Intermittent Light Stimulation Research Articles

Multiunitary activity naalysis of cortical and subcortical structures in paroxysmal discharges and grand mal seizures in photosensitve baboons

Cortical and subcortical multiunitary activities (MUA) and EEG were s0imultaneously recorded in baboons made photosensitive bu a subconvulsant does of dl-allglycine. Intermittent light stimulation (ILS) trains induced in these animals fronto-rolandic (FR) paroxysmal discharges (PDs, constituted as spikes and waves) and grand mal seizures. During the induction of FR PDs by ILS trains, the visual structures (occipital cortex, colliculi superiors, pulvinar) showed a significant MUA increase which was not related to teh PD spike or wave but correlated with the flashes. The first structure showing bursts of MUA that frequently preceded the PD appearance was the FR cortex. When PDs appeared, the brusts were related to the spikes of PDs and were followed by an inhibition during the slow wave. The pontine and mesencephalic formations and the facial nuclei were activated in bursts after the FR PDs had reached a certain amplitude. The thalamic nuclei ventralis lateralis, centrum medianum and lateralis posterior were activated only later, when the FR PDs had reached an even greater amplitude. It is suggested that the activation of visual structures is necessary for FR PD appearance. The secondary pontine and mesencephalic activation could reinforce that of the FR cortex and then the thalamus, and could determine the myoclonus observed in unparalysed animals. When the ILS is continued, grand mal seizures appear. The onset of the seizures could be linked to the loss of FR cortical control of the subcortical structures. The resulting reticular activation would be responsible for the vasomotor modifications which constitute the first clinical signs of a seizures.

Analyse de l'activite multiunitaire du cortex et des structures sous-corticales lors des decharges paroxystiques et des crises grand mal chez le babouin photosensible

Cortical and subcortical multiunitary activities (MUA) and EEG were simultaneously recorded in baboons rendered photosensitive by a subconvulsant dose of DL-allylglycine. Intermittent light stimulation (ILS) trains induce in those animals fronto-rolandic (FR) paroxysmal discharges (PDs, constituted as spikes and waves) and grand mal seizures. During the induction of FR PDs by ILS trains, the visual structures (occipital cortex, colliculi superioris, pulvinar) show a significant MUA increase which is not related to the PD spike or wave but is correlated to the flashes. The first structure showing bursts of MUA that frequently precede the PD appearance is the FR cortex. When PDs appear, the bursts are related to the spikes of PDs and are followed by an inhibition during the slow wave. The pontine and mesencephalic reticular formations and the facial nuclei are activated in bursts after the FR PDs have reached a certain amplitude. The thalamic nuclei ventralis lateralis, centrum medianum and lateralis posterior are activated only later, when the FR PDs have reached an even greater amplitude. It is suggested that the activation of visual structures is necessary for FR PD appearance. The secondary pontine and mesencephalic activation could reinforce that of the FR cortex and then the thalamus, and could determine the myoclonus observed in unparalyzed animals.

Convulsant effect of Ro 5-4864, a peripheral type benzodiazepine, on the baboon ( Papio papio)

The effects of Ro 5-4864, a 1,4-benzodiazepine with a high affinity for the peripheral-type benzodiazepine (Bz) binding site, were investigated in the baboon ( Papio papio), which is genetically predisposed to epilepsy. A proconvulsant effect of low doses (1–3 mg/kg, i.v.) of Ro 5-4864 was observed by studying its effect on the photic responses induced by intermittent light stimulation in non-photosensitive baboons. Higher doses of Ro 5-4864 (10 mg/kg, i.v.) were overtly convulsant. The Bzs clonazepam and diazepam blocked these convulsant actions of Ro 5-4864 whereas neither Ro 15-1788, an antagonist of central Bz binding sites, nor PK 11 195, an antagonist of peripheral Bz binding sites, had any effect. It thus appeared that the convulsant effect of Ro 5-4864 was not mediated by Bz binding sites of either the central or the peripheral type. It is possible that Ro 5-4864 exerts its convulsant action at the picrotoxin site of the central Bz receptor - γ-aminobutyric acid receptor-chloride ionophore complex.

The influence of light stimulation on subcortical potentials evoked by single flashes in photosensitive Papio papio.

