Television epilepsy--the role of pattern.

Patients with photosensitive epilepsy were asked to view normally functioning 625-line televisions while the EEG was monitored. In the first of two studies paroxysmal EEG activity was reliably induced by television at a viewing distance related to a patient's sensitivity to intermittent photic stimulation (IPS); patients who were sensitive to diffuse IPS at 50 Hz were sensitive to the television at greater viewing distances than those who were not. No such relationship was obtained with patterned IPS. On the other hand, patterned IPS was generally more epileptogenic than diffuse IPS with the same luminance. In the second study, where the angular subtense of the television screen and the subtense of its lines were manipulated independently, the convulsive response was found to be a function of both factors, the relative contribution of each depending on the viewing distance at which the patient was sensitive. For patients sensitive at normal viewing distances, where 50 Hz diffuse flicker appeared to be responsible for the induction of paroxysmal activity, the probability with which paroxysmal activity was induced was closely related to the subtense of the screen. For patients sensitive only at closer viewing distances the probability was influenced not by the subtense of the screen but by the subtense of its lines, suggesting that the paroxysmal activity was induced by the 25 Hz pattern alternation produced by the scan. A television with a small screen was considerably less epileptogenic than one with a large screen for all patients, presumably due to the reduced contribution of both diffuse flicker and pattern alternation.     

EEG sensitivity to television: effects of ambient lighting

The effect of ambient lighting on EEG sensitivity to television has been tested in 16 photosensitive epileptic patients. Those who were not sensitive to 50 Hz IPS responded to TV at a viewing distance of 1 m or less and showed a consistent increase of EEG activation by television when the room was brightly lit. Most of those who were sensitive to 50 Hz IPS were also TV-sensitive at viewing distances greater than 1 m and the effect was most marked with lights off. The results are discussed in the context of previous work showing that some patients with TV epilepsy respond to the raster pattern of the screen and some, at greater distance, to 50 Hz flicker.     

A new adaptive temporal filter: application to photosensitive seizure patients

A new adaptive temporal filtering (ATF) technique was developed to prevent heath hazards due to flicker stimuli from televisions, videos or other displays. This ATF method could reduce frame-to-frame or field-to-field flicker stimuli at around 10-30 Hz which are particularly risky for photosensitive individuals. The present ATF efficacy with a computer simulation was studied in 11 photosensitive epilepsy patients. In order to control visual stimuli and induce photoparoxysmal response (PPR), we employed a problematic scene of the Pocket Monster incident containing 12 Hz red/blue flicker images lasting for 4 s. This image, shown with a 14-inch, television set 2 m in front of subjects, promptly elicited generalized PPR in all cases, while the filtered image did not induce any PPR. These results suggest that the present ATF method may be useful as a preventive measure of photosensitive seizures triggered by stimulative images from televisions or other displays.     

The Effect of Television Frame Rate on EEG Abnormalities in Photosensitive and Pattern-Sensitive Epilepsy

Summary: Purpose: Seizures provoked by television viewing may be triggered by patterns in the television image or by flicker from the display itself. We examined the incidence of EEG abnormalities elicited by patterns displayed on television sets with two different frame rates to evaluate the likely contribution of photosensitive and pattern-sensitive mechanisms to television- and video-game epilepsy.
Methods : Televisions with frame rates of 50 and 100 Hz were used to present 35 patients who were photosensitive or pattern-sensitive with grating patterns. These patterns comprised vertical square-wave and sine-wave gratings of 90% contrast, and the spatial frequency was varied between 0.25–7 cycles/degree. EEGs were analysed for laboratory sensitivity to patterned and unpatterned intermittent photic stimulation (IPS).
Results : Significantly fewer EEG abnormalities were elicited by patterns displayed on the 100 Hz frame-rate television than on the 50-Hz frame-rate television. No abnormalities were observed in response to the blank screens of either television. Thirty-three patients showed abnormalities in response to patterned IPS but only 15 in response to diffuse flash. Two patients showed no laboratory evidence of photosensitivity. Patients who were sensitive to patterned IPS at 50 Hz were significantly more likely to demonstrate abnormalities to patterns displayed on the 100-Hz frame-rate television than were patients who were not sensitive to 50-Hz patterned IPS.
Conclusions : We suggest that for many patients, the combination of high-contrast patterns and screen flicker may elicit the observed EEG abnormalities. For patients with sensitivity to screen flicker, the use of a high frame-rate television may be beneficial in reducing the risk of seizures.     

