Effects of ethyl alcohol on the electrooculogram and color vision

Color vision tests and electrooculography (EOG) were performed in 6 male and 2 female healthy young trichromatic volunteers between 60 and 130 min after finishing consumption of ethyl alcohol leading to blood levels of approximately 0.07% to 0.16%. The average number of errors in the desaturated Panel D-15 arrangement test rose from 0.86 to 2.0; the average error score in the Farnsworth-Munsell 100-Hue test rose from 26 to 79. The axis of errors in both tests was clearly tritanopic and tetartanopic, pointing to a specific effect of ethyl alcohol on the function of blue-sensitive cones and/or their interaction with longer wavelength-sensitive cones.Ethyl alcohol decreased the size of the light-peak, apparently in a dose-dependent fashion, in each of the 16 eyes by values between 3% and 79%. The effect of alcohol on the EOG light peak was stronger between 30 and 95 min (23% decrease in average) than between 95 and 130 min (14% decrease) after the finish of alcohol administration.     

Premovement slow cortical potentials on self-paced hand movements and thalamocortical and corticocortical responses in the monkey

Chronically implanted electrodes on the surface and in the depth of the motor cortex in the monkey could record slowly increasing, surface negative-depth positive potentials that precede self-paced hand movements. Such premovement slow cortical potentials were interpreted to be composed mainly of currents due to excitatory postsynaptic potentials in superficial parts of the apical dendrites of pyramidal neurons through certain thalamocortical projections. To test the interpretation, the same electrodes were utilized to record cerebellothalamocortical responses and corticocortical responses evoked by electrical stimulation of the cerebellar nucleus and of the cerebral cortex. These results were compared with the laminar field potentials of cerebellothalamocortical and corticocortical responses recorded with glass microelectrodes in acute experiments with monkeys. The present study revealed a similarity of the cortical depth profile of premovement slow cortical potentials to that of the dentatothalamocortical responses, and supported the interpretation.     

Brain stem control of masseteric reflex activity during sleep and wakefulness: Mesencephalon and pons

Previous studies from our laboratories showed that stimulation of the pontomesencephalic reticular formation resulted in two distinct changes in masseteric reflex excitability which were dependent on the behavioral state of the animal (Chase, M. H., and M. Babb. 1973. Brain Res.59: 421–426). During wakefulness and quiet sleep, reticular stimulation resulted in an increase in reflex excitability. However, during active sleep, the identical stimulus delivered to the same reticular site led to profound reflex suppression. This phenomenon was termed “response-reversal.” The present study was designed to explore the presence of state-dependent control of motor excitability at rostral mesencephalic and pontine levels of the brain stem in chronic freely moving cats during sleep and wakefulness. Conditioning stimulation of mesodiencephalic sites induced only slight reflex facilitation or was without effect during wakefulness and quiet sleep; however, a dramatic suppression of reflex excitability was evoked with the identical stimulus during active sleep. At the level of the pontomesencephalic junction an effective region for “response-reversal” was found to coincide with the nuclei reticularis mesencephali and pontis oralis. The major effect resulting from stimulation of sites surrounding this region occurred exclusively during active sleep and consisted of reflex suppression. During active sleep, from all sites at both levels of the brain stem, only reflex suppression was obtained in conjunction with conditioning stimulation. These findings are discussed in terms of a model of state-dependent regulation of motor activity which accounts for the emergent capability of widespread regions of the brain stem to suppress reflex excitability solely during active sleep.     

Analysis of slow cortical potentials preceding self-paced hand movements in the monkey.

Cortical potentials related to the self-paced “voluntary” hand movement were recorded in unanesthetized, freely moving monkeys with the electrodes implanted chronically on the surface and in the depth of the cortex, and analyzed with the method of electronic averaging. Prior to the movement, surface negative — deep positive slow potential changes appeared in the motor and premotor cortices contralateral to the moving hand. The potential changes started about 1 s before the hand movement and increased gradually to about 100 ms before the movement. The contours of the potential changes preceding the movement were remarkably constant in daily recording for several weeks. Based on the laminar field potential analyses of cortical evoked potentials made in previous acute experiments, the slow potential was interpreted to be due to the currents of slowly increasing EPSPs that were generated in superficial parts of the cortical pyramidal neurons via certain thalamocortical projections. The EPSPs would activate the neurons in the motor and premotor cortices and contribute to the initiation of voluntary movement.     

Role of the nucleus reticularis tegmenti pontis on visually induced eye movements

Optokinetic nystagmus (OKN) and visual suppression of caloric nystagmus were tested in cats with electrolytic lesions in the nucleus reticularis tegmenti pontis (NRT) or with hemicerebellectomies. The animals with a NRT lesion could follow higher stimulus velocities, but the eye movement output saturated at 10°/s. In the hemicerebellectomized cats, on the other hand, slow-phase OKN velocity was normal at stimulus velocities less than 30°/s. In addition, OKN impairment was more transient in the cats with hemicerebellectomies than in those with NRT lesions. In the cats with a NRT lesion, loss of visual suppression of caloric nystagmus was apparent in nystagmus with the slow phase toward the lesion side, whereas in cats with hemicerebellectomies, it was toward the contralateral side to the lesion. These findings suggest that the NRT may be a part of the relay nuclei mediating optokinetic signals responsible for OKN at all optokinetic stimulus velocities and the flocculus may be responsible for OKN at higher optokinetic stimulus velocities. In addition, the NRT may also be one of the prefloccular nuclei conveying visual input signals responsible for visual suppression of caloric nystagmus to the contralateral flocculus.