PSYCHEDELICS - Sciencemadness.org

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____________________________________________________ Psychedelics
LSD-25 (either by mouth or injected into the peritoneal cavity),
he invariably noted an increase in threshold, i.e., an impairment
of vision, whereas motor and discriminative functions
were not grossly disturbed. The rise in threshold could
again be related to the reduction in transmission in the thalamus,
as noted by Evarts.
The present author studied the effect of LSD-25 on visually
evoked responses in rabbits (Koella and Wells, 1959). The
animals were supplied with chronically implanted electrodes
to record the signals in the visual projection area of the cortex
in response to repetitive (one every five seconds) light flashes.
During the experiments the rabbits were semi-restricted in
their movements by being wrapped in burlap sacking, but
were otherwise unrestrained by either mechanical devices or
drugs. We confirmed Purpura's observations that LSD-25
(25-50 µg total dose) increased somewhat the cortical
evoked response (figure 5, A).
More significant, however, was an additional observation
pertaining to variability of response. It is common knowledge
that under physiological conditions and particularly in awake
animals, indicators such as evoked responses vary greatly in
amplitude when the stimulus is given repetitively to produce
a whole series of evoked signals. In our experimental situa-
tion, the evoked responses (to constant, standardized stim-
uli) changed in amplitude over a range as great as 1:20 or
more. LSD-25, in the dose mentioned, drastically decreased
this variability down to about 25 per cent of the original
value (figure 5, VA, and figure 6 ) . The latency of the re-
sponse (i.e., the time elapsed between the stimulus and the
appearance of the response, signaling the transmission time
from the retinal light receptors to the cortex) was somewhat
decreased, and again its variability was greatly reduced under
LSD-25 (figure 5, VL).
amplitude and latency) at each time for each of seven animals.
In the case of variability, they indicate variance of the ten meas-
urements. The full lines represent the means for all seven ani-
mals. Note slight protracted increase in amplitude and decrease
in latency after LSD-25 (given at o hours). Note decrease and,
after one to two hours, increase of variability of amplitude and
latency. (From Koella and Wells, 1959; reprinted by permission
of the American Journal o f Physiology.)