Epilepsies and video games: results of a multicentric study

Objectives: The purpose of this study was to research whether or not video games may induce paroxysmal discharges (PD) in different groups of patients.Methods: One hundred and fifteen subjects from 5 different French laboratories were studied: 33 had seizures exclusively under visual stimuli, 42 had both photogenic seizures and spontaneous seizures occuring independently, and 40 had non-photogenic seizures. The same protocol which included one TV sequence, 3 sequences of video games selected on particular criteria (pattern, luminosity and nature of the scene), were presented at different distances from the TV screen at 50 and 100 Hz.Results: Among the factors provoking paroxysmal discharges (PD) some seem crucial: the frequency of the TV screen (the 100 Hz screen was significantly safer than 50 Hz), the distance from the screen (1 m safer than 50 cm), and, particularly for the 50 Hz screen, the specific pattern of the images and the act of playing.Conclusions: Video games are ineffective for subjects known as having a non-photosensitive epilepsy, but may induce PD on subjects known as photosensitive even when intermittent light stimulation (ILS) is not effective. These results based on a different approach than in other publications confirm data which were suggested by the literature, and suggest that 100 Hz TV screens should be recommended to patients with TV-induced attacks.     

A new color vep procedure discloses asymptomatic visual impairments in optic neuritis and glaucoma suspects

OBJECTIVE: To evaluate the reliability of visual evoked potentials obtained with a set of multiple chromatic and achromatic patterns (C-VEPs) in differentiating asymptomatic perifoveal retinal impairment from central conduction impairment. METHODS: We propose a set of colored pattern stimuli that allows relatively differential activation of the magnocellular and parvocellular pathways. The system runs on a standard Pentium PC with peripherals that present stimuli and collect, analyze and print data. P1 latencies of C-VEPs obtained with achromatic (black/white) and chromatic (blue/black and red/black isocontrast) checkerboards were evaluated in normal subjects and patients with subclinical retinal impairment (glaucoma suspects) or mild neural conduction impairment (optic neuritis), none of whom had subjective visual defects. RESULTS: The procedure evoked robust cortical signals and statistically distinguished the 3 groups of subjects. The achromatic and chromatic stimuli used distinguished controls from glaucoma suspects and patients with optic neuritis. Glaucoma suspects had greater impairment of C-VEPs to blue/black checkerboards whereas patients with optic neuritis had greater impairment of responses to red/black stimuli. CONCLUSIONS: Our data suggest that chromatic patterns (color/ black, red and blue), that may activate the parvocellular and magnocellular systems differentially but not selectively, can distinguish between mild perifoveal or foveal conduction impairment. They have the additional advantage of evoking large, stable responses across all the subjects.     

Comparison of fiber optical and video monitor stimulators in normals and multiple sclerosis patients

A comparison of VEP findings using a fiber optical stimulator with three color combinations (black/red, black/green and red/green) and a conventional video monitor stimulator in black/white was performed in 3 groups of subjects: a group with definite lesions in the visual pathway, a group with suspected lesions and a control group. No significant correlations of P100 latency were found in the normative group, probably because of the small range of their values. All correlations were significant in the two patient groups, except for the red/green stimuli in the definite group. In general, the red/green combination was inferior to other color combinations in eliciting VEPs. The patient groups with definite, as well as suspected, lesions indicated no benefit from the color stimuli, as compared with black/white. The major advantage of the fiber optical stimulator is its simplicity, the lack of stimulus artifacts and the accessibility to the patient's bed side, thanks to its small size. Stimulators with higher illuminance and improved pattern element shape should narrow the still unacceptable normative variability of the wave forms recorded.     

Photic- and pattern-induced seizures: expert consensus of the Epilepsy Foundation of America Working Group

