Tables of normal values of average and long latency auditory potentials

INTRODUCTION AND OBJECTIVE: In view of the disparity of data and methodology concerning medium (MAEP) and long latency (LAEP) acoustic evoked potentials, we have obtained tables of normal values using a reliable method and statistical study of these potentials in 30 healthy persons, in order to serve as a basis for clinical reference and for possible further studies. MATERIAL AND METHODS: In the MAEP we used the two types of stimuli most commonly employed, first a click and then a rising-plateau-falling tone (2-6-2). We observed that this did not affect the latency or amplitude of the different waves, although the best defined waves are obtained with tones. In the LAEP we always used a tone with rise-plateau-fall of 10-50-10, as recommended by the American Electroneurophysiological Society. In all cases the intensity was of 70 db, with rarefaction and masking of the contralateral ear with an intensity of 50 db. Self-adhesive electrodes were used for captation; the active one was placed on the ipsilateral ear lobe and the reference electrode in Cz for the LAEP. For the LAEP the lower filter was of 1 Hz and the higher of 70 Hz. In view of the variety of filters recommended, 10 Hz at the lower level and 500, 1000 and 2000 at the higher level were used successively for the MAEP. We observed that these did not affect the latency or amplitude of the waves, so these three values may all be used equally well. RESULTS AND CONCLUSIONS: In the inter-sexual study, no differences were seen between men and women. Nor were there significant differences between the acoustic evoked potentials on the right and left sides of the same person.     

Peculiarity of soleus motor potentials evoked by transcranial magnetic stimulation and electrical stimulation of tibial nerve

Fas (Apo-1/CD95) ligand (FasL) is a cytotoxic molecule used by T lymphocytes and natural killer cells for target-cell killing and by nonmalignant and malignant cells in the suppression of immune responses. In this study, FasL expression in B- and T-cell non-Hodgkin's lymphomas was investigated by paraffin immunohistochemical analysis. FasL expression was found to be weak in nonaggressive lymphomas (chronic lymphocytic leukemia/small lymphocytic lymphoma, lymphoplasmacytoid lymphoma, Grade 1 follicular center cell lymphoma) and mantle cell lymphoma but strong in aggressive B-cell lymphomas (diffuse large B-cell lymphoma, Burkitt's-lymphoma). Precursor B-lymphoblastic lymphomas were more heterogeneous, with expression varying from weak to strong. In T-cell lymphomas (anaplastic large-cell lymphoma; peripheral T-cell lymphoma, unspecified), strong FasL expression was observed. Apparently, FasL expression is not limited to neoplasms derived from T cells or natural killer cells, and it might play a supporting role in the progression of non-Hodgkin's lymphomas.     

One-week test-retest reliability of spinal and cortical somatosensory evoked potentials by tibial nerve stimulation

Spinal (Th12) and cortical somatosensory evoked potentials by right and left posterior tibial nerve stimulation at the ankle were performed in 20 healthy volunteers (10 females and 10 males) aged 23-50 years. The procedure was repeated after one week to assess the reliability of the parameters and to establish upper normal variability limits. Reliability was measured by the intraclass correlation coefficient and was excellent for all absolute latencies and at least good for amplitudes and for the spinal-cortical conduction time. Upper variability limits were calculated using a method based on the within-subject mean square, which can be also applied in the case of more than two repetitions.     

Recovery functions of short and long latency reflexes in hand muscles evoked by paired stimulation of peripheral nerves

