Basic HTML Version
50
DONALD
R.
ROBERTS
pyramidal cells (see diagram
of
Papez,
1956,
p.
124;
Li
e t al.,
1956;
Clare and Bishop,
1956).
Such
a
blocking could be effected by either a
“depression” of the granule cells
of
layer
2,
or
by
a
desynchronous pacing
of specific and unspecific impulses.
On
the other hand, inhibition could be conceived as occurring through
an interruption of intrathalamic connections, particularly those leading
t o the intrinsic nuclei. Inhibition a t
this
point would help to explain not
only the normality of the hypnotic
EEG,
but also the diversity and
lability of hypnotic effects, which would appear t o be correlated with
selective blockages in channels between thalamus and cortex.
Cortical
DC
standing potential is directly correlated with incidence
and with depth of hypnosis (Ravitr,
1951).
Recordings from the tem-
poral lobe, with a second electrode
on
the chest, showed a sharp shift,
positive
or
negative, during induction;
a
smoothing during trance; al-
terations with every alteration of the trance state; and a marked con-
trary shift of potential a t trance end. (The potential changes of up t o
40mv. compare with those occurring during “spreading depression.”)
It
would appear that the gradations of the hypnotic state are to be referred
t o
alterations in cortical DC standing potential.
It
is
possible that these
potential changes may be connected with
a
summatory effect of the
monotonous stimuli employed in hypnotic induction.
The confusing diversity of effectsproduced by the methods of medical
hypnotism can best be interpreted, from a logical and speculative stand-
point, by the hypothesis of
a
single mechanism operating selectively on
various brain channels.
It
is proposed that this mechanism may be the
slow sleep rhythms, the so-called “delta” rhythms with a normal fre-
quency of about
3
c/s.
Rhythms
of
this frequency, not encountered in simultaneous scalp
records, have been recorded from the depths
of
the frontal lobe in psy-
chotics (Sem-Jacobsen et al.,
19551,
indicating t ha t intracortical
or
subcortical delta activity can occur without being visible in the electro-
encephalogram.
Sem-Jacobsen and his associates
(1956)
have also observed focally
arrhythmic rhythms of
2 4
c/s in the region
of
the hypothalamus,
syn-
chronous with activity in the depths of frontal and temporal zones, “in-
dicating connections.” The slow delta rhythms disappear from the corti-
cal record during artificial hibernation (Gastaut,
1954;
BBrard and
Lairy,
1955)
,
a condition in which autonomic functions, such as body
temperature and metabolism,
regulated
by
the hypothalamus are grossly
disturbed. These rhythms have been observed
to
disappear from frontal
cortex with lesion
of
the anterior hypothalamus, but not with lesion of
the posterior hypothalamus. They seem t o be part
of
a different system
Downloaded by [University of Macedonia] at 02:09 29 March 2012