Photoconvulsive Response Research Articles

EEG activation by use of stroboscope and visual stimulator SLS-5100.

The efficiency of the following visual stimuli in activating high amplitude (over 50 μV) photic driving (PD) and photoconvulsive response (PCR) was studied in 536 cases of patients including 340 (63%) epileptics. Their ages ranged from 3 to 78 years. An intermittent photic stimulation (IPS) of 5 and 15 Hz produced by a stroboscope was given to the subjects with eyes closed and open. A visual stimulator which was designed by us and is now commercially available (SLS-5100, Nihon Kohden) was used to give red-flicker, flickering-dot-pattern and flickering-grating-pattern. The average brightness of the illuminated screen of the SLS-5100 was 20 cd/m2 and the flicker frequencies were 5 and 15 Hz. The number of cases in which high amplitude PD was evoked by (1) 5 Hz IPS to eyes closed, (2) 5 Hz IPS to eyes open, (3) 5 Hz red-flicker, and (4) 5 Hz flickering-dot-pattern was 28 (5.2%), 6 (1.1%), 44 (8.2%), and 36 (6.7%), respectively. On the other hand, PCRs provoked by the above 4 kinds of stimuli as well as (5) 15 Hz IPS to eyes closed, (6) 15 Hz IPS to eyes open, (7) 15 Hz red-flicker, and (8) 15 Hz flickering-grating-pattern were found in 5 (0.9%), 2 (0.4%), 6 (1.1%), 4 (0.7%), 5 (0.9%), 6 (1.1%), 44 (8.2%), and 36 (6.7%) cases, respectively. The total number of cases in which PCR was provoked by these 8 stimuli was 56 (10.4%) out of 536 cases. From these results, it was concluded that the visual stimuli of flickering-patterns and red-flicker produced by the visual stimulator SLS-5100 are superior to the IPS produced by the commonly used stroboscope for EEG activation.

Photoconvulsive Responses Induced by Use of “Visual Stimulator”

Using the visual stimulator, the effects of the following visual stimuli in provoking generalized photoconvulsive responses (PCRs) were studied in 72 photosensitive cases with normal color sensation. The visual stimuli were either separate or combined stimulus of 15 Hz flicker, red-light, and dot and grating patterns with a constant brightness of 20 cd/m2. The number of the cases in which each of the 11 kinds of visual stimuli provoked PCRs was as follows: (1) flicker of white light, 9 (13%); (2) red-light, 0; (3) dot-pattern, 8 (11%) ; (4) grating-pattern, 16 (22%); (5) red-flicker, 65 (90%); (6) red-dot-pattern, 10 (14%); (7) red-grating-pattern, 10 (14%); (8) flickering-dot-pattern, 34 (47%); (9) flickering-grating-pattern, 36(50%); (10) red-flickering-dot-pattern, 31 (43%); and (11) red-flickering-grating-pattern, 37 (51%). The results of serial examinations in 29 cases were as follows: (1) 6 (21%), (2) 0, (3) 4 (14%), (4) 11 (38%), (5) 29 (100%), (6) 3 (10%), (7) 5 (17%), (8) 18 (62%), (9) 21 (72%), (10) 21 (72%) and (11) 19 (66%). These numbers indicate positive effects of visual stimuli in provoking PCRs in more than a single examination. From these results, it was concluded that, in addition to the activation with pattern stimuli, those with red-flicker as well as flickering-patterns are necessary for routine EEG examination.

Observations on the electroencephalogram and photosensitivity of South African Black albinos.

An EEG survey of 70 normal South African black albinos was carried out to determine whether the lack of pigment in the retinae and eyelids would have any effect on the photoconvulsive response during intermittent photic stimulation. Only 2 out of the 70 (2.85%) showed photosensitivity on intermittent photic stimulation. The results do not confirm the "pigmentary protection theory." Other intrinsic inhibitory factors must be responsible for the level of the photoconvulsive threshold.

