Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section最新文献

The present study assessed the effect of age on time and frequency components of auditory evoked potentials in two groups of adults, young (18–30 years old) and middle-aged (50–55 years old). Averaged and single-sweep potentials were analyzed. Analysis of single alpha and theta responses was performed for 3 parameters – single-sweep amplitude, phase-locking, and enhancement. Significant age differences were revealed only at the level of single sweeps: (i) at the 3 mid-line locations (Fz, Cz, and Pz), middle-aged adults manifested theta phase-locking and enhancement which were significantly stronger than those in young adults; and (ii) in contrast, only over the frontal brain area were the alpha responses stronger in phase-locking and enhancement in the middle-aged than in young subjects. Thus, the analysis of frequency responses at the level of single sweeps enabled us to reveal age differences in simple auditory stimulus processing that were otherwise not detectable in the averaged potential. The results imply that the alpha response system may relate to frontal brain functioning during aging.

Objectives and mehtods: Four sets of measurements were obtained from 11 patients (44–80 years old) with small, localized pontine lesions due to vascular disease: (1) Monaural auditory brain-stem evoked potentials (ABEPs; peaks I to VI); (2) Binaural ABEPs processed for their binaural interaction components (BICs) in the latency range of peaks IV to VI; (3) magnetic resonance imaging (MRI) of the brain-stem; and (4) psychoacoustics of interaural time disparity measures of binaural localization. ABEPs and BICs were analyzed for peak latencies and interpeak latency differences. Three-channel Lissajous' trajectories (3-CLTs) were derived for ABEPs and BICs and the latencies and orientations of the equivalent dipoles of ABEP and BICs were inferred from them.

Results: Intercomponent latency measures of monaurally evoked ABEPs were abnormal in only 3 of the 11 patients. Consistent correlations between sites of lesion and neurophysiological abnormality were obtained in 9 of the 11 patients using 3-CLT measures of BICs. Six of the 11 patients had absence of one or more BIC components. Seven of the 11 had BICs orientation abnormality and 3 had latency abnormalities. Trapezoid body (TB) lesions (6 patients) were associated with an absent (two patients with ventral-caudal lesions) or abnormal (one patient with ventral-rostral lesions) dipole orientation of the first component (at the time of ABEPs IV), and sparing of this component with midline ventral TB lesions (two patients). A deviant orientation of the second BICs component (at the time of ABEPs V) was observed with ventral TB lesions. Psychoacoustic lateralization in these patients was biased toward the center. Rostral lateral lemniscus (LL) lesions (3 patients) were associated with absent (one patient) or abnormal (two patients) orientation of the third BICs component (at the time of ABEPs VI); and a side-biased lateralization with behavioral testing.

Conclusions: These results indicate that: (1) the BICs component occurring at the time of ABEPs peak IV is dependent on ventral-caudal TB integrity; (2) the ventral TB contributes to the BICs component at the time of ABEPs peak V; and (3) the rostral LL is a contributing generator of the BICs component occurring at the time of ABEP peak VI.

To evaluate conduction abnormalities of the corticospinal tracts (CSTs) in Pelizaeus-Merzbacher disease (PMD), magnetic stimulation at three levels was carried out in 3 boys with PMD aged between 9 and 12 years. They were all diagnosed as having a duplicated proteolipid protein gene. The motor cortex and cervical spinal roots were stimulated with a round coil, whereas a double cone coil was used for brain-stem stimulation. Surface electromyographic (EMG) recording was performed on the first dorsal interosseous muscles. Despite a normal EMG response to cervical stimulation, magnetic shock of the motor cortex elicited no EMG activity, even in the case with less motor symptoms. This discrepancy between the electrophysiological and clinical findings is likely due to slowing conduction, which reduces the temporal summation of multiple descending volleys magnetically elicited. A partial conduction block may also occur because of the lack of an EMG response to brain-stem stimulation. Thus, we speculated that the spastic paresis in PMD is associated with both slowing conduction and a partial conduction block in the CSTs.

Objective: To characterize the sympathetic skin responses (SSRs) recorded from non-palmar and non-plantar (non-Pa/Pl) skin sites and to evaluate their clinical usefulness.

