Mismatch negativity to speech stimuli in 8-month-old infants and adults

The mismatch negativity (MMN) was measured in 15 normal awake 8-month-old infants and 10 adults to the speech consonants /da/ and /ta/. ERPs were analyzed at 11 electrodes (Fz, Cz, Pz, C3, C4, T3, T4, T5, T6, P3, P4). Four-hundred trials were presented: the /da/ standards with 80% probability and the /ta/ deviants with 20% probability. The ISI was 600 ms.An MMN was observed for both adults and infants but with different scalp distributions. A clear infant MMN was observed only at C3 and T3 electrodes, whereas the adult MMN was present at Fz, Cz, C3, C4 and Pz. A repeated-measures ANOVA on the normalized summed area between 200 and 250 ms revealed an age (adult vs. infant) × electrode interaction. Paired t-tests indicated that adults and infants showed significant differences at the C3, Cz, T3, Pz and T6 electrodes. The adult MMN was largest at Cz and C3 whereas the infant MMN was largest at T3. These data are discussed in terms of possible maturational changes in the MMN.     

Event-related potential (ERP) asymmetries to emotional stimuli in a visual half-field paradigm

To investigate the hypothesis of a right hemispheric superiority in negative emotional processing, event-related potentials (ERPs) were recorded from 17 sites (Fz, Cz, Pz, F3/4, F7/8, C3/4, T7/8, P3/4, P7/8, O1/2) in a visual half-field paradigm. While maintaining fixation, right-handed women viewed pictures of patients with dermatological diseases before (negative) and after (neutral) cosmetic surgery. A principal components analysis with Varimax rotation performed on ERPs revealed factors identified as N1, N2, early P3, late P3, late P3, and slow wave. Repeated measures analyses of variance performed on factor scores revealed a significant effect of emotional content for all factors except for N1. However, asymmetries in emotional processing were restricted to N2 and early P3, with maximal effects over the right parietal region. N2–P3 amplitude was augmented for negative and reduced for neutral stimuli over right hemisphere regions. Visual field presentation interacted with these asymmetries in enhancing amplitudes contralaterally for early but ipsilaterally for late ERP components. Overall, findings for N2 and P3 support theories of an asymmetry in emotional processing.     

EEG alpha activity and the ERP to target stimuli in an auditory oddball paradigm.

Peak-to-peak amplitudes of the N1P2 and N2P3 components in the target ERPs from a fixed interstimulus interval auditory oddball paradigm were investigated as a function of within-subject pre-stimulus levels of alpha activity. Fourteen subjects were each presented with 600 auditory stimuli in a two-tone auditory oddball paradigm which required a button-press to targets, presented with 50% probability. Pre-stimulus alpha activity at Pz was assessed for each trial by digital filtering from 8 to 13 Hz, and alpha RMS amplitude was used to sort the ERPs at Pz and Cz. A direct relationship was obtained between component amplitudes at both Pz and Cz and pre-stimulus alpha level at Pz. Component latencies were strongly related to post-stimulus alpha peaks and troughs. These data confirm the intimate relationship between central nervous system activation, as evidenced by spontaneous EEG in the pre-stimulus period, and the ERP resulting from stimulus presentation.     

Event-related potentials in autistic and healthy children on an auditory choice reaction time task

Event-related potentials (ERPs) were recorded from midline (Fz, Cz, Pz) and lateral sites (F3, F4, P3, P4) in autistic children (n = 7) and age-matched controls (n = 9) on an auditory choice reaction time task. Subjects were asked to press a button to an infrequent target (500 Hz, P = 0.14) and to ignore higher pitched infrequent (2000 Hz, P = 0.14) and frequent (1000 Hz) non-targets. Autistic subjects made twice as many errors of omission as controls and showed a higher criterion (beta) for targets. Maximum ERP peak amplitudes showed a more varied scalp distribution in the autistic group. N1 latencies were consistently shorter in the autistic group and in 3 subjects the target P3 latencies were markedly longer than for the controls. Compared to controls, the N1 amplitude of the autistic response was larger to the rare stimuli (particularly to non-targets). The amplitude of the P3 component was smaller in the autistic group (particularly to the target). The stimuli were also presented in a passive condition requiring no response. After subtraction of the waveform obtained in the passive condition from that obtained in the active condition or subtraction of the waveform elicited by the rare non-target from that elicited by the target, N1 target amplitude was larger in control than in autistic children. Autistic subjects showed more early negativity to the rare non-target at left frontal and a larger P3 to the target at right parietal sites. ERPs of autistic children are more responsive to stimulus features (e.g. high/rare non-target tone) and less responsive to their associations or meaningfulness (e.g. target P3). Attention-related ERPs of autistic children show signs of precocious (right dominance for P3) and delayed development (P3 not maximal at parietal sites).     

