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Results for “Photic Stimulation”

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At least 19 recordsLinked to original sources

PubMed1977

[Response of neurons of the anterior and posterior regions of the hypothalamus to stimulation of the vagus and sciatic nerves and photic stimulation].

Evoked activity of single units in anterior and posterior hypothalamus to vagal, sciatic nerves, and photic stimulation was studied in anesthetized and immobilized cats. The responsiveness of neurons of the posterior hypothalamus was 66, 77 and 37% to vagal, sciatic nerves and photic stimulation, respectively, and of the anterior hypothalamus -- 47, 62 and 48%. Vagal stimulation was found to be the more effective for units of the posterior hypothalamus. Responses of units to a flash prevailed in the anterior hypothalamus. 78% of convergence of viscero-somatic afferentation on neurons of the posterior hypothalamus and 62% -- on anterior hypothalamic neurons, were revealed. The responses to all kinds of afferent stimuli were phasic and of excitatory character. Possible role and mechanisms of vagal interoceptive activation of hypothalamic units are discussed.

Animals↗

PubMedDate not supplied

[The induction of seizures in "Papio papio" following allylglycine alone or in combination with intermittent photic stimulation (author's transl)].

Allylglycine, an inhibitor of GABA synthesis, produces increased sensitivity to photic stimulation and in convulsant doses spontaneous seizures arising occipitally in the baboon (Horton and Meldrum, 1973). In this study, convulsant doses of allylglycine induced either sharp wave and polyspike frontorolandic discharges (FR) or critical posterior discharges which then reinforce the fronto-rolandic spikes. A seizure may then arise from the fronto-rolandic region and secondarily spread to the rest of the cerebral cortex. Intermittent photic stimulation produces a reinforcement of the fronto-rolandic sharp waves and can also induce self-maintaining mechanisms similar to those just described. In this situation, however, and with the animals paralysed with Flaxedil no seizures arising occipitally have been observed. The role of the occipital cortex as the sensory visual and somatic afferent in photosensitive epilepsy in the baboon is discussed in the light of these results.

Allyl Compounds↗

PubMed1978

Intermittent photic stimulation. Clinical usefulness of non-convulsive responses.

The clinical usefulness of non-convulsive responses induced by intermittent photic stimulation (IPS) was studied in 46 patients whose evaluation included both electroencephalography (EEG) and computerized cranial tomography (CT scan). Three patterns of photic responses were identified and related to background EEG activity and type of lesion seen on CT scan. An asymmetry in photic driving manifested only by a consistent amplitude difference greater than 50% was rarely associated with other EEG changes such as focal slowing or significant asymmetry in the alpha rhythm. In contrast, an asymmetry in development of the photic response correlated well with ipsilateral focal slowing and CT scan evidence of parenchymatous brain disease. Bilateral, symmetrical high amplitude single spikes evoked by individual light flashes were seen only in patients with diffuse encephalopathies. In no patient with structural brain disease as judged by CT scan was an abnormality in IPS the only EEG finding. There was also no apparent relationship between the anatomical site of a focal cerebral lesion and the type of response induced by IPS. Photic stimulation is of limited value in non-epileptic patients. Little clinical significance can be attached to nonconculsive responses in the absence of associated EEG changes which by themselves are generally more informative.

Adult↗

PubMed1975

EEG responses to photic stimulation in persons experienced at meditation.

The EEG responses to intermittent photic stimulation were examined in a group of subjects experienced in meditation, and compared with those of a control group. The meditators exhibited a significantly smaller decrement in alpha activity and alpha blocking over the course of the experiment than did the control group, and alpha induction occurred earlier and more frequently in the meditators. These findings support the hypothesis that experienced meditators spontaneously enter the meditative state on closing the eyes, and also the view that physiologically the meditative state is one of prolonged drowsiness. An alternative interpretation, that meditation is a state of sustained attention, is discussed.

Adult↗

PubMed1976

The EEG response to repetitive photic stimulation in various regions of the chicken brain.

The EEG response in the chicken to repetitive photic stimulation was studied by frequency analysis and by the averaged response. Evoked responses were observable not only in stations along the visual pathway but also in broad areas apart from the visual pathway. The electrical activity in the archistriatum showed a marked response to flickering stimuli, indicating that this area is involved in the visual function in the chicken. In other telencephalic areas, photically evoked potentials could not be clearly demonstrated in the EEG records. In the hypothalamus and the nucleus rotundus of the diencephalon and in the nucleus reticularis superior of the mesencephalon, sinusoidal waves appeared during stimulation at 8-13/sec. No rhythmic after-discharge was observed following termination of photic stimulation. These finding are indicative of the difference of the visual response in the chicken from previously reported responses in other species.

Animals↗

PubMed1979

Interaction between intermittent photic stimulation and auditory stimulation on the human EEG. Preliminary investigation through power spectral analysis.

The effects of flicker photic stimulation (6, 8, 9, 10, 11, 12, 14, 16 flashes/sec) and of white noise (80 dB SPL) on the EEG of man were investigated with the aid of power spectral analysis. In order to evaluate both the alpha attenuation response (AAR) and the 'driving' reaction induced by flicker as well as the effect of noise, the analysis was carried out on broad (delta, theta, alpha, beta) and on narrow (bandwidth: 1 Hz) spectral bands. A significant correlation between the amount of AAR induced by noise and a measure of the tendency to exhibit photic driving was found, though there was no clear-cut interaction between the photic stimuli and noise when delivered stimultaneously.

Acoustic Stimulation↗

PubMed1976

The involvement of the preoptic-suprachiasmatic region in the photosexual reflex in quail: Effects of selective lesions and photic stimulation.

Small bilateral lesions of the preoptic and anterior hypothalamic regions completely suppressed the light-induced testicular growth in quail. Photic stimulation was selectively applied to this region using a small pellet of radioluminous paint (RLP). This local photostimulation induced no testicular growth in short day quail. On the contrary, testes were markedly enlarged after RLP was implanted in the tuberal or in the dorsal area of the infundibular complex of short day quail. This response was as large as in controls reared under 18L-6D. It is therefore confirmed that neuronal populations located in the infundibular complex are directly photosensible. No direct photosensitivity was observed in the preoptic and anterior hypothalamic regions and it is suggested that these areas can serve as a relay for retinal information.

Animals↗

PubMed1977

Electroencephalographic responses to photic stimulation in habitual smokers and nonsmokers.

Two studies are reported in which electroencephalograms (EEGs) of habitual cigarette smokers and of nonsmokers were taken before and after they were required to smoke a cigarette. The EEGs were scored for incidence of EEG "driving" responses to photic stimulation, an index that appears to reflect the balance between central adrenergic and cholinergic nervous systems. The findings suggest that smokers tend to have a central autonomic balance less in favor of adrenergic functioning than do nonsmokers. Cigarette smoking may alleviate a possible central adrenergic insufficiency of smokers. These findings suggest a solution to "Nesbitt's paradox," which has reference to the fact that while nicotine is a central adrenergic stimulant, smokers describe the effect of smoking in sedational terms (i.e., as relaxing or calming).

Adolescent↗

PubMed1976