Age-related variations in evoked potentials to auditory stimuli in normal human subjects

A review of the evidence for P2 being an independent component process: age, sleep and modality

This article reviews the event-related potential (ERP) literature in relation to the P2 waveform of the human auditory evoked potential. Within the auditory evoked potential, a positive deflection at approximately 150-250 ms is a ubiquitous feature. Unlike other cognitive components such as N1 or the P300, remarkably little has been done to investigate the underlying neurological correlates or significance of this waveform. Indeed until recently, many researchers considered it to be an intrinsic part of the 'vertex potential' complex, involving it and the earlier N1. This review seeks to describe the evidence supportive of P2 being the result of independent processes and highlights several features, such as its persistence from wakefulness into sleep, the general consensus that unlike most other EEG phenomena it increases with age, and the fact that it can be generated using respiratory stimuli.

P300: avaliação eletrofisiológica da audição em crianças sem e com repetência escolar

OBJETIVO: Esta pesquisa foi realizada com o objetivo de comparar os valores da latência do P300 em crianças de 8 a 13 anos de idade, do sexo feminino e do sexo masculino, sem e com repetência escolar. FORMA DE ESTUDO: Estudo clínico com coorte transversal. MATERIAL E MÉTODO: Foram examinadas 60 crianças sem repetência e 43 crianças com repetência escolar. Todas as crianças foram submetidas à anamnese, audiometria tonal liminar, curva timpanométrica, reflexos auditivos contralaterais e o P300. RESULTADOS E CONCLUSÕES: Ao final desta pesquisa, concluiu-se que as crianças do grupo sem repetência escolar apresentaram valor da média aritmética da latência do P300 menor (332,25 ms), comparando-se ao grupo de crianças com repetência escolar (413,23 ms). As crianças do sexo feminino sem repetência escolar apresentaram valor da média aritmética da latência do P300 menor (328,37 ms), comparando-se às crianças do sexo masculino do mesmo grupo (337,68 ms). No grupo de crianças com repetência escolar, as crianças do sexo feminino também apresentaram valor da média aritmética da latência do P300 menor (387,50 ms), comparando-se às crianças do sexo masculino (423,19 ms). Finalmente, observou-se que os valores das médias aritméticas da latência do P300 apresentaram-se menores nas crianças do sexo feminino (328,37 ms) e do sexo masculino (337,68 ms) sem repetência escolar, comparando-se com os valores das médias aritméticas da latência do P300 nas crianças do sexo feminino (387,50 ms) e do sexo masculino (423,19 ms) com repetência escolar.

Principles and clinical applications of auditory evoked potentials in the geriatric population

Age-related changes in auditory evoked potentials are complex and complicated by the confounding effects of gender; concomitant high-frequency hearing sensitivity loss; and, in the case of event-related responses, the nature of the task used to elicit the response. There is a tendency for amplitude to decline and latency to increase, but these trends are not always clear-cut. There is also a tendency for activation patterns to move forward from parietal to frontal areas as age increases. The dichotic listening tool has revealed age-related changes in interaural and interhemispheric asymmetries. These asymmetries seem to be related to loss in the efficiency of interhemispheric transfer via the corpus callosum.

Aging: A Switch From Automatic to Controlled Processing of Sounds?

In this article, the authors show that aging differentially affects peoples' ability to automatically and voluntarily process auditory information. Young, middle-aged, and older adults matched behaviorally in an auditory discrimination task showed similar patterns of neural activity indexing the voluntary and conscious detection of deviant (i.e., target) stimuli. In contrast, a negative wave indexing automatic processing (the mismatch negativity) was elicited only in young adults for near-threshold stimuli. These results indicate that aging affects the ability to automatically register small changes in a stream of homogeneous stimuli. However, this age-related decline in automatic detection of small change in the auditor environment can be compensated for by top-down controlled processes.

Event-related brain potential changes after Choto-san administration in stroke patients with mild cognitive impairments

RATIONALE

Few drugs have been reported to be effective for the treatment of vascular dementia. Choto-san is a herbal medicine expected to be effective in this condition, but it is unclear how this drug modulates brain activities and cognitive functions. P3 event-related brain potentials (ERP) provide reliable electrophysiological indices for some aspects of cognitive functions.

OBJECTIVES

We measured P3 ERP to assess the effect of Choto-san administration on stroke patients with mild cognitive impairments.

METHODS

Choto-san was given for 12 weeks to ten chronic stroke patients. P3 ERP were recorded before and after drug administration in a modified auditory oddball paradigm including occasional novel sounds using a high-density array EEG recording system. The reproducibility of ERP was also assessed in other ten stroke patients with a 12-week interval. Cognitive functions were assessed with the Mini Mental State Examination (MMSE) and verbal fluency test.

RESULTS

Twelve-week administration of Choto-san significantly improved MMSE and verbal fluency test scores. The reproducibility of P3 latency and amplitude to target and novel sounds was excellent. P3 latency to target sounds was shortened in association with reduced reaction time to the sounds after drug administration. Furthermore, P3 amplitude to novel sounds was enlarged and its topography shifted from central to frontal sites.

CONCLUSIONS

These results indicate that Choto-san improves electrophysiological indices related to attention and decision making, in addition to neuropsychological test scores in stroke patients with mild cognitive impairments.

Increased rate of P300 latency prolongation with age in drug-naive and first episode schizophrenia

OBJECTIVE

Previous studies have found an increased rate of P300 latency prolongation with age in medicated chronic patients with schizophrenia, suggesting a pathological neurodegenerative process. In this study, we investigated whether this abnormality was identified in drug-naive and first episode patients with schizophrenia.

METHODS

P300 from auditory stimuli was recorded from 20 drug naive and first episode male patients with schizophrenia and compared with 23 age and handedness matched healthy male controls. The relationship of P300 latency and P300 amplitude to age in each group was evaluated using polynomial regression analyses.

RESULTS

Reduction of P300 amplitude was significant in drug-naive and first episode schizophrenia patients. P300 amplitude negatively correlated with age in schizophrenia patients but not in controls. Although the prolongation of P300 latency with age was observed in both groups, the regression slope for P300 latency with age was significantly steeper in patients with schizophrenia than in normal controls. Significant overall curvilinear correlations with age were also found for P300 latency and amplitude in patients with schizophrenia, and for P300 latency in normal controls.