Reliability analysis of event-related brain potentials to olfactory stimuli

Olfactory event-related potentials (OERP) have been used to investigate olfactory processing in health and disease. However, the reliability of the OERP has yet to be established statistically. The present study examined test-retest reliability of the OERP over a 4-week interval. EEG was recorded from Fz, Cz, and Pz, using a single-stimulus paradigm with amyl acetate. Reliabilities for ERP component latencies and interpeak amplitudes were assessed as intraclass and Pearson product-moment correlation coefficients. Reliabilities were higher for latency than for amplitude. Highest correlation coefficients were observed for P2 latency, specifically at Cz and Pz P3 amplitude and latency exhibited high reliability at Cz and Pz. Fz demonstrated weakest correlation coefficients. The data suggest that OERP reliability is comparable to that of auditory and visual ERPs, supporting the use of OERPs in both basic research and clinical assessment.     

Effects of aging on event-related brain potentials and reaction times in an auditory oddball task

Auditory event-related potentials (ERPs) were recorded from 71 healthy individuals between 18 and 82 years of age during performance of a disjunctive reaction time task in an auditory oddball paradigm. The effects of aging on reaction times and on the latencies, amplitudes, and distributions of each of the main ERP components were examined. No significant slowing of the reaction times of the elderly subjects was observed in relation to the younger ones. The peak latencies of both the N1 and P2 components elicited by standard tones were slightly but significantly slowed with age. In the ERPs of target tones, the later, endogenous components (N2, P3, and SW) showed linear increases in latency as a function of age; the later the component, the longer the age-related delay. In general, aging was associated with less negativity (both N2 and SW) and more positivity (P3) over the anterior scalp, together with a smaller P3 and a more pronounced N2 over posterior scalp areas. Most of the effects observed in target ERPs were also evident in the difference waves derived from subtraction of the standard from the target ERPs, although the slope of the age-related latency increase of N2 was shallower and that of the P3 was steeper in the difference ERPs. These findings are discussed in relation to previous accounts of ERP changes with aging.     

Selective attention in the presence of music: an event-related potentials (ERP) study

The present study was aimed at investigating selective attention in the presence of music as expressed by ERPs. The experiments were performed with 7 subjects. A two-channel auditory frequency discrimination task (target - 1000 Hz, standard - 1550 Hz tones) in a dichotic listening environment was employed. The EEG was recorded from Fz, Cz, Pz, C3 and C4. The EOG and performance data were also collected. A smaller and delayed N1 amplitude as well as changes in the two components of the processing negativity in the presence of music were found. N2 and P3 components only delay with music was observed. The changes in the level of performance were not significant.     

老年慢性精神分裂症患者事件相关电位P300改变的意义

目的观察老年慢性精神分裂症(SCS)患者P300的变化.方法共有40例正常老人和34例SCS患者,应用丹麦仪器及两种短音刺激,完成P300检查.结果部分SCS患者波形有切迹.Fz、Cz和Pz三记录点比较无差异.N1靶潜伏期在额区右侧延长于左侧.与正常老人比较, SCS患者靶潜伏期主成分(N1-P2-N2-P3)前移(P＜0.01),靶波幅P2和P3降低(P＜0.01).非靶改变同靶刺激.结论P300可以辅助评定SCS患者的认知功能状态.     

