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Cochlear summating potential detected from the external auditory meatus. A normative study
$65 areas induced a strong inhibition of the flexion reflex, lasting for 30 min or more. EA to the distal parts of limbs was more effective than that to the body trunk, and EA to a different dermatome from the vibrating area also induced inhibition. The simultaneous application of EA to the acupuncture point and a nearby area caused summation of inhibition. These results suggested that the acupuncture point was not the most effective point and both segmental and non-segmental spinal mechanisms might participate in the inhibition of flexion reflex induced by EA stimulation of the skin.
W15.10 PHOTO-EVOKED EYELID MICROVIBRATION: DEVELOPMENTAL CHANGES AND CLINICAL APPLICATION.
function retain the response if otolith function remains. In hemiplegic patients with cortical lesions, the response on the weak side is retained but does not habituate, whereas with deeper lesions the response is frequently delayed or absent. Lesions of the spinal cord can delay or abolish the response on the weak side. We conclude that this vestibulo-spinal response depends upon otolith function, has a subcortical pathway which is under a degree of cortical control and has a descending course with the pyramidal tract.
W15.12 TRANSCORTICAL REFLEX (C-RESPONSE) IN NORMAL SUBJECTS AND NEUROLOGICAL PATIENTS. Y. Takanashi, T. Takegami, T. Motonaga, E. Sugimoto and K. Yamaguchi
S. Sanada, C. Kohno, S. Miyake and S. Ohtahara (Kyoto, Japan) (Okayama, Japan) Photo-evoked eyelid microvibration (MV) is regarded as a new method for assessing brain-stem function, and its clinical application is anticipated. The shortening of MV latency with age is known, but details, particularly normative data, indispensable for clinical application of the method, need to be clarified. Developmental changes in MV latency were investigated in 155 normal humans, ranging from 0 to 35 years of age. The results were as follows: 1) The peak latencies were 199_+10 msec at the age from 0 to 2 months, 165_+18 msec at 3 to 5 months, 154+16 msec at 6 to 11 months, 148_+18 msec at 1 year, 123_+18 msec at 2 years, and 89_+6 msec at 3 years; 2) after age of three, latency was stable between 70 and 80 msec. 3) These findings disclose developmental changes in the latency of MV and the remarkable shortening of latency in the first 6 months of life and at age 1 to 3 years; 4) Clinically, MV was studied on 80 cases with various forms of encephalitis, epilepsy, mental retardation and cerebral palsy. The results indicate that MV is a useful method for evaluation of both organic and functional disorders of the brain-stem.
Electrical stimulation of the median nerve during voluntary contraction of abductor pollicis brevis (APB) muscle produces the direct muscle response (M-wave) and a few late responses such as V1 and V2 responses. The V2 response (C-response) is considered to be a transcortical reflex, although the nature of this wave is still uncertain. We studied the extent of potentiation of the V2 response by strengthening the voluntary muscle contraction of APB, recording somatosensory evoked potential (SEP) at the same time, in normal subjects and several neurological diseases. In control subjects, onset and peak latencies of V2 were 44.2 + 5.8 msec and 49.8_+6.7 msec respectively, during isometric contraction of APB at 50% of maximal contraction. The stronger the isometric contraction the higher the amplitude of V2 became. In OPCA cases only the M-wave was observed at rest and V2 appeared by muscle contraction with longer latency. In LCCA V2 was obtained even at rest. In a case of small pontine haemorrhage, affecting the left medial lemniscus, abducens and facial nerve, V2 was not obtained in the right APB and the SEP was not elicited by stimulating the right median nerve. This suggests that the medial lemniscus system might play a r61e in the generation of the V2 response.
W15.11 VESTIBULO-SPINAL EVOKED RESPONSES.
A.M. Bronstein, H.J. Barratt, M.A. Gresty and L.J. Findley
AUDITORY EVOKED POTENTIALS AND MULTIMODALITY STUDIES.
(London, UK) The characteristics of the vestibular startle responses were investigated in neurological patients using an experimental technique in which they lay supine on a bed which was suddenly launched into 'free fall' and arrested by springs. The fall was monitored with a head mounted accelerometer whilst EMG responses were recorded with surface electrodes. The normal response is a generalised activation of skeletal muscles with typical mean latency for quadriceps of 75 msec and an estimated spinal conduction velocity of 60 m / s e c and habituates with repeated stimuli. Patients with absent vestibular canal
W16.01 COCHLEAR SUMMAT1NG POTENTIAL DETECTED FROM THE EXTERNAL AUDITORY MEATUS. A NORMATIVE STUDY.