CONCLUSIONS

The greater increase in P300 latency and reduction in P300 amplitude with age may be a primary neuropathological effect of schizophrenia.

SIGNIFICANCE

This study suggests that neurodegenerative processes are involved in the etiology of schizophrenia.

Effects of age and age-related hearing loss on the neural representation of speech cues

OBJECTIVE

To examine the effects of aging and age-related hearing loss on the perception and neural representation of a time-varying speech cue.

METHODS

P1, N1 and P2 cortical responses were recorded from younger and older normal-hearing adults, as well as older adults with age-related hearing loss. Synthetic speech tokens representing 10 ms increments along a /ba/-/pa/ voice-onset-time (VOT) continuum were used to evoke the responses. Each participant's ability to discriminate the speech tokens was also assessed.

RESULTS

Compared with younger participants, older adults with and without hearing loss had more difficulty discriminating 10 ms VOT contrasts. In addition, both older groups elicited abnormal neural response patterns. There were no significant age-related findings for P1 latency; however, N1 latencies were prolonged for both older groups in response to stimuli with increased VOT durations. Also, P2 latencies were delayed for both older groups. The presence of age-related hearing loss resulted in a significant increase in N1 amplitude in response to voiceless stimuli.

CONCLUSIONS

Aging and age-related hearing loss alter temporal response properties in the central auditory system. Because both older groups had difficulty discriminating these same speech stimuli, we conclude that some of the perceptual difficulties described by older adults might be due to age-related changes regulating excitatory and inhibitory processes.

SIGNIFICANCE

Some of the speech understanding difficulties expressed by elderly adults may be related to impaired temporal precision in the aging auditory system. This might explain why older adults frequently complain that wearing a hearing aid makes speech louder, but does not necessarily improve their ability to understand speech.

Developmental neurocircuitry of motivation in adolescence: a critical period of addiction vulnerability

OBJECTIVE

Epidemiological studies indicate that experimentation with addictive drugs and onset of addictive disorders is primarily concentrated in adolescence and young adulthood. The authors describe basic and clinical data supporting adolescent neurodevelopment as a biologically critical period of greater vulnerability for experimentation with substances and acquisition of substance use disorders.

METHOD

The authors reviewed recent literature regarding neurocircuitry underlying motivation, impulsivity, and addiction, with a focus on studies investigating adolescent neurodevelopment.

RESULTS

Adolescent neurodevelopment occurs in brain regions associated with motivation, impulsivity, and addiction. Adolescent impulsivity and/or novelty seeking as a transitional trait behavior can be explained in part by maturational changes in frontal cortical and subcortical monoaminergic systems. These developmental processes may advantageously promote learning drives for adaptation to adult roles but may also confer greater vulnerability to the addictive actions of drugs.

CONCLUSIONS

An exploration of developmental changes in neurocircuitry involved in impulse control has significant implications for understanding adolescent behavior, addiction vulnerability, and the prevention of addiction in adolescence and adulthood.

Neurodevelopment, impulsivity, and adolescent gambling

The prevalence of problem and pathological gambling in adolescence and young adulthood has been found to be two- to fourfold higher than in adulthood. Given that these high rates might predict future increases across all age groups, it is important to explore the causes of the elevated rates of problem and pathological gambling among youths. This article reviews evidence for a neurobiological basis for adolescent vulnerability to problem and pathological gambling behaviors. We propose that a common trait motif of impulsivity might underlie phenomenology of pathological gambling, commonly comorbid psychiatric disorders, and related aspects of adolescent behavior. Recent advances in understanding the brain mechanisms involved in motivation, reward, and decision-making allow a discussion of neural circuitry underlying impulsivity. Emerging data indicate that important neurodevelopmental events during adolescence occur in brain regions associated with motivation and impulsive behavior. We hypothesize that immaturity of frontal cortical and subcortical monoaminergic systems during normal neurodevelopment underlies adolescent impulsivity as a transitional trait-behavior. While these neurodevelopmental processes may confer advantage by promoting a learning drive for optimal adaptation to adult roles, they may also confer an increased vulnerability to addictive behaviors such as problem and pathological gambling. An exploration of the developmental changes in neural circuitry involved in impulse control has significant implications for understanding adolescent behaviors and treating problem and pathological gambling among youths.

Effects of hormone replacement therapy on perceptual and cognitive event-related potentials in menopausal insomnia

The influence of a combined estrogen-progestin regimen (Climodien, Lafamme) on auditory event-related potentials (ERPs) was investigated in a double-blind, placebo-controlled, comparative, randomized 3-arm trial phase (Climodien 2/3=estradiol valerate 2 mg+the progestin dienogest 3 mg, EV=estradiol valerate 2 mg, and placebo), followed by an open-label phase in which all patients received Climodien 2/2 (estradiol valerate 2 mg+dienogest 2 mg). Both the double-blind and the open-label phase lasted 2 months. ERPs were recorded from 19 EEG leads in a two-tone odd-ball paradigm in 49 patients aged between 46 and 67 yr with the diagnosis of insomnia (G 47.0) related to postmenopausal syndrome (N 95.1). Climodien reduced standard N1 and target P300 latencies as compared to placebo, while EV did not affect N1 latency but similarly reduced P300 latency. Climodien increased N1, P2 and P300 amplitudes dose-dependently, predominantly at frontal leads. Estrogen alone had only minor effects on ERP amplitudes. The shortening of standard N1 latency and enhancement of N1 and P2 amplitudes indicates a positive effect of Climodien on perceptual processing, most likely due to vigilance improvements also observed in EEG mapping. Concerning target P300, it seems that estradiol is responsible for the improvement in stimulus evaluation time, as reflected by the shortening of the peak latency, while dienogest seems to account for the improvement in cognitive information processing capacity, whereby 3 mg induced a more pronounced augmentation of P300 amplitudes than 2 mg. Based on the spatial distribution of this increase, it can be speculated that Climodien mainly affects the more frontally distributed P3a subcomponent, which is associated with attention and orientation. Furthermore, the observed changes in ERP-components are consistent with recent studies showing significant positive effects of hormone replacement therapy on cholinergic functions. Thus, Climodien seems to be of interest in preventing cognitive decline and treating cognitive disorders in postmenopausal women. Indeed, there is increasing evidence of beneficial effects of estrogen in dementia. Our present findings suggest that the estrogen effects may be augmented by dienogest.

