PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Photic Stimulation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1997

Induction of NGFI-A gene expression in the rat suprachiasmatic nucleus by photic stimulation.

Photic induction of NGFI-A gene expression was investigated in the rat suprachiasmatic nucleus (SCN) using in situ hybridization histochemistry. Following light exposure for 30 min, NGFI-A mRNA appeared in the ventral portion of the rostral SCN, in the ventrolateral and in part of the dorsomedial portion at the middle level, and in the lateral portion of the caudal SCN. The distribution of NGFI-A mRNA was wider than that of c-fos mRNA which was confined to the ventrolateral portion at the middle level of the SCN. By double labeling in situ hybridization, approximately half of NGFI-A mRNA-positive cells in the SCN were shown to coexpress vasoactive intestinal peptide (VIP) mRNA, while 16% of cells positive for c-fos mRNA coexpressed VIP mRNA. These findings indicate that the broadness of NGFI-A mRNA and c-fos mRNA expression after photic stimulation are different. NGFI-A gene induced in these cells of the SCN including VIP neurons may be involved in circadian entrainment by light.

Animals↗
PubMed2006

Spectral F-test power evaluation in the EEG during intermittent photic stimulation.

Intermittent photic stimulation (IPS) is an important functional test, which can induce the photic driving in the electroencephalogram (EEG). It is capable of enhancing latent oscillations manifestations not present in the resting EEG. However, for adequate quantitative evaluation of the photic driving, these changes should be assessed on a statistical basis. With this aim, the sampling distribution of spectral F test was investigated. On this basis, confidence limits of the SFT-estimate could be obtained for different practical situations, in which the signal-to-noise ratio and the number of epochs used in the estimation may vary. The technique was applied to the EEG of 10 normal subjects during IPS, and allowed detecting responses not only at the fundamental IPS frequency but also at higher harmonics. It also permitted to assess the strength of the photic driving responses and to compare them in different derivations and in different subjects.

Adolescent↗
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↗
PubMed1999

Photic stimulation: standardization of screening methods.

PURPOSE: Differences in methodology of intermittent photic stimulation within and between countries in Europe make collaborative research and interpretation of results difficult. METHOD: Experts in the field of photic stimulation from European countries have given an overview of methods used in routine photic stimulation. A consensus meeting was organized in May 1996 in the Netherlands. RESULTS: Methodology, including specification of a photo stimulator, procedure of photic stimulation, and interpretation of EEG results, has been defined according to available scientific and clinical knowledge. CONCLUSIONS: Consensus was reached in setting up a safe, quick, simple and reliable method to determine whether or not patients are photosensitive. A specification of an international standard for intermittent photic stimulation in the routine EEG examination is given with the purpose of improving patient care and facilitating collaborative research.

Electroencephalography↗
PubMed1980

The effect of background illumination on sensitivity to intermittent photic stimulation.

Sensitivity to intermittent photic stimulation (IPS) was tested in 23 photosensitive epileptic subjects under conditions of normal and reduced ambient lighting. Darkening the room to 20 lux did not increase either the incidence of photosensitivity or the effective range of flash frequencies. It is concluded that for routine clinical EEG examination there is no advantage in the current practice of darkening the room during IPS. For exhaustive testing of photosensitivity it is, however, necessary to perform IPS both in light and darkness.

Adolescent↗
PubMed1997

EEG-driven photic stimulation effect on plasma cortisol and beta-endorphin.

The effect of EEG-driven photic stimulation on stress-related endocrine function was studied. Subjects were 16 healthy males divided into a photic stimulation group (n = 8) and a control group (n = 8). Electrodermal and emotional lability measures were assessed by nonspecific skin conductance response and the Maudsley Personality Inventory, respectively. Plasma cortisol and beta-endorphin concentrations were measured both before and after EEG-driven photic stimulation as well as the resting condition. Subjects with electrodermal, emotional, or both lability showed comparable decreases of plasma beta-endorphin on photic stimulation as did the stable subjects. Under resting control conditions, however, they showed significant increases of beta-endorphin compared to both stable subjects as well as the photic stimulation condition. In addition, labile subjects showed significant alpha enhancement on photic stimulation compared to stable subjects and to the resting control condition. The data suggest that increases of plasma beta-endorphin in labile control subjects may denote a stress response to the conditions of these experiments, and that any decrease by EEG-driven photic stimulation may indicate a reduction of responsiveness to an acute stress.

Adult↗
PubMed1999

Age-dependent alteration of metabolic response to photic stimulation in the human brain measured by 31P MR-spectroscopy.

Effects of photic stimulation (PS) on energy metabolism were examined in the occipital cortex of 25 healthy volunteers aged 23-69 years old using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). A significant effect of photic stimulation was found only for intracellular pH (p<0.05 by repeated measures analysis of variance) but not for any peak area ratios. An interaction between intracellular pH and age were statistically significant (p<0.005), and the interaction between phosphocreatine and age was close to significance (p=0.06). In subjects aged more than 40 years old, phosphocreatine was significantly decreased during the photic stimulation (p<0.05, multiple comparison by Dunnett's method), and intracellular pH tended to be elevated just after the stimulation (p=0.07). There were no significant changes in these values in younger subjects. These results suggest that no significant effect of photic stimulation on brain energy metabolism was found in younger subjects, and that significant effects of photic stimulation on intracellular pH and phosphocreatine were found in middle-aged subjects. Metabolic response of the human brain to photic stimulation may be dependent on age.