PURPOSE: In August, 2004, the Epilepsy Foundation of America convened a workshop to begin to develop an expert consensus on photosensitive seizures. METHODS: Literature and data were reviewed, and consensus was derived from discussion. RESULTS: A flash is a potential hazard if it has luminance >or=20 cd/m2, occurs at a frequency of >or=3 Hz, and occupies a solid visual angle of >or=0.006 steradians (approximately 10% of the central visual field or 25% of screen area at typical viewing distances). A transition to or from saturated red also is considered a risk. A pattern with the potential for provoking seizures contains clearly discernible stripes, numbering more than five light-dark pairs of stripes in any orientation. When the light-dark stripes of any pattern collectively subtend at the eye from the minimal-expected viewing distance a solid angle of >0.006 steradians, the luminance of the lightest stripe is >50 cd/m2, and the pattern is presented for >or=0.5 s, then the pattern should display no more than five light-dark pairs of stripes, if the stripes change direction, oscillate, flash, or reverse in contrast; if the pattern is unchanging or smoothly drifting in one direction, no more than eight stripes. These principles are easier to apply in the case of fixed media, for example, a prerecorded TV show, which can be analyzed frame-by-frame, as compared with interactive media. CONCLUSIONS: A consensus view of stimuli likely to provoke visually evoked seizures can be developed.     

Evaluation of the laboratory and environmental factors that induce seizures in photosensitive epilepsy.

This paper evaluates the laboratory and environmental factors that induce seizures in photosensitive epileptic patients. The aims are (i) to identify those factors that trigger seizures so that the patients could take preventive measures, (ii) to advise the patients on appropriate preventive measures that could be taken to avoid spontaneous seizures. Thirty-six photosensitive epileptic patients were studied. The electroencephalographic laboratory seizure-inducing factors identified were intermittent photic stimulation (IPS), flickering lights from both the TV and the visual display unit (VDU) at various flashes per second, grid patterns (vertical, horizontal lines, squares, black and white lines) of various cycles per degree, and blank screens. In the environmental factor investigation, 10 out of 36 patients had series of seizures induced by narrow stripes of black and white, or white and red striped coloured dresses especially, when stepping outdoors on sunny days. Other environmental factors identified include moving escalators; 'moving' trees, bushes, and houses when travelling in a vehicle, including trains; faceted patterns in the bathroom windows with light passing through; swirling light patterns especially on displayed objects of black and white colours; telegraphic post, gantry post, and luminance variance when stepping outdoors from the dark in bright sunlight. The effective preventive measures were: (i) patients should occlude one eye when travelling in a vehicle or using computers or when stepping outdoors on a sunny day, or when there are various patterns before them, (ii) patients should sit at least 3 metres away from the TV when watching a programme, (iii) they should avoid any object that transmits luminance variance; if this is not possible, they should occlude one eye.     

Television Viewing and Its Impact on Childhood Behaviors

Despite the emergence of new media technologies, television remains the most widely used screen media format. Unfortunately, concerns have arisen about its effects on the health and well-being of children and adolescents. This article reviews television usage trends and television’s impact on sleep, attention, and interpersonal relationships. American Academy of Pediatrics recommendations on television use are also discussed. Many studies on television viewing have cross-sectional designs, and longitudinal research is limited. However, research to date suggests that excessive television viewing is associated with negative effects on sleep, attention, and interpersonal relationships. As use of different media formats escalates, research across multiple specialties (including child psychiatry) will need to incorporate evaluation of media use into its assessments. More research and education are needed on the appropriate use of media in youth. Information on the health effects of television may also increase awareness of potential issues with less well-studied media formats.     

Two Visual Mechanisms of Photosensitivity

PURPOSE: Photosensitive epilepsy is the most common of the "reflex" epilepsies. Precipitated by television viewing, flickering light, or specific visual patterns, it is the cause of seizures in 10% of young people with epilepsy. Photosensitivity is associated with two types of EEG abnormalities: photoparoxysmal responses (PPRs) and occipital spikes (OSs). It is unclear whether these abnormalities are mediated by different mechanisms, and furthermore, the clinical significance of OS is unknown. METHODS: By using our previously established population of patients with photosensitive epilepsy, all showing EEG abnormalities on intermittent photic stimulation or pattern stimulation, we examined the effects of pattern contrast, spatial and counterphase temporal frequency, and colour on these abnormalities. RESULTS: PPRs and not OSs show linear contrast dependency and are elicited by stationary stimuli and by non-colour-opponent isoluminant stimuli. CONCLUSIONS: PPRs and OSs are generated independently by the parvocellular and magnocellular visual systems, respectively. The results add support to the hypothesis that only PPRs and not OSs are clinically significant.     