The relationship between P3 and neuropsychological function in an adult life span sample

The relationship of P3 to age and neuropsychological performance was investigated in a sample of 71 well-functioning adults ranging in age from 21.8 to 94.7 years. ERPs were recorded while the participants performed an auditory two-stimuli oddball task in which the rare tones were to be counted. The Wechsler Abbreviated Scale of Intelligence (WASI) and the digit span subtest from the Wechsler Adult Intelligence Scale-R (WAIS-R) were administered. Regression analyses showed significant, linear effects of age on P3 latency and amplitude. Significant relationships between P3 and neuropsychological measures were found, in that P3 latency correlated moderately in predictable ways with scores on matrices, block design, and digit span. Overall, these relationships are best characterized by a linear function, but a non-linear component is involved in the relationship between P3 latency and fluid tests. Finally, a linear relationship between ERP components and age was found, while a curvilinear relationship was found between age and block design and matrices, respectively. There appears to be either partially different functions or structures underlying performance on these tests, the P3 component and performance on neuropsychological tests, or one must assume some variant of a multiplicative, as opposed to an additive, model of cognition.

Abnormalities in event-related potential and brainstem auditory evoked response in children with nocturnal enuresis

To evaluate central nervous system functioning involvement in nocturnal enuresis, P300 and N200 event-related brain potentials and brainstem auditory-evoked potentials (BAER) were assessed in a group of 35 enuretic boys aged 7-9 years. The measurements of enuretic group were compared to those of age and sex matched non-enuretics. P300 latency in the enuretic group was significantly longer than in non-enuretic group (420 ms at parietal scalp (Pz), 414 ms at central scalp (Cz) versus 386 ms at Pz, 376 ms at Cz; P < 0.01 and P < 0.01, respectively). Both enuretic and non-enuretic subjects were divided into three subgroups his age. There was no significant difference in terms of both P300 amplitude and N200 latency and N200 amplitude between non-enuretic age subgroups. But, P300 latency over central scalp in 8 years old non-enuretic subgroup was significantly longer than in 9 years old non-enuretic subgroup (P < 0.01). No significant difference was found in latency and amplitude of P300 and N200 latency between enuretic subgroups. However, N200 amplitude at Cz in 8 years old enuretic subgroup was significantly lower than both in 7 years old enuretic subgroup and in 9 years old enuretic subgroup (P < 0.01 and P < 0.01, respectively). There were significant topographical differences in latency and amplitude of P300 and in N200 latency in enuretic age subgroups, only. There was no significant difference in interpeak latencies I-III, I-V and III-V and wave latencies I, III and V of BAERs between enuretic group and non-enuretic subgroup. Longer interpeak and wave latencies of BAERs were found both in 8 years old enuretic subgroup and 8 years old non-enuretic subgroup.

CONCLUSION

Longer P300 latency in primer enuretics compare to non-enuretics is an evidence of a maturational delay of central nervous system functioning.

One-year test-retest reliability of auditory ERPs in young and old adults

The reliability of ERP measures was investigated in a sample covering the adult life span (n = 59, age 21-92). This sample was divided into a young and an old group. ERPs to an auditory two-stimuli oddball task were recorded in the sample at two occasions separated by 12-14 months (T1 and T2). The recordings of T1 were split in half, to assess within session reliability. Correlations were calculated for N1, P2 and P3 peak latency and amplitude, for average amplitude during 50 ms epochs within the defined P3-window 250-550, and for average amplitude in successive 15 ms epochs from 1 to 705 ms. The results show that amplitude measures were more reliable than the latency measures at all electrodes. Time window/epoch amplitude measures yielded reliabilities in the same range as peak amplitude. Reliabilities peaked around the conventionally studied N1, P2 and P3, and this is seen as a validation of the components. In general, the old group exhibited weaker P3 peak latency reliabilities than the young group. However, many of these differences did not reach statistical significance. Implications of the findings are discussed.

Maturational change of parallel auditory processing in school-aged children revealed by simultaneous recording of magnetic and electric cortical responses

OBJECTIVES

To elucidate the maturational change of cortical auditory processing, we analyzed simultaneously recorded auditory evoked potentials (AEPs) and magnetic fields (AEFs) in school-aged children.

METHODS

Simultaneous recording of AEP and AEF were performed in 32 healthy children of age ranging from 6 to 14 years and 10 adults. Tone bursts of 1 kHz were presented to the left and right ears alternately with 3 different within-ear stimulus onset asynchronies (SOAs) (1.6, 3.0 and 5.0 s for each ear) under attention-distracted condition.

RESULTS

All subjects showed clear N100 and N100m peaks under the longest SOA condition (5.0 s). Under the shortest SOA condition (1.6 s), 4 out of 19 subjects under 12 years (21%) failed to show the N100m component. By contrast, N250 and N250m were observed in the majority of children (29/32: 91%) while those were detected in only 4 out of 10 adults (40%). The spatial distribution of N100 in children under 9 years differed from that in older subjects, whereas the dipole orientation of N100m was constant among age groups, suggesting that radially oriented sources might make additional contribution to the generation of N100 in early childhood. N250 was significantly larger in children than in adults. The strength of N250 was suppressed with longer SOAs, whereas that of N100 was enhanced. The dipole of N250m was located around Heschl's gyrus on the superior temporal plane which was significantly medial, anterior and inferior to that of N100m.

CONCLUSIONS

Dissociation of maturational change between the tangential and radial components of N100 suggests that auditory processing at around 100 ms consists of multiple parallel pathways which mature independently. Furthermore, a negative peak at around 250 ms specifically seen in children has different generators from N100 and might represent a special auditory processing which takes an active part until acquisition of the efficient cortical networks of the adult brain.