Adult↗
PubMed1993

[Stimulus time dependence of cerebral blood flow response to photic stimulation].

The time dependency of rCBF response to photic stimulation in the primary visual cortices was studied using H215O bolus-injection and PET. The subjects consisted of 5 normal volunteers aged from 25 to 40 years old. Their regional CBF was measured at 2 min and 7 min after the start of photic stimulation (frequency, 10 Hz). The percentage increases of rCBF were 19.6 +/- 7.9% (mean +/- SD, range: 8.9-27.6%) in the primary visual cortex on the left side and 23.2 +/- 13.6% (2.5-35.8%) on the right side at 2 min, respectively, while, in comparison, they were 25.3 +/- 20.0% (1.8-49.7%) on the left side and 25.3 +/- 16.4% (3.5-44.5%) on the right side at 7 min, respectively. No significant difference was found in the rCBF responses between at 2 min and 7 min. Therefore, the taming effect does not need to be considered when carrying out a photic stimulation study.

Adult↗
PubMed1998

Sex and electroencephalographic synchronization after photic stimulation predict signal changes in the visual cortex on functional MR images.

PURPOSE: We evaluated factors that influence MR signal changes during photic stimulation of the visual cortex. We also tested the hypothesis that functional MR imaging response corresponds to electroencephalographic (EEG) synchronization after photic stimulation. METHODS: Thirty-eight healthy subjects, 20 men and 18 women, underwent photic stimulation of the visual cortex. They were studied with a 1.5-T MR unit, and photic stimulation was induced via 8-Hz LED goggles. Seven subjects with and seven without detectable functional MR imaging response to photic stimulation underwent further studies with 16-channel EEG after 2- to 30-Hz stroboscopic stimulation. RESULTS: Thirteen men and 18 women had a significant increase in MR signal in the visual cortex; seven men showed no visual cortex activation during more than two repeated studies. Six of seven volunteers with increased functional MR imaging signal after photic stimulation also showed signs of EEG synchronization when an 8-Hz stroboscopic flash was used; six of seven subjects with no functional MR imaging lacked EEG synchronization at 8-Hz stimulation. CONCLUSIONS: Men were more likely than women to have undetectable MR signal changes after photic stimulation. This finding should be considered when interpreting results of functional MR imaging studies. EEG with stroboscopic examination is a good predictor of functional MR imaging sensitivity to changes in regional cerebral blood flow induced by sensory stimulation.

Adult↗
PubMed1997

Electroencephalographic abnormalities in patients with presenile dementia of the Alzheimer type: quantitative analysis at rest and during photic stimulation.

In the present study, quantitative electroencephalographic (EEG) analysis was performed at rest and during photic stimulation (5, 10, and 15 Hz) in nine patients with presenile dementia of the Alzheimer type (AD; mean age at onset, 55 years) and nine sex- and age-matched control subjects. Compared with the normal controls, the AD patients had a significantly lower alpha-2 and beta band power in the resting EEG as well as a significant increase in delta and theta band power. EEG analysis during the photic stimulation demonstrated that the AD patients had a significantly lower EEG power during photic stimulation for the alpha (9.8-10.2 Hz) and beta bands (14.8-15.2 Hz) corresponding to photic stimulation at 10 Hz and 15 Hz, respectively. In addition, when we examined EEG changes from rest to the stimulus condition, the AD patients were found to show significantly smaller changes in EEG power mainly over the posterior regions, irrespective of the stimulus frequency. These findings provide evidence that AD patients have EEG abnormalities in both non-stimulus and stimulus conditions, and suggest diminished EEG reactivity to photic stimulation.

Alzheimer Disease↗
PubMed2006

[Relaxation induced by photic stimulation in tinnitus patients].

The therapeutic effect of applying photic stimulation was evaluated in a sample of 17 patients with chronic tinnitus. The employed optical stimulation technique triggers the activity of brain waves and induces deep relaxation characterized by increased EEG activity in the theta and delta spectrum. The expected therapeutic effect beyond relaxation was a decrease in subjective tinnitus distress and further improvements in well-being. All patients received ten applications of photic stimulation, each lasting 30 min. Every application markedly increased the peripheral blood circulation, thus indicating a relaxation effect. The emotional and cognitive impairments as well as the subjective tinnitus distress significantly decreased during treatment while sleep disturbances showed a tendency towards improvement. Overall, tinnitus distress markedly decreased and general well-being improved. The photic stimulation technique is proposed as a relief for tinnitus patients who do not respond to conventional relaxation techniques.

Adult↗
PubMed1996

Treatment of a depressive disorder patient with EEG-driven photic stimulation.