Characterizing the patterned images that precipitate seizures and optimizing guidelines to prevent them

The use of guidelines to prevent the broadcast of epileptogenic television program content has reduced the incidence of seizures in Britain and Japan. Epileptogenic content includes both flicker and patterns. The guidelines for flicker were developed on the basis of a model that related stimulus parameters to the proportion of patients affected. We here extend the model to pattern stimuli. A set of rules is advocated that keeps the level of risk to a consistent minimum and simplifies compliance. We propose that striped patterns that last > 0.5 s, occupy more than one fourth the area of the screen, and have bright stripes > 50 cd/m2 in luminance be restricted as regards the number of cycles admissible. The guidelines are estimated to protect at least two thirds of susceptible patients.     

Photic- and pattern-induced seizures: a review for the Epilepsy Foundation of America Working Group

PURPOSE: This report summarizes background material presented to a consensus conference on visually provoked seizures, convened by the Epilepsy Foundation of America. METHODS: A comprehensive review of literature was performed. RESULTS: Photosensitivity, an abnormal EEG response to light or pattern stimulation, occurs in approximately 0.3-3% of the population. The estimated prevalence of seizures from light stimuli is approximately 1 per 10,000, or 1 per 4,000 individuals age 5-24 years. People with epilepsy have a 2-14% chance of having seizures precipitated by light or pattern. In the Pokemon cartoon incident in Japan, 685 children visited a hospital in reaction to red-blue flashes on broadcast television (TV). Only 24% who had a seizure during the cartoon had previously experienced a seizure. Photic or pattern stimulation can provoke seizures in predisposed individuals, but such stimulation is not known to increase the chance of subsequent epilepsy. Intensities of 0.2-1.5 million candlepower are in the range to trigger seizures. Frequencies of 15-25 Hz are most provocative, but the range is 1-65 Hz. Light-dark borders can induce pattern-sensitive seizures, and red color also is a factor. Seizures can be provoked by certain TV shows, movie screen images, video games, natural stimuli (e.g, sun on water), public displays, and many other sources. CONCLUSIONS: Recommendations on reducing risk of seizures have been developed by agencies in the United Kingdom, Japan, and the International Telecommunications Union, affiliated with the United Nations. The Epilepsy Foundation of America has developed a consensus of medical experts and scientists on this subject, reported in an accompanying work.     

Developmental changes of pattern reversal visual evoked potentials

Analysis of developmental changes in pattern reversal visual evoked potentials (PVEPs) was performed on 141 normal children ranging in age from 1 month to 19 years 4 months. The stimulus was a black and white checkerboard pattern on a television screen, and the check edge subtended 50 min of retinal arc. The major positive peak (P2) was observed in all subjects, and the incidence of other peaks tended to increase with age. The P2 latency decreased rapidly during the first six months of life and reached a constant value after the age of 2 years. The P2 latency with monocular stimulation was significantly longer than that with binocular stimulation in most age groups. Developmental changes of the N1-P2 or P2-N2 amplitudes were unclear, and the standard deviation of the amplitude in each age was too large for clinical application. The P2 latency with binocular stimulation was shorter for females than for males only at the age of 8-11 years.     

Brain response to visual sexual stimuli in heterosexual and homosexual males

Although heterosexual and homosexual individuals clearly show differences in subjective response to heterosexual and homosexual sexual stimuli, the neurobiological processes underlying sexual orientation are largely unknown. We addressed the question whether the expected differences in subjective response to visual heterosexual and homosexual stimuli may be reflected in differences in brain activation pattern. Twenty-four healthy male volunteers, 12 heterosexuals and 12 homosexuals, were included in the study. BOLD signal was measured while subjects were viewing erotic videos of heterosexual and homosexual content. SPM02 was used for data analysis. Individual sexual arousal was assessed by subjective rating. As compared to viewing sexually neutral videos, viewing erotic videos led to a brain activation pattern characteristic for sexual arousal in both groups only when subjects were viewing videos of their respective sexual orientation. Particularly, activation in the hypothalamus, a key brain area in sexual function, was correlated with sexual arousal. Conversely, when viewing videos opposite to their sexual orientation both groups showed absent hypothalamic activation. Moreover, the activation pattern found in both groups suggests that stimuli of opposite sexual orientation triggered intense autonomic response and may be perceived, at least to some extent, as aversive.     