The Delayed Effect of Sodium Valproate on the Photoconvulsive Response in Man

The acute effect of a single oral dose of sodium valproate on the photoconvulsive response has been studied. In 7 of 9 patients naive to this drug photosensitivity was abolished or reduced. A similar effect was seen in only 2 of 7 already receiving chronic sodium valproate therapy. The effect appeared 1 to 5 hr (mean, 3 hr) after attainment of peak sodium valproate concentration and lasted up to 5 days.

Photosensibilité et filtres colorés (étude systématique sur 1 500 sujets)

The reinforcing, activating, inhibiting or negative action of yellow, orange, red, green, and blue filters was studied in 1500 patients. A reinforcing action is seen much more frequently in subjects photosensitive to white light who are under twenty years old, while an inhibiting or negative action is more frequent in those over twenty. Two other factors seem to play a role in the reinforcing action of orange and red filters in subjects under twenty years old: epilepsy and cerebral immaturity. None of the non-epileptic subjects who developed a photo-convulsive response to yellow, orange, or red filters only, became epileptic during the two-year follow-up period.

Photoconvulsive response and disposition.

A total of 21 siblings of 17 cases (16 epileptics and one patient with atypical psychosis), in which generalized paroxysmal discharges were provoked either by red-flicker or flickering-pattern and/or pattern, was examined by giving the same stimuli. Similar generalized paroxysmal dischages were provoked in five siblings (23.8%). Of these, two pairs of siblings were identical twins. As a control group, the same EEG activation was carried out in 37 normal healthy 11-year-old children (18 males and 19 females); there were no activation effects. The difference between the two groups was highly signifcant (p less than 0.005). From this study, it was stressed that possible functional vulnerability in the centrencephalon due to disposition might play an important role in the appearance of the GPD's provoked by the visual stimuli as described above. A discussion was also given about the exogenic factor influencing this mechanism.

Influence of color on the photoconvulsive response

Using the visual stimulator, the effect of color on the photoconvulsive response (PCR) was studied in 14 photosensitive patients. When stimuli of 15 c/sec flickers of white, red, yellow, green and blue light of 20 cd/m 2 were given to the subjects, generalized PCRs were provoked only by the red-flicker. These PCRs were all inhibited by blue light of 1.9 cd/m 2 when given either after the appearance of the PCRs or simultaneously with the red-flicker from the start. When blue light was given after the appearance of the PCRs, the latency of appearance of the PCRs in response to the red-flicker showed an inverse relation to the disappearance latency of the PCR in response to the blue light. With blue light of 1 cd/m 2, however, inhibition of the PCRs was seen in only 2 cases when it was given after the appearance of the PCR, and in only 1 case when the blue light was simultaneously given with the red-flicker from the start. These results clearly disclosed the following findings: (1) among various colored lights, an excitatory effect on generalized PCR was always seen only with red light at 15 c/sec and 20 cd/m 2; (2) the PCRs provoked by the red-flicker were inhibited by blue light of 1.9 cd/m 2, but not by blue light of 1 cd/m 2.

Epileptic discharges triggered by blinking and eye closure

Two children manifested EEG discharges which were triggered by blinking and/or eye closure in light and in darkness. The first case demonstrated single focal posterior discharges with eye blinks and repetitive focal posterior sharp wave discharges with eye closures. No photoparoxysmal responses were obtainable. Case 2 manifested generalized epileptic discharges triggered by eye closure which were sometimes associated with clinical seizures. In addition she showed photoconvulsive responses. Since the discharges triggered by eye blink and by eye closure occrred in both bright light and in darkness it is suggested that sensory afferents arising from contraction of the orbicularis oculi muscles may have been the epileptic trigger in Case 1 and could have contributed to the epileptic triggering mechanism in Case 2.

Generalized paroxysmal discharges induced by visual stimuli and eye movements.