Investigação da estabilidade inter e intra-examinador na identificação do P300 auditivo: análise de erros

Introdução: A possibilidade de correlacionar aspectos do comportamento auditivo (habilidades auditivas) a fenômenos fisiológicos observáveis (potencial cognitivo - P300) tem despertado o interesse dos profissionais interessados no estudo das disfunções auditivas. Porém, os métodos de análise do P300 e interpretação dos resultados ainda não estão padronizados e devem ser explorados e discutidos visando maior segurança para aplicação clínica e científica. Objetivo: Este estudo investigou a estabilidade na análise e interpretação do P300 auditivo seguindo um conjunto de regras (critério) pré-determinadas. Forma de estudo: Clínico prospectivo. Material e método: Traçados de P300 de crianças e adolescentes saudáveis foram analisados, em 2 momentos diferentes, seguindo as mesmas regras para a identificação e marcação das ondas N1, P2, N2 e P3. As medidas de latência da onda P300 foram submetidas a análises qualitativa e quantitativa. A análise qualitativa investigou os tipos de erros cometidos pelo examinador no uso do critério de determinação do P300 (5,9% do total de 560 medidas obtidas). A análise quantitativa investigou a variabilidade da medida da latência do P300 atribuível ao examinador. Resultado: Os resultados mostraram que não houve diferença significante entre as análises inter e intra-examinador, tendo sido encontradas correlações significantes entre as medidas de latência, indicando boa fidedignidade no teste-reteste e alta concordância entre os examinadores no modo como analisaram os traçados das ondas. Conclusão: O critério usado neste estudo demonstrou ser útil na determinação do P300, podendo ser sugerido com segurança para uso clínico e científico.

Avaliação auditiva central com BERA e P300 na Doença de Parkinson

Introdução: A Doença de Parkinson (DP) é um dos distúrbios do movimento mais encontrados na população idosa. Cursa com perda progressiva e irreversível de células da substância negra (locus niger) do mesencéfalo, o que resultará numa diminuição da produção de dopamina, levando à sintomatologia da DP. Objetivo: Averiguar a relevância de testes eletrofisiológicos, capazes de monitorar a integridade funcional das vias cerebrais, no diagnóstico e/ou prognóstico de pacientes com DP, uma vez que tais testes não-invasivos são de fácil aplicabilidade, rápidos e facilmente compreendidos por quem participa de sua aplicação. Forma de estudo: Prospectivo clínico randomizado. Material e Método: Grupo de 32 pacientes com diagnóstico prévio de DP, submetidos aos testes de potencial evocado BERA e P300. Pacientes de ambos os sexos, entre 44 e 85 anos, com tempo de doença variando de 8 meses a 21 anos de evolução. Resultados: os valores do BERA e do P300 encontrados em pacientes com DP não se mostraram diferentes dos limites de normalidade para a idade. Conclusão: Observou-se integridade das vias auditivas em pacientes portadores de DP. Uma vez que a latência do P300 aumenta de forma linear com a idade, a partir dos 45 anos, aceitando-se um aumento de 1 a 1,5ms por ano¹; observou-se integridade nas vias cerebrais que refletem a habilidade de performance cognitiva em pacientes portadores de DP sem comprometimento demencial exuberante.

Speech perception and cortical event related potentials in children with auditory neuropathy

OBJECTIVES

1) To investigate the unaided and aided speech perception abilities of children with auditory neuropathy (AN) and to compare their performance to children with sensorineural hearing loss. 2) To establish whether cortical event related potentials (ERPs) could be recorded in children with AN, and to determine the relationship between the presence of these responses and speech perception.

DESIGN

Unaided and aided speech perception assessments (PBK words), and cortical-ERP testing was carried out in a group of 18 children with AN. Data also were obtained from a cohort of age and hearing level matched children with sensorineural hearing loss.

RESULTS

The speech perception performance of the 15 children with AN able to complete a PBK-word assessment, fell into two distinct categories. The children either showed no open-set speech perception ability (7/15 cases), or performance levels similar to their sensorineural counterparts (8/15 cases). Approximately 50% of children with AN showed ERPs of normal latency, amplitude and morphology. In all cases, response presence (at normal latencies) was consistent with reasonable speech perception ability, and response absence was consistent with negligible speech perception.

CONCLUSIONS

In approximately 50% of children with auditory neuropathy, the provision of amplification results in significant open-set speech perception improvements. The results confirm the previously published reports that speech perception ability cannot be reliably estimated from the behavioral audiogram in children with AN. Obligatory ERP test results may offer a means of predicting perceptual skills in newly diagnosed youngsters as the presence of ERPs (with age-appropriate latency and morphology) was correlated with significant open set speech perception abilities and amplification benefit. The absence of the ERP in contrast, indicated profound hearing disability evidenced by profound hearing loss and/or extremely poor speech perception.

EAP recordings in ineraid patients--correlations with psychophysical measures and possible implications for patient fitting

OBJECTIVE

Objective measurements can be helpful for cochlear implant fitting of difficult populations, as for example very young children. One method, the recording of the electrically evoked compound action potential (EAP), measures the nerve recruitment in the cochlea in response to stimulation through the implant. For coding strategies implemented at a moderate stimulation rate of 250 pps per channel, useful correlations between EAP data and psychophysical data have been already found. With new systems running at higher rates, it is important to check these correlations again.

DESIGN

This study investigates the correlations between psychophysical data and EAP measures calculated from EAP amplitude growth functions. EAP data were recorded in 12 Ineraid subjects. Additionally, behavioral thresholds (THR) and maximum acceptable loudness levels (MAL) were determined for stimulation rates of 80 pps and 2,020 pps for each electrode.

RESULTS

Useful correlations between EAP data and psychophysical data were found at the low stimulation rate (80 pps). However, at the higher stimulation rate (2,020 pps) correlations were not significant. They were improved substantially, however, by introducing a factor that corrected for disparities due to temporal integration. Incorporation of this factor, which controls for the influence of the stimulation rate on the threshold, improved the correlations between EAP measures recorded at 80 pps and psychophysical MALs measured at 2,020 pps to better than r = 0.70.

