The effects of donepezil on the P300 auditory and visual cognitive evoked potentials of patients with Alzheimer's disease.

Donepezil is a cholinesterase inhibitor used for the treatment of patients with mild to moderately severe Alzheimer's disease (AD). The purpose of this study was to determine the effect of treatment with donepezil 5 mg qd on cognitive evoked potentials (EPs) of patients with AD. Although treatment with donepezil did not normalize EP latencies, treatment was associated with a significant decrease in the auditory P300 latency (mean latency pretreatment=401. 5 msec; posttreatment=392.7 msec.; P=0.04), and the visual P300 latency (mean latency pretreatment=605.7 msec; posttreatment=580.3 msec; P=0.04). Treatment with donepezil had no discernible effect on auditory or visual P300 EP amplitudes.     

男性青少年暴力攻击行为脑诱发电位研究

目的探索男性青少年暴力攻击行为的部分神经电生理学基础。方法以47例有官方暴力型违法乱纪记录的青少年(16~20岁)为研究组,无暴力攻击行为的职业高中学生41例为对照组,进行脑干听觉诱发电位、体感诱发电位和P300测验,比较两组间的差异。结果与对照组相比,有暴力攻击行为组脑干听觉诱发电位V潜伏期显著延长(P<0.01),波Ⅲ波幅显著降低(P<0.01),提示外周听觉刺激被过度过滤;P300的靶P3波潜伏期显著延长(P<0.05),提示认知信息加工过程速度减慢;体感诱发电位N1波潜伏期显著缩短(P<0.05),P2波波幅显著增高(P<0.01),提示体感刺激皮层反应增强。结论有暴力攻击行为的青少年脑诱发电位异常,提示大脑皮层唤醒水平低下,认知功能损害,存在对体感刺激的感觉搜寻增强。     

Auditory stimulus processing at different stimulus intensities as reflected by auditory evoked potentials

The influence of stimulus intensity on the components of auditory evoked potentials was investigated at different levels of attention and task relevance in six healthy adult subjects. A negative component with a latency of 130 msec (N130) was produced by stimuli applied as targets or nontargets in a random sequence. The N130 amplitude had an inverse U-shaped relationship to stimulus intensity, with its maximum value at a stimulus intensity of 70 dB SL. The P300 latency showed a U-shaped relationship to stimulus intensity and obtained its minimum value at 70 dB. Thus, evoked-potential equivalents of cognitive auditory stimulus processing could be shown to be loudness driven and to have highest amplitudes or shortest latencies at a stimulus loudness of 70 dB SL.     

Reduction of the postexcitatory cortical inhibition upon paired-click auditory stimulation in patients with Parkinson’s disease

ObjectivesThe aims of this study were: to investigate the postexcitatory inhibition of cortical evoked potentials on auditory paired-click stimulation in patients with Parkinson’s disease (PD), to analyze the correlation of N1–P2 amplitude ratios (A2/A1) with latency of the P300 auditory event-related potential and to determine the influence of Levodopa intake on postexcitatory inhibition and P300 latency.MethodsThe central (Cz) auditory evoked potentials were recorded in 61 patients with PD and 21 age-matched healthy subjects.ResultsPostexcitatory inhibition in auditory cortex in PD was significantly reduced for interstimulus intervals 500, 700 and 900 ms compared to control group. The degree of this reduction correlated positively with the potential P300 latency and negatively with the summary score of the Mini Mental State Examination (MMSE) which was used to study general cognitive status of the PD patients. Increase of the postexcitatory inhibition towards normal values and decrease of the P300 latency were observed (P < 0.001) following the administration of Levodopa.ConclusionsThe findings of this study testify that inhibitory processes in auditory cortex are deficient in PD patients. The positive effect of Levodopa administration indicates an important role of dopamine-dependent neural mechanisms in modulation of inhibitory processes in the auditory sensory system.SignificanceThe results show that inability of the brain to provide normal inhibition in PD is accompanied by the decline of cognitive indices, including parameters of evoked potential P300 that is related to fundamental aspects of cognitive functions, such as attention and memory.     

