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Maturation of visual cortical and subcortical evoked responses and EEG after discharge in unanesthetized kittens
692
INTERNATIONAL FEDERATION - 7TH CONGRESS
Self-induced photo-sensitive seizures have been shown to possess certain common features, such as female predominance in the younger age group, light sensitivity and prevalence of mental retardation, regardless of exact clinical or electrographic manifestations involved. In spite of increasing attention paid to these problems, the mechanism underlying self-seizure induction remains obscure. It is the intention of this presentation to describe results of some of our preliminary exploration in this area in photo- sensitive patients, with a tendency to self-stimulation, who have been given complete control of a photic stimulator in a laboratory setting. It was found that these patients were capable of desensitizing themselves from flicker-induced electrographic and clinical seizures when they were given control of a photic stimulator which was preset at a given parameter. This finding will be contrasted with the results of our study in a group of photogenic Senegalese baboons which have similarly selfphoto-desensitized themselves for a maximum period of up to three months in a comparable laboratory situation.
107. Maturation of visual cortical and subcortical evoked responses and EEG after discharge in unanesthetized kittens.-G. H. Rose and S. P. Gruenau (Omaha, Neb., U.S.A.). Algebraically summated cortical responses evoked by light flash obtained in 60 cross-sectional and longitudinal age samples from 35 unanesthetized kittens with implanted electrodes and 25 preparations under Flaxedil are compared with similar recordings previously obtained by Rose and Lindsley from lightly anesthetized kittens. Pilot data on subcortical responses were also obtained. These results show that the maturational changes in the wave form of the visual electrocortical responses in the first two weeks of life are highly similar in the anesthetized and unanesthetized kitten. The responses begin with a long latency negative wave at 0-4 days which is preceded, between 8-10 days, by a shorter latency positive-negative complex resulting in a clearly differentiated positive-negative-negative wave form at 14 days of age. Such a sequence, present in both unanesthetized conditions, is best obtained in the preparations under Flaxedil which permit maximal conditions of controlled focused stimulation identical to that utilized in the original studies on anesthetized kittens. Beyond two weeks of age, differences occur in the wave form of the visual evoked potentials as a function of anesthesia. Whereas in the anesthetized preparations the adult-like wave form at 30 days consists of a single diphasic positive-negative response, the evolvement of the adult-like wave
form in unanesthetized kittens is more complex, usually consisting of an initial double positive deflection. In addition to maturational changes in cortical evoked activity, there exists in the unanesthetized kittens, parallel changes in the cortical after-discharge to flash characterized by large amplitude spindling in the youngest animals to be gradually replaced, between 10-14 days, by low voltage desynchronized activity typical of adult electrocortical arousal.
108. Prospective study of EEGs in children of low birth weight.-N. L. Auckland, M. Cox, ]. U. Criehton, and H. G. Dunn (Vancouver, Canada). In a prospective study of 500 children with a birth weight of 2041 g or less, 278 had EEGs recorded in the nursery, 249 at about 1½ years, and so far 127 at 6½ years. Among the neonatal records 30% were considered borderline or abnormal. At 1½ years, 22% were interpreted as borderline or abnormal, in contrast to only 2% of the tracings recorded from 98 control children of full birth weight (above 2500 g) at the same age. The correlation between EEG abnormalities in individual children of low birth weight in the neonatal period and at 1½ years is poor, and most of the neonatal abnormalities appear to resolve. At 6½ years, no fewer than 63 (50%) of the 127 children of low birth weight examined to date have borderline (18) or abnormal (45) records. The commonest EEG abnormalities (sometimes combined) in these cases are spike-wave or sharpand-stow wave discharges in 21, bilateral spikes or sharp waves in 11, slow dysrhythmia in 11, persistent asymmetry in 10, mixed dysrhythmia in 8, and focal spikes or sharp waves in 7. Only 6 of the 39 children with discharges have ever had seizures. Positive spikes at 14 and 6/sec were found in 5 cases. Thrity-five of the 63 children with abnormal or borderline records previously had an EEG performed at a mean age of 17 months, and only about 1/3 (13) of these previous tracings were interpreted as abnormal. It is concluded that EEG abnormalities occur in nearly ½ of school entrants with a birth weight of 2000 g or less and that about 2/3 of these abnormalities only became evident after the age of 1½ years.
109. Phase of alpha wave, habituation and contingent blocking.-V. Milstein (Portland, Ore., U.S.A.). This research tested the hypothesis that habituation of the alpha attenuation response (AAR) will be more rapid when the stimulus is presented on the surface negative phase of the alpha wave than when it is presented at other points on the wave.