Methods: SSRs were recorded from 6 non-Pa/Pl sites as well as palmar and plantar (Pa/Pl) sites using magnetic neck stimulation in 33 normal subjects, 17 neurological patients with dysautonomia and one patient with lumbar sympathectomy. A conventional thermoregulatory sweat test (TST) was also carried out in 3 patients.

Results: Clear and reproducible SSRs were obtained from all recording sites in all of the normal subjects when the skin temperatures of the subjects were maintained above 34°C and the subjects drank 100–200 ml of hot water. The distribution of absent SSRs was closely correlated with that of anhidrosis or a sweating delay shown by the TST in the patients. Nine of the 17 neurological patients (53%) showed normal responses at Pa/Pl sites, and abnormal responses at non-Pa/Pl sites.

Conclusions: Recording SSRs from multiple skin sites including non-Pa/Pl sites after magnetic stimulation is more sensitive in detecting sudomotor dysfunction than is the conventional method of recording SSRs from only Pa/Pl sites. In addition, this new method is very useful for the objective clinical evaluation of thermal sweating.

The P3(00) event-related potentials (ERPs) elicited by visual stimuli in two visual tasks were assessed in depressed patients (12 patients with major depression and 11 patients with bipolar disorder) and compared with those of 20 age-matched normal controls. At remission, the ERPs from 18 of the depressed patients were again recorded. The visual oddball (VO) paradigm presented both target and standard visual stimuli and the simple visual (SV) paradigm presented a target but no standard visual stimulus. Subjects performed the VO task significantly less accurately than the SV task, as reflected by the behavioral measures (reaction-time and task accuracy). Depressed patients of the bipolar group showed longer P3 peak latency for the VO task and no change in P3 amplitude. No significant differences were found in any other ERP component between the groups. During remission, slowing RTs and reduced P3 peak latencies were observed for both major depression and bipolar disorder groups. Thus, the P3 ERP may be an index of the contribution of the slowed central processing to psychomotor retardation in clinically homogenous samples of depressive patients performing an appropriately demanding task.

Objectives: Landau–Kleffner Syndrome (LKS) is an epileptic syndrome characterised by a deficit in language comprehension and production, paroxysmal epileptiform activity in the posterior temporal leads, and by the inconsistent presence of epileptic fits. Its interest lies in the fact that it stands as a model for the study of interference of epileptiform activity on cognitive function, although the pathophysiology of the decline in language skills that follows its onset has not yet been clarified.

Methods: We have recorded spike-triggered auditory evoked responses in a group of 6 children with LKS, to investigate whether the occurrence of individual EEG paroxysms is able per se to induce a decline in the response of the auditory cortex.

Results: Results have indicated that left hemisphere spikes are associated with a greater reduction in amplitude and an increase in latency of the N1, than spikes occurring in the right hemisphere. No stable change in the evoked response has been detected outside of the EEG paroxysm.

Conclusions: We postulate EEG interictal activity is able to induce impairment in processing auditory information and that this may play a role in the pathogenesis of language deficit (deficiency?) in LKS.

To evaluate the diagnostic utility of dermatomal and mixed nerve somatosensory evoked potentials (SEPs) in patients with thoracic outlet syndrome (TOS) and to compare their value with routine electrodiagnostic methods, we studied a group of 44 patients with neurogenic TOS and 30 healthy controls. In addition to bilateral median and ulnar SEPs, evoked potentials were recorded after stimulation of C6 and C8 dermatomes from the first and fifth digits, respectively. The patients were classified into 3 groups according to the nature of their clinical condition. The abnormality rate for both ulnar and C8 dermatomal SEPs was 100% in a small group of patients with severe neurological signs like atrophy. In groups of patients with lesser degrees of neurogenic damage, abnormality rates for ulnar and C8 dermatomal SEPs on affected limb(s) were 67 and 50%, respectively. Same abnormality rates were 25 and 18% in patients with only subjective symptoms. In patients with objective neurological signs, the major increase in sensitivity was with electromyography (EMG). Abnormalities of routine nerve conduction studies and F-wave latency were observed in patients with severe neurogenic damage. We concluded that the most useful tests in the diagnosis of neurogenic TOS are needle EMG and ulnar SEPs.