Visual evoked potentials (VEPs) from the frontorolandic (FR) cortex and from subcortical nuclei (colliculi superioris, pulvinar, corpori geniculati lateralis, centrum medianum, ventralis lateralis) and from pontine reticular formation were analyzed in Papio papio monkeys rendered photosensitive by a subconvulsant dose of allylglycine. The VEPs induced by single flashes were compared statistically with those induced by flashes preceded by trains of intermittent light stimulation (ILS). This latter mode of stimulation provoked the appearance of paroxysmal VEPs (PVEPs) in the FR cortex with the same morphology as the spikes and waves induced in this area by the ILS. The aim of our research was to provide evidence for the possible implication of the subcortical structures which we have studied in the elaboration of PVEPs and thus of spikes and waves. The VEPs recorded at the thalamic and pontine levels were modified when PVEPs were present. These modifications varied according to the site, but subcortical VEPs were never paroxysmal. In structures with visual functions (colliculi superioris, corpori geniculati lateralis), the VEPs were modified by the ILS, but showed more marked changes when PVEPs were present. Thus, these structures may contribute to the genesis of PVEPs. In the other structures (centrum medianum, ventralis lateralis, and pontine reticular formation), modifications of the VEPs occurred only when PVEPs were present. Thus, these structures would be only secondarily involved. We also present preliminary results concerning the effects of lesioning the pulvinar and the ventralis lateralis on the susceptibility of the FR cortex to produce spikes and waves during ILS.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of suriclone in naturally and allyglycine-induced photosensitive baboons, Papio papio

Suriclone (SC) is a new anxiolytic compound with a chemical structure different from that of benzodiazepines (BZD) but SC possesses a high affinity for the so-called BZD receptors. SC was tested in the naturally or the allylglycine-treated photosensitive baboon Papio papio. As active BZD administered by the intramuscular or oral route, this new compound possesses a marked protective effect against the excessive photosensitivity of the baboons, it blocks myoclonus following EEG spike and waves discharges induced by intermittent light stimulation; as BZD again, SC can induce spontaneous myoclonus not accompanied by EEG spike and wave discharges.

Thalamic kindling: Electrical stimulation of the lateral geniculate nucleus produces photosensitive grand mal seizures

Kindling is traditionally viewed as a chronic, focal epilepsy model which consistently induces complex partial seizures from limbic structures in animals. This study revealed that primary or exceedingly rapid secondary generalized seizures could also be kindled when stimulation was applied to the lateral geniculate nucleus, a thalamic region involved in sleep regulation and possibly also photosensitive epilepsy. Two experiments were conducted in cat. Experiment 1 compared the development of generalized tonic-clonic convulsions and associated sleep disorders following electrical stimulation of the lateral geniculate nucleus ( N = 4) and the amygdala ( N = 4). Experiment 2 described the effects of intermittent light stimulation on seizure thresholds in both groups. Three primary findings distinguished the epileptogenic process in those two brain regions. First, generalized electroencephalographic and clinical seizures accompanied the first afterdischarge obtained with thalamic stimulation. In contrast, focal seizures with secondary generalization appeared during a 3- to 4-week period of afterdischarge elicitations from the amygdala. Second, amygdala-kindled cats showed fewer sleep spindles during slow-wave sleep whereas cats kindled in the lateral geniculate nucleus had abnormal sleep spindles approaching spike wave-like activity. Third, only the latter cats showed reduced seizure thresholds in response to photic stimulation. Based on the anatomic substrates involved, the clinical and electrographic profiles observed during kindling and the type of sleep disturbance shown, we concluded that lateral geniculate nucleus kindling may represent primary generalized epilepsy, possibly of a photosensitive nature; alternatively, the rapid propagation of abnormal discharge was also consistent with the important role of the thalamus in secondary seizure generalization.

The influence of intermittent light stimulation of potentials evoked by single flashes in photosensitive and non-photosensitive Papio papio

The effect of intermittent light stimulation (ILS) on visual potentials (VEPs), evoked in different cortical areas, were statistically studied in baboons either naturally photosensitive or made photosensitive by allyglycine at a subconvulsant dose, as well as in non-photosensitive animals. VEPs were induced by single flashes (paradign a) or by flashes preceded by trains of ILS (paradigm) b). In every baboon, photosensitive or not, the VEPs induced by paradigm b in the striate area show a decrease of amplitude compared to VEPs induced by paradigm a. The ERG evolves in the same way. Therefore, these effects do not depend on photosensitivity; they depend on the intensity of stimulation. In photosensitive animals the single flash in paradigm b can induce a paroxysmal VEP in the fronto-rolandic (FR) area. In parietal and peristriate areas the VEPs induced by paradigm b show new late components when compared to those induced by paradigm a. These changes are observed even if no FR paroxysmal VEP is induced; they depend on the presence of a train of ILS preceding the single flash and on the predisposition to epilepsy (both natural and due to allylglycine); in the non-photosensitive animals the VEPs recorded in the same areas do not show such differences. We consider that among afferents which could act in inducing FR paroxysmal activities some cortico-cortical visual afferents can come from non-specific cortical areas (parietal or peristriate), but would not directly originate in the striate cortex; anatomical data in this species may support such a hypothesis.