Electrophysiologic Studies of Cervical Vagus Nerve Stimulation in Humans: II. Evoked Potentials

Evidence from studies of experimental animals indicates that electrical stimulation of the vagus nerve not only can alter the EEG but evokes activity in specific brain areas. We report effects of electrical stimulation of the vagus nerve in 9 patients with medically intractable seizures as part of a clinical trial of chronic vagal stimulation for control of epilepsy. The left vagus nerve in the neck was stimulated with a programmable implanted stimulator. Effects of stimulus amplitude, duration, and rate were studied. Noncephalic reference recording of the vagus nerve evoked potential showed some unusual properties: a scalp negative component occurred with a latency of 12 ms, very high amplitude (< or = 60 microV), and widespread scalp distribution. Field distribution studies indicated that this potential was myogenic in origin and generated in the region of the stimulating electrodes in the neck area. Chemically induced muscle paralysis confirmed this observation. Bipolar scalp recording showed several small-amplitude topographically distinct potentials occurring in 30 ms. No effect, either acute or chronic, could be detected on pattern-reversal evoked potentials, auditory brainstem evoked potentials, auditory 40-Hz potentials, or cognitive evoked potentials.     

Auditory and visual P300 cognitive evoked responses in patients with COPD: relationship to degree of pulmonary impairment.

Twenty-two subjects with documented COPD and no other significant illnesses were studied to assess the effect of varying degrees of COPD on cognitive P300 auditory and visual evoked potentials. The severity of COPD was determined by spirometry with assessment of FEV1, FVC, and FEV1/FVC. Auditory P300 latency was significantly correlated with the FEV1/FVC ratio (Pearson Product Moment correlations r = -.56, N = 20, probability level = 0.1), indicating that increasingly severe airflow impairment is associated with longer auditory P300 latencies. There was no significant association of FEV1/FVC with visual P300 latency or with auditory or visual evoked potential amplitude measures. Progressive impairment of the auditory P300 evoked potential latency occurs with increasing severity of COPD. This impairment is present even in patients with mild COPD, suggesting some degree of accompanying cognitive decline early in the course of COPD with worsening as the disease progresses.     

Scalp potentials following sudden coherence and discoherence of binaural noise and change in the inter-aural time difference: a specific binaural evoked potential or a "mismatch" response?

When uncorrelated random noise signals presented to the two ears suddenly become identical (coherent), a centrally located sound image is abruptly perceived and long latency scalp potentials are evoked. When the same signals are presented monaurally there is no perceived change and no potentials are evoked: hence the response must be purely a function of the binaural interaction. P70, N130 and P220 components were consistently recorded to both coherence and discoherence. N130 was usually largest at Fz and P220 at Cz. No potentials of shorter latency were identified, even after averaging 5000 or more sweeps. When the noise became coherent with an inter-aural time difference (delta T) of +/- 0.5 msec (giving rise to an off-centre sound image), the responses were of slightly longer latency and showed no significant asymmetries between C3 and C4. In binaurally coherent noise, delta T changes of +/- 0.5 or +/- 1.0 msec evoked similar responses which showed no significant asymmetries on the scalp. N130 was of longer latency when delta T was changed from +/- 0.5 msec to zero, as compared with the converse change. In view of the similarity of all these responses it is considered unlikely that they were due to specific populations of binaurally responsive cortical neurones. The N130 and P220 components are thought to be non-specific potentials which are elicited by any perceptible change in steady auditory stimulus conditions, due to a "mismatch" between the stimulus and the contents of a short-term auditory memory.     