Objective: The aim of this study was to investigate the influence of odorant concentration on the olfactory event-related potential (OERP).

Design and Methods: OERP were evaluated in 8 men and 8 women (17–34 years of age) in response to 4 concentrations of vanillin (7, 28, 56 and 84% v/v). Sixteen presentations of each concentration (stimulus duration 200 ms, interval 40 s, flow 8 l/min) were applied in a randomized order. EEG recordings were made at 3 midline sites (pos. Fz, Cz, Pz). Amplitudes and latencies of four peaks were measured (latencies in ms at Pz after stimulation with 84% v/v vanillin): P1 (277), N1 (348), P2 (412) and P3 (496). Statistical analysis was performed with MANOVAs (`concentration', `recording site'=within-subject-factors; `age' as covariate).

Results: With increasing stimulus concentration amplitudes became significantly larger; this was most pronounced for P3 (P1N1: F=2.90, P<0.05; N1P2: F=5.15, P<0.01; N1P3: F=35.7, P<0.001; P3: F=38.6; P<0.001). Correspondingly, latencies shortened with increasing concentrations (P1: F=25.2; N1: 17.51; P2: 14.8; P3: 13.4; all P<0.001). While there was no correlation between OERP amplitudes and butanol odor detection thresholds, latencies were the shorter the lower the subjects' thresholds (coefficients of correlations for peak latencies at Cz for 84% v/v: P1 r₁₅=minus0.59; N1 r₁₅=minus0.58; P2 r₁₅=minus0.55; P3 r₁₅=minus0.45).

Conclusions: The results indicated that both OERP amplitudes and latencies are related to the concentration of olfactory stimuli. They also suggested that latencies exhibit a stronger relation to changes in stimulus intensity compared to OERP amplitudes.

Objectives: To characterize the effects of normal aging on the amplitude, latency and scalp distribution of the N400 congruity effect.

Methods: Event-related brain potentials (ERPs) were recorded from 72 adults (half of them men) between the ages of 20 and 80 years (12/decade) as they performed a semantic categorization task. Participants listened to spoken phrases (e.g. `a type of fruit' or `the opposite of black') followed about 1 s later by a visually-presented word that either did or did not fit with the sense of the preceding phrase; they reported the word read and whether or not it was appropriate. ERP measurements (mean amplitudes, peak amplitudes, peak latencies) were subjected to analysis of variance and linear regression analyses.

Results: All participants, regardless of age, produced larger N400s to words that did not fit than to those that did. The N400 congruity effect (no-fit ERPs−fit ERPs) showed a reliable linear decrease in the amplitude (0.05–0.09 μV per year, r=0.40) and a reliable linear increase peak latency (1.5–2.1 ms/year, r=0.60) with age.

Conclusions: In sum, the N400 semantic congruity effect at the scalp gets smaller, slower and more variable with age, consistent with a quantitative rather than qualitative change in semantic processing (integration) with normal aging.

The current experiment attempts to investigate (1) the effect of semantic information on the ERP correlate of visual short-term memory (VMP) and (2) the utilizing of the ERP as an objective investigative tool for the clinical observation of the existence of category-specific brain systems. Event-related potentials (ERPs) were recorded from 61 locations on the scalp of 39 healthy adults in a category (either animals or fruits/vegetables) match/non-match S1-S2 paradigm. The ERPs revealed a substantially smaller amplitude for the category matching than for non-matching pictures at the posterior brain regions, with greater activation of temporo-occipital brain regions changing from the right hemisphere at first to the left hemisphere later, as demonstrated by the current source density (CSD) maps. The ERPs elicited by the category of animal were larger than the vegetable category, similarly, the animal-animal matching condition elicited larger ERPs than did the vegetable-vegetable matching condition. In addition, the topographic distribution of the vegetable-elicited ERPs revealed additional involvement of the right frontal cortex which was absent in the topographic distribution of the animal-elicited ERPs. The spatial pattern of the VMP possesses features specific to semantic processing, and the ERPs differentiate the animal category from the vegetable category, suggesting an objective on-line method to investigate the category-specific information processing among brain-damaged patients.