Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Photic Stimulation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 91 records · Page 5Linked to original sources
PubMed1977

Nystagmus induced by intermittent photic stimulation (flash induced nystagmus (FIN).

In man, as has been shown previously in rabbits and monkeys, a nystagmus can be elicited by monocular intermittent photic stimulation. The direction of nystagmus (FIN) is always towards the stimulated eye. This nystagmus strongly resembles latent nystagmus. Here the fast phase is always directed towards the 'non-occluded' eye. The FIN may, therefore, be used as a model for the study of mechanisms underlying these pathological conditions. For further elucidation of FIN, studies were made in rabbits.

Animals↗
PubMed1993

Human visual cortical function during photic stimulation monitoring by means of near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) was used to monitor human visual cortical function during and after photic stimulation (PS) in five adult volunteers. Cerebral blood volume (CBV) increased on the occipital surface during PS, but NIRS parameters did not change on the frontal surface. The increase in CBV was caused by a rapid increase in oxyhemoglobin with but a small increase in deoxyhemoglobin, suggesting cerebral vascular dilatation with decreased oxygen consumption. After PS stopped, CBV promptly decreased and then slightly increased again. Cytochrome aa3 did not show any change during and after PS. These phenomena reappeared following repeated PS in all five subjects. These results may represent the first step in the development of NIRS imaging.

Adult↗
PubMed1983

Electrical responses to direct and indirect photic stimulation of the pineal gland in the pigeon.

Spontaneous electrical activity was recorded from pineal cells in intact and blinded pigeons. Modification of the activity by photic stimulation applied to the lateral eyes or directly to the pineal gland was observed in both groups of birds. The pattern of responses was different in the blinded compared to the sighted pigeons. In the birds with intact lateral eyes, the majority of responses to light were excitatory while in the blinded group more inhibitory effects were recorded. The results indicate that cells in the pigeon pineal gland retain a photoreceptive capacity although the sensitivity of the responsive units is low.

Animals↗
PubMed1998

Abnormal functional connectivity in Alzheimer's disease: intrahemispheric EEG coherence during rest and photic stimulation.

Electroencephalography (EEG) coherence provides a measure of functional correlations between two EEG signals. The present study was conducted to examine intrahemispheric EEG coherence at rest and during photic stimulation (PS; 5, 10 and 15 Hz) in ten unmedicated patients with presenile dementia of the Alzheimer type (AD; mean age at onset 56 years). In the resting EEG, the AD patients had significantly lower coherence than gender- and age-matched control subjects in the alpha-1, alpha-2 and beta-1 frequency bands. The EEG analysis during PS also showed that the patients had significantly lower coherence in the frequency corresponding to PS at 10 and 15 Hz. In this study, the changes in coherence from the resting state to the stimulus condition (i.e. PS-related coherence reactivity) were examined. The patients were found to show significantly smaller coherence reactivity to PS at 5 and 15 Hz. These findings suggest that, in addition to the resting state, AD patients have an impairment of intrahemispheric functional connectivity during PS. They also suggest that AD shows a failure of PS-related functional reorganization.

Aged↗
PubMed1986

[Reactions of neostriatal neurons to direct electric stimulation of the optic tract and to photic stimulation in the alert cat].

Responses of 98 cells in the head and body of caudate nucleus to direct electric stimulation of the optic tract and to visual stimuli were recorded extracellularly in awake chronic cats. 34.6 and 36.2% of the studied cells, respectively, have responded to these types of stimulation. Long-latency (over 40 ms for optic tract and over 80 ms for visual stimulations) excitatory responses prevailed in both cases. Small number of units responded to optic tract stimulation with short (5-14 ms) latencies. Eight of 58 tested cells were activated by both electric and visual stimuli. In this case, responses of the same cells could differ (relatively to the type of applied stimulus) either in pattern or sign. These data are discussed relative to the possible pathways for transfer of the visual information to non-specific brain structures.

Animals↗
PubMed1988

Ictus emeticus induced by photic stimulation.

It has been recently established that ictus emeticus originates from mesial temporal lobe structures. We herein report a patient with generalized epilepsy who exhibited ictus emeticus reflexly triggered by intermittent photic stimulation accompanied by generalized photoparoxysmal responses on the electroencephalogram. All seizures and EEG abnormalities ceased after treatment with valproic acid. The occurrence of ictus emeticus in generalized epilepsy is an apparent paradox, better explained by the theory of "secondary temporalization" implying the selective engagement of temporal lobe structures during generalized seizures.

Electroencephalography↗
PubMed2002

Uniform decrease of alpha-global field power induced by intermittent photic stimulation of healthy subjects.

