Cortical evoked potentials elicited by real speech words and human sounds.

Averaged evoked potentials were recorded from PZ and left and right temporo-parietal electodes to real speech words and human sounds in 8 right-handed subjects. Stimuli were presented in a "no task" condition where the subject was instructed to listen attentively, and a vigilance condition where the subject responded to a particular word or sound during a run of such stimuli. The vigilance condition produced two classes of stimuli:signals and non-signals. Evoked potentials to physically identical words or sounds were examined when they were "no task", non-signal and signal stimuli. P300 amplitude increased significantly as a function of increasing task demands going from "no task" to non-signal to signal. When a strict statistical criterion for multiple comparisons (Bonferroni test) was applied in looking for asymmetries between hemispheres, only 2 isolated left greater than right differences turned out to be significant. Review of the literature concerning evoked potential correlates of differential hemispheric processing pointed up flaws in design, statistical technique, and inconsistencies in reported findings which suggested that while evoked potentials may sometimes reflect differences in hemispheric functioning, this effect is marginal at best.     

Sympathetic skin response evoked by respiratory stimulation as a measure of sympathetic function.

OBJECTIVES: To compare respiratory and electrical methods of evoking a sympathetic skin response (SSR). METHODS: SSRs evoked by both electrical and respiratory stimulation were recorded from the palms of 47 healthy volunteers. Expiration and inspiration were used as separate stimuli. The correlation coefficients between the amplitude and latency of the SSR from the palm electrodes and the various components of heart rate variability were calculated. RESULTS: Waveform patterns of the SSRs obtained from electrical stimulation showed varied responses to and habituation to this type of stimulation. On the other hand, no subjects showed a phase change in SSR waveform patterns between the first and last expiratory stimuli. The potentials recorded after expiratory stimulation had significantly greater amplitudes than those recorded after electrical stimuli. The low frequency component of heart rate variability induced by expiratory stimulation was significantly greater than that induced by electrical stimulation. The SSR may also correlate strongly with the change of respiratory rate since a more rapid pressure change occurs during expiratory movement than during inspiratory movements. CONCLUSIONS: The SSR evoked by expiratory stimulation is more reliable than either electrical stimulation or inspiratory stimulation for determining sympathetic function.     

Influence of stimulus intensity on waveform of sympathetic skin response evoked by magnetic stimulation.

OBJECTIVE: The aim of this study was to investigate the influence of stimulus intensity on the waveform of sympathetic skin response (SSR). The origin of the SSR waveform was discussed. METHODS: A total of 12 SSRs from palm skin were analyzed in 40 normal subjects. SSR was evoked by magnetic stimulation to the neck at 3 different intensities (10, 35, and 70% of the maximum output). The 3 stimuli were repeatedly applied in 4 separate sets. Waveforms were classified as either the P type, in which the positive component was larger than the negative one, or the N type, in which the negative component was larger than the positive one. Amplitude values of peak-to-peak, the first negative (N1), and subsequent positive (P1) components were compared among the 12 responses. RESULTS: When the stimulation was increased, the SSR size became larger. The P type SSR was most frequently found in the maximum stimulation. Strong stimulation generally produced a large P1. Only the N type SSR exhibited a large N1 response to the maximum stimulation. There was a significant, negative correlation between N1 peak duration (difference between the SSR onset and N1 peak latencies) and P1 amplitude. CONCLUSIONS: These results suggested that strong responses probably produced a P type SSR with a large P1 component. In this condition, a rapid change of potential from negative to positive prevented any correlation between N1 amplitude and the magnitude of the response. In the N type SSR, however, a large N1 was associated with a strong response. These findings can be explained by a newly presented theory on the neurophysiological origin of the negative and positive components, based on a model of equivalent current dipole dependent on the Na+ concentration gradient. SIGNIFICANCE: The present study provided some suggestions on the neurophysiological mechanism of SSR waveform.     