老年慢性精神分裂症患者的听觉P300初步研究

应用丹表仪器，完成３４例患者和４０例正常老人的Ｐ３００检测。结果表明与正常老人比较，患者组靶潜伏期主成分（Ｎ１－Ｐ２－Ｎ２－Ｐ３）前移（Ｐ＜０．０１），靶波幅Ｐ２和Ｐ３降低（Ｐ＜０．０１）。非靶改变同靶刺激。提示老年慢性精神分裂症患者的听觉Ｐ３００仍有待进一步研究。     

An ERP study of age‐related differences in the central cost of interlimb coordination

The study investigated event‐related EEG potentials during concurrent performance of interlimb coordination and visual oddball tasks by younger and older adults. Coordination task difficulty was equated between age groups by allowing participants to perform the task at self‐determined frequencies. The amplitude of the P3b component of the event‐related potentials (ERPs) elicited by visual task targets showed a different pattern across midline sites (Fz, Cz, Pz) for younger and older adults. While younger adults showed a parietal maximum, P3b amplitudes in older adults did not differ across midline site, with lower amplitudes at central and parietal sites than younger adults but higher amplitude at the frontal site. Younger adults also had significantly shorter P3b latency than older adults. The results suggest that older adults may rely more on cognitive control of their movements than younger adults.     

Visual stimulus change and the orienting reaction: event-related potential evidence for a two-stage process.

In a previous study it was found that infrequent deviant visual stimuli, in a series of standards, elicited event-related potentials (ERPs) with enhanced P2-N2s and P3 amplitudes, suggesting that these parameters reflect processes related to the orienting reaction (OR). In the present study a similar oddball series was presented against the background of a second class of stimuli. With respect to the latter stimuli, subjects had to perform either a very involved (hard) or an easy task. EEG was recorded to oddball (probe) stimuli from Oz, Pz, Cz, and Fz. Analysis of average ERPs revealed that, in the easy condition, deviant probes elicited both enhanced P2-N2s and enhanced P3s, relative to the standards. In contrast, in the hard condition P2-N2, but not P3, was enhanced by stimulus change. In addition, overall P3 amplitude to probes was smaller in the hard condition (sequence-independent load effect). Analysis of single-trial ERPs (SERPs) with orthogonal polynomial trend analysis largely replicated these effects. In addition, SERP analysis also revealed a sequence-independent load effect on P2, as well as a decreasing P3 to deviant stimuli in the Easy condition, which was observed at Cz and Fz, but not at Pz or Oz. The results are interpreted as suggesting that P2-N2 and P3 reflect different stages of the OR, one of automatic and one of capacity-limited processing.     

Physiological arousal and attention during a week of continuous sleep restriction

Waking brain physiology underlying deficits from continuous sleep restriction (CSR) is not well understood. Fourteen good sleepers participated in a 21-day protocol where they slept their usual amount in a baseline week, had their time in bed restricted by 33% in a CSR week, and slept the desired amount in a recovery week. Participants slept at home, completing diaries and wearing activity monitors to verify compliance. Each day participants completed an RT task and mood and sleepiness ratings every 3 h. Laboratory assessment of electrophysiology and performance took place at the end of baseline, three times throughout the CSR week, and at the beginning of recovery. Participants reported less sleep during CSR which was confirmed by activity monitors. Correspondingly, well-being and neurobehavioural performance was impaired. Quantitative EEG analysis revealed significantly reduced arousal between the 1st and 7th days of restriction and linear effects at anterior sites (Fp2, Fz, F8, T8). At posterior sites (P4, P8), reductions occurred only later in the week between the 4th and 7th nights of restriction. Both the immediate linear decline in arousal and precipitous drop later in the week were apparent at central sites (C4, Cz). Thus, frontal regions were affected immediately, while parietal regions showed maintenance of function until restriction was more severe. The P300 ERP component showed evidence of reduced attention by the 7th day of restriction (at Pz, P4). EEG and ERPs deficits were more robust in the right-hemisphere, which may reflect greater vulnerability to sleep loss in the non-dominant hemisphere.     