INTERNATIONAL FEDERATION - 7TH CONGRESS
Self-induced photo-sensitive seizures have been shown to possess certain common features, such as female predominance in the younger age group, light sensitivity and prevalence of mental retardation, regardless of exact clinical or electrographic manifestations involved. In spite of increasing attention paid to these problems, the mechanism underlying self-seizure induction remains obscure. It is the intention of this presentation to describe results of some of our preliminary exploration in this area in photo- sensitive patients, with a tendency to self-stimulation, who have been given complete control of a photic stimulator in a laboratory setting. It was found that these patients were capable of desensitizing themselves from flicker-induced electrographic and clinical seizures when they were given control of a photic stimulator which was preset at a given parameter. This finding will be contrasted with the results of our study in a group of photogenic Senegalese baboons which have similarly selfphoto-desensitized themselves for a maximum period of up to three months in a comparable laboratory situation.
107. Maturation of visual cortical and subcortical evoked responses and EEG after discharge in unanesthetized kittens.-G. H. Rose and S. P. Gruenau (Omaha, Neb., U.S.A.). Algebraically summated cortical responses evoked by light flash obtained in 60 cross-sectional and longitudinal age samples from 35 unanesthetized kittens with implanted electrodes and 25 preparations under Flaxedil are compared with similar recordings previously obtained by Rose and Lindsley from lightly anesthetized kittens. Pilot data on subcortical responses were also obtained. These results show that the maturational changes in the wave form of the visual electrocortical responses in the first two weeks of life are highly similar in the anesthetized and unanesthetized kitten. The responses begin with a long latency negative wave at 0-4 days which is preceded, between 8-10 days, by a shorter latency positive-negative complex resulting in a clearly differentiated positive-negative-negative wave form at 14 days of age. Such a sequence, present in both unanesthetized conditions, is best obtained in the preparations under Flaxedil which permit maximal conditions of controlled focused stimulation identical to that utilized in the original studies on anesthetized kittens. Beyond two weeks of age, differences occur in the wave form of the visual evoked potentials as a function of anesthesia. Whereas in the anesthetized preparations the adult-like wave form at 30 days consists of a single diphasic positive-negative response, the evolvement of the adult-like wave
form in unanesthetized kittens is more complex, usually consisting of an initial double positive deflection. In addition to maturational changes in cortical evoked activity, there exists in the unanesthetized kittens, parallel changes in the cortical after-discharge to flash characterized by large amplitude spindling in the youngest animals to be gradually replaced, between 10-14 days, by low voltage desynchronized activity typical of adult electrocortical arousal.
108. Prospective study of EEGs in children of low birth weight.-N. L. Auckland, M. Cox, ]. U. Criehton, and H. G. Dunn (Vancouver, Canada). In a prospective study of 500 children with a birth weight of 2041 g or less, 278 had EEGs recorded in the nursery, 249 at about 1½ years, and so far 127 at 6½ years. Among the neonatal records 30% were considered borderline or abnormal. At 1½ years, 22% were interpreted as borderline or abnormal, in contrast to only 2% of the tracings recorded from 98 control children of full birth weight (above 2500 g) at the same age. The correlation between EEG abnormalities in individual children of low birth weight in the neonatal period and at 1½ years is poor, and most of the neonatal abnormalities appear to resolve. At 6½ years, no fewer than 63 (50%) of the 127 children of low birth weight examined to date have borderline (18) or abnormal (45) records. The commonest EEG abnormalities (sometimes combined) in these cases are spike-wave or sharpand-stow wave discharges in 21, bilateral spikes or sharp waves in 11, slow dysrhythmia in 11, persistent asymmetry in 10, mixed dysrhythmia in 8, and focal spikes or sharp waves in 7. Only 6 of the 39 children with discharges have ever had seizures. Positive spikes at 14 and 6/sec were found in 5 cases. Thrity-five of the 63 children with abnormal or borderline records previously had an EEG performed at a mean age of 17 months, and only about 1/3 (13) of these previous tracings were interpreted as abnormal. It is concluded that EEG abnormalities occur in nearly ½ of school entrants with a birth weight of 2000 g or less and that about 2/3 of these abnormalities only became evident after the age of 1½ years.
109. Phase of alpha wave, habituation and contingent blocking.-V. Milstein (Portland, Ore., U.S.A.). This research tested the hypothesis that habituation of the alpha attenuation response (AAR) will be more rapid when the stimulus is presented on the surface negative phase of the alpha wave than when it is presented at other points on the wave.