卒中后抑郁患者的交感神经皮肤反应与事件相关电位对照研究

目的探讨交感神经皮肤反应(SSR)与事件相关电位(ERP)对卒中后抑郁患者的诊断价值。方法对55例卒中后抑郁患者和52例正常健康者分别进行了SSR和ERP测定,并将结果加以比较。结果卒中后抑郁组中SSR和ERP测定中的P300成分异常率分别为87.3%(48/55)和83.6%(46/55),两者异常吻合率为76.4%(42/55)。卒中后抑郁组SSR测定结果中,SSR潜伏期和波幅值较对照组延长和降低,其差异具有显著性(P<0.01),ERP测定中N2、P3波潜伏期和P3波幅较对照组分别延长和降低,存在显著性差异(P<0.01)。其中N2、P3波潜伏期与SSR测定中潜伏期以及波幅与波幅之间呈正相关(r=0.29~0.36,P<0.01),而两者潜伏期与波幅之间呈负相关(r=-0.32~-0.33,P<0.01)。结论交感神经皮肤反应和事件相关电位测定可作为卒中后抑郁患者的诊断指标应用于临床。     

Characterisation of the sympathetic skin response evoked by own-face recognition in healthy subjects

The ability to recognise one's own face is crucial for self-identity formation and it plays a key role in the development of social interactions. Our starting hypothesis was that own-face recognition may be a psychophysiological phenomenon capable of activating the vegetative system in a peculiar manner, via sympathetic pathways. To test this hypothesis we studied the sympathetic skin responses (SSRs) evoked in 18 healthy subjects by the image of their own faces and by six other different visual stimuli. The SSRs were enhanced when participants were shown their own faces. Both SSR area and SSR amplitude contributed to this phenomenon. This work may offer new insights into the psycho- physiological processes involved in own-face recognition; moreover, the SSR could be a useful tool for future studies of patients affected by neuropsychiatric disorders presenting impairment of own-face recognition or representation of self-identity.     

Vector analysis of visual evoked potentials elicited by pattern reversal and photic stimuli.

OBJECTIVE: The 2D VEPs to pattern reversal (PR) and LED goggle were studied in order to obtain a stable parameter for the functional assessing of posterior visual pathways regardless of the stimulus type used. DESIGN AND METHODS: Apex c latency, bc segment amplitude (V), and bc vector orientation angle (theta) in voltage space were computed from VEPs recorded in 50 normal human beings and two patients with left posterior brain lesions, in an orthogonal Fpz-Oz and T3-T4 montage and displayed as a two channel Lissajous' trajectory. The effects of stimulus type and stimulated eye were analyzed in the normal group by a two-way ANOVA. RESULTS: The stimulated eye had no effect on any parameter. Apex c latency was slightly longer, and V was greater and more variable in the responses to goggle stimuli, but there was no significant difference in theta, oriented to mid-occipital scalp with very low variability for both stimulus types. The patients showed significant deviations of theta towards the affected hemisphere. CONCLUSIONS: The bc vector orientation (theta) is a stable parameter for the evaluation of the posterior visual pathways using both pattern reversal and LED stimuli, specially the latter, useful in unconscious or uncooperative patients.     

Multimodality evoked potentials and electrically elicited blink reflex in optic neuritis

Summary Pattern shift visual evoked potentials, brain stem auditory evoked potentials, spinal and scalp recorded somatosensory evoked potentials, and electrically elicited blink reflexes were investigated in 32 patients with isolated optic neuritis. Eleven patients were shown to have one additional lesion in the central nervous system outside the optic nerve. Therefore, cases with optic neuritis of unknown origin should be considered as possible cases of multiple sclerosis.

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Zusammenfassung Visuelle, durch Musterumkehr evozierte Potentiale, akustisch evozierte Hirnstammpotentiale, somatosensorisch evozierte Potentiale mit Ableitung über dem unteren Cervicalmark und über dem kontralateralen Handfeld sowie elektrisch ausgelöste Blinkreflexe wurden bei 32 Patienten mit einer isolierten Opticusneuritis untersucht.Bei 11 Patienten konnten mit Hilfe dieser elektrophysiologischen Untersuchungen eine oder mehrere, weitere Läsionen im Bereich des Zentralnervensystems nachgewiesen werden. Es wird vorgeschlagen, Fälle mit einer isolierten Opticusneuritis unklarer Ursache deshalb in die Kategorie mögliche MS einzureihen.

