Auditory evoked transient and sustained potentials in the human EEG: II. Effects of small doses of ethanol.

The effect of small doses of ethanol (0.4 g/kg) on auditory evoked transient and sustained potentials was studied. Tones of 1-second duration were presented in trains of four stimuli (interstimulus interval = 1 second; intertrain interval = 1 minute). The electroencephalogram was recorded from derivation Cz-Al. Ethanol depressed the transient responses both at the first stimulus of the train and during repeated stimuli. The sustained potentials elicited by the first stimuli of the train were not affected by ethanol, whereas the sustained potentials elicited by repeated stimuli were larger in amplitude under the influence of ethanol than during control experiments. It is suggested that the decrease of the transient responses under the influence of ethanol is mainly due to depression of the reticular formation, whereas the increase of sustained potentials reflects ethanol-induced release of intracortical inhibition.     

Auditory evoked transient and sustained potentials in the human EEG: I. Effects of expectation of stimuli

The characteristics of auditory evoked transient and sustained potentials were recorded using trains of four-tone stimuli of 1-second duration (interstimulus interval = 1 second) presented once every minute. The subject either attentively expected the stimuli or ignored them while reading. The electroencephalogram was recorded from derivations Cz-Al and Fz-Al. Expectation of the stimuli was associated with increased amplitudes of the transient responses both at the first stimulus of the train and during stimulus repetition. In contrast, the sustained potential at the first stimulus of the train was unchanged or smaller when the subject expected the stimuli. During stimulus repetition, however, the amplitude of the potential was enhanced by expectation of the stimuli. The results support the hypothesis of two sustained potential components and stress the importance of stimulus repetition rate when sustained potentials are studied.     

Effects of lithium on evoked potentials and performance during sustained attention

Two versions of the continuous performance test (CPT) differing in complexity were administered to 15 patients with bipolar affective disorder, manic type before and after treatment with lithium. Reaction time, performance accuracy, and the late positive component (LPC) of the event related potential evoked by the task were measured concurrently. Lithium treatment decreased errors of commission on both CPT tasks, although the difference was significant only for the simpler task. Reaction time was significantly increased by lithium treatment on the more difficult CPT task. LPC amplitude to the target stimulus on the difficult CPT was significiantly increased by lithium. The data are interpreted as consistent with an attention-enhancing effect of lithium, coupled with a general reduction in the tendency to respond to stimuli.     

Auditory evoked potentials recorded from conscious sheep

The auditory evoked potentials produced in response to a click stimulus were measured in the conscious sheep. The early components, the brain stem evoked potentials (BSEPs) were reproducible and similar to those observed in the other animals as well as man and appeared to have frequencies that are the three subharmonics of the main frequency component of the click stimulus. The longer latency components were more variable in latency and amplitude, but the frequencies were similar to that observed in humans.     

Auditory double click evoked potentials in multiple sclerosis

Brain stem electric responses (BSER), evoked by acoustic stimuli, were investigated in 29 patients with multiple sclerosis and compared with the responses in a control group of 26 young adults without neurological disease or hearing defect. The procedure included monaural and binaural stimulus presentation of single clicks and pairs of clicks. In the evaluations the vertex-positive Jewett I, III and V response components, and the vertex-negative "FFP₇" peak were considered. In the assessment of the BSER components, the FFP₇ (the vertex-negative 7 ms far field potential following the Jewett_v wave) proved to be the best single component with respect to reproducibility in normal subjects. In addition the FFP₇ was the single most consistently abnormal component in the patient group. Determination of the latency of the Jewett components and the interpeak conduction times, however, contributed further to the disclosure of the abnormal cases. Five of the patients whose hearing was impaired were considered separately. Of the remaining 24 patients, 20 (83 %) had BSER abnormalities. Further analysis did not reveal a clear correlation between BSER abnormalities and clinical signs of brain stem dysfunction.     