Functional Mapping of Dynamic Happy and Fearful Facial Expression Processing in Adolescents

This paper assessed the neural systems involved in processing of dynamic facial expressions in adolescents. The processing of facial expressions changes as a function of age, and it is thus important to understand how healthy adolescent subjects process dynamic facial expressions prior to analyzing disease-related changes. We hypothesized that viewing of dynamic facial expressions with opposing valences (happy vs. fearful) induces differential activations and deactivations in the brain. 27 healthy adolescents (9 ♀, 18 ♂, mean age = 14.5 years; age range 11.6–17.3 years) were examined by using the ASSQ and K-SADS-PL and scanned with 1.5-T fMRI during viewing of dynamic facial expressions and mosaic control images. The stimuli activated the same areas as previously seen in dynamic facial expression in adults. Our results indicated that opposing-valence dynamic facial expressions had differential effects on many cortical structures but not on subcortical limbic structures. The mirror neuron system is activated more during viewing of fearful compared to happy expressions in bilateral inferior frontal gyrus (IFG) and superior temporal sulcus (STS) left dominantly. We also detected more deactivation in the ventral anterior cingulate gyrus (ACG), showing more automated attentional processing of fearful expressions during passive viewing. Females were found to deactivate the right frontal pole more than male adolescents during happy facial expressions, while there were no differences in fear processing between genders. No clear gender or age effects were detected. In conclusion fear induces stronger responses in attention and mirror neurons probably related to fear contagion.     

Conversion of photosensitive to scotosensitive epilepsy: report of a case

A 13-year-old girl had had two grand mal attacks induced by viewing television when she was aged 10 and 11 years, and again a year later. Clinical and electroencephalographic (EEG) findings were typical of photosensitive television epilepsy. However, a further grand mal seizure when the patient was age 13 years occurred in darkness. Two additional EEG studies showed continuous paroxysmal activity during darkness. The epileptiform discharges were abolished by light and eye opening.     

The pattern reversal VEP in short-gestation infants

Visual evoked potentials (VEPs) to pattern reversal stimulation have been obtained in 10 premature babies. The babies were born between 32 and 35 weeks gestational age and had pattern reversal VEPs recorded on at least 2 separate occasions. The responses were obtained from 33 weeks gestational age, and all babies had their initial recording at or before 37 weeks gestational age. The pattern reversal stimulation was produced on a small hand-held television monitor. The black and white checks subtended a visual angle of 2 degrees. Flash VEPs were also recorded on each occasion for comparison. The pattern reversal response consisted of a major positive (P1) component around 280 msec. The latency of the P1 component correlated negatively with gestational age. Although the flash VEP in the same babies was often dominated by the initial negative component no similar negative components were seen in the pattern reversal response.     

Stereo correspondence is optimized for large viewing distances

Stereo '3D' vision depends on correctly matching up the differing images of objects seen by our two eyes. But vertical disparity between the retinal images changes with binocular eye posture, reflecting for example the different convergence angles required for different viewing distances. Thus, stereo correspondence must either dynamically adapt to take account of changes in viewing distance, or be hard-wired to perform best at one particular viewing distance. Here, using psychophysical experiments, we show for the first time that human stereo correspondence does not adapt to changes in physical viewing distance. We examine performance on a stereo correspondence task at a short viewing distance (30 cm) and show that performance is improved when we simulate the disparity pattern for viewing infinity, even though these disparities are impossible at the physical viewing distance. We estimate the vertical extent of the retinally fixed 'search zones' as < 0.6° at 14° eccentricity, suggesting that most V1 neurons must be tuned to near-zero vertical disparity. We also show that performance on our stereo task at 14° eccentricity is affected by the pattern of vertical disparity beyond 20° eccentricity, even though this is irrelevant to the task. Performance is best when vertical disparities within and beyond 20° eccentricity both indicate the same convergence angle (even if not the physical angle), than when the pattern of vertical disparity across the visual field is globally inconsistent with any single convergence angle. This novel effect of the periphery may indicate cooperative interactions between disparity-selective neurons activated by the same eye postures.     

Designing instructional media for severely retarded adolescents: a theoretical approach to trait-treatment interaction research.

Moderately and severely retarded adolescents (N=70) individually viewed a cartoon, a live action film, and a pixilation film in color or black and white. A distractor method was used to measure frequency and duration of eye movement to visual stimuli. Content of visual stimuli was controlled, presentation of a distractor randomized, and all eye movement monitored to the nearest second. Black and white visual presentations had greater attentional value than color presentations and use of real human beings appeared to be more salient as an attention-holding technique than was use of animated characters. Implications of the results for use with severely retarded adolescents were discussed.