     

Visual evoked potentials elicited by a moving unidimensional noise pattern

(1) Motion onset and offset visual evoked potentials (VEPs) were recorded in normal human subjects using a unidimensional noise pattern moving at 1, 8 and 64 degrees/s. The maximum N1-P1 amplitude of the motion onset response was obtained when using a fine noise pattern (maximum energy at 5.2 cpd) moving at 8 degrees/s. (2) At a velocity of 8 degrees/s, the motion onset response (fine pattern, 0.70 contrast) showed a morphology similar to the pattern disappearance response. Both at a lower (1 degrees/s) and a higher velocity (64 degrees/s) the N1-P1 amplitude of the motion onset complex was significantly reduced. The latency of the motion onset response (8 degrees/s) and the pattern disappearance complex were significantly different. (3) The effect of lowering the spatial content of the noise pattern on the amplitude of the motion onset response was different for the 3 velocities tested: the largest effect was at the lower velocity of 1 degrees/s; there was no similar effect on the pattern disappearance response. (4) With decreasing contrast, the N1-P1 amplitude of the motion onset response at 8 degrees/s decreased, but this reduction in amplitude was much less than that of the disappearance response. The contrast dependency of the motion onset complex was identical for binocular and monocular recordings. (5) Increasing the motion duration or the duration of the interstimulus interval did not alter the general morphology of the motion response.     

Somatosensory evoked potentials elicited by dorsal penile and posterior tibial nerve stimulation

SEPs were elicited by stimulation of the dorsal penile nerve (DPN) or posterior tibial nerve (PTN) under 3 conditions of stimulation: random and constant interstimulus intervals, and subject-initiated stimulation. Within these conditions, the effects of repeated stimulation were also examined. The latency of the N90 peak decreased with repeated stimulation. N90 amplitude decreased with increased foreknowledge as well as with repeated stimulation. Factors extracted by principal components analysis revealed similar effects. A difference between DPN and PTN stimulation was seen in a factor associated with the N90 peak, wherein the condition involving subject self-initiation of the stimulus reflected a significantly greater decrease in SEP amplitude when the DPN was stimulated. Morphological commonalities were observed in the SEPs elicited by DPN and PTN for a given subject.     

Early-latency somatosensory evoked potentials elicited by electrical acupuncture after needling acupoint LI-4.

The stimulating methods of prior studies on somatosensory evoked potentials (SEPs) elicited by acupoint stimulus had involved surface electrodes, while the clinical practice of acupuncture is mostly performed by inserting the acupuncture needle inside the body. Clinical observations show that there are often some special sensations when LI-4 is needled. To observe if the SEPs produced by acupoint acupuncture had a distinguishing property, we studied the SEPs elicited by electrical acupuncture after the acupuncture needle was inserted into LI-4 and its control point, and then mapped them with the 128-channel Electric Brain Signal Image system. We also compared this to SEPs by median nerve stimuli. Results showed that the most interesting finding was the marked differences of N1-P1 and N2-P2 amplitude between SEPs at LI-4 (SEP-LI) and its control point (SEP-CP), which were in the opposite direction. Marked differences were also found between latencies and amplitudes of the SEPs elicited by acupuncture and by median nerve stimulus (SEP-M). The differences between SEP-LI and SEP-CP might be due to the additional effects of the activation of nerve endings and muscle spindles in LI-4 to the SEPs formed by the activation of superficial and deep radial nerves during electrical acupuncture. The differences between SEPs to acupoint and median nerve stimuli might be mainly due to the different distances from the stimulated regions to the cerebral cortex, the diversity and the number of activated fibers.     

Postexercise facilitation of motor evoked potentials elicited by ipsilateral voluntary contraction

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) increase in amplitude when obtained immediately after a period of exercise of the target muscle (postexercise facilitation). We studied postexercise facilitation of MEPs to TMS after periods of voluntary activation of either the ipsilateral or contralateral primary motor cortex (simple finger movements) or supplementary motor area (complex finger movements). Postexercise facilitation of the first dorsal interosseous MEPs occurred ipsilaterally even after simple, unilateral finger movements of the dominant hand. The findings are taken to suggest transcallosal transfer of excitability from the dominant to nondominant cerebral hemisphere, perhaps related to mechanisms involved in bimanual motor coordination.     

Early and late lower limb motor evoked potentials elicited by transcranial magnetic motor cortex stimulation.