Double-shock bifocal peripheral nerves stimulation with varying interstimulus intervals (ISI) from 1 ms to 5000 ms was applied to healthy human subjects. Short (SLRs) and long latency reflexes (LLRs) from the slightly active first interosseus dorsalis muscle were recorded after an electrical conditioning stimulation of the index finger and test stimulation of the median nerve. It was found that with intervals from 1 to 5 ms the size of the SLR and LLRs after the second shock was unstable and almost oscillated around that evoked by a single shock, possibly due to transmitter depletion at these short ISIs. With intervals of 10 ms and longer, the test responses progressively increased: the SLR to 100 ms ISI, the LLR1 to 500 ms ISI and the LLR2 to 2000 ms ISI, probably due to temporal summation and some release of the transmitter substance after the conditioning cutaneous stimulus. All the recovery curves fully returned to the control value at 2000 ms and 3000 ms ISI, respectively. The main result is that cutaneous conditioning stimulation is not able to reduce or even to block the test SLR and LLRs. Interference phenomena did not occur between different afferents when paired stimulation was applied bifocally as the conditioning input in respect to a test nerve volley, was very limited. On the contrary, the test responses were far larger than the control response, probably due to some temporal summation with double-shock stimulation and because of the enhanced spinal excitability during slight voluntary contraction.     

Transient and steady-state electroretinograms and visual evoked potentials to pattern and uniform-field stimulation in humans

I recorded simultaneously transient and steady-state electroretinograms (ERGs) and visual evoked potentials (VEPs) in response to pattern and uniform-field stimulation in 21 normal subjects, in order to study their physiological characteristics. ERGs and VEPs to pattern stimulation (P-ERGs and P-VEPs, respectively) showed different physiological features from those to uniform-field stimulation (U-ERGs and U-VEPs, respectively). With transient stimulation at a rate of 1Hz for both pattern and uniform-field stimulation, the b-wave latency of U-ERG tended to be shorter than that of P-ERG, while the P100 latency of P-VEP was significantly shorter than that of U-VEP. With steady-state stimulation at a rate of 4Hz for pattern stimulation and of 8Hz for uniform-field stimulation, the phase analysis revealed the first (1F) and the second (2F) harmonics as stable components for the U-ERG and U-VEP, while only 2F harmonic was a stable component for the P-ERG and P-VEP. The phase values of these components were different each other, and the maximal amplitude of the ERGs was shown by the 1F of U-ERG while that of the VEPs was shown by the 2F of P-VEP. These results suggest that the pattern and uniform-field stimulation allows us to separate pattern (contrast)-specific responses from luminance-specific responses both in ERGs and VEPs. Four patients with optic atrophy showed normal U-ERG while all of them showed abnormal P-ERG, U-VEP and P-VEP except one, who showed normal U-VEP. P-ERGs and P-VEPs may offer the information about the proximal inner retinal layer (or the ganglion cells) and the contrast channel of the visual cortex. U-ERGs and U-VEPs may be useful in evaluating the functions of the preganglionic cell activity in the retina and the luminance channel of the visual cortex. Therefore, simultaneous recording of ERGs and VEPs to pattern and uniform-field stimulation under both transient and steady-state conditions increase the diagnostic value of electrophysiologic testing in the visual pathways.     

Off-effect in visual cortex evoked potentials of humans under several conditions of photic stimulation

Visually evoked potentials (EP) to light were recorded from the occipital cortical area under conditions of changes in stimulus duration and of different intensity of retinal illumination. The work was aimed at establishing the appearance and development of the EP off-effect in humans at these conditions of photic stimulations. This was necessitated by the large dispersion of data obtained in establishing the conditions of photic stimulation, which many authors consider essential for recording the off-effect. The off-effect was studied in greater detail also to elucidate its role in EP generation to a high-frequency photic stimulation. The data recorded are discussed and compared with those of other authors, obtained in studying electrical responses of the retina and the cerebral cortex.     