G.- E. Chatnan (Seattle, WA, USA) The cochlear summating potential (SP) preceding the auditory nerve compound action potential (AP) was elicited by broadband alternating condensation and rarefaction clicks and re-
$66 corded by non-invasive electrodes from the external auditory meatus (EAM) of 60 volunteers of both sexes, 12-67 years old, who had normal hearing for age. Quantitative data were obtained on: the number of ears displaying measurable SPs; the SP detection level; the SP onset, peak and rise times; the duration of the SP-AP complex; the SP amplitude and the S P / A P amplitude ratio. Previously unknown relationships were unveiled between the amplitude, but not the temporal, measures of the SP and laterality, sex, age, and audiometrically determined hearing thresholds to 4-8 kHz tones. The highest correlations were obtained with these last thresholds, which suggested that receptors in the basalturn of the cochlea played a dominant role in the generation of the EAM-detected SP. To improve on existing techniques for determining abnormal SP elevation as an indication of endolymphatic hydrops, a multiple regression method was devised that utilized sex, age, 4-8 kHz hearing thresholds and AP voltage to establish upper normal limits of SP amplitude for individual subjects and ears.
W16.02 MINUTE R H Y T H M S IN T H E STEADY-STATE R E S P O N S E S TO AUDITORY, VISUAL AND TACTILE STIMULI. S. Makeig, R. Galambos and D.R. Stapells (San Diego, CA, USA) A train of discrete stimuli (auditory clicks, visual flashes, tactile vibrations) delivered at rates near 40 per second evokes a corresponding train of roughly sinusoidal brain potentials (the 40 Hz ERP, the high-rates or steady-state response, etc.). Since the response train lasts as long as the stimuli continue (minutes, hours) it may be used as an ongoing probe of changes within the CNS. We have been studying the variations of response amplitude, phase, and phase coherence during threshold estimation, masking, sleep, and behavioral experiments. In quiet, waking subjects, quasi-rhythmic fluctuations in response amplitude and phase occur spontaneously, with periods of 20-120 seconds ('minute-rhythms') in all three modalities. Amplitudes may vary by 100 per cent or more, especially as the subject drifts into or out of sleep (in the auditory modality, at least). We have also observed these minute-rhythms in concurrent measures of performance and of EEG-band amplitudes obtained during a vigilance task. Evidently, minute-rhythms are a natural feature of brain electrophysiology. (Work supported by N.I.H.)
WI6.03 INTRACRANIAL S T U D I E S ON SURFACE AND DEPTH POTENTIAL GENERATORS IN MAN: 11. BIPOLAR SOMATIC, AUDITORY AND VISUAL VERTEXLIKE ACTIVITIES. M. Velasco and F. Velasco
(Mexico City, Mexico) Bipolar EEG responses correlated to somatic+ auditory and visual vertex activities (VA) were studied in different subcortical structures of patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. Typical subcortical VA, evoked by somatic, auditory and visual stimuli, were recorded together from a single structure of a non-specific system including: reticulo, rnedial, dorsal thalamic, orbitofrontal, limbic and striatal structures. Typical subcortical VA were formed by four consecutive components O, A, B and C correlated to PI, N1, P2 and N2 of the surface VA. Polarity of component A was inverted between reticulo and medial-thalamic while that of component B was inverted between medial and dorsal thalamic and between dorsal thalamic and fronto-limbic structures. Typical subcortical VA were absent within specific thalamic nuclei (VPL, MG and LG) and pathways (medial and lateral lemniscus and optic radiations) in presence or absence of short latency responses evoked by specific sensory stimuli.
W16.04 BRAIN TRANSPLANTS REVERSE AUDITORY BRAIN-STEM R E S P O N S E S ABOLISHED BY COAGULAT I O N OF T H E RAT'S INFERIOR COLLICULI. M. Shkurovich, G. Cornejo, F. Fernfindez, B. Fernfindez and R. Drucker-Col]n
R.