Transcranial magnetic motor cortex stimulation can elicit a series of responses recorded with different latencies from relaxed muscles of the lower limbs. In 7 healthy subjects, ranging in age from 16 to 62 years, stimulation was delivered by a 9 cm coil centered over Cz with the subject in the supine position. Surface polyelectromyography was used to record motor evoked potentials (MEPs) from the quadriceps (QD), hamstrings (HS), tibialis anterior (TA) and triceps surae (TS) muscles bilaterally. Three characteristic responses were identified in each muscle group on the basis of amplitude and latency criteria, identified by latencies: the direct oligosynaptic response MEP30 appeared with a latency of 24.3 msec in the QD, 26.3 msec in the HS, 30.5 msec in the TA and 31.3 msec in the TS; MEP70 with latencies of 64 msec in the QD, 59 msec in the HS, 79 msec in the TA and 72 msec in the TS; MEP120 with latencies of 115 msec in the QD, 126 msec in the HS, 117 msec in the TA and 124 msec in the TS. These 3 responses have distinct latencies, amplitudes and durations. MEP70 appears to be the result of activation of long descending tracts which end on spinal interneuronal circuits. As MEP120 has different features, it may have a different mechanism.     

Peak latency differences in evoked potentials elicited by painful dental and cutaneous stimulation

Long-latency evoked potentials (EPs) (50-400 msec) have been obtained from humans during both noxious stimulation of tooth and cutaneous sites in studies of pain and analgesic states. This study investigated whether EPs elicited by tooth and lip stimulation differed in peak latency and whether EPs obtained during painful cutaneous stimulation showed increasing peak latency values with increased conduction distance. Twelve volunteers received painful electrical stimulation at four sites: tooth, lip, thumb, and toe in counterbalanced orders. Evoked potentials recorded at vertex were summation averaged over 128 trials. Multivariate stepwise discriminate analysis was used to determine whether any of the peak latencies of the event-related potentials differed across stimulation sites. No significant latency differences were observed across lip, thumb or toe at any of the major peaks. Since peaks of these EPs did not vary in latency with conduction distance, they appear to reflect processing at higher levels rather than sensory transmission. The negative 140 msec peak of the dental waveform occurred significantly later than the same peak at cutaneous sites.     

Comparison of short-latency trigeminal evoked potentials elicited by painful dental and gingival stimulation

Painful stimulation of tooth pulp and of the maxillary gingiva was undertaken in 16 volunteers. Short-latency evoked potentials (15-50 msec) were recorded over 800 trials in each case at F3-P3 of F4-P4, and the resultant averaged wave forms were compared. The gingival wave was distinct in all subjects and could be averaged across subjects while the dental waves were either noise or very inconsistent over subjects. Averaging of the dental wave forms across subjects yielded an uninterpretable result. It was clear that dental evoked potentials could not be recorded at the sites. These findings could be explained by either or both of two hypotheses: dental afferents are predominantly small fiber, nociceptive end organs that conduct more slowly than soft tissue afferents whereas gingival stimulation activates both large and small fiber populations; and dental representation in somatosensory cortex is different and phylogenetically more primitive than that of neighboring soft tissue. Therefore, the location of the generator sites in cortex and the orientation of the dipole may be different for dental than for gingival wave forms.     

Waveform of sympathetic skin response in diabetic patients.

OBJECTIVE: The aim of this study was to investigate whether there were differences in amplitude and latency among the different waveform patterns of sympathetic skin response (SSR) in diabetic patients. The authors also investigated whether the proportion of the SSR waveform patterns was influenced by diabetic polyneuropathy (DP), symptoms of dysautonomia, and impaired R-R interval variation of the heart rate. DESIGN/METHODS: Twenty SSRs from palm skin were analyzed in 53 diabetic patients and 45 normal subjects. Waveforms were classified as either the P type, in which the positive component was larger than the negative one, or the N type, in which the negative component was larger than the positive one. The patterns of occurrence in these two waveform types were classified into 3 kinds, i.e. P, N, and M patterns. In the P and N patterns, all the SSRs were of the P and N types, respectively. The M pattern had both P and N types during consecutive recordings. RESULTS: The patients' age and glycosylated hemoglobin values did not differ among the 3 SSR patterns. The P pattern, however, had a larger amplitude and shorter latency than the N pattern, just as previously reported in a normal population. The distribution of the SSR patterns in diabetic patients was not statistically different from that in the normal controls, and it was not influenced by the DP, symptoms of dysautonomia, or impaired R-R interval variation of the heart rate. CONCLUSIONS: The distribution of the SSR waveform patterns was not influenced by the pathological conditions related to diabetes. It might be advised to confirm the balanced distribution of the SSR waveform patterns in patient and control groups before comparing the values of amplitude and latency between the two groups.     