CONCLUSIONS

EAP data as such can only be used to predict behavioral THRs or MCLs at low stimulation rates. To cope with temporal integration effects at higher stimulation rates, EAP data must be rate corrected. The introduction of a threshold-rate-factor is a promising way to achieve that goal. Further investigations need to be performed.

Age-related slowing in face and name recognition: evidence from event-related brain potentials

Age-related slowing in recognizing famous names and faces was investigated with event-related brain potentials (ERPs). In a group of young adults, item repetition induced early (220-340 ms) and late (400-700 ms) ERP modulations, apparently signaling the access to, respectively, domain-specific representations of faces and names and domain-general semantic knowledge about the persons. These repetition effects and other ERP components were then used as process-specific time markers in middle-aged and elderly participants. For both faces and names, the elderly participants' responses were slowed, but repetition priming in reaction times was not. The ERP latencies suggested that most of the age-related slowing occurred in the access to domain-specific representations and during response decision, whereas sensory and perceptual processing was largely spared.

Effects of maternity on auditory event-related potentials to human sound

Auditory event-related brain potentials (ERPs) were recorded in response to an emotional (a baby's cry) and a neutral (a word) stimulus in a group of mothers 2-5 days after childbirth (n = 20) and in control women (n = 18) who were not in the state of early motherhood. For each mother, her own infant's cry was recorded and used as the cry stimulus, whereas a strange baby's cry was used for control women. The word stimulus was identical for both groups. Stimuli were presented in intermittent trains in order to study the arousal responses to the first stimuli of the trains, and refractoriness of ERPs during stimulus repetition. The N100 responses were significantly larger in amplitude in mothers than in control women, not only to the emotional cry stimuli but also to the neutral word stimuli. The finding suggests a general increase in alertness and arousal in mothers, which may be necessary in enabling the mother to be continuously alert to her infant's needs. This allows good care of the infant and may be essential in building an emotional tie between the mother and her child.

Seizure frequency affects event-related potentials (P300) in epilepsy

To analyse the effect of epilepsy an P300 event-related potentials we studied 27 patients with idiopathic generalized epilepsy (IGE), 13 patients with temporal lobe epilepsy (TLE) and 60 normal controls. The prolongation of P300 latencies was highly cor related with increasing age in controls but not epileptic patients. The age-corrected P300 latency used in this study was actual P300 latency-predicted P300 latency (predicted P300 (msec)=306.20+0.79 age, P=0.001, R2=0.32). By using ANOVA analysis, the age-corrected latencies of P300 were significantly longer in TLE patients (19.72+/-47.82 msec, mean+/-SD) than in IGE patients (10.97+/-36.97 msec) and controls (0.23+/-20.28 msec). Likewise, significantly prolonged P300 latencies were seen in the epileptic patients with a seizure frequency more than 400 times (37.21+/-47.50 msec). The multivariate-adjusted odds ratio for those who had TLE was 10.97 (95% CI=3.99 - 30.14 ) in the prolonged latencies of P300 compared with that of IGE patients. The odds ratio of longer latencies of P300 was 7.43 (95% CI=2.75 - 20.08) among those who had a high seizure frequency (> or =400 times) compared with those who had a low seizure frequency. No interaction between TLE and high frequency of attacks was found. The age at onset of seizure and duration of illness was not associated with P300 latency prolongation. From the above results, we might infer that the seizure type of TLE and a high frequency of seizure are two major independent precipitate factors for abnormal latencies of P300 in the epileptic patients.

Spatiotemporal maturation of the central and lateral N1 components to tones

This paper examines maturational changes in the spatiotemporal features of central and lateral N1 components of the auditory evoked potentials (AEPs) to tone stimuli presented with a long stimulus onset asyncrony (SOA; 4200 ms) using the scalp current density (SCD) technique. A group of typically developing children ranging from 6 to 12 years of age and a group of adults were studied. Recently studies have begun to explore the topography of these components in children. These studies, however, often used rapidly presented stimuli and did not elicit observable central N1s in the younger children. Our stimuli elicited both central and lateral N1s. Peak latencies of both components decreased with age. Peak amplitude also decreased with age for the lateral N1 but not for the central N1. Consequently, the difference between the lateral N1 and the central N1 amplitudes (or the ratio of lateral N1 amplitude to central N1 amplitude) also decreased with age, dramatically altering the morphology of the elicited AEP waveforms. Topography of the lateral N1 did not change with age. The location of maximal activation for the central N1 appeared to move more medially with age but this 'apparent' movement is probably due to the decreasing impact of the partially overlapping lateral N1 component whose amplitude is significantly smaller in adults than in children.

Visual event-related potential in mild dementia of the Alzheimer's type

Visual event-related potentials (ERP) and behavioral measures were recorded during a geometrical-figure discrimination task to examine sensory processing in 10 patients with mild dementia of the Alzheimer's type (DAT) and 10 age-matched controls. No difference existed between the groups in P1, N1, and P2 potentials, which reflects the early stage of sensory processing, as well as in NA potential, which reflects pattern recognition. The patients showed reduced amplitude of P3 potential, retarded reaction time, and increased behavioral errors compared to controls. These findings suggest that the patients with mild DAT were intact in early sensory processing including pattern recognition but were selectively compromised in higher-level processing, including integration of information and memory matching, which may influence behavioral deviation.

Neurophysiological signals of working memory in normal aging

To examine how neurophysiological signals of working memory (WM) change with normal aging, we recorded EEGs from healthy groups (n=10 each) of young (mean age=21 years), middle-aged (mean=47 years), and older (mean=69 years) adults. EEGs were recorded while subjects performed easy and difficult versions of a spatial WM task. Groups were matched for IQ (mean=123; WAIS-R) and practiced in task performance. Responses slowed with age, particularly in the more difficult task. Advanced age was associated with decreased amplitude and increased latency of the parietal P300 component of the event-related potential and an increase in the amplitude of a frontal P200 component. Spectral features of the EEG also differed between groups. Younger subjects displayed an increase in the frontal midline &theta; rhythm with increased task difficulty, a result not observed in older subjects. Age-related changes were also observed in the task-related alpha signal, the amplitude of which decreases as more neurons become involved in task-related processing. Young adults showed a decrease in alpha power with increased task difficulty over parietal regions but not over frontal regions. Middle-aged and older adults showed decreased alpha power with increased task difficulty over both frontal and parietal regions. This suggests that normal aging may be associated with changes in the fronto-parietal networks involved with spatial WM processes. Younger subjects appear to use a strategy that relies on parietal areas involved with spatial processing, whereas older subjects appear to use a strategy that relies more on frontal areas.