Action of progabide in the photosensitive baboon, Papio papio.

Progabide is a GABA agonist which is nontoxic and crosses the blood-brain barrier. Progabide was tested in naturally and allylglycine-induced photosensitive baboons (Papio papio). Intravenous injection of various doses (30 to 100 mg/kg) of progabide induced a protective effect against intermittent light stimulation (25 Hz) in both test situations. This protection lasted 10 to 120 min. This duration was dose-dependent and was generally shorter in allylglycine-treated than in naturally photosensitive baboons. At all doses, progabide reinforced rhythmic activities in the frontorolandic and occipital regions. At doses greater than 50 mg/kg, progabide produced a mild sedation with somnolence and myorelaxation, all effects which could be reversed by sensory stimulation. These data confirm the anticonvulsant properties of progabide in another animal model.

Characteristics and origin of frontal paroxysmal responses induced by light stimulation in the Papio papio under allylglycine

In the Papio papio, curarized and rendered photosensitive by injection of a subconvulsant dose of dl-allylglycine, single flashes induce frontal paroxysmal evoked responses on condition that they be preceded by trains of intermittent light stimulation (ILS). The characteristics of these responses have been compared to those of non-paroxysmal responses induced in the same cortical area by isolated flashes (not preceded by trains of ILS). The paroxysmal responses resemble spikes and waves and consist of one or two positive spikes followed by a slow negative wave. The intracortical distribution of these responses has been studied in the motor cortex. The non-paroxysmal responses are probably not generated at this level. On the other hand, observations made during paroxysmal responses show the existence of two cortical generators; this demonstration follows from the existence of an inversion in some response components, linked to a negativity and a local cellular activation. A generator, situated in the pyramidal cell layer, is active during the positive surface spikes; the other generator, situated in the more superficial cortical layers, is active at the beginning of the slow negative surface wave. The cortical and subcortical afferents likely to bring these generators into play are discussed.

Opposite effects of lorazepam on two kinds of myoclonus in the photosensitive Papio papio

The action of lorazepam was studied in photosensitive baboons. Animals were either naturally very photosensitive or rendered photosensitive by a previous injection of allyglycine. Intravenous administration of varying doses, from 0.05 to 0.5 mg/kg, of lorazepam blocked the myoclonus induced by intermittent light stimulation in all the animals. However, in the naturally photosensitive baboon the injection of lorazepam favoured the appearance of spontaneous myoclonus with no important EEG modification. This myoclonus is different from that induced by intermittent light stimulation, which is always preceded by spike-wave cortical discharges. Lorazepam-induced myoclonus appears during the period when the animal is not photosensitive and its origin is probably in the medulla or in the brain stem.

Modifications de l'excitabilite corticale (frontale et occipitale) par des trans d'eclairs chez le singe Papio papio

The experimental conditions necessary for obtaining an evoked paroxysmal response from the frontal cortex were studied in the baboon Papio papio. The trigger stimulus was comprised of an isolated flash preceded by a train of intermittent light stimulation (SLI). Two conditions were necessary for the appearance of paroxysmal responses: a subconvulsant dose of DL-allylglycine had to be injected at least 3 h previous to recording, and a sufficient number of SLI trains had to be presented to the animal. The paroxysmal responses disappeared as soon as SLI trains were stopped. At the same time, modifications in the evoked occipital potential continue, although these do not become paroxysmal. These modifications appear either simultaneously with or previous to the paroxysmal frontal response.