Aguilar,
(Mexico City, Mexico) There is little information on the functional and electrical recovery of adult Central Nervous System (CNS) lesions in the central auditory system with intra-cephalic implants of embryonic CNS tissue. Auditory brain-stem evoked potentials (BAEP) were recorded from adult male Wistar rats during intraperitoneal chloral hydrate anaesthesia. Under stereotaxic surgery, bilateral collicular coagulation was performed through trephine holes, and embryonic collicular grafts dissected from 17-day old foetuses were stereotaxically implanted into the cavities after the lesion. A group of rats were not grafted. The animal's BAEPs were recorded 4, 8, 12 and 16 weeks after surgery. The animals were killed and their brains processed for histological studies. Bilateral collicular lesions abolished waves 5 and 6 of the BAEP, grafted animals showed recovery of waves 5 and 6 of the BAEP from the fourth week after transplantation, while control animals did not recover. It is concluded that embryonic grafting is capable of correct
W15.10 PHOTO-EVOKED EYELID MICROVIBRATION: DEVELOPMENTAL CHANGES AND CLINICAL APPLICATION.
function retain the response if otolith function remains. In hemiplegic patients with cortical lesions, the response on the weak side is retained but does not habituate, whereas with deeper lesions the response is frequently delayed or absent. Lesions of the spinal cord can delay or abolish the response on the weak side. We conclude that this vestibulo-spinal response depends upon otolith function, has a subcortical pathway which is under a degree of cortical control and has a descending course with the pyramidal tract.
W15.12 TRANSCORTICAL REFLEX (C-RESPONSE) IN NORMAL SUBJECTS AND NEUROLOGICAL PATIENTS. Y. Takanashi, T. Takegami, T. Motonaga, E. Sugimoto and K. Yamaguchi
S. Sanada, C. Kohno, S. Miyake and S. Ohtahara (Kyoto, Japan) (Okayama, Japan) Photo-evoked eyelid microvibration (MV) is regarded as a new method for assessing brain-stem function, and its clinical application is anticipated. The shortening of MV latency with age is known, but details, particularly normative data, indispensable for clinical application of the method, need to be clarified. Developmental changes in MV latency were investigated in 155 normal humans, ranging from 0 to 35 years of age. The results were as follows: 1) The peak latencies were 199_+10 msec at the age from 0 to 2 months, 165_+18 msec at 3 to 5 months, 154+16 msec at 6 to 11 months, 148_+18 msec at 1 year, 123_+18 msec at 2 years, and 89_+6 msec at 3 years; 2) after age of three, latency was stable between 70 and 80 msec. 3) These findings disclose developmental changes in the latency of MV and the remarkable shortening of latency in the first 6 months of life and at age 1 to 3 years; 4) Clinically, MV was studied on 80 cases with various forms of encephalitis, epilepsy, mental retardation and cerebral palsy. The results indicate that MV is a useful method for evaluation of both organic and functional disorders of the brain-stem.
Electrical stimulation of the median nerve during voluntary contraction of abductor pollicis brevis (APB) muscle produces the direct muscle response (M-wave) and a few late responses such as V1 and V2 responses. The V2 response (C-response) is considered to be a transcortical reflex, although the nature of this wave is still uncertain. We studied the extent of potentiation of the V2 response by strengthening the voluntary muscle contraction of APB, recording somatosensory evoked potential (SEP) at the same time, in normal subjects and several neurological diseases. In control subjects, onset and peak latencies of V2 were 44.2 + 5.8 msec and 49.8_+6.7 msec respectively, during isometric contraction of APB at 50% of maximal contraction. The stronger the isometric contraction the higher the amplitude of V2 became. In OPCA cases only the M-wave was observed at rest and V2 appeared by muscle contraction with longer latency. In LCCA V2 was obtained even at rest. In a case of small pontine haemorrhage, affecting the left medial lemniscus, abducens and facial nerve, V2 was not obtained in the right APB and the SEP was not elicited by stimulating the right median nerve. This suggests that the medial lemniscus system might play a r61e in the generation of the V2 response.
W15.11 VESTIBULO-SPINAL EVOKED RESPONSES.
A.M. Bronstein, H.J. Barratt, M.A. Gresty and L.J. Findley
AUDITORY EVOKED POTENTIALS AND MULTIMODALITY STUDIES.
(London, UK) The characteristics of the vestibular startle responses were investigated in neurological patients using an experimental technique in which they lay supine on a bed which was suddenly launched into 'free fall' and arrested by springs. The fall was monitored with a head mounted accelerometer whilst EMG responses were recorded with surface electrodes. The normal response is a generalised activation of skeletal muscles with typical mean latency for quadriceps of 75 msec and an estimated spinal conduction velocity of 60 m / s e c and habituates with repeated stimuli. Patients with absent vestibular canal
W16.01 COCHLEAR SUMMAT1NG POTENTIAL DETECTED FROM THE EXTERNAL AUDITORY MEATUS. A NORMATIVE STUDY.