Brain potentials in a memory-scanning task. II. Effects of aging on potentials to the probes

Brain potentials accompanying the classification of probe items as being members of a previously presented list were recorded from subjects ranging in age from 18 to 86 years old. A group of older subjects (average age = 66 years) was compared to a younger group (average age = 29 years). The items tested were verbal (digits) and non-verbal (musical notes). Digits were presented in the auditory and visual modalities, and notes were presented acoustically. Reaction times (RTs) and performance accuracy were computed. Potentials are described in terms of scalp distribution, latency and amplitude as a function of the type of stimulus (verbal/non-verbal, auditory/visual) and age group (younger/older). Evoked potentials to target notes in an auditory target-detection ('odd-ball') task were also recorded for comparison with the memory tasks. Potentials evoked by probes consisted of a sequence of sensory components in the first 250 msec followed by a cognitive component that was positive in polarity and sustained in duration (approximately 700 msec labeled P3), consisting of an earlier frontal component, P3a (mean latency: younger = 385 msec, older = 406 msec), and a large (15 microV) and later parietal constituent, P3b (mean latency: younger = 574 msec, older = 630 msec). The frontal derivation of the younger subjects showed a sustained negative bias of the wave forms in the latency range of 200-500 msec (P2 to P3) compared to the older subjects. Reaction times were longer in older subjects than in younger subjects for all stimulus types and set sizes. For the potentials evoked by the probes the younger group had consistently larger late parietal components (P3b) than the older group, whereas the late frontal potentials (P3a) were larger for the older than younger subjects. Except for visual stimuli, the latencies of the parietal sustained potentials were not influenced by subject age in contrast to the uniform changes in RT for all stimulus types. Significant amplitude and latency effects on the parietal sustained potentials accompanied the different stimulus types and memorized-set sizes which were similar for the two age groups. These results suggest that the effects of aging on short-term memory are primarily on response selection, as evidenced by RT slowing with aging, and not on memory-scanning processes as evidenced by the similarity of the latency measures of the accompanying brain potentials between the two age groups.     

Two varieties of long-latency positive waves evoked by unpredictable auditory stimuli in man.

Two distinct late-positive components of the scalp-recorded auditory evoked potential were identified which differed in their latency, scalp topography and psychological correlates. The earlier component, called "P3a" (latency about 240 msec), was elicited by infrequent, unpredictable shifts of either intensity or frequency in a train of tone pips whether the subject was ignoring (reading a book) or attending to the tones (counting). The later component, called "P3a" (mean latency about 350 msec), occurred only when the subject was actively attending to the tones; it was evoked by the infrequent, unpredictable stimulus shifts, regardless of whether the subject was counting that stimulus or the more frequently occurring stimulus. Both of these distinct psychophysiological entities have previously been refered to as the "P3" or "P300" in the literature.     

Human auditory and somatosensory event-related potentials: effects of response condition and age

In order to develop an experimental paradigm for clinical application of cognitive event-related potentials we have recorded these potentials in a group of 27 healthy Japanese, aged 20-78 years, using all 4 stimulus/response combinations of auditory or somatosensory stimuli requiring a counting or button-press response. In an oddball paradigm we recorded N1 and P2 components to frequent auditory stimuli and P100, N150 and P200 components to frequent somatosensory stimuli. These components were also observed in the target responses for their respective modalities together with N2, P270, P3 and slow-wave components. P3 latency increased linearly with age for all 4 experimental conditions, although this increase was not statistically significant for the somatosensory stimulus/button-press response combination. The latency of P270 also increased significantly with age for the auditory stimulus/button-press response combination but did not do so in either of the counting response conditions. The principal difference between the latencies of ERPs to auditory compared with somatosensory stimuli was that P3 was significantly longer for somatosensory stimulation, although differences in task difficulty may have influenced this finding. With regard to amplitude, N2, P3 and slow-wave were all significantly more positive for somatosensory compared with auditory stimulation. The topography of P3 evoked by somatosensory stimuli was most predominant at central electrodes, whereas the auditory P3 was larger parietally. The button-press response was associated with potentials which were smaller in amplitude and shorter in latency than those associated with the count response. The button-press response had a marked effect on the amplitude of P3 recorded at the vertex and the central electrode contralateral to the moving finger.     

Evoked potential decrements in auditory cortex. I. Discrete-trial and continual stimulation.