Cortical unit activity during intermittent photic stimulation in Papio Papio. Relationship with paroxysmal fronto-rolandic activity

Extracellular records have been made in the fronto-rolandic (FR), parietal and occipital cortical areas in Papio papio injected with allylglycine and paralysed with a synthetic curarizing agent. The organization of the unit discharges in the absence of intermittent light stimulation (ILS) is normal. During ILS, unit discharges in the FR cortex are organized in bursts of high frequency that are synchronous with the spikes of the EEG paroxysmal discharges (PD) in the same territory; this burst-organized FR activity is reversible, and bursts disappear when the ILS stops. In addition, in the FR cortex, triple or single flashes induced paroxysmal visual evoked potentials (PVEP) whose spikes were accompanied by bursts identical to the preceding ones. The slow waves which constituted The PD and the PVEP corresponded to a transitory inhibition of the FR neuronal activity. From the unit discharge patterns, no difference was observed between the two EEG paroxysmal activities recorded. No pattern of discharge in bursts was ever observed in the parietal and occipital cortex. The synchronizing role of the light stimulation in the FR cortex in Papio papio under allylglycine is discussed and the results are used to compare the experimental model with the naturally highly photosensitive animal. The Particular reactivity of the FR cortex with respect to other regions is also discussed. Finally, the results bring forth new information in favour of a similarity between PD and PVEP.

Paroxysmal visual evoked potentials (PVEPs) in Papio papio. II. Evidence for a facilitatory effect of intermittent photic stimulation

The existence of fronto-rolandic (FR) visual evoked potentials of very large amplitude (>1000 μV) in the photosensitive Papio papio, or in those made photosensitive by an injection of allylglycine, is related to the presentation of intermittent light stimulation (ILS). The temporal evolution of these paroxysmal visual evoked potentials (PVEPs) after standardized series of stimuli has been evaluated in two contexts. First, it has been compared with the evolution of the paroxysmal discharges (PDs) occurring during ILS. Secondly, it has been studied either in awake animals placed in a restraining chair or paralysed by a curare agent and ventilated artificially. In non-paralysed baboons, either photosensitive or having received an injection of allylglycine, ILS induces FR PDs grouped in bursts and possibly followed by generalized seizures. In this situation the PVEPs are difficult to obtain and occur consecutive to the appearance of the PDs. In the paralysed photosensitive baboon PDs only occur after the repetition of a considerable number of stimuli and no seizure can be induced. The frequency of occurrence of the PVEPs is low for the first stimulation but increases subsequently to reach high values. In the paralysed baboons after an injection of allylglycine, the PVEPs most often precede the PDs, have a high frequency of occurrence and have an average amplitude larger than that observed in non-paralysed animals. In all these experimental situations the temporal evolution of the PEVPs presents two aspects: facilitation of brief duration marked by higher voltage PVEPs for the stimuli which immediately follow the ILS, and a longer term facilitation marked by an increase in the average amplitude of the PVEPs as the series of ILS are repeated. FR evoked potentials of large amplitude were also obtained for subcutaneous electrical stimulation of the hand, in the paralysed baboon after allylglycine. Following these observations, the question arises of the origin of the facilitation of PVEPs. Our results furnish no argument in favour of a facilitation having its origin in the non-specific structures such as the reticular formation. Finally, our observations confirm the different reactivity of the PDs and the PVEPs to certain experimental conditions. This, in turn, raises the problem of the exact similarity of these two types of paroxysmal activity.

Paroxysmal visual evoked potentials (PVEPs) in Papio papio. I. Morphological and topographical characteristics. Comparison with paroxysmal discharges

This study describes a method of stimulation capable of inducing fronto-rolandic (FR) visual evoked potentials of very large amplitude (up to an even greater than 1000 μV) to isolated flashes in the naturally photosensitive Papio papio and in those made photosensitive by an injection of allylglycine. The morphological and topographical characteristics of these FR paroxysmal visual evoked potentials (PVEPs) are described in two experimental situations: the animals either awake and placed in a restraining chair, or paralysed with a synthetuc curare agent and ventilated artificially. During thes study, the following observations were made: 1. (1) The morphology of the PVEPs is similar to that of the paroxysmal discharges (PD) induced by intermittent light stimulation (ILS) in photosensitive animals. 2. (2) The PVEPs are observed in the FR cortex; those of maximal amplitude are located in the precentral area. Simultaneously, the specific occipital responses retain their usual characteristics and never become paroxysmal. 3. (3) PVEPs have never been observed in non-photosensitive animals in the absence of allyglycine. In non-paralysed photosensitive or allyglycine-injected animals the PVEPs are hard to obtain, while the PDs and seizures on the contrary are easily induced by the ILS. Conversely, in paralysed and allyglycine-injected animals, the PDs and seizures are difficult to obtain whereas the PVEPs occur with increased amplitude and frequency. Several questions arise from these observations concerning the origin of the visual afferents to the FR cortex which induce the PVEPs, and concerning the possible relationships between the PVEPs and the PDs induced by ILS. In response to the latter question, it seems that despite the similarities of morphological and topographical characteristics, the PVEPs and PDs evolve differently after curaruzation of the animal.