The generalized paroxysmal discharges (GPDs) induced by the visuo-sensory and oculomotor activations in a total of 30 patients were investigated. The patients consisted of 27 epileptics and 3 with sequelae of head trauma; all of them showed photoconvulsive response. The visuo-sensory activation with red-flicker of 15 cycles/sec or with visual stimuli containing patterns, "pattern," was carried out under the constant condition of 20 cd/m-2. In 22 cases (73%), G-type (simultaneous occurrence of GPD over all the areas) was induced by red-flicker, while in 28 cases (93%) P-type (GPD was preceded by posterior spikes) was induced by "pattern." With the oculomotor activation, paroxysmal discharges were induced in 11 cases of photogenic epilepsy; 10 cases (91%) were of A-type (GPD was preceded by anterior spikes), and one case (9%) showed focal spikes over the right frontal area. In 21 cases (70%), the type of GPD changed from G-type to P-type as the red-flicker activation was replaced by the "pattern" activation. Further, in seven (33%) out of the 21 cases it changed from P-type to A-type as the activation with "pattern" was replaced by the oculomotor activation. It was suggested that the non-specific thalamo-cortical system, the visual cortex, and the frontal eye field are chiefly concerned with the occurrences of G-type, P-type, and A-type, respectively, when such stimuli as described above are given independently.

Effectiveness of photic stimulation on various eye-states in photosensitive epilepsy

The photoconvulsive effect of photic stimulation on various eye states has been studied, in patients suffering from photosensitive epilepsy as well as in patients with epilepsy and photoconvulsive responses evoked by intermittent photic stimulation (IPS). Particular emphasis has been given to the state of eye-closure i.e. the state immediately following the closure of the eyes. Our findings indicate that IPS is more potent in eliciting photoconvulsive responses during the eye-closure state. IPS with the eyes open is more provocative than with the eyes closed or with monocular stimulation. Electroencephalographic abnormalities induced on eye-closure in the resting EEG are not evoked when eye-closure is performed in darkness, thus indicating that the light is the important factor in the causation of the above EEG abnormalities.

Selective photoconvulsive responses to intemittent diffuse and patterned photic stimulation

Over one hundred epileptic and non-epileptic patients were photostimulated, during routine EEG recordings, with both diffuse and patterned intermittent light. Stimuli consisted of the standard discharge tube flicker with and without a checkerboard pattern affixed to the lamp face. For pattern stimulation patients were instructed to focus on the center of the checkerboard. Selective photoconvulsive EEG responses evoked by only one type of stimulus were found in 12 patients. Five responses only to pattern flicker while 7 responded only to diffuse flicker. Both stimuli evoked photoconvulsive responses in 16 other patients but 4 clearly responded better to pattern and 2 clearly better to diffuse flicker. It was concluded that selective photosensitivity to both diffuse and pattern flicker occurs and that exclusive routine use of either stimulus alone reduces the effectiveness of photostimulation as an activating procedure. Thirty-seven patients were tested with intermittent pattern reversal. This stimulus evoked diffuse paroxysms in only 2 patients, both of whom were even more sensitive to diffuse and patterned flicker. Of the 28 photosensitive patients, 13 had a history compatible with primary generalized epilepsy while 12 had some focal features, 2 had progressive myoclonus epilepsy and one had no history of seizures. Although preferential sensitivity to either diffuse or patterned flicker could not be significantly correlated with these diagnostic categories, the group of patients who responded only to diffuse flash did differ significantly from the remainder with respect to some clinical criteria. The possibility that this selective photosensitivity indicates a specific epileptogenic mechanism is suggested.

The photoconvulsive response. Modification by monocular occlusion in man.

Thirty-six subjects found to have a photoconvulsive electroencephalographic response to flashing light were studied systematically for monocular sensitivity. Thirteen had the abnormal response only if both eyes were stimulated. Eight were equally sensitive with one as with both eyes. Fifteen subjects had reduced or variable response with only one eye stimulated.