Auditory evoked potentials recorded intracranially from the brain stem in man

Auditory evoked potentials were recorded in patients undergoing neurosurgical operations to manage cranial nerve dysfunctions. Recordings were made intra-operatively from the distal portion of the eighth nerve, from the entrance of the eighth nerve into the brain stem, and from a site overlying the superior olivary complex (rostral and medial to the entrance of the eighth nerve). The potentials at the three different loci showed characteristic differences: the responses recorded at the entrance of the eighth nerve into the brain stem showed three peaks about 1 ms apart. The earliest peaks had longer latencies than did those recorded at a distal locus on the eighth nerve, which is consistent with what we know about propagation of nerve impulses in the auditory nerve. The responses recorded on the brain stem, rostral-medial to the eighth nerve, also showed three peaks but the amplitude of the third peak was greater than those of the other two. It is assumed that the first peak originates in the auditory nerve, the second peak in the cochlear nucleus, and the third peak in the lateral superior olive. The latencies of these peaks match the latencies of peaks II, III, and IV of scalp-recorded brain stem evoked potentials.     

Auditory and somatosensory evoked potentials (AEPs and SEPs) and ballistic movements in parkinson disease

In five patients with initial idiopathic Parkinson disease AEPs (early and late components of auditory evoked potentials), SEPs (somatosensory evoked potentials) and arm ballistic movements (abduction of the humerus) were studied. Experimental sessions were conducted before starting treatment (L-Dopa plus Carbidopa) and at two and six month intervals. Before treatment evoked potential abnormalities were found in four out of five patients; EMG patterns underlying ballistic arm abduction movements were altered in all patients; corresponding prolonged duration of initial movements and low mean velocities were found. After treatment AEP and SEP showed a reduction of previously observed abnormalities and both EMG patterns and kinematic variables consistently improved. It is suggested that the electrophysiological investigations employed in this preliminary study may be a useful tool in clinical and pharmacological researches on Parkinson disease.

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Sommario Sono stati studiati in 5 pazienti affetti da sindrome di Parkinson idiopatica iniziale gli AEPs (componenti precoci e tardive), i SEPs ed i movimenti balistici (abduzione dell'omero). Lo studio è stato condotto prima dell'inizio della terapia (L-Dopa+Carbidopa), e due e sei mesi dopo l'inizio della terapia. Anomalie dei potenziali evocati sono state riscontrate prima dell'inizio della terapia in 4 pazienti. I dati elettromiografici relativi ai movimenti balistici di abduzione del braccio erano alterati in tutti i pazienti ed erano caratterizzati da un ritardo nell'inizio del movimento e da una diminuizione della velocità media.Dopo la terapia si è rivelata una riduzione delle anomalie precedentemente riscontrate per gli AEPs ed i SEPs ed anche i patterns EMG e le variabili kinematiche sono apparse notevolmente migliorati. Dall'analisi di questi risulati sembra emergere la possibilità che queste metodiche neurofisiologiche possano essere utilizzate quale mezzo per controllare la progressione della sindrome e l'efficacia di eventuali trials farmacologici.

     

Auditory evoked potentials in schizophrenic patients before and during neuroleptic treatment

Summary The auditory evoked potential (AEP) components N1 and P2 were investigated under a no-task condition in a group of 14 acutely ill unmedicated schizophrenic patients and compared with the findings in an age- and sex-matched control group. In the patients, N1 latency was significantly increased, P2 latency and N1-P2 interpeak latency were reduced. There were significant relationships between AEP parameters and the psychopathological state evaluated by means of the brief psychiatric ratings scale (BPRS). The N1 and P2 latencies were negatively correlated with the BPRS subscore anergia and positively correlated with agitation. In 8 of the patients, a standardized neuroleptic treatment was started with 10 mg haloperidol/day. After 2 weeks of treatment, BPRS scores and N1 amplitude had significantly decreased. However, there was no relationship between BPRS improvement and N1 amplitude reduction. N1 latency in the unmedicated state was negatively correlated with subsequent therapeutic response measured as proportional improvement of the BPRS score within 2 weeks. Thus, N1 latency may be seen as a psychophysiological measure with prognostic applications.     