This study examined the effects of electroencephalographic- (EEG-) driven photic stimulation on a case of depressive disorder, as measured by a psychometric test of mood states, EEG parameters, and several autonomic indices. The EEG-driven photic stimulation enhances the alpha rhythm of brain waves using photic signals, the brightness of which is modulated by a subject's own alpha rhythm. The patient was a 37-year-old businessman, who was treated for depression with medication during the 13 months prior to his first visit to our hospital. He underwent two sets of inpatient treatment sessions, comprising first 16 and then 18 treatment sessions. The treatments brought about the following changes: an improvement in general mood state, alpha rhythm increase, cardiac parasympathetic suppression, and increased skin conductance level. In addition, significant correlations between alpha rhythm increase and cardiac parasympathetic suppression or cardiac sympathetic predominance were observed with each inpatient treatment. Significant correlations between alpha rhythm increase, cardiac parasympathetic suppression, or cardiac sympathetic predominance and the improvement of general mood state were also observed. Thus, from these observations, it was concluded that the alpha enhancement induced by EEG-driven photic stimulation produced an improvement in the patient's depressive symptomatology connected with cardiac parasympathetic suppression and sympathetic predominance.

Adult↗
PubMed1993

The dorsal hippocampus modifies the negative feedback effect of glucocorticoids on the adrenocortical and median eminence CRF-41 responses to photic stimulation.

In the present study we have evaluated the role of the dorsal hippocampus on the negative feedback effect of glucocorticoids (GC) following photic stimulation. In hippocampectomized rats the recovery of serum corticosterone (CS) to basal levels following photic stimulation, was significantly attenuated in relation to sham hippocampectomized rats. The inhibitory effect of either systemic dexamethasone administration or CS implanted in the paraventricular nucleus (PVN), on the adrenocortical responses to photic stimulation, was completely prevented in hippocampectomized rats in comparison to sham operated animals. In rats with sham operation, the depletion of median eminence CRF-41 induced by photic stimulation, was prevented by pretreatment with CS PVN implants or systemic dexamethasone. These effects were reversed in rats with dorsal hippocampectomy. The results suggest that the dorsal hippocampus modulates the negative feedback of GC on the adrenocortical response following photic stimulation at the PVN level and this effect is mediated by median eminence CRF-41.

Adrenal Cortex↗
PubMed2002

Improving the detection of evoked responses to periodic stimulation by using multiple coherence--application to EEG during photic stimulation.

The coherence between the stimulation signal and the electroencephalogram (EEG) has been used in the detection of evoked responses. However the detector's performance depends on both the signal-to-noise ratio (SNR) of the responses and the number of data segments (M) used in coherence estimation. In this work, a technique for detecting evoked responses was developed based on the extension to the multivariate case of this coherence. Thus, instead of using the EEG collected at a unique region, the estimation is proposed using two EEG derivations. As for the univariate case, this multiple coherence is independent of the stimulation signal. In addition, considering equal SNR in both signals, the detection rate with this multiple coherence is always greater than that one using only one signal. This was verified in Monte Carlo simulations, which also showed that a superior performance is still expected in practical situations, when a smaller SNR is found in the second signal. The results with EEG from 12 normal subjects during photic stimulation confirm this better performance. Since the proposed technique allows a higher detection rate without the need of increasing M, it permits evoked responses to be detected faster, which is very useful during monitored surgeries.

Adolescent↗
PubMed1998

Interhemispheric EEG coherence in never-medicated patients with paranoid schizophrenia: analysis at rest and during photic stimulation.

We assessed functional relationships between hemispheres by calculating interhemispheric EEG coherence at rest and during photic stimulation in 18 never-medicated patients with paranoid schizophrenia and 30 control subjects. Although no significant group differences were found in the resting EEG, the schizophrenic patients had significantly higher coherence on EEGs recorded during photic stimulation, compared to the control subjects. In this study, we also examined the changes in interhemispheric coherence from rest to the stimulus condition (i.e., stimulation-related coherence reactivity); the patients were found to show significantly greater coherence reactivity to photic stimulation. These findings provide further evidence that schizophrenic patients have a higher degree of interhemispheric functional connectivity and thus have less lateralized cerebral organization than normal subjects. Our results also suggest that schizophrenic patients have excessive functional reorganization between hemispheres in association with photic stimulation.

Adolescent↗
PubMed1994

Occipitotemporal seizures with ictus emeticus induced by intermittent photic stimulation.

We recorded occipitotemporal seizures induced by intermittent photic stimulation in three children with brain injuries, aged 10 to 13 years. All had a history of seizures and showed occipital spikes on EEG, but were seizure free and were not being treated at the time of investigation. In all, photic stimulation induced seizures in the right occipital lobe. They were followed by clinical and EEG signs suggesting infrasylvian spreading to ipsilateral mesiotemporal limbic structures and by vomiting, appearing at late stages of the attacks. Seizure spread was very slow in two patients in whom attacks lasted 16 and 25 minutes. Patients with occipital epileptiform abnormalities presenting with ictal vomiting are often diagnosed as having vague migraine-epilepsy syndromes. We conclude that vomiting can be a late ictal phenomenon resulting from temporal lobe spread of seizures originating in the occipital lobe.

Adolescent↗