Event-related potential correlates of serial-position effects during an elaborative memory test

Twenty undergraduate students participated in an elaborative learning test to evaluate the relationship between electrical brain activity and subsequently recalled and not-recalled words. Data collected from the midline (Fz, Cz, Pz) and lateral scalp sites (F3, F4, C3, C4, P3, P4) were analysed. The difference between event-related potentials (ERPs) elicited by subsequently recalled and not-recalled words, the ERP memory effect, was evaluated for each portion (primacy, plateau and recency) of the serial-position curve (SPC). We compared peak amplitudes for the P1, N1, P2, N400, P3 and frontal positive slow wave (FPSW) components. The electrophysiological data support the hypothesis that different mechanisms underlie primacy and recency effects during free recall paradigms. There was no support for the hypothesis that an association arises between memory and the FPSW when subjects utilise elaborative learning strategies. The P2 component predicted subsequent recall at the primacy portion of the SPC, and P1 predicted recall at the primacy and plateau portions of the curve. The findings suggest that the early positive components of the ERP (i.e. P1 and P2) are useful indices of the differential stimulus processing during elaborative learning which predicts later recall.     

P300 and traffic scenes: the effect of temazepam.

The present research investigated the effects of a minor tranquillizer (temazepam) on P300 in a paradigm that may be relevant for traffic behaviour. Because accident scenes have not been used previously in P300 research, Experiment 1 (n = 8) examined whether the P300 elicited by safe traffic scenes and scenes of imminent road accidents were sensitive to the probability of occurrence. Event-related potentials were recorded from C3, Cz, C4, P3, Pz and P4 within an oddball paradigm. The type of stimulus to which subjects responded (pictures of imminent accidents or safe road scenes) was crossed with the probability (0.1 or 0.5) of the relevant (to which a response was required) event. The results indicated that P300 amplitude increased with decreasing probability of the relevant stimulus and that P300 was most pronounced at Pz. Experiment 2 (n = 12) employed a drug treatment (10 mg temazepam) and a placebo treatment (100 mg Vitamin E). An oddball paradigm with a probability of the relevant stimulus of 0.1 was used and P300 was recorded from Cz, C3, C4, Pz, P3 and P4. Generally, the ingestion of temazepam decreased P300 amplitude and increased P300 latency at all sites. Reaction time, on the other hand, was not influenced by drug administration. The data demonstrate the clear effect of minor tranquillizers on the psychological processes associated with P300.     

The relationship between reaction time and response variability and somatosensory No-go potentials

We investigated the relationship between reaction time (RT) and response variability and somatosensory Go/No-go potentials. Event-related potentials following electrical stimulation of the second (Go stimulus) or fifth (No-go stimulus) digit of the left hand were recorded from 16 subjects, and Go and No-go stimuli were presented at an even probability. The subjects were instructed to respond to the Go stimuli by pushing a button with their right thumb. We analyzed the correlation between RT and the N140 and P300 components, and between the standard deviation (SD) of RT and the N140 and P300. Neither the amplitude nor latency of the No-go-N140 (N140 evoked by No-go stimuli) or the Go-N140 (N140 evoked by Go stimuli) related significantly with RT and the SD of RT. There was a significant negative correlation between RT and the amplitude of the No-go-P300 (P300 evoked by No-go stimuli) at Fz and C3, indicating that subjects with a shorter RT had a No-go-P300 of larger amplitude. The latency of the Go-P300 (P300 evoked by Go stimuli) at Pz and C3 showed a significant correlation with RT. The SD of RT was significantly correlated with the amplitudes of the No-go-P300 at C3 and Go-P300 at Pz and C4, and the latency of the No-go-P300 at Cz and Go-P300 at Fz, Cz, Pz, C3, and C4. Our results suggest that response speed and variability for the Go stimulus in Go/No-go paradigms affect No-go-related neural activity for the No-go stimulus.     

焦虑症患者VEP及AEP临床研究

目的：观察焦虑症患者听觉诱发电位(AEP)及视觉诱发电位(VEP)的特点。方法：对30例符合CCMD-Ⅱ-R诊断标准的焦虑症患者进行VEP和AEP检查，并以30例正常人作对照。结果：VEP在Fz及Cz处的P2、P3波幅明显降低，在Cz处N1潜伏期延长；AEP在Cz及P2处的P2、P3波波幅明显降低，N1潜伏期延长，在Cz处P2潜伏期延长。结论：焦虑症患者的VEP、AEP有波幅降低，潜伏期延长。     

Apolipoprotein E epsilon4 positive individuals demonstrate delayed olfactory event-related potentials