The effects of cortical stimulation, anesthesia and recording site on somatosensory evoked potentials in the rat

The purpose of this study was to standardize the method of spinal cord monitoring with evoked potentials in the rat. Seventeen male Wistar rats were anesthetized with alpha-chloralose and urethane. Somatosensory evoked potential (SEP) and cerebellar evoked potential (CEP) following sciatic nerve stimulation were mapped at different time points after induction of anesthesia. SEP peaks at latencies of 13-18 ms (P13, N18) were localized to an extremely small area over the sensory cortex. In contrasts, a negative peak of the SEP at 11 ms (N11) and the CEP were widely distributed over the cerebral or cerebellar surface. Anesthesia significantly influenced the cortical components of the SEP. In 10 rats, MEP or posterior fossa evoked potential (PFEP) following stimulation of the sensorimotor or cerebellar cortices respectively, were recorded at T9. Stimulation of different points produced little change on the waveforms of the MEP or PFEP. Successive recordings of MEP and SEP revealed that the P13-N18 complex of the SEP was markedly suppressed after MEP recordings were made. In conclusion, this study identified several factors which alter SEP waveforms in the rat including location of recording, anesthesia and sequence with respect to MEP recording. MEP by stimulation of the same sensory cortex as SEP recordings should not be used for concurrent monitoring, since cortical stimulation will change the waveforms of the SEP.     

Eye movement evoked by stimulation of lateral posterior nucleus and pulvinar in the alert cat

The carcinogenic effects of diisopropanolinitrosamine (DIPN) were tested in Sprague-Dawley rats and were then compared with results produced earlier by the same substance in Syrian hamsters. In addition to the similarities, several differences were noted; for example, DIPN caused pancreatic tumors in all the hamsters, but only 1 pancreatic tumor was observed among the 150 rats. Administration of DIPN to rats led to the development of neoplasms in the nasal and paranasal cavities, lungs, thyroid gland, esophagus, liver, and kidneys. The highest tumor incidence in rats was in the nasal cavities. Almost all the pulmonary neoplasms were malignant and were usually squamous cell carcinomas. We found a 15.4-50% incidence of malignant tumors of the thyroid gland; we also noted that thyroid neoplasms occurred at almost the same rate (36.4-50%) in the groups given 1/5, 1/10, and 1/20 the median lethal dose.     

Middle and long latency auditory evoked potentials in cat. II. Component distributions and dependence on stimulus factors

The middle (10-50 ms) and long (50-600 ms) latency periods of the auditory evoked potential (AEP) were investigated in muscle-paralyzed, artificially respired cats with respect to two issues: (1) the distribution of components across the skull, and (2) the effects of changing stimulus intensity on component latencies and amplitudes. The distributional data were gathered during a behavioral study in which four behavioral tasks related to classical pupillary conditioning were used to vary attentional and arousal processes. The distributions across the skull surface (averaged across tasks) of 12 peaks and troughs (P10, N13, P17, N22, P31, N41, P55, N70, N100, N140, P260 and N520) and seven principal components derived from the set of waveforms collected during this experiment are reported. Both peak amplitudes and principal component scores were distributed differentially across the skull surface. In the second experiment, acoustic stimulus intensity was varied, and AEPs collected from a vertex and temporal electrode site. In general, increasing stimulus intensity had a stronger influence on the earlier portions of the AEP, where increased amplitude and decreased latency was the rule, than on later ones. The relationships between cat and human AEP components were discussed based on both the data presented in this paper and in previous papers.     

Long latency evoked potentials in a case of corpus callosum agenesia

Following monoaural stimulation, long latency auditory evoked potentials (LLAEPs) recorded from contralateral temporal areas have a shorter latency and larger amplitude than those recorded from the ipsilateral temporal areas. This observation agrees with the operational model drawn up in 1967 by Kimura, which assumes that only anatomically prevailing crossed auditory pathways are active during dichotic hearing, while direct pathways are inhibited. The inputs may then be conveyed to the contralateral cortex, from where they finally reach the ipsilateral temporal areas by means of interhemispheric commissures. It is this mechanism which may underline the right ear advantage for verbal stimuli and the left ear advantage for melodies observed when administering dichotic listening tasks. With the aim of verifying this hypothesis, we recorded temporal LLAEPs in a 21 year-old woman suffering from complex partial seizures, whose CT scan and MRI showed corpus callosum agenesia. Our data support the hypothesis that ipsilateral pathways are greatly inhibited by the contralateral pathways, and therefore auditory stimuli can be supposed to reach the contralateral auditory cortex from where they are transferred through the corpus callosum to the ipsilateral auditory cortex.     