Nineteen-channel EEGs were recorded from the scalp surface of 30 healthy subjects (16 males and 14 females, mean age: 34 years, SD: 11.7 years) at rest and under trains of intermittent photic stimulation (IPS) at rates of 5, 10 and 20 Hz. Digitalized data were submitted to spectral analysis with fast fourier transformation providing the basis for the computation of global field power (GFP). For quantification, GFP values in the frequency ranges of 5, 10 and 20 Hz at rest were divided by the corresponding data obtained under IPS. All subjects showed a photic driving effect at each rate of stimulation. GFP data were normally distributed, whereas ratios from photic driving effect data showed no uniform behavior due to high interindividual variability. Suppression of alpha-power after IPS with 10 Hz was observed in about 70% of the volunteers. In contrast, ratios of alpha-power were unequivocal in all subjects: IPS at 20 Hz always led to a suppression of alpha-power. Dividing alpha-GFP with 20-Hz IPS by alpha-GFP at rest (R = alpha-GFP(IPS)/alpha-GFP(rest)) thus resulted in ratios lower than 1. We conclude that ratios from GFP data with 20-Hz IPS may provide a suitable paradigm for further investigations.

Adult↗
PubMed1998

Aberrant functional organization in schizophrenia: analysis of EEG coherence during rest and photic stimulation in drug-naive patients.

EEG coherence provides a measure of functional correlations between two EEG signals. The present study was conducted to examine intrahemispheric EEG coherence at rest and during photic stimulation (PS) in 18 drug-naive patients with paranoid schizophrenia and 30 control subjects. Compared with the controls, the schizophrenic patients had significantly higher intrahemispheric coherence of the resting EEG for the delta band, although no significant group differences were found for other frequency bands. EEG analysis during PS showed that the patients also had significantly higher EEG coherence over the left posterior regions. In this study, we also examined the changes in intrahemispheric coherence from rest to the stimulus condition (i.e., PS-related coherence reactivity); the patients were found to show significantly smaller changes, with significant group differences being also confined to the posterior regions in the left hemisphere. These findings provide evidence that schizophrenic patients have abnormal EEG coherence in both resting and stimulus conditions and suggest more diffuse, undifferentiated functional organization within hemispheres. In addition, diminished coherence reactivity suggests a failure of PS-related functional reorganization in schizophrenia.

Adult↗
PubMed1980

Monosynaptic reflexes during generalized spike and wave activity, provoked by intermittent photic stimulation.

Achilles tendon (T) and Hoffmann (H) reflexes were evoked during spike and wave activity (SWA) in 6 patients with generalized epilepsy, selected on the basis of their photosensitivity. SWA was provoked by intermittent photic stimulation (IPS). It was demonstrated that monosynaptic reflex amplitudes were larger during SWA than at rest. Although IPS caused by itself a slight increase in amplitudes, there was an obvious difference from the larger increase during SWA. T reflexes showed a more explicit increment than H reflexes. The activity changes in the spinal motor circuits were nearly always present in the absence of any clinical manifestation of motor activity. The possible mechanisms are discussed.

Adolescent↗
PubMedDate not supplied

Interhemispheric EEG coherence during photic stimulation: sex differences in normal young adults.

The present study was conducted to examine sex differences in interhemispheric EEG coherence in 15 male and 15 female healthy young adults. EEG was recorded during rest and photic stimulation (PS) at 5, 10 and 15 Hz using a linked earlobe reference. Interhemispheric coherence of the resting EEG revealed no significant sex-related differences for any frequency band. In contrast, significant sex-related differences were found in EEG coherence during PS; the females had a significantly higher coherence than the males for F3-F4 and C3-C4 in the frequency band (4.5-5.5 Hz) corresponding to 5 Hz PS. In addition, the changes in interhemispheric coherence from rest to the stimulus condition (i.e. PS-related coherence reactivity) showed sex-related differences at the brain region primarily involved in visual functioning; the females had significantly greater coherence reactivity for O1-O2 in EEG during PS at 5 and 15 Hz. These findings indicate sex-related differences in interhemispheric EEG coherence during PS, and support the well-demonstrated evidence that sex differences exist in the degree of lateralization of cerebral function.

Adult↗
PubMed1980

Gonadotropic activation induced by local photic stimulation of the lobus paraolfactorius in male quail.

Radioluminous material (RLM) was implanted in the paraolfactory area (a region which is linked to the gonadotropic infundibular complex by nervous pathways) of sexually quiescent quail exposed to short day lengths. Direct photic stimulation of the paraolfactory lobe (POL) resulted in significant testicular growth and increase in the plasma testosterone level. Red light (620 nm) emitting RLM was revealed to be somewhat more effective than green light (530 nm) emitting material. No difference appeared between the effect of local photostimulation of either the anterior or the posterior part of the POL. The gonadotropic response to paraolfactory lighting no longer occured after neural isolation of the infundibular complex.

Animals↗
PubMed1997

Age-related reduction in functional MRI response to photic stimulation.

Many functional imaging studies have demonstrated age-related alterations in cerebral blood flow during the resting state. However, few studies have addressed possible differences in functional response to cerebral activation. We assessed the response of visual cortex to photic stimulation in 9 normal elderly subjects and 17 normal younger subjects with blood oxygenation level dependent functional magnetic resonance imaging. We found that the amplitude of response in elderly subjects was significantly decreased compared to younger subjects (2.5 +/- 1.0% versus 4.0 +/- 1.6%, p = 0.01), suggesting a reduction in functional activation or an age-related alteration in the coupling of blood oxygenation to focal activation.