Sleep, sleep deprivation, photosensitivity and epilepsy.

In order to investigate whether sleep deprivation activates the photoconvulsive response 35 patients were investigated electroencephalographically after 24–36 h of waking. In 34 cases with sleep deprivation photostimulation showed a clear photosensitivity which was not present before sleep deprivation. This pathological response to photostimulation was unchanged after the short sleep period, in some even potentiated. Long-term anticonvulsive therapy could not suppress the positive photic reaction after sleep deprivation. No correlation between the blood glucose level and photosensibility could be determined. In summary it can be stated that sleep deprivation appears to have a activating effect on photosensitivity. The clinical employment and the neurophysiological mechanisms are discussed.

Serum Concentrations of Diazepam in Subjects With Epilepsy

Serum diazepam concentrations were monitored during a series of intravenous diazepam injections in patients with epilepsy. Suppression of spontaneous specific epileptiform paroxysmal discharges and protection against stroboscopic stimulation in photosensitive subjects were correlated with the serum concentrations, and the results were compared to a series of patients taking diazepam orally. Our results confirm the unique sensitivity of photoconvulsive responses, but suggest that suppression of spontaneous discharges is more a function of high serum concentrations of diazepam than it is of the clinicalelectroencephalogram classification. The results also suggest that failure of diazepam orally as an anticonvulsant in many subjects is related to serum concentrations significantly lower than those found necessary to suppress interictal epileptiform discharges following intravenous injection.

The effect of geometric patterns combined with intermittent photic stimulation in photosensitive epilepsy

During routine EEG investigation of patients with photosensitive epilepsy and of patients with EEG abnormalities induced by intermittent photic stimulation (IPS) it was noted that two different photostimulators had different efficiencies in provoking occipital spikes and photoconvulsive responses. The difference appeared to be related to the presence of a metal grid. Comparison was made of the intensity of the photic stimulus of each lamp and the method is described. Ten patients were studied in detail in order to establish which patterns, when combined with IPS, were the most effective in inducing a photoconvulsive response. It was found that most patterns enhanced the effect of IPS, but the grid and “small squares” pattern were the most potent. It is therefore suggested that a square pattern in which the squares subtend approximately 20′ should be fitted to photostimulators for routine use.

Occipital spikes and their relation to visual evoked responses in epilepsy, with particular reference to photosensitive epilepsy

The responses to intermittent photic stimulation (IPS) at rates of 1–10 fl/sec were studied in seventy-two subjects, eighteen being normal controls, thirty-eight having photosensitive epilepsy and sixteen having epilepsy which was not clinically photosensitive. All patients showed abnormal responses to IPS. In most of the patients photic stimulation evoked negative occipital spikes with or without photoconvulsive responses. Comparison was made between the occipital spikes and the VERs in the same patient. This showed that there was no simple time relation between occipital spikes and components of the VERs. The VERs of the normal subjects showed no component with a latency corresponding to that of the negative occipital spikes seen in the patients. It is suggested that the non-specific thalamo-cortical system may be responsible for the genesis of the “epileptogenic” occipital spikes and that increased sensitivity of the occipital cortex is present in most photosensitive patients.

Mechanisms of epileptic susceptibility to photic activation. Case study of the photoconvulsive response.