Nonlinear analysis of visual evoked potentials elicited by color stimulation

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.     

Eye movements evoked by proprioceptive stimulation along the body axis in humans

Proprioceptive input arising from torsional body movements elicits small reflexive eye movements. The functional relevance of these eye movements is still unknown so far. We evaluated their slow components as a function of stimulus frequency and velocity. The horizontal eye movements of seven adult subjects were recorded using an infrared device, while horizontal rotations were applied at three segmental levels of the body [i.e., between head and shoulders (neck stimulus), shoulders and pelvis (trunk stimulus), and pelvis and feet (leg stimulus)]. The following results were obtained: (1) Sinusoidal leg stimulation evoked an eye response with the slow component in the direction of the movement of the feet, while the response to trunk and neck stimulation was oriented in the opposite direction (i.e., in that of the head). (2) In contrast, the gain behavior of all three responses was similar, with very low gain at mid- to high frequencies (tested up to 0.4 Hz) but increasing gain at low frequencies (down to 0.0125 Hz). We show that this gain behavior is mainly due to a gain nonlinearity for low angular velocities. (3) The responses were compatible with linear summation when an interaction series was tested in which the leg stimulus was combined with a vestibular stimulus. (4) There was good correspondence of the median gain curves when eye responses were compared with psychophysical responses (perceived body rotation in space; additionally recorded in the interaction series). However, correlation of gain values on a single-trial basis was poor. (5) During transient neck stimulation (smoothed position ramp), the neck response noticeably consisted of two components -- an initial head-directed eye shift (phasic component) followed by a shift in the opposite direction (compensatory tonic component). Both leg and neck responses can be described by one simple, dynamic model. In the model the proprioceptive input is fed into the gaze network via two pathways which differ in their dynamics and directional sign. The model simulates either leg or neck responses by selecting an appropriate weight for the gain of one of the pathways (phasic component). The interaction results can also be simulated when a vestibular path is added. This model has similarities to one we recently proposed for human self-motion perception and postural control. A major difference, though, is that the proprioceptive input to the gaze-stabilizing network is weak (restricted to low velocities), unlike that used for perception and postural control. We hold that the former undergoes involution during ontogenesis, as subjects depend on the functionally more appropriate vestibulo-ocular reflex. Yet, the weak proprioceptive eye responses that remain may have some functional relevance. Their tonic component tends to stabilize the eyes by slowly shifting them toward the primary head position relative to the body support. This applies solely to the earth-horizontal plane in which the vestibular signal has no static sensitivity.     

Somatosensory evoked potentials during hypoxia and hypocapnia in conscious humans

PURPOSE: The objective of the study was to evaluate the effects of moderate hypoxia and hypocapnia on the latency and amplitude of cortical somatosensory evoked potentials (SSEPs) in conscious human subjects. METHODS: In ten volunteers the amplitude and latency of the cortical somatosensory evoked potentials were recorded during stimulation of the left posterior tibial nerve. Measurements of SSEPs and respiratory variables were made breathing ambient air, air containing a reduced oxygen percentage (17% O2, 14% O2 (n = 6) or 11% O2 (n = 10)), and again during voluntary hyperventilation breathing ambient air (PETCO2 = 20 mmHg, n = 10). RESULTS: Hypoxia (11% O2) caused mild stimulation of ventilation (P < 0.05) but had no effects on the latency or amplitude of the SSEP. Lesser degrees of hypoxia had no effects. Hyperventilation caused a small (2-4%) decrease) in the latency of the SSEP and an increase in the amplitude of the SSEP (P < 0.05). CONCLUSIONS: These findings in conscious subjects were consistent with previous observations in anaesthetized humans and anaesthetized dogs and show that the decrease in latency of the SSEP associated with hypocapnia is not due to changes in the depth of anaesthesia. These effects of hypocapnia may contribute to small variations in the latency of the SSEP when monitoring is performed during surgery, but are unlikely to be large enough to be of clinical concern.     

