Evening star., 1936-02-18
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
laboratory and Stu
BY THOMAS r. HENRY.

With the brain Of an unconscious cat
electrical waves amplifled over a mil
lionfold, physiologists at the George
washington University School Of Medi-
cine, here, are listening to the cerebral
cortex, popularity known as the gray
matter" talk, sing, purr and thunder.
Some Of the strange phenomena, which
still await adequate explanation, were
described at q meeting OF prominent
neurologists and brain surgeons here the
other night by DR.. Wade II. Marshall
of the university staf. The apparatus
being used first was assembled by DR..
Marshall at the University of Chicago
few years ago, and he is continuing the
work here.
A cat is placed under ether and its
brain cortex exposed Then q minute
electrode is inserted in the brain tissue,
which picks up the tiny nerve impulses,
carries them to an oscillograph, where
they appear as q moving spot of light.
and to the loud speaker where they take
the form of waves of sound.
BY placing the electrode in the partic-
ular part of the brain through which
any given impulses habitually pass it is
possible to "tap the wires" and find out
what activity is going on.
A man sings into the unconscious cats
ear. The melody-Somewhat distorted,
but recognizable If one is familiar with
it-emerges from the loud speaker.
Characteristic sounds and oscillograph
wave pictures can be obtained by flash
ing a light before the animals eye and,
in some instances, by stroking parts OF
the body, provided the electrode has been
inserted in the right spot.
The fact that the completely anaes-
thetized animal is unconscious does not
seem to make any difference. The music
is "going round and round" in its brain
just the same, even If it cannot hear the
sounds. The nerve cells Of the whole
auditory tract are singing" as is evi-
denced by the melody coming out OF the
loud speaker. In fact, the responses
actually change very little as the ether
anaesthesia is deepened, until they
abruptly disappear.
When the electrode first is inserted
the loud speaker emits curious rasp-
ing sound, which Is due largely to a
mechanical effect and can be observed
even in dead tissue. This soon ceases
and wierd phenomenon follows. Roars
and howls begin coming from the loud
speaker. 1t actually sounds as If the
nerve cells were protesting this invasion
of their ancient mystery. Part 'of this
sound. Dr.. Marshall holds, is due to
impulses conveyed along the nerve tracts
from outside the brain, but some of 1t is
due to spontaneous discharges Of cells
and tracts. The spontaneous effects
show essential differences from sounds
which can be elected by outside stimula-
ton. For example, as ether anaesthesia Is
deepened they first increase and then
decrease, instead Of remaining un-
changed, and then terminating abruptly.
"The optic responses" said DR.. Mar
shall, showed fascinating popularity.
As in the case of the auditory responses,
we were able to trace the action poten-
tials produced by turning light on and
of through the essential optic tracts,
up to the cortex. With the tip Of the
needle just buried in the occipital cor
tex (where the center of vision is To-
Gated and which is mechanically stim-
ulated when one bumps the back of the
head hard enough to "see stars'9 or
almost anywhere on the optic tracts it
was possible 10 get good response by
merely moving the tips Of o pair Of fore
ceps before the animals eyes.