O potencial evocado cognitivo em adultos normais

O objetivo deste estudo foi avaliar os resultados do potencial cognitivo auditivo em um grupo de adultos normais. Os testes foram realizados registrando-se a resposta evocada em Cz e Fz. Os dados obtidos foram analisados estatisticamente. São descritas neste trabalho as latências médias de N1, P2, P2AP, N2 e P3, a amplitude de P3, bem como o desvio padrão destas variáveis. Comentam-se algumas dificuldades encontradas na interpretação do teste destacando as limitações de seu uso clínico.

Impairment of an event-related potential correlate of memory in schizophrenia: effects of immediate and delayed word repetition

OBJECTIVE

We investigated the nature of the memory impairment in schizophrenia using an event-related potential (ERP).

METHODS

Visual ERPs were recorded while 20 schizophrenics and 20 controls performed semantic categorization tasks with incidental word repetitions. Participants responded to occasional target words. Half of the non-target words were repeated immediately after initial presentation (lag 0) or after 5 intervening words (lag 5).

RESULTS

In both groups, ERPs to words at lag 0 were more positive than those to non-repeated words, though this positive-going effect was attenuated in the schizophrenics, especially around 400-500 ms. The effect at lag 5 was smaller and shorter than that at lag 0 but was comparable between groups. Attenuation of the N400 peak occurred for word repetition at lag 0 in controls but not in schizophrenics, whereas a peak increment in the late positive component induced by word repetition at both lags was observed in both groups.

CONCLUSIONS

Findings indicate that patients with schizophrenia have a deficit in a brain process modulating ERP correlates of memory, when words are repeated immediately. This deficit might be related to an abnormal N400 priming effect in schizophrenia.

Age-related changes of evoked potentials

The aim of this review is to analyse the current state of our knowledge on evoked potentials (EPs) in ageing and to report some conclusions on the relation between EPs and elder age. Evoked potentials provide a measure of the function of sensory systems that change during the different stages of life. Each sensory system has its own time of maturation. The individuation of the exact period of life when brain ageing starts is difficult to define. Normally, the amplitude of EPs decreases, and their latency increases from adult to elder life. Many authors speculate that these modifications might depend on neuronal loss, changes in cell membrane, composition or senile plaques present in older patients, but there is no evidence that these changes might modify the cerebral function in healthy aged individuals. This review emphasises some incongruities present in different studies confirmed by daily neurophysiologic practice. Different techniques as event-related desynchronization (ERD), contingent negative variation (CNV) and Bereitschaftspotential, are available to study central neuronal changes in normal and pathologic ageing.

Cognitive functions of adolescent childhood cancer survivors assessed by event-related potentials

BACKGROUND

Neurophysiological methods were applied to examine subtle central nervous system (CNS) adverse effects for adolescent childhood cancer survivors. We analyzed auditory event-related potentials (ERPs)-P300 and MMN/P3a complex-to find out whether there was impaired attention orientation in asymptomatic cancer survivors, and whether these ERP methods could be used as more objective tools in detecting those survivors who might need academic testing. Previous clinical studies of P300 have focused on leukemia survivors. MMN for cancer survivors has not been reported.

PROCEDURE

The subjects were survivors of childhood leukemia (n=11) and solid tumors (n=8), as well as healthy controls (n=10). The mean age was 15.5 years for survivors and 15.9 years for controls. Pure sine-wave tones (500 and 553 Hz, 100 ms) were used as stimuli in an oddball paradigm. The ERPs to frequency change were measured. MMN recordings were performed in a passive non-attended situation where the subject was watching a voiceless video cartoon. P300 was produced thereafter, but in an active attend situation, by the same auditory oddball paradigm as MMN.

RESULTS

A significant difference was detected between the groups for the latency of P300 at electrodes Cz (P = 0.03) and C4 (P = 0.05). The cancer survivors had prolonged P300 latencies as an indication of prolonged short-term memory processing. The area and latency parameters of MMN did not differ significantly between the study groups, but in cancer survivors, the area and the mean amplitude of the subsequent P3a wave were diminished. The results indicate that the discrimination process was not as easy for the survivors as for the controls. However, it seems that in cancer survivors the basic mechanism starting attention shift to novel stimuli is not impaired.

CONCLUSIONS

These results indicate that it is important to carefully evaluate the proper methods for the teaching of children who are survivors of malignancies. The auditory information may not always lead to the best possible learning results.

The neurophysiological meaning of auditory P300 in subtypes of schizophrenia

Event-related potentials are a powerful tool to investigate the real-time course of brain electrical mass activation during cognitive processing. In several psychiatric disorders, differences compared to healthy subjects have been reliably described. The specificity and the pathophysiological meaning of the findings were unclear in most studies, however. This review summarizes methodological aspects and findings, in healthy subjects and psychiatric patients, of investigations based on the auditory oddball paradigm, which evokes the P300 component of event-related potentials. Recent convergent results from P300 and brain imaging studies allowed the interpretation of P300 findings in psychotic disorders in terms of different specific and meaningful neurophysiological disturbances. Namely, core schizophrenia is characterized by a left-temporal dysfunction associated with deficits in verbal processing. Acute remitting schizophrenia-like psychoses (cycloid psychosis, ICD-10 F23), on the other hand, show normal hemispheric balance but consistent signs of cerebral hyperarousal. Recent studies further indicate that the drive for action of manic patients does not rely on over-excitation but rather on frontal disinhibition. The findings may help to further advance the understandings and sub-grouping of functional psychoses based on pathophysiological mechanisms.