Fever and evoked potentials in multiple sclerosis

Summary The somatosensory evoked potentials (SEPs) and visual evoked potentials (VEPs) were studied in 19 patients with multiple sclerosis; 17 controls were studied during fever (38.0°–39.7°C) and 2–3 days following return to normal temperature. The latencies of components N₂₀ and P₁₁₄ were measured and specified as abnormal when their value exceeded the standard deviation of the controls by 2.5 times. The corresponding criterion for the evaluation of the amplitude of components N₂₀ and P₁₁₄ was a reduction in amplitude of more than 50%. In the controls fever did not cause significant changes in evoked potentials. On the other hand, patients with multiple sclerosis showed abnormalities in evoked potentials during fever in a greater number of recordings (26 of SEPs and 33 of VEBs) than after return to normal temperature (19 and 27 respectively). In addition, the average latency of components N₂₀ and P₁₁₄ was clearly greater in the patients during fever (N₂₀=29.5±5.2 ms and P₁₁₄=143±18.1 ms) than after return to normal temperature (N₂₀=6.6±3.5 ms and P₁₁₄=134±16 ms). The amplitude of components N₂₀ and P₁₁₄ in patients during fever was clearly smaller than after return to normal temperature. These differences were statistically significant. Finally, in two patients, a decrease was found, during fever, in the conduction velocity of the peripheral somatosensory pathway from the median nerve to the wrist at Erb's point.

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Zusammenfassung Wir studierten die somatosensorisch evozierten Potentiale (SSEP) sowie die visuell evozierten Potentiale (VEP) bei 19 Patienten mit Multipler Sklerose und 17 Kontrollpersonen. Die somatosensorisch und visuell evozierten Potentiale wurden in beiden Gruppen unter dem Einfluß von Fieber als auch zwei bis drei Tage nach dem Abklingen des Fiebers untersucht.Die Latenzzeit der Komponenten N₂₀ und P₁₁₄ wurde als pathologisch bewertet, wenn ihre Werte 2,5 Standardabweichungen über dem Mittelwert von Normalpersonen lagen.Der entsprechende Maßstab für die Bewertung der Höhe der Komponenten N₂₀ und P₁₁₄ war eine Höheminderung über 50%.Wir fanden, daß Fieber bei den Kontrollpersonen keinen wesentlichen Einfluß auf SSEP und VEP hatte. Bei den MS-Patienten haben wir wesentlich mehr Abnormitäten der SSEP und VEP während des Fiebers (26 SSEP und 33 VEP) als nach dem Abklingen des Fiebers (19 SSEP und 27 VEP).Darüber hinaus war der Mittelwert der Latenzzeit der Komponenten N₂₀ und P₁₁₄ bei den MS-Patienten während des Fiebers höher (N₂₀=29,5±5,2 ms; P₁₁₄=143±18,1 ms) als nach dessen Abklingen (N₂₀=26,6±3,5 ms; P₁₁₄=134±16,8 ms).Abgesehen davon war die Höhe der Komponenten N₂₀ und P₁₁₄ während des Fiebers wesentlich kleiner als nach dem Abklingen des Fiebers.Diese Unterschiede sind statistisch signifikant.Ferner fanden wir während des Fiebers bei zwei Patienten eine Verminderung der Erregungsleitungsgeschwindigkeit im N. medianus zwischen Handgelenk und Erbschen Punkt.

     

运动诱发电位联合体感诱发电位监测在脊髓髓内肿瘤手术中的应用

目的 探讨全静脉麻醉下运动诱发电位(MEP)联合体感诱发电位(SEP)术中监测应用于脊髓髓内肿瘤手术的优越性、可靠性及临床应用价值.方法 对72例脊髓髓内肿瘤患者术中行SEP和MEP联合监测,参照McCormick评分标准对术前、术后脊髓功能的改变和诱发电位变化之间的关系进行统计分析.结果 14例脊髓神经功能改善,18例术后脊髓神经功能下降者与诱发电位监测结果具有一致性(P＜0.05).结论 对脊髓髓内肿瘤手术进行SEP与MEP监测有利于避免"假阴性/假阳性"结果及术后神经功能障碍的发生.     

Visual and auditory evoked potentials in the early diagnosis and follow-up of neurosarcoidosis

Visual and brainstem auditory evoked potentials (VEPs, BAEPs) were recorded in 23 patients with neurosarcoidosis. Eight patients (35%) had abnormal BAEPs, and 10 (43%) had abnormal VEPs. Four of the 8 patients with abnormal BAEPs had facial paresis, one had impaired memory and only 3 had symptoms and signs compatible with brainstem lesion. Seven of the patients with abnormal VEPs had no visual symptoms. These findings suggest that BAEP and VEP can reveal subclinical nervous system involvement in sarcoidosis and can also help in the early diagnosis of neurosarcoidosis. Successive recordings of 5 patients showed that BAEP and VEP were useful in the follow-up of these patients.     

Auditory event-related potentials in the squirrel monkey: Parallels to human late wave responses

Event-related potentials (ERPs) were recorded from the brain surface in squirrel monkeys during the presentation of two auditory stimulus paradigms which have previously been utilized to elicit scalp-recorded ERPs in humans. In the first paradigm, inter-stimulus interval (ISI) was systematically varied during the presentation of a series of tone pips. The tones produced a negative (70 ms)-positive (130 ms) sequence of components similar in morphology to the human scalp-recorded N1-P2 'vertex' potential. The amplitude of the N70 and P130 components recorded from midline electrodes decreased with decreasing ISI, as previously shown for the human vertex potential. However, this amplitude change with ISI was not observed in ERPs recorded from lateral frontal and temporal electrodes. These results agree with previous studies of monkeys and humans which suggest at least two different sources contribute to N1-P2 components recorded in response to tones. The effects of stimulus probability and novelty on ERP morphology and amplitude were studied in the second paradigm. ERPs elicited by frequent (P = 0.92) and infrequent (P = 0.08) tone pips presented in an unpredictable order were compared. N70 - P130 components were produced by both stimuli, and the infrequent stimuli also elicited a broad, long latency (300 ms) positive complex that decreased in amplitude with repeated presentations. In humans the same infrequent auditory stimuli produce a frontally distributed late positive component that has been interpreted as indicating the activation of orientation mechanisms or of a 'mismatch detector'. These data suggest that in these paradigms squirrel monkeys exhibit ERPs which are similar in several respects to ERPs recorded to identical stimuli in humans.     

体温过高对豚鼠耳蜗电图-脑干听觉诱发电位综合波的影响

目的：探讨体温过高对耳蜗电图-脑干听觉诱发电位综合波(ECochG-BAEP SW)的影响。方法：计算机平均叠加技术记录豚鼠脑干听觉诱发电位(BAEP)、耳蜗电图(ECochG)和：ECochG—BAEP SW，体表物理升温法逐步升高豚鼠体温，观察3组电位波形、波峰潜伏期(PL)、波峰间潜伏期(IPL)和波幅的变化。结果：随体温升高(36℃至42℃)，ECochG-BA：EPSW波形始终兼具BAEP和ECochG的特点，有十分突出的1波，其波幅为BA：EP的I波波幅的数倍，且明显大于ECochG的N1波波幅；与BAEP和ECochG一致，ECochG-BAEPSW的PL和IPL随体温升高而逐渐缩短；与BAEP的Ⅰ，Ⅱ，Ⅲ波和ECochG的N1，N2，N3波波幅相似，ECochG-BAEP SW的1，2波波幅也在体温过高至40℃后开始出现显著降低。结论：体温过高对豚鼠ECochG-BAEPSW的影响与BAEP和ECochG相似，且其波形始终兼具两者特点。     

Effects of carnosine on olfactory bulb EEG, evoked potentials and DC potentials

Carnosine is a dipeptide found in great quantities in the primary olfactory nerve and has been suggested to be the neurotransmitter of the olfactory receptor axons. The aim of the present study was to describe some of its electrophysiological actions in the olfactory bulb (OB) of rabbits under anesthesia. Carnosine as a 10% solution in amounts of 2-5 microliter was injected to the OB at the level of the glomerular layer by means of a pipette attached to a Hamilton syringe. Average evoked potentials (AEPs) on the stimulation of the lateral olfactory tract (LOT-AEP), electroencephalographic (EEG) activity and slow potential (DC) recordings were obtained. The LOT-AEPs were analyzed by fitting damped sine waves to them. The parameters of amplitude, frequency, decay rate, phase and rise rate were measured and statistically compared to the values obtained prior to the carnosine injection. An increase in frequency and decreases in the phase and the decay rate of the AEP were found. Carnosine also produced a sustained oscillation in the EEG and a surface negative, deep positive shift in the DC recording. The changes were maximal within the first minute after injection and lasted 2-7 min. Tyrodes' solution, which was used as the carnosine vehicle, did not produce any changes, nor did beta-alanine, which is one of the constituents of carnosine, at equivalent osmotic concentrations. It is concluded that carnosine has an excitatory action on the mitral/tufted cells, and that this effect is obscured by a secondary increase in granule cell (inhibitory) activity.     

Somatosensory evoked potentials in a case of neurosyphilis

Here we report median and common peroneal nerve SEPs in a patient with tabes dorsalis. SEPs were within normal limits following median nerve stimulation, but of prolonged latency for common peroneal nerve. This was in keeping with clinical findings of posterior column involvement confined to the lumbosacral tract and with pathological features of tabetic neurosyphilis.

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Sommario Gli autori riportano le caratteristiche dei potenziali evocati somatosensoriali del nervo mediano e peroneo comune in un paziente affetto da tabe dorsale. I potenziali evocati somatosensoriali sono risultati nei limiti della norma stimolando il nervo mediano ma di latenza aumentata per il nervo peroneo comune. Ciò risultava in accordo sia con le caratteristiche cliniche di segni di interessamento dei cordoni posteriori limitato al tratto lombosacrale che con le caratteristiche anatomopatologiche della neurosifilide.

     

Serial changes in motor and somatosensory evoked potentials in putaminal haemorrhage

Little is known about evoked potential changes in putaminal haemorrhage. In this study, somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) have been serially evaluated and their role in the prognosis of putaminal haemorrhage is now reported. Nineteen patients with CT- or MRI-proven putaminal haemorrhage were examined after a mean duration of 13 days (range 2–30); there were 4 females and 9 males, ranging in age between 25 and 70 years. The haematomas were of medium size in 13 and large or small in 3 patients each. The changes in the clinical picture and the SEPs and MEPs were evaluated on admission, and after 30 and 90 days. Central motor conduction time (CMCT) could not be recorded in 13, but was prolonged in 2 and normal in 4 patients. Median SEPs revealed the absence of near field potentials in 11 and prolongation of N9–N20 conduction time in 1 patient. In the follow-up period MEP and SEP abnormalities only changed in 5 patients; MEPs changed in 4 and SEPs in 2. The period of normalisation of MEPs ranged between 1 and 6 months. CMCT correlated with motor and N9–N20 conduction time with sensory impairment. Eight patients had poor, 6 partial and 5 complete recovery. Power, sensation, CMCT, and size and location of haematoma made positive contributions to recovery.     

Friedreich''s ataxia: clinical involvement and evoked potentials

In 15 patients definitely affected by Friedreich's ataxia, precocious SEP abnormalities were constantly recorded independent of the duration of symptoms and the severity of clinical involvement; VEPs were frequently involved, but neither VEP abnormalities, nor visual impairment could be correlated with the severity or duration of Friedreich's ataxia clinical involvement; BAEPs were, to different extents, abnormal. These were completely dissociated from hearing disorders and significantly correlated (P less than 0.001) with Friedreich's ataxia clinical disability. Our observation of increased latency of the VEP P100 component and the early disappearance of BAEP Wave V with persistence of Wave I is in contrast with the hypothesis that changes are related to primary axonal degeneration. For practical purposes SEPs could help in the early diagnosis of Friedreich's ataxia, and BAEPs could be used for the electrophysiological monitoring of its clinical progression.