EEG and anticonvulsant effects of dipropylacetic acid and dipropylacetamide in the Baboon Papio papio

The ability of dipropylacetic acid (DPA) and dipropylacetamide (DPM) to modify EEG and seizure activity was assessed in 4 female and 3 male Papio papio. Doses of 30–60 mg/kg of DPA given at intervals over an 8 h period produced blood levels of 19–44 μ/ml which were not protective against intermittent light stimulation (ILS). Administration of 150–200 mg/kg doses at intervals over a 36 h period produced blood levels greater than 150 μg/ml and were highly protective against ILS. Similar results were obtained following administration of DPM; however, DPM appeared to offer greater protection against ILS. A moderate amount of seizure control was obtained at blood levels of 60–91 μg/ml (DPA) and complete blockade occurred at levels greater than 100 μg/ml DPA. Background EEG changes were similar following either DPA or DPM and consisted of a striking increase in total spectral power with relative power changes in 10–20 c/sec range, the magnitude of which was related to blood levels of DPA. Both agents produced a quieting effect on behavior without severe depression.

Circadian periodicity of brain activity and urinary excretion in the epileptic baboon.

A 24-H rhythm in the proclivity of the baboon Papio papio to exhibit a seizure response to intermittent light stimulation (ILS) has been uncovered. Seizure response to ILS was found to be greatest in the morning at about 0900 h, 2 h after lights on, and least severe in the evening at about 2000 h 1 h after lights off. Urine cortisol and potassium excretion rhythms followed the same pattern as seizure susceptibility and sodium rhythms were 3 or 4 delayed. Mean values for urine cortisol per 4 h ranged from 25 microgram/4 h at the maxima (0400 to 0800 h) to 2 microgram/4 h at the minima (2000 to 2400 h). Electrolyte rhythms ranged from 13 to 3 meq/4 h for potassium and 1 to 5 meq/4 h for sodium. Changes in electroencephalographic (EEG) activity also accompanied the change in urine cortisol and potassium, and seizure sensitivity, Changes in the EEG at the diurnal minima (2000 h) consisted of a decrease in slow waves concomitant with an increase in fast activity in the 18-25 Hz range,

Electroencephalographic and behavioral effects of a GABA agonist (muscimol) on photosensitive epilepsy in the baboon, papio papio.

Muscimol, 0.25-1.0 mg/kg, i.v., was administered acutely to 4 adolescent baboons, Papio papio, that show photically induced epilepsy. On the EEG, slowing of background rhythms was associated with the appearance of spikes, polyspikes, and recurring symmetrical spike-wave complexes. These changes were maximal 0.5-2 hr after muscimol injection. Regular testing with intermittent light stimulation showed either no change from control responses or a more severe epileptiform EEG 0.1-3 hr after muscimol. Photically induced myoclonus was not modified by muscimol. Despite its GABA-abonist properties, muscimol is not an effective anticonvulsant.

Myoclonus developing after vermisectomy in photosensitive Papio papio

Two vermisectomized photosensitive baboons exhibited two different types of myoclonus, one induced by intermittent light stimulation (ILS) and the other occuring ‘spontaneously’. The characteristics of these two types of myoclonus are described from a clinical and from an ECoG point of view. Myoclonus induced by ILS (ML) started at the eyelids and secondarily invaded the face and body; it was always preceded by fronto-rolandic spike-waves or polyspike-waves. The ‘spontaneous’ myoclonus which followed vermisectomy (MV) was ‘massive’, but involved firstly the trunk and secondarily the face and limbs; no ECoG paroxysm accompanied this myoclonus, but we observed a parietal evoked potential of small amplitude, 10–15 msec after its onset. If MLs can be considered as consequences of the fronto-rolandic paroxysmal discharges, MVs seem to originate in the brain stem but appear similar to action myoclonus. This experimental situation showing two types of myoclonus resembles human hereditary degenerative syndromes (dyssynergic cerebellar myoclonus, progressive myoclonic epilepsy), without being exactly comparable. The conditions in which MVs were seen and their modifications during sleep and by different drugs are described. The relationships between MVs and MLs and myoclonic epilepsy are discussed.

Laminar segregation of afferents to lateral geniculate nucleus of the cat: an analysis of current source density.