The development of auditory evoked dipole source activity from childhood to adulthood

OBJECTIVE

Multi-channel recordings show that observed developmental changes of late auditory evoked potentials (LAEP) depend on the location of the scalp electrode. These findings suggest that different LAEP generators have a distinct developmental course. The goal of this study was to investigate the maturational process of cortical LAEP generators.

METHODS

Eighty-seven healthy children and adolescents with normal hearing, ages 5-16 years, and 21 adults, ages 20-30 years, participated in the study. Pure tone LAEP were recorded from 21 derivations. Dipole source analysis was performed by means of brain electric source analysis (BESA). Peak latencies and amplitudes of dipole source activity were estimated.

RESULTS

While the number, location, and direction of dipole sources were similar in children and adults, the course of their activity differed greatly. The latencies shortened and the amplitudes decreased during development. In adolescence a new component appeared in the activity of the tangential dipole, which reflects the generators in the supra-temporal plane. The variability of parameters was greater in children than in adults.

CONCLUSIONS

Since the dipole source activity of LAEP in childhood differs considerably from that in adulthood, dipole source analysis could be a useful tool for studying both normal and disturbed maturation of the auditory perceptual function.

Speech-evoked neurophysiologic responses in children with learning problems: development and behavioral correlates of perception

OBJECTIVES

To evaluate the maturational progression of speech-evoked P1/N1/N2 cortical responses over the life span, determine whether responses are distinctive in clinical populations experiencing learning problems and elucidate the functional significance of these responses.

DESIGN

The P1/N1/N2 complex was measured in 150 normal subjects (5 to 78 yr) and 86 subjects with learning problems (LP) (8 to 15 yr) to a synthetic CV syllable. Analyses included description and comparison of the developmental time course in both groups and evaluation of the relationship between P1/N1/N2 and children's performance on speech discrimination tasks and standardized learning measures.

RESULTS

Findings revealed significant changes in waveform morphology, latency and amplitude as a function of age. Maturational patterns in the group of children with learning problems did not differ from the normal group. P1/N1/N2 parameters were significantly correlated with standardized tests of Spelling, Auditory Processing and Listening Comprehension in the LP group. Moreover, there was a predictive relationship between Auditory Processing and N2 latency.

CONCLUSIONS

The P1/N1/N2 complex changes throughout life from school-age to old age. The developmental sequence throughout the school-age years is similar in normal and LP children. Thus, differences in the rate of P1/Nl/N2 latency and amplitude development do not appear to be distinctive in these two populations. The relationship between P1/N1/N2 parameters and standardized measures of learning (particularly between Auditory Processing and N2 latency) provides new information about the role of these responses in hearing and highlights the potential value in characterizing auditory processing deficits.

Emotion/cognition-coupling in word recognition memory of depressive patients: an event-related potential study

Depressive patients show deficits in memory functions. However, the underlying mechanisms remain unclear. Experiments with a special emphasis on the link between emotion and cognition appear challenging. The aim of this study is to investigate the influence of the emotional content of words on memory in non-medicated depressive patients (n=11) compared with a control group (n=11) utilizing event-related brain potentials (ERPs). In a continuous word recognition paradigm brain responses to repeated items are characterized by more positive waveforms of ERPs. This recognition effect ('old/new effect') has been shown to be sensitive to parameters relevant for memory processing. For the purpose of this ERP experiment visually presented words were classified into three different categories of emotional content. The ERPs for the correctly detected 'old' (repeated) words showed an increased positivity beginning approximately 250 ms post-stimulus, concurring with a good recognition performance. In addition, old/new effect and behavioral data were sensitive to words' different emotional connotations in the control group. In contrast, the depressive patients performed worse and showed no significant old/new effect. Nevertheless, their recognition performance was also enhanced by the emotional content. Furthermore, a differential effect of the emotional content on frontal ERPs was found between groups. In contrast to the control group, a reduced old/new effect indicates a reduced working memory capacity in the moderately depressed patients. This is suggested to be partially due to changes of the emotion/cognition coupling related to ruminations with preferably negative emotional connotation. However, the emotional content also affects recognition performance in the depressive patients.

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.

Frontal P300 decrements, alcohol dependence, and antisocial personality disorder

BACKGROUND

The purpose of this study was to examine the independent and interactive effects of alcohol dependence, antisocial personality disorder (ASPD), and age on brain function.

METHODS

P300 event-related potentials (ERPs) were recorded from 393 alcohol-dependent and 170 non-alcohol-dependent adults while they performed a visual oddball task. The two subject groups were further subdivided based upon age and the presence/absence of ASPD.

RESULTS

Alcohol dependence was associated with a significant P300 amplitude decrement at anterior electrode sites only. Antisocial personality disorder was also associated with reduced P300 amplitudes at anterior electrode sites; however, the effects were only significant among subjects 30 years of age or younger. To validate this association between ASPD and P300 amplitude a correlational analysis was performed; the correlation between anterior P300 amplitude and the total number of childhood conduct disorder and adult ASPD symptoms was significant.

CONCLUSIONS

The P300 amplitude decrement found at anterior electrode sites among subjects with ASPD is consistent with the results of numerous ERP, neuroimaging, or neuropsychologic studies of anterior brain function. Our study is unique in suggesting that the effects of ASPD on anterior brain function are best detected during early adulthood. The study also suggests that the detrimental neurophysiologic effects of alcohol dependence predominantly involve the anterior brain.

Olfactory event-related potentials and aging: normative data

Unlike the clinical usages of evoked potentials (e.g. brain stem auditory evoked potentials for the assessment of auditory function), normative data for the olfactory event-related potential (OERP) have been unavailable. The principal objective was to establish normative data across the human life span for OERPs with a given set of parameters. Participants were 140 persons from seven age groups (16-19, 20-29, 30-39, 40-49, 50-59, 60-69 and 70-79 years of age), with equal numbers of males and females, screened for nasal health and dementia. The odor stimulus was amyl acetate, presented at nasal temperature in a humidified airstream delivered by an air-dilution olfactometer at a constant flow rate, using a 60-s inter-stimulus interval. OERPs were recorded at Fz, Cz, and Pz electrode sites, amplified and averaged over trials. Amplitudes of the N1/P2 and P3 and latencies of the P2 and P3 were analyzed. Processing speed decreased at a constant rate over decades for the sensory (P2 latency) as well as cognitive (P3 latency) components. Decline in amplitude over decades was also apparent. Normative data will be useful in research on olfactory function and in clinical assessment of olfactory functional status.