Auditory evoked potentials and response to lithium prophylaxis

Auditory evoked potentials were recorded in 28 euthymic patients with affective psychosis who had received lithium prophylaxis for at least 5 years. Binaural clicks at 4 intensities were presented in randomized order via headphones. Potentials were recorded from Cz, C3, and C4 referenced to linked mastoid electrodes. N1-P2 amplitudes, N1 and P2 latencies, and the slope of the amplitude/stimulus intensity function (ASF) were determined in each patient. The patients were divided into responders and nonresponders on the basis of whether or not they had been hospitalized for treatment of relapses during the last 5 years of lithium prophylaxis. The ASF was steeper for all leads in responders than in nonresponders. In addition, N1 latencies were shorter for all leads in responders than in nonresponders. Age played a role in the differences observed between responders and nonresponders for ASF, but not for N1 latencies.     

脊椎旁刺激法体感诱发电位在脊髓病变中的临床应用

目的 探讨脊椎旁刺激法体感诱发电位（SEPs）在脊髓病变患者中进行脊髓功能判断的临床应用价值，并将诱发电位结果与脊髓MRI结果进行比较，初步探讨该方法在脊髓病变中的生理定位价值。方法 应用脊椎旁刺激、头皮记录的直接SEPs法对脊髓病变患者进行SEPs测定及脊髓传导速度（SCCV）测定。结果 共有96例脊髓病变患者行脊椎旁刺激法SEPs及SCCV测定，男53例，女43例，年龄15-75岁，平均46．78岁。其中脊髓脱髓鞘病36例，脊髓亚急性联合变性26例，脊髓病19例，急性脊髓炎10例，脊髓压迫性疾病5例。96例脊髓病变患者均做脊椎旁刺激法SEPs检查，脊髓诱发电位及SCCV的异常率在各脊髓病变中阳性率均较高，总异常率为81．25％（78／96）。其中脊髓脱髓鞘病异常率75．00％（27／36），脊髓亚急性联合变性异常率88．46％（23／26），脊髓病19例中有15例异常，脊髓炎异常率10例中有8例异常，脊髓压迫症5例均异常。共有68例患者做脊髓MRI检查，其中42例MRI异常，26例MRI正常。42例MRI异常患者中35例诱发电位结果异常，26例MRI正常患者中21例诱发电位结果异常。结论 脊椎旁刺激法SEPs及SCCV的测定客观地记录了脊髓病变的异常电生理改变，其异常电生理改变可能会出现在脊髓结构改变及影像学改变之前，可为脊髓病变患者早期脊髓功能性改变提供比较可靠的客观诊断依据，尤其在脊髓MRI少有阳性所见的营养代谢性脊髓病中意义更大。本方法简单、无创、具有可重复性，可在临床中应用。     

Sympathetic skin response evoked by laser skin stimulation

The objective of this study was to evoke sympathetic skin responses (SSRs) in healthy subjects using laser stimulation and to compare these responses with those induced by conventional electrical stimuli. Twenty healthy subjects were investigated. SSRs were obtained using electrical and laser stimuli delivered to the wrist controlateral to the recording site. The sympathetic sudomotor conduction velocity (SSFCV) was measured in 8 subjects by simultaneously recording the SSR from the hand and the axilla. The latency (L) of the laser-induced SSR (ISSR) was significantly longer than that of the electrically-evoked SSR (eSSR) (mean ISSRL= 1.7 +/- 0.145 ms, mean eSSRL= 1.56 +/- 0.14 ms, p<0.05). The amplitude (A) of the ISSR was lower than the eSSR amplitude (mean ISSRA = 1.31 +/- 0.26 mV, mean eSSRA = 2.59 +/- 0.49 mV, p<0.05). No significant difference between the ISSR and eSSR was observed in either the SSFCV or the variability and reproducibility parameters. Our findings show that SSRs can easily be induced by laser stimuli and that this method shares the technical limitations of conventional eSSRs.