In experiment 1 cats were exposed to sets of clicks (trials) with 1 min inter-trial-intervals to determine if the effects of repetitive stimulation on potentials evoked in the auditory cortex would be cumulative despite discrete-trial stimulation. Evoked potentials were averaged to give one average evoked potential (AEP) for each trial for each electrode; there were four cortical electrodes per subject. To test for dishabituation pawshocks were given between trials 60 and 61. Subjects were paralyzed to insure stimulus constancy. The latency and peak-to-peak amplitude of each component of each AEP was measured; significant amplitude decremented; and decrements were more frequent in components with latencies greater than 15 msec. A few amplitude increments and latency changes were also observed...     

Magnetic stimulation of muscle evokes cerebral potentials

Somatosensory evoked potentials (SEPs) were recorded from the scalp in man to magnetic stimulation of various skeletal muscles. The potentials consisted of several components, the earliest of which decreased in latency as the stimulated site moved rostrally, ranging from 46 msec for stimulation of the gastrocnemius, to 14 msec for stimulation of the deltoid. Experiments were performed to distinguish the mechanisms by which magnetic stimulation of the muscle was effective in evoking these cerebral potentials. For the gastrocnemius, the intensity of the magnetic stimulus needed for evoking cerebral potentials was less than that required for activating mixed or sensory nerves in proximity to the muscle belly (eg, posterior tibial nerve in the popliteal fossa, sural nerve at the ankle). Vibration of the muscle or passive lengthening of the muscle, procedures which activate muscle spindles, were accompanied by a significant attenuation of the potentials evoked by magnetic stimulation of the muscle. Anesthesia of the skin underlying the stimulating coil had no effect on the latency or amplitude of the early components of the magnetically evoked potentials, whereas electrically evoked potentials from skin electrodes were abolished. Thus, the cerebral potentials accompanying magnetic stimulation of the muscle appear to be due to activation of muscle afferents. We suggest that magnetic stimulation of muscle can provide a relatively simple method for quantifying the function of muscle afferents originating from a wide variety of skeletal musculature.     

Oesophageal afferent pathway sensitivity in non-erosive reflux disease

Abstract  Patients with non-erosive reflux disease (NERD) report symptoms which commonly fail to improve on conventional antireflux therapies. Oesophageal visceral hyperalgaesia may contribute to symptom generation in NERD and we explore this hypothesis using oesophageal evoked potentials. Fifteen endoscopically confirmed NERD patients (four female, 29–56 years) plus 15 matched healthy volunteers (four female, 23–56 years) were studied. All patients had oesophageal manometry/24-h pH monitoring and all subjects underwent evoked potential and sensory testing, using electrical stimulation of the distal oesophagus. Cumulatively, NERD patients had higher sensory thresholds and increased evoked potential latencies when compared to controls ( P  = 0.01). In NERD patients, there was a correlation between pain threshold and acid exposure as determined by DeMeester score ( r  = 0.63, P  = 0.02), with increased oesophageal sensitivity being associated with lower DeMeester score. Reflux negative patients had lower pain thresholds when compared to both reflux positive patients and controls. Evoked potentials were normal in reflux negative patients but significantly delayed in the reflux positive group ( P  = 0.01). We demonstrate that NERD patients form a continuum of oesophageal afferent sensitivity with a correlation between the degree of acid exposure and oesophageal pain thresholds. We provide objective evidence that increased oesophageal pain sensitivity in reflux negative NERD is associated with heightened afferent sensitivity as normal latency evoked potential responses could be elicited with reduced afferent input. Increased oesophageal afferent pain sensitivity may play an important role in a subset of NERD and could offer an alternate therapeutic target.     

Auditory and visual event-related perturbations in the 40 Hz auditory steady-state response.

