-Abstracts of the Conference on Effects of Diffuse Electrical Curr-,nts on Physiological Mechanisms with Application to Electroanesthesia and Electrosleep, Vol.. Wilson Marquette Univers
Trang 1'f
-Abstracts of the Conference on Effects of Diffuse Electrical Curr-,nts on Physiological Mechanisms with Application to Electroanesthesia and Electrosleep, Vol 4, ~ (Milwaukee, ll"isconsin)
1q,7
The influence of electroonesthesio on the visual pothwo.ys
Edward J Zuperku Anthony Sances, .Jr
Sanford J Larson Arthur S Wilson
Marquette University; Wood \I A Hospital, Milwaukee
Unresponsiveness to mechanical and electrical stimulation was produced by 70 Hz, 3 ms duration, rectangular currents biased 2.5 ma above zero level Sinusoidal currents at various
frequencies were al so used For these studies the currents were applied between nasion and
inion of squirrel monkeys Jm taposed, bipolar electrodes were clmmically implanted in the optic
tract, lateral geniculate nucleus (LGN), optic radiation, and calcarine fissure area of 18 animals
Averaged evoked responses elicited by photic and electrical tract stimulation were retrieved
during current application
Responses in optic tract, LGN, and optic radiation decreased grndually with increased rectangular current levels Minimal change in evoked response occurre<l at the 2.5 ma de level
The responses were reduced to 20 per cent of control or less at the anesthetic level of 2.5 ma de
with 2.5-3.5 ma average rectangular current (ar) The cortical response due to photic stimulation
increased to appioximately 250 per cent of control at 2.5 ma de and 1.0 ma ar It decreased to
10-20 per cent of control at 2.5 ma de a.rid 3.5 ma ar The increased cortical potential did not occi1r with electrical stimulation of the optic tract or when photic stimulation and Nembutal
anesthesia were used With tract stimulation the response in LGN and optic radiation was
minimally affected by the rectangular current, however, the cortical response decreased with
increased current
Anesthetic levels of sinusoidal currents above 300 Hz minimally affected responses in the visual pathways Below 300 Hz the response in LGN was decreased It was necessary to
in-crease the current level with inin-creased frequency to maintain unresponsiveness
The results suggest that rectangular currents block at the retinal and cortical levels The increased cortical response also suggests the suppression of inhibition at low current levels
A mathematical model has been derived to explain the effects of rectangular current on the visual
pathways The model is based on excitatory a11d inhibitory interaction at the retina and cortex
36
I