Adult↗
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↗
PubMed2002

Differences in EEG harmonic driving responses to photic stimulation between normal aging and Alzheimer's disease.

In order to investigate whether Alzheimer's disease (AD) is the end result of aging of the brain or the result of some other mechanism, we analyzed EEGs showing the absolute power of harmonic responses to photic stimulation (PS) in younger subjects, non-demented elderly subjects and AD patients. At rest, the AD patients generally showed less absolute power than the younger and elderly subjects, with significant differences found at 10 Hz and 20 Hz. Analysis of EEGs recorded during PS indicated that the elderly subjects generally demonstrated more absolute power than the younger subjects and AD patients. These findings suggest a failure of stimulation-related brain activation in AD patients, and provide further evidence that normal aging and AD employ different mechanisms for functional organization during PS.

Adult↗
PubMed2000

Changes in baseline cerebral blood flow in humans do not influence regional cerebral blood flow response to photic stimulation.

The effect of changes in baseline regional cerebral blood flow (rCBF) values on the cerebral blood flow response during neuronal activation was studied with functional magnetic resonance imaging (fMRI). Using a breath-holding challenge as a hypercapnic stimulus, rCBF alterations during photic stimulation under normo- and hypercapnia were determined in nine volunteers. With breath-holding, baseline rCBF in areas corresponding to the visual cortex significantly increased from 54 +/- 5 ml/100 g/min to 85 +/- 9 ml/100 g/min (P < 0.001). Despite this significant change in baseline flow values, the rCBF increase during visual stimulation was very similar under normo- and hypercapnic conditions (28 +/- 8 ml/100 g/min versus 26 +/- 8 ml/100 g/min, respectively). This study supports the notion that within wide physiologic variations, task-induced cerebral blood flow changes are independent of baseline rCBF values.

Adult↗
PubMed1982

Facilitatory effects of intermittent photic stimulation on visual cortical kindling.

There are few reports on kindling preparation by daily electrical stimulation to the primary visual cortex. In our previous studies on cats, it was demonstrated that repeated stimulation to the primary visual cortex brought a similar progress in seizure development as in amygdaloid kindling, although it took more trials. In this study, we examined the effects of intermittent photic stimulation (IPS) (2.5 Hz) on the visual cortical kindling preparation to clarify more underlying mechanisms of photosensitivity. Under IPS, afterdischarges synchronizing to IPS were seen and a duration of afterdischarge was extremely prolonged, even in the early stage of the kindling process. The threshold of stimulus intensity inducing afterdischarge was significantly reduced and the generalized convulsive seizure was obtained with fewer times of stimulation, as compared to visual cortical kindling without IPS. In visual cortical kindling myoclonic responses were sometimes caused by IPS for a few minutes immediately after cessation of the electrically induced generalized seizure. Such phenomena were never seen in amygdaloid kindling. These results indicate that IPS facilitates a seizure development in all stages of visual cortical kindling.

Animals↗
PubMed2001

Intermittent 20-HZ-photic stimulation leads to a uniform reduction of alpha-global field power in healthy volunteers.

19-channel-EEGs were recorded from scalp surface of 30 healthy subjects (16m, 14f, mean age: 34 ys, SD: 11.7 ys) at rest and under IPS (Intermittent Photic Stimulation) at rates of 5, 10 and 20 Hertz (Hz). Digitalized data underwent spectral analysis with fast fourier transfomation (FFT) yielding the basis for the computation of global field power (GFP). For quantification GFP values in the frequency ranges of 5, 10 and 20 Hz at rest were divided by the corresponding data gained under IPS. While ratios from PDE data showed no stable parameter due to high interindividual variability, ratios of alpha-power turned out to be uniform in all subjects: IPS at 20 Hz always led to a suppression of alpha-power. Dividing alpha-GFP at rest by alpha-GFP under 20-Hz IPS thus resulted in a ratio < 1. We conclude that ratios from GFP data are a stable diagnostic paradigma.

Adult↗
PubMed2005

Intermittent photic stimulation as an activation method for electroencephalographic screening of aircrew applicants.

Disqualifying criteria for aircrew in Europe (JAR-FCL 3) are, besides a diagnosis of epilepsy after the age of 5 and a history of episode(s) of disturbance of consciousness, epileptiform paroxysmal electroencephalographic abnormalities and focal slow waves. Intermittent photic stimulation (IPS) provokes in about 0.5% of healthy subjects (range 0-2%) a photoparoxysmal response and is most often the only abnormality (70-90%). The literature is scarce and shows great diversity in methodology. Standardized IPS with simultaneous video will not only allow collection of sufficient data for proper epidemiological studies, but can also reveal clinical and often unnoticed or misinterpreted signs and symptoms like myoclonia, loss of consciousness, and occipital seizures with visual auras. The pilot (sleep deprivation, strong sunlight) and the traffic controller (stress, monitors) are more prone to visually induced seizures. Furthermore, the increasing exposure to potentially seizure-triggering visual stimuli might have its impact in a more indirect or cumulative way.

Aerospace Medicine↗