The effects of salient auditory and visual 'foreground' stimuli on responses to 'background' probe stimuli were investigated. The foreground stimuli were given at long and aperiodic intervals and required a discriminative judgment. Simultaneously, evoked potentials were obtained in response to background probe auditory stimuli presented in a continuous train at about 40/sec. The 40 Hz steady-state rhythm (SSR) evoked under such conditions was extracted using digital averaging and filtering techniques and examined continuously for evidence of change in latency or amplitude during the period surrounding the foreground stimulus. Within the first 200-300 msec after the onset of an acoustic foreground stimulus the latencies of individual peaks in the rhythm were momentarily reduced by a mean of 5.5 msec. A shift in the 40 Hz rhythm was also seen following visual foreground stimuli, although the shift was about one-third that following acoustic stimuli. A latency shift of comparable magnitude was not produced by deliberate manipulation of intensity or signal-to-noise ratio of the stimuli used to evoke the rhythm. The latency shift response is discussed in terms of a transient period of sensory facilitation during orienting or alerting associated with the foreground stimuli.     

Effects of stimulus sequence on event-related potentials and reaction time during target detection in Alzheimer's disease.

OBJECTIVES: To examine evoked potentials and behavior as a function of stimulus sequence in an auditory target detection paradigm in Alzheimer's disease (AD). METHODS: Evoked potentials and reaction times were collected from 12 healthy elderly controls and 10 patients with mild AD. Subjects pressed a response button to high-pitched target tones (P=0.20) that were randomly intermixed with low-pitched frequent tones. We measured pre-stimulus readiness potential (RP), event-related potentials (P50, N100, P200, N200 and P300), and reaction time as a function of the stimulus sequence. RESULTS: AD subjects performed at comparable levels of accuracy as controls, but had significantly increased reaction times. Grand averaged potentials in AD showed a significant reduction of the amplitude of the RP, and an increase of P300 latency. Both controls and AD showed speeding of reaction time, increases in RP amplitude, and decreases in P300 latency as a function of the number of frequents preceding the target. Sequential changes of other components (P200 and N200) were found in controls but not AD. CONCLUSIONS: AD patients have systematic changes of both RT and certain of the evoked potential components as a function of stimulus sequence. Moment-by-moment changes in target expectancy are largely preserved in AD, even though overall performance and evoked potential measures of expectancy (RP) and stimulus classification (P300 latency) are abnormal.     

卡马西平对诱发电位的影响及意义

目的研究长期口服卡马西平治疗癫对诱发电位的影响,并讨论其意义。方法选择尚未治疗的癫病人31例作为试验组;以性别、年龄与癫组相匹配的健康正常人26例作为对照组。两组先分别做脑干听觉诱发电位(BAEP)、事件相关电位P300、视觉诱发电位(VEP)和体感诱发电位(SEP),之后癫组开始卡马西平治疗,服药一年后再作上述各项检查。结果癫组病人治疗前各项电生理学指标与正常对照组相比无显著性差异;癫组卡马西平治疗后各项电生理指标与治疗前相比BAEP各波、P300以及VEP的P100波潜伏期均显著延长;SEP的潜伏期无显著变化。结论神经电生理学检查可以早期发现长期服用卡马西平导致的亚临床毒性。     

Pure word deafness due to left subcortical lesion: Neurophysiological studies of two patients

ObjectiveThis study investigated the auditory processing in two patients with pure word deafness (PWD) using neurophysiological experimental methods.MethodsWe recorded the auditory brainstem response (ABR), the middle latency auditory-evoked response (MLR) and the auditory-evoked event-related potentials (ERPs) in two patients with PWD after subcortical hemorrhage in the left temporal lobe.ResultsBoth patients showed normal response in ABR and abnormality in MLR. The latency of P300 evoked by right-ear stimulation was 51 ms longer in one patient and 26 ms longer in the other patient than that evoked by left-ear stimulation.ConclusionsOur results suggested that the prolongation of P300 latency could be caused by the deterioration of auditory stimulus processing and supported the hypothesis that the defect in auditory temporal resolution was an important factor in the development of PWD.SignificanceThis study demonstrated that recordings of ERP with auditory-evoked response such as ABR and MLR are useful to elucidate the deterioration of auditory stimulus processing in patients with PWD.     

