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46
DONALD
R.
ROBERTS
Behavioral arousal.
The hypnotic symptoms, especially somnambu-
lism and the abolition of the primary fear and anger reactions
to
pe-
ripheral stimulation, seem
to
demand the inhibition of the mechanism
of behavioral arousal
as
a
primary condition of hypnosis.
It
is
an
es-
tablished paradox that electrocortical arousal
is
not necessarily accom-
panied by the behavioral signs
of
arousal,
indicating different mech-
anisms for the two forms of
arousal.
Behavioral arousal
has
been
associated with activity of the posterior hypothalamus
(R.
Hess,
1954)
and with activity of the corticofugal projections into the brain stem
(French et al.,
1955;
Segundo et al.,
1955).
It
is
possible that both of
these are involved through reciprocal connections.
R.
Hess found that,
while electrical stimulation of mesencephalon, intralaminar thalamus,
and posterior hypothalamus produce virtually identical signs of bioelec-
trical arousal, with desynchronization of electrical activity in the cortex,
the posterior hypothalamus alone of these three areas will upon stimula-
tion effect “clearcut and often dramatic arousal, characterized by gen-
eral excitation, by fear and escape reactions and
also
by pronounced
searching.”
While the nature of the mechanism of behavioral arousal has not been
fully established, the present postulate
is
that
an
inhibition of behavioral
arousal is associated with the inhibition of the corticofugal projections
into the brain stem reticular formation which may be held to cause
sensory suppression in hypnosis,
so
that inhibition of arousal may be
regarded as either a consequence
or
a parallel of the suppression of
sensory data discussed in the next paragraphs of this paper. A number
of indications in recent research suggest that
it
may ultimately be es-
tablished that general excitation of the organism,
or
the state of alert
awareness of environment, which is notably absent in hypnosis, is ac-
tivated primarily through the neurons1 pathways from hypothalamus
through the anteromedial nucleus
of
the thalamus to anterior cingulate
cortex,
together
wi th
the powerful projections from this cortex back into
the center median and other parts
of
the central integrating system (see
Jasper et al.,
1952).
Sensory
suppression.
The modes
of
interaction between the specific
sensory system and the central integrating system have been intensively
investigated. Jasper and his associates
(1952)
speculated that the cen-
tral system “must have the patterns of cortical elaboration available to
it,”
and traced corticofugal projections from parastriate, frontal, tem-
poral, and anterior cortex
into
the central brain stem system a t dien-
cephalic and mesencephalic levels. Further experiment
on
these projec-
tions (Sloan and Kaada,
1953;
Segundo et
al.,
1955;
French et al.,
1955)
has corroborated and extended these findings:
a
recent study (Adev et
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