SUMMARYA study of the photoconvulsive response to photic activation in a single subject was undertaken using the methods of generalized harmonic analysis. This paper presents such methods and the preliminary results of their application to the problem of defining the mechanisms of moment to moment variation in susceptibility to epileptic activation by intermittent photic stimulation.The EEG was divided into the following contiguous blocks of time: (1) a steady state period; (2) the first trial of photic activation, i.e., without a paroxysmal response; (3) a second trial of activation which did provoke a paroxysmal response; and (4) a non‐contiguous post‐paroxysmal trial of photic stimulation which was not associated with a photoconvulsive response.Spectral analysis of the first trial revealed that this period differed from the steady state by increased per cent power and coherence in the δ‐range and decreased percent power and coherence in the α‐range. These changes were found to be qualitatively similar to those seen in photoconvulsive response to the second trial. It was suggested that the first trial of activation served to partially activate the same seizure processes which were to appear in the photoconvulsive response. A later failure to obtain the photoconvulsive response was found to be coincident with lack of the above partial activation. These findings are discussed in the framework of the reflex theory of stimulus dependent epilepsies.RÉSUMÉAvec la méthode d'analyse harmonique globale, on a étudié, chez un sujet, la réponse photoconvulsive.Ce travail présente les premiers résultats obtenus par ces méthodes appliquées à l'étude de la définition des mécanismes impliqués, à chaque instant, dans les variations de la susceptibilitéà l'activation photoconvulsive.L'EEG a été ainsi divisé en périodes de temps successives: (1) une période de repos; (2) le premier essai d'activation photique sans période paroxystique; (3) un second essai d'activation provoquant une période paroxystique. Ensuite (4) on a fait un autre essai espacé dans le temps par rapport aux précédents, dans lequel la stimulation lumineuse intermittente ne provoquait pas de réponse convulsive.L'analyse spectrale du premier essai a démontré que cette période était différente de la période de repos du fait de Faugmentation du pourcentage en énergie et en cohérence de l'activité de la bande delta et du fait de la diminution du pourcentage en énergie et cohérence de la bande alpha. Ces changements étaient qualitativement semblables à ceux observés dans la réponse photoconvulsive du second essai. On a ainsi pensé que la première partie de l'activation servait à activer partiellement les mêmes processus paroxystiques qui apparaissaient ensuite dans la réponse photoconvulsive. Lorsqu'il n'y avait pas la réponse photoconvulsive, de même on ne retrouvait pas les signes d'activation partielle précédemment décrits. Les résultats sont discutés dans le cadre de la théorie réflexe des épilepsies déclenchees par des stimuli.

Photomyoclonic response of epileltic and non-epileptic subjects during wakefulness, sleep and arousal

1. 1. The clinical photomyoclonic response (PMR) of eleven photosensitive epileptic patients and two non-epileptic subjects was studied by polygraphic EEG and ultraviolet apparatus recording of single responses and by computer summation. The responses spread after single light flashes over the deltoid, biceps, forearm flexors, quadriceps and gastrocnemius muscles with latencies of about: 61, 64, 65, 83 and 95 msec respectively. Agonists and antagonists contracted almost simultaneously. 2. 2. These latencies are virtually identical to those of the sub-clinical physiological reflex described by Bickford as the “photo-motor response”. The PMR is considered as an enhancement of it. 3. 3. In NREM sleep, following arousal from NREM sleep and during REM sleep, the PMR and the photoconvulsive response were diminished. Following arousal from REM sleep they were less diminished and quickly became those of wakefulness. 4. 4. In patients with petit mal absences and petit mal myoclonus, arousal from NREM sleep, unlike that from REM sleep, provoked prolonged myoclonus associated with EEG poly-spike and wave discharges while the PMR and PCR remained suppressed.

Photic activation and photoconvulsive responses in a nonepileptic subject

Photic activation and photoconvulsive responses in a nonepileptic subject

The anticonvulsant properties of urethane contained as a solvent in commercial preparations of trimethadione (tridione)

Experiments were conducted on 3 cats, one human normal control and 10 patients, to compare the actions of urethane and tridione on the following: (1) the Metrazol-induced response to light in the cat, (2) the photomyoclonic and photoconvulsive response in the human. It is concluded that urethane has an evanescent anticonvulsant action which mistakenly could be attributed to tridione. Because of its uncertain and transitory effects, as well as its unpleasant and sometimes harmful side reactions, urethane is not suitable as an anti-convulsant.