Apolipoprotein E epsilon4 positive individuals have deficits in the ability to identify and remember odors, as demonstrated by psychophysical measures of olfactory function. The purpose of the present study was to identify olfactory deficits in this population using an objective electrophysiological measure: the olfactory event-related potential (OERP). Olfactory and auditory ERPs were recorded from the Fz, Cz, and Pz electrode sites in 10 epsilon4 positive individuals and 10 age and gender-matched epsilon4 negative individuals in a single-stimulus paradigm. The results indicate: (1) individuals who are positive for the apolipoprotein E epsilon4 allele demonstrated delays (of approximately 100 ms) in the processing of olfactory information compared to those who are epsilon4 negative; (2) OERP latency is more sensitive than psychophysical measures of olfactory function; (3) delays in the cognitive P3 component of the OERP are associated with deficits in the ability to identify an odor; and (4) unlike the moderate ranges found in auditory ERP, OERP latency showed high sensitivity and specificity in classifying epsilon4 positive and negative individuals.     

The normal scalp topography of the middle latency auditory evoked potential Pa component following monaural click stimulation

Summary The scalp topography of the middle latency auditory evoked potential (MLAEP) Pa component following left and right ear click stimulation was investigated in 15 normal hearing and neurologically intact right-handed subjects. An unbiased reference was employed. The Pa component showed a broad voltage field that was recorded maximally at the Cz and Fz leads regardless of which ear was stimulated. A broad negative voltage field that occurred coincident in time with the Pa component was recorded posterior to the T3, P3, Pz, P4 and T4 electrode leads. This negative voltage field peaked in amplitude at the T5, O1, Oz, O2, and T6 electrode leads. An unexpected finding was that the peak latency of the Pa component occurred significantly earlier following stimulation of the right ear.     

EEG activity in Carmelite nuns during a mystical experience

Mystical experiences relate to a fundamental dimension of human existence. These experiences, which are characterized by a sense of union with God, are commonly reported across all cultures. To date, no electroencephalography (EEG) study has been conducted to identify the neuroelectrical correlates of such experiences. The main objective of this study was to measure EEG spectral power and coherence in 14 Carmelite nuns during a mystical experience. EEG activity was recorded from 19 scalp locations during a resting state, a control condition and a mystical condition. In the mystical condition compared to control condition, electrode sites showed greater theta power at F3, C3, P3, Fz, Cz and Pz, and greater gamma1 power was detected at T4 and P4. Higher delta/beta ratio, theta/alpha ratio and theta/beta ratio were found for several electrode sites. In addition, FP1–C3 pair of electrodes displayed greater coherence for theta band while F4–P4, F4–T6, F8–T6 and C4–P4 pairs of electrodes showed greater coherence for alpha band. These results indicate that mystical experiences are mediated by marked changes in EEG power and coherence. These changes implicate several cortical areas of the brain in both hemispheres.     

Human electroencephalographic (EEG) response to olfactory stimulation: Two experiments using the aroma of food

The present studies sought to examine the effect of olfactory stimulation on human Central Nervous System activity. In the first experiment (n=21), EEG response to the ‘synthetic' odours of chocolate, spearmint, almond, strawberry, vegetable, garlic and onion, and cumin or no odour was recorded from 19 electrodes (F3, F4, F7, F8, Fz, T3, T4, T5, T6, P3, P4, Pz, O1, O2, C3, C4, Cz) in all EEG frequencies (delta, theta, alpha, beta1 and beta2). Exposure to the odour of chocolate was associated with significant reductions in theta activity when compared with the odours of almond and cumin, with a trend towards significance when compared with no-odour control. Exposure to the odour of spearmint was associated with a significant reduction in EEG theta when compared with the no-odour control. No significant effects were observed in other frequencies. In a second experiment (n=15), EEG response to the odours of real foods (chocolate, baked beans, rotting pork) and two controls (no odour and hot water) was recorded as in Experiment 1. The odour of chocolate was associated with significantly less theta activity than was any other stimulus. It is hypothesised that the alterations in theta reflect shifts in attention or cognitive load during olfactory perception, with a reduction in theta indicating a reduced level of attention.