P300 reduction and prolongation with illness duration in schizophrenia

BACKGROUND

The P300 component of the auditory event-related potential (ERP) is both reduced in amplitude and delayed in schizophrenia. P300 is prolonged and, less consistently, reduced with normal aging. Additional latency delays are observed in neurodegenerative disorders. We asked whether P300 is reduced and delayed with longer illness duration in schizophrenia, consistent with a neurodegenerative process.

METHODS

P300 amplitude and latency were recorded to infrequent auditory target stimuli from 35 men with schizophrenia (DSM-III-R) and 26 control men. Effects of current age, age of onset, and duration of illness on P300 were assessed using regression analysis.

RESULTS

P300 amplitude showed no age-related decrease in either group; however, among schizophrenic participants, P300 amplitude correlated positively with onset age and negatively with illness duration. P300 latency correlated positively with age in schizophrenic participants and also tended to increase with age in controls. Slopes of the latency-age relationships were significantly greater in schizophrenic participants than in control participants. Latency also correlated positively with illness duration but showed no relationship to onset age.

CONCLUSIONS

P300 amplitude and latency are reduced and delayed with longer illness duration in schizophrenia, consistent with a progressive pathophysiological process. Reduced P300 amplitude may also be a marker of an early onset variant of schizophrenia.

Tracking the development of the N1 from age 3 to adulthood: an examination of speech and non-speech stimuli

OBJECTIVES

To examine developmental changes in the N1a, N1b and N1c evoked by a tone and a speech consonant (/da/).

METHODS

Subjects (n=70 for tones; n=69 for /da/) were grouped into 2 year intervals (age 3-16) and adults. They listened to a tone (2 kHz; 36 ms; 77 dB SL; ISI=600 ms; n=346) or a speech consonant /da/ (female voice recording; 7 ms VOT; 212 ms; 72 dB SL; ISI=600 ms; n=349) while watching a Disney((R)) screensaver. EEG was recorded from 26 electrodes referenced to Cz. An averaged reference was computed off-line. Amplitude and latency data were analyzed with repeated-measures ANOVAs for agexelectrode, and agexN1 component, respectively.

RESULTS

Left hemisphere N1a was mature before age 3 whereas the right hemisphere N1a matured around 7-8 years. The vertex N1b showed a parietal distribution which shifted anteriorly with age. The N1c showed age- and stimulus-related changes. The N1c measured over the left hemisphere matured earlier than the N1c over the right hemisphere. The N1c to /da/ matured earlier than that to tones.

CONCLUSIONS

Auditory processing undergoes steady and subtle developmental changes. These changes follow different maturational patterns depending on the type of stimuli. The evidence suggests earlier development of the left hemisphere and earlier development of the generators underlying speech processing.

Sex effects on rate of change of P300 latency with age

OBJECTIVE

Recent MRI evidence suggests that neuroanatomic structures may change more rapidly with age in males compared with females. Sex differences for P300 latency were tested to determine whether similar results might appear for P300 latency, a neurophysiological measure sensitive to age and neurodegenerative processes.

METHODS

Auditory event related potentials (ERPs) were recorded using an auditory 'oddball' to elicit the N200 and P300 components. Forty-two male and 42 female healthy normal subjects (age range 15-85 years) were entered in this study. Both linear and curvilinear correlations of N200 and P300 latency/amplitude with age were tested.

RESULTS

The slope of P300 latency on age for males was steeper than for females at Pz in subjects who were 30 years of age and older. N200 and P300 latencies were inversely correlated with age in young adult males (<30 years old).

CONCLUSIONS

Males may experience more rapid change of P300 latency, but not amplitude, than females in middle to old age. Further research is required to determine whether those change reflects neural pathophysiology, or is mediated by such factors as neuroanatomic differences, body temperature, or mild auditory deficits.

Event-related brain potentials in response to novel sounds in dementia

OBJECTIVE

Non-target, deviant stimuli generate an earlier latency, front-central novelty P3, whereas correctly detected task-relevant stimuli generate a parietal maximal target P3. We examined whether the P3 component to novel stimuli is affected by dementing processes, and is therefore useful for distinguishing Alzheimer's type dementia (AD) from vascular dementia (VD).

METHODS

We recorded ERPs to task-relevant stimuli (target P3) and novel task-irrelevant stimuli (novelty P3) in an auditory oddball task in AD (n = 16), VD (n = 16), and age-matched controls (n = 18). The amplitude, latency, and scalp topography of target and novelty P3 were compared among 3 groups using ANOVA. The relationship between P3 measures and intelligence scores were evaluated by correlation analysis.

RESULTS

The amplitude, latency and scalp topography of the target P3 were comparably affected by both AD and VD. However, the amplitude of the novelty P3 was markedly reduced in VD, but not in AD, and the scalp topographics were different in the 3 groups. The amplitude was maximal at frontal sites in controls, at central sites in AD, and at parietal sites in VD. The target P3 latency was prolonged in both AD and VD, whereas the novelty P3 latency was only prolonged in VD. AD was discriminated satisfactorily from VD by using the novelty amplitude at Cz and the ratio of the amplitudes at Fz and Pz as independent variables.

CONCLUSIONS

These results suggest that the response to novel stimuli is differentially affected by dementia with degenerative and vascular etiology.

Auditory P300 development from an active, passive and single-tone paradigms

The P300 (P3) event-related brain potential (ERP) was elicited with auditory stimuli in order to compare three different tasks and to assess the effect of ageing from childhood to adolescence. Seventy-two subjects, ranging in age from 6 to 14 divided into three age groups, were selected for this study. In the active task, the subject was required to discriminate between standard and target tones (oddball); in the passive task condition, the subject did not respond to either the standard or target stimulus; in the single task, a target but