Low frequency subthalamic stimulation and event-related potentials in Parkinson disease

BackgroundHigh frequency (130 Hz) subthalamic Deep-Brain-Stimulation (STN-DBS) optimally improves cardinal motor symptoms in Parkinson disease (PD). Low stimulation frequencies (60–80 Hz) improve axial symptoms in some patients and, according to preliminary evidences, may also have a beneficial effect on the cognitive component of motor planning.ObjectiveTo analyze the configuration of the P300 component of cortical event-related auditory potentials (ERPs), a reliable index of attentive cognitive functions, at different stimulation frequencies in STN-DBS in PD patients.Methods12 PD patients underwent ERPs recordings using a standard oddball auditory paradigm with STN-DBS at 60 Hz, 80 Hz, 130 Hz, and OFF-stimulation, applied in a randomized double-blind sequence. ERPs analysis considered the peak amplitude and latency of the P300 components at midline electrode positions (Fz, Cz, Pz).ResultsP300 latency over Cz and Pz electrodes significantly increased with STN-DBS at 130 Hz compared to OFF-stimulation. P300 latency was also significantly increased, though to a lesser degree, over Pz electrode with stimulation at 80 Hz. No significant P300 latency modifications were detected at 60 Hz stimulation compared to OFF-stimulation condition. P300 amplitude did not change significantly for any of the stimulation conditions tested.ConclusionsLow frequency STN-DBS is associated with minor modifications of P300 latency compared to conventional stimulation at 130 Hz, possibly suggesting that 60 and 80 Hz may have less interference with attentive and cognitive processes in PD patients.     

Effects of stimulation intensity, gender and handedness upon auditory evoked potentials.

Left handers and women show less anatomical brain asymmetry, larger corpus callosum and more bilateral representation of specific functions. Sensory and cognitive components of cortical auditory evoked potentials (AEP) have been shown to be asymmetric in right handed males and to be influenced by stimulus intensity. In this study the influence of sex, handedness and stimulus intensity upon AEP components is investigated under basal conditions of passive attention. 14 right handed males, 14 right handed females, 14 left handed males, and 14 left handed females were studied while lying awake and paying passive attention to auditory stimulation (series of 100 binaural clicks, duration 1 msec, rate 1/sec, at four intensities). Cz, C3 and C4 referenced to linked mastoids and right EOG were recorded. Analysis time was 400 msec, average evoked potentials were based on 100 clicks. Stimulus intensity and gender affect early sensory components (P1N1 and N1P2) at central leads, asymmetry is influenced only by handedness, right handers showing larger P1N1 amplitudes over the right hemisphere.     

Technical details for recording trigeminal evoked potentials in the cat

Experiments were undertaken to establish technical standards for recording of trigeminal evoked potentials (TEP) as a tool for assessment of the effectiveness of various therapeutic procedures for trigeminal neuralgia. Serial changes in the action potentials of the maxillary nerve and TEP were studied when parameters of electrical stimulation, namely, intensity and frequency, and position of electrodes were altered. The effects of use of muscle relaxants and change of body temperature of animals on TEP were also studied. On the basis of these experimental results, the technical details most suitable for TEP recording in cat were explored. The most distinct TEP was recorded under the following animal conditions and parameters: keeping rectal temperature between 37.5 degrees C and 38.5 degrees C, slackening with muscle relaxants, stimulating the infraorbital nerve with 10 volts of square-pulse electricity 5 times per second in short latency TEP and 2 times per second in long latency TEP, placing the active electrode on the vertex for short latency TEP and on the primary sensory area for long latency TEP. Eight positive peaks and three negative peaks were recorded under these conditions. The average and standard deviations of peak latency of potential from 10 cats were as follows: P 1, 0.67 +/- 0.04 msec; N 1, 0.89 +/- 0.07 msec; P 2, 1.35 +/- 0.10 msec; P 3, 1.89 +/- 0.08 msec; P 4, 2.43 +/- 0.26 msec; P 5, 3.17 +/- 0.15 msec; P 6, 3.36 +/- 0.21 msec; P 7, 5.02 +/- 0.39 msec; P 8, 6.07 +/- 0.35 msec; N 2, 10.4 +/- 1.15 msec; N 3, 18.5 +/- 1.74 msec.(ABSTRACT TRUNCATED AT 250 WORDS)