “diencephalic sleep center” of W.
R.
Hess
(1954).
Together with the
known
association of the posterior
hypothalamus with behavioral arousal, these indications combine
to
suggest that the hypothalamus may exercise
a
two-way “autonomic”
regulatory control over cephalic homeostasis (sleep and arousal) par-
allel and coordinate with the hypothalamic control over somatic sympa-
thetic-parasympathetic activities. The hypothalamus would appear
to
act in normal coordination in hypnosis, wth sympathetic inhibition and
parasympathetic activation.
Under this view the delta rhythms may be supposed to function to
maintain the excitability of cortex and subcortical pathways
at
the un-
conscious level of “sleep,” which is not the lowest level a t which the
organism can maintain life. The reciprocal connections
of
hypothalamus
and anterior cingulate
gyrus
(which is
known
to be concerned in somatic
autonomic activity) are presumed to be significant.
Such a theory strongly implies
a
hypnogenic function
for the delta
rhythms. The literature of experiment offers little to confirm or to con-
fute such a hypothesis, but
it
would seem that
a
dynamic mechanism
must be found to account for voluntary sleep induction, fainting, the
long comas accompanying brain injuries, and other behavioral symp-
toms indicative of
a
protective mechanism. A functional antagonism be-
tween the delta and the waking rhythms is implied, with hypnosis as
counternormal in the simultaneous maintenance, in different brain chan-
nels, of the functional activity of the opposing rhythms.
A
purely conjectural hypothesis of
antidromic
action of the delta
rhythms in hypnosis can be advanced,
on
physical grounds,
if
it
is pos-
tulated that the delta rhythms, which often exhibit large potential
oscillations, operate to clear and level field potentials in the brain (as
in the wave-and-spike discharges)
,
and that counternormal conduction
would therefore have the contrary effect of building up
a
localized
massed inhibitory field potential su5cient
to
block whole channels be-
tween midbrain and cortex. The instantaneous reversibility of hypnosis
and of hypnotic effecta
in
some subjects favors a theory of electrotonic
blockage by mass field potentials.
The following hypotheses for hypnotic inhibition are presented
for
experimental investigation
:
(a) dromic
or
antidromic rhythms
at
the delta frequency, cortically
induced by sleep suggestions, reinforced by rhythmic sensory
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