G.- E. Chatnan (Seattle, WA, USA) The cochlear summating potential (SP) preceding the auditory nerve compound action potential (AP) was elicited by broadband alternating condensation and rarefaction clicks and re-
$66 corded by non-invasive electrodes from the external auditory meatus (EAM) of 60 volunteers of both sexes, 12-67 years old, who had normal hearing for age. Quantitative data were obtained on: the number of ears displaying measurable SPs; the SP detection level; the SP onset, peak and rise times; the duration of the SP-AP complex; the SP amplitude and the S P / A P amplitude ratio. Previously unknown relationships were unveiled between the amplitude, but not the temporal, measures of the SP and laterality, sex, age, and audiometrically determined hearing thresholds to 4-8 kHz tones. The highest correlations were obtained with these last thresholds, which suggested that receptors in the basalturn of the cochlea played a dominant role in the generation of the EAM-detected SP. To improve on existing techniques for determining abnormal SP elevation as an indication of endolymphatic hydrops, a multiple regression method was devised that utilized sex, age, 4-8 kHz hearing thresholds and AP voltage to establish upper normal limits of SP amplitude for individual subjects and ears.
W16.02 MINUTE R H Y T H M S IN T H E STEADY-STATE R E S P O N S E S TO AUDITORY, VISUAL AND TACTILE STIMULI. S. Makeig, R. Galambos and D.R. Stapells (San Diego, CA, USA) A train of discrete stimuli (auditory clicks, visual flashes, tactile vibrations) delivered at rates near 40 per second evokes a corresponding train of roughly sinusoidal brain potentials (the 40 Hz ERP, the high-rates or steady-state response, etc.). Since the response train lasts as long as the stimuli continue (minutes, hours) it may be used as an ongoing probe of changes within the CNS. We have been studying the variations of response amplitude, phase, and phase coherence during threshold estimation, masking, sleep, and behavioral experiments. In quiet, waking subjects, quasi-rhythmic fluctuations in response amplitude and phase occur spontaneously, with periods of 20-120 seconds ('minute-rhythms') in all three modalities. Amplitudes may vary by 100 per cent or more, especially as the subject drifts into or out of sleep (in the auditory modality, at least). We have also observed these minute-rhythms in concurrent measures of performance and of EEG-band amplitudes obtained during a vigilance task. Evidently, minute-rhythms are a natural feature of brain electrophysiology. (Work supported by N.I.H.)
WI6.03 INTRACRANIAL S T U D I E S ON SURFACE AND DEPTH POTENTIAL GENERATORS IN MAN: 11. BIPOLAR SOMATIC, AUDITORY AND VISUAL VERTEXLIKE ACTIVITIES. M. Velasco and F. Velasco
(Mexico City, Mexico) Bipolar EEG responses correlated to somatic+ auditory and visual vertex activities (VA) were studied in different subcortical structures of patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. Typical subcortical VA, evoked by somatic, auditory and visual stimuli, were recorded together from a single structure of a non-specific system including: reticulo, rnedial, dorsal thalamic, orbitofrontal, limbic and striatal structures. Typical subcortical VA were formed by four consecutive components O, A, B and C correlated to PI, N1, P2 and N2 of the surface VA. Polarity of component A was inverted between reticulo and medial-thalamic while that of component B was inverted between medial and dorsal thalamic and between dorsal thalamic and fronto-limbic structures. Typical subcortical VA were absent within specific thalamic nuclei (VPL, MG and LG) and pathways (medial and lateral lemniscus and optic radiations) in presence or absence of short latency responses evoked by specific sensory stimuli.
W16.04 BRAIN TRANSPLANTS REVERSE AUDITORY BRAIN-STEM R E S P O N S E S ABOLISHED BY COAGULAT I O N OF T H E RAT'S INFERIOR COLLICULI. M. Shkurovich, G. Cornejo, F. Fernfindez, B. Fernfindez and R. Drucker-Col]n
R.
Aguilar,
(Mexico City, Mexico) There is little information on the functional and electrical recovery of adult Central Nervous System (CNS) lesions in the central auditory system with intra-cephalic implants of embryonic CNS tissue. Auditory brain-stem evoked potentials (BAEP) were recorded from adult male Wistar rats during intraperitoneal chloral hydrate anaesthesia. Under stereotaxic surgery, bilateral collicular coagulation was performed through trephine holes, and embryonic collicular grafts dissected from 17-day old foetuses were stereotaxically implanted into the cavities after the lesion. A group of rats were not grafted. The animal's BAEPs were recorded 4, 8, 12 and 16 weeks after surgery. The animals were killed and their brains processed for histological studies. Bilateral collicular lesions abolished waves 5 and 6 of the BAEP, grafted animals showed recovery of waves 5 and 6 of the BAEP from the fourth week after transplantation, while control animals did not recover. It is concluded that embryonic grafting is capable of correct