Evoked responses of the lateral geniculate body to photic stimulation in intact and visually deprived rabbits

Evoked responses of the lateral geniculate body and visual cortex to stimulation of the contralateral eye with flashes were recorded in rabbits kept in total darkness from birth until the age of 2–3 months. The experiments were carried out under pentobarbital anesthesia and dark adaptation conditions. By contrast with the marked decrease in amplitude of primary visual cortical responses in the visually deprived animals, the amplitudes and temporal parameters of the LGB evoked responses were virtually identical with the corresponding parameters in the control animals. These results suggest that disturbances arising in rabbits as a result of early visual deprivation are localized mainly at the cortical level. The possible mechanisms lying at the basis of the functional disturbances in rabbits reared under conditions of visual deprivation are discussed.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 504–509, September–October, 1978.     

Ventilatory response of the cat to hypoxia in sleep and wakefulness.

This study characterized ventilation, the airflow waveform, and diaphragmatic activity in response to hypoxia in the intact adult cat during sleep and wakefulness. Exposure to hypoxia for up to 3 h caused sustained hyperventilation during both wakefulness and sleep. Hyperventilation resulted from significant increases in minute ventilation due to increases in both tidal volume and frequency. Diaphragmatic activity changed significantly from augmenting activity with little postinspiratory-inspiratory activity (PIIA) in normoxia to augmenting activity with increased PIIA in hypoxia. The increase in PIIA was least in rapid eye movement sleep. These changes in diaphragmatic activity were associated with changes in airflow waveforms in inspiration and expiration. We conclude that the ventilatory response to hypoxia involves a change in the output of the central pattern generator and that the change is dependent in part on the state of consciousness.     

Unit responses of the cat lateral geniculate bodies to visceral and somatic stimulation

Acute experiments on cats anesthetized with pentobarbital and immobilized with Diplacin or Listhenon showed that electrical stimulation of the vagus, splanchnic, pelvic, and sciatic nerves and also of the mesencephalic reticular formation induces either a prolonged change in the frequency of unit activity or phasic responses of single units of the lateral geniculate body. During stimulation of the visceral nerves tonic changes in unit activity were predominant, whereas phasic responses were found more often during somatic stimulation. Most neurons tested responded to all types of stimulation used and only 15–18% responded only to the specific stimulus: photic stimulation of the receptive field. The results suggest that interaction of visceral, somatic, and sensory-specific excitation takes place on single neurons of the lateral geniculate body.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Ivano-Frankovsk Medical Institute. Translated from Neirofiziologiya, Vol. 5, No. 3, pp. 246–252, May–June, 1973.     

Influence of the motor cortex on lateral geniculate responses evoked in the cat by contralateral superior colliculus stimulation

It is shown that in nembutal anesthetized cats, a single stimulation of motor cortex (MC) causes a response in lateral geniculate nucleus (LGN). The development of this response had a conditioning effect on the LGN response evoked by stimulation of the contralateral superior colliculus (SC), markedly inhibiting it. The degree of this inhibition depended on the time interval between the cortical conditioning stimulation and the tectal test stimulation. A single conditioning MC stimulation did not noticeably change the LGN responses evoked by a light stimulus, but markedly inhibited visual responses from deep SC layers (those regions which on stimulation gave rise to LGN responses). From the results, it is suggested that the MC monitors the execution of tectal influences on LGN function at the tectal level rather than the geniculate level, and it is precisely by this means that it regulates saccadic suppression of LGN function, in the realization of which, as presumed earlier, the SC takes part.A. I. Karaev Institute of Physiology, Azerbaijan Academy of Sciences, Baku. Translated from Neirofiziologiya, Vol. 24, No. 4, July–August 1992.     

Characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons of cat in response to changes in photic stimulation parameters

The effect of parameters of local photic stimulation of different points of the receptive field on the characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons within microintervals of time observed previously was studied in computer-controlled experiments on unanesthetized, curarized cats. Dependence on the degree of widening of the receptive field and the temporal characteristics of this process on the background illumination level, intensity, contrast, area, duration, energy, and orientation of a local rectangular or circular photic stimulus flashing in random order at 100 points of the tested part of the visual field was studied. It was concluded that the background illumination level and the intensity, size, duration, and orientation of the stimulus have a specific effect on dynamic reorganization of the receptive field. The effects of all the parameters studied on the dynamics of the receptive field were shown to be nonlinear functions with optimal values that differed for different cells. The possible functional role of this effect and also the probability that it may participate in information coding in the visual system are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 339–346, July–August, 1983.     

Plastic response changes in neurons from lateral geniculate body in rats submitted to conditional reflectory stimulation]

In alert curarized rats the influence of an electric stimulation of the tail skin on the flash-evoked activity of single units of the dorsal part of the lateral geniculate body (CGLd) was investigated. The light flashes were applied 400 msec prior to the electric shocks. 50% of the units showed a change of the response pattern to flash. In the majority of cases the response shifts consisted in a facilitation, which developed gradually and persisted in most of the units examined, even when the electrical stimulus was no longer given in combination with the light. The results are discussed taking into consideration the possibility of an altered emotional or motivational status of the animal, which could play a role in the development of plasticity at the unitary level.     

Compensatory sleep response to 12 h wakefulness in young and old rats

There is a pronounced decline in sleep with age. Diminished output from the circadian oscillator, the suprachiasmatic nucleus, might play a role, because there is a decrease in the amplitude of the day-night sleep rhythm in the elderly. However, sleep is also regulated by homeostatic mechanisms that build sleep drive during wakefulness, and a decline in these mechanisms could also decrease sleep. Because this question has never been addressed in old animals, the present study examined the effects of 12 h wakefulness on compensatory sleep response in young (3.5 mo) and old (21.5 mo) Sprague-Dawley and F344 rats. Old rats in both strains had a diminished compensatory increase in slow-wave sleep (SWS) after 12 h of wakefulness (0700-1900, light-on period) compared with the young rats. In contrast, compensatory REM sleep rebound was unaffected by age. To assess whether the reduced SWS rebound in old rats might result from loss of neurons implicated in sleep generation, we counted the number of c-Fos immunoreactive (c-Fos-ir) cells in the ventral lateral preoptic (VLPO) area and found no differences between young and old rats. These findings indicate that old rats, similar to elderly humans, demonstrate less sleep after prolonged wakefulness. The findings also indicate that although old rats have a decline in sleep, this cannot be attributed to loss of VLPO neurons implicated in sleep.     

Viscosity increase of holothurian body wall in response to photic stimulation

• 1.1. The dermis of body wall of Holothuria leucospilota Brandt rapidly increased in viscosity in response to a flashlight.
• 2.2. The response was inhibited in a preparation from which the epidermis had been removed or in a preparation anaesthetized with menthol.
• 3.3. The results strongly suggest that the viscosity of the connective tissue is controlled through nervous activities.

     

Spatial frequency response function of lateral geniculate neurons

In 1969 Campbell et al. reported five spatial frequency response curves. Here a good curve fit is found to three of them based on a model of lateral inhibition from four off-centered geniculate cells whose receptive fields were at a common distance from that of an on-centered geniculate cell. The distance was 0.5° when the experimental curve was fitted by a difference of two Gaussians and 1.4° when fitted by a difference of two Bessel Functions. Of the remaining two response curves one was best fitted assuming no lateral inhibition and the other remains to be fitted.