ArticlesLaminar segregation of afferents to lateral geniculate nucleus of the cat: an analysis of current source densityU. Mitzdorf, and W. SingerU. Mitzdorf, and W. SingerPublished Online:01 Nov 1977https://doi.org/10.1152/jn.1977.40.6.1227MoreSectionsPDF (6 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByEarly Postnatal Development of the Lamination in the Lateral Geniculate Nucleus A-Layers in Cats17 April 2018 | Cellular and Molecular Neurobiology, Vol. 38, No. 5Adult-Onset Hearing Impairment Induces Layer-Specific Cortical Reorganization: Evidence of Crossmodal Plasticity and Central Gain Enhancement13 April 2018 | Cerebral Cortex, Vol. 168Dipolar extracellular potentials generated by axonal projections5 September 2017 | eLife, Vol. 6A quantitative theory of gamma synchronization in macaque V131 August 2017 | eLife, Vol. 6Linking canonical microcircuits and neuronal activity: Dynamic causal modelling of laminar recordingsNeuroImage, Vol. 146An NMDA receptor-dependent mechanism for subcellular segregation of sensory inputs in the tadpole optic tectum23 November 2016 | eLife, Vol. 5The horizontal brain slice preparation: a novel approach for visualizing and recording from all layers of the tadpole tectumAli S. Hamodi and Kara G. Pratt1 January 2015 | Journal of Neurophysiology, Vol. 113, No. 1Electrical neuroimaging based on biophysical constraintsNeuroImage, Vol. 21, No. 2Coupling of Total Hemoglobin Concentration, Oxygenation, and Neural Activity in Rat Somatosensory CortexNeuron, Vol. 39, No. 2on and off Channels of the Frog Optic Tectum Revealed by Current Source Density AnalysisHideki Nakagawa, and Nobuyoshi Matsumoto1 October 1998 | Journal of Neurophysiology, Vol. 80, No. 4Premature bifurcation of the apical dendritic trunk of vibrissa-responding pyramidal neurones of X-irradiated rat neocortex22 September 2004 | The Journal of Physiology, Vol. 512, No. 2The influence of transcortical relationships on visual responses in ratsBrain Research Bulletin, Vol. 23, No. 1-2Modular organization of on and off responses in the cat lateral geniculate nucleusNeuroscience, Vol. 32, No. 3Epileptic discharges induced by intermittent light stimulation in photosensitive baboons: a current source density studyEpilepsy Research, Vol. 2, No. 1The development of soma size changes in the C-laminae of the cat lateral geniculate nucleus following monocular deprivationDevelopmental Brain Research, Vol. 35, No. 2Current source density analysis of frequency coding in the inferior colliculusHearing Research, Vol. 25, No. 2-3Evoked potentials from passive elbow movements. I. quantitative spatial and temporal analysisElectroencephalography and Clinical Neurophysiology, Vol. 61, No. 5Intracortical generators of the flash VEP in monkeysElectroencephalography and Clinical Neurophysiology/Evoked Potentials Section, Vol. 62, No. 4The distribution of acetylcholinesterase in the lateral geniculate nucleus of the cat and monkeyBrain Research, Vol. 244, No. 1Chapter 4 Morphological types and central projections of ganglion cells in the cat retinaProgress in Retinal Research, Vol. 1Parallel visual pathways: A reviewVision Research, Vol. 20, No. 7 More from this issue > Volume 40Issue 6November 1977Pages 1227-1244 Copyright & PermissionsCopyright © 1977 the American Physiological Societyhttps://doi.org/10.1152/jn.1977.40.6.1227PubMed925725History Published online 1 November 1977 Published in print 1 November 1977 Metrics

Neutralization of sensory-input modification of seizure thresholds in rats.

In this series of experiments it was demonstrated that the result of exposing rats to various parameters of either intermittent sound or intermittent light stimulation significantly decreased the threshold to chemically induced generalized seizures. Furthermore, simultaneous presentation of intermittent light with intermittent sound resulted in a mutual intersensory inhibition (cancellation, neutralization) of the preexisting seizurogenic potential of each stimulus. In these cases, the seizure thresholds did not differ from control values. Several working hypotheses are extended to probe the mechanism of the above results. The probable significance of these observations are (a) that the corroboration of results of other experiments on bimodal inhibitory interactions in normal animals suggests that intersensory inhibition is a property of the nervous system presented simultaneously with certain inputs and (b) that if generalizable to humans, the principle of intersensory inhibition may find an application in the abortion of sensory-precipitated seizures.