Effects of tobacco smoking and abstinence on middle latency auditory evoked potentials

OBJECTIVE: To evaluate the effects of tobacco cigarette smoking and overnight abstinence on middle latency auditory evoked potentials among smokers and nonsmokers. METHODS: Groups of 9 to 10 adult male and female nonsmokers and smokers participated in the study. Each person volunteered for two laboratory sessions conducted in the early afternoon on 2 separate days. Smokers abstained from tobacco products 6 to 15 hours before the abstinent session and maintained their usual smoking behavior before the smoking session. The nonsmokers had a similar laboratory experience but sham smoked by means of inhaling air. Middle latency auditory evoked potentials were recorded from Cz to both ears as reference. RESULT: The latencies of the Na and Pa potentials during the smoking session were significantly (p < 0.01) shorter than those in abstinent smokers and nonsmokers. After smoking, peak-to-trough amplitudes for the V-Na, Na-Pa, and Pa-Nb potentials were larger than those after abstinence and significantly larger than those among nonsmokers. CONCLUSIONS: The shorter latencies of the middle latency brain wave components in the smoking session suggest faster processing of sensory information after cigarette smoking. Larger Pa amplitudes after cigarette smoking suggest a higher arousal level than that among partially abstinent smokers and nonsmokers.     

The cortical representation of somatosensory evoked potentials of the phrenic nerve

Parasitic third-stage larvae of the sheep abomasal nematode Haemonchus contortus develop and molt in vitro to the fourth stage (L4) in 48-72 hr, at which time they begin feeding. Coincident with the third molt, larvae begin to secrete significant amounts of protein into culture fluids, including a zinc metalloproteinase. This culture-derived zinc metalloproteinase differs from a previously described metalloproteinase from infective third-stage larvae (L3[2M]), which mediates the ecdysis process. These differences include time of expression, molecular mass, and substrate specificity. The purified proteinase, from cultures of L4, has a molecular weight of approximately 46 kDa, functions as an endopeptidase, and digests several native proteins of host origin including fibrinogen and fibronectin.     

A simple method for recording motor evoked potentials of lingual muscles to transcranial magnetic and peripheral electrical stimulation

A 1.8 kg chromosomally normal child was suspected antenatally to have a cloacal anomaly and oligohydramnios. Both parents had a chromosome 9 inversion (inv [9] [p11 q13]). Postnatal study showed a high confluence of the urinary, genital and intestinal tracts. Because of prematurity, a right colostomy was performed on a short colon, but the genitourinary tract was not drained. Poor weight gain, urinary tract infection and septicaemia led to a one-stage reconstruction at 5 months of age and a weight of 3.2 kg. Follow-up although short at 15 months, is encouragingly suggestive of urinary and faecal continence. The vagina is patent. This paper considers concepts in cloacal management and submits for evaluation an alternative surgical plan to the presently almost exclusively accepted posterior sagittal approach of Pe?a and De Vries.     

Effects of styrene exposure on middle latency auditory evoked potentials and glial cells in rat

The demand for health care and social welfare services for the elderly has increased and in Japan, there is a need in the social system to improve the quality of life, especially for those who are disabled. This article directs attention to bed-ridden elderly persons from the standpoint of social problems attending economic development and population changes based on data from Japan, the United States, Sweden, and OECD countries. Compared to the United States, there are more bed-ridden elderly in Japan, and inadequate public resources for caring. Physicians, nurses, care workers, and rehabilitation specialists such as physiotherapist and occupational therapist per 1000 aged sixty-five or over are 89.5 in Japan while 237.4 in Sweden. Japan has the fewest such health and welfare personnel among developed countries. Even with increases in such personnel through the New Gold Plan, future increase in aged population would off-set the effect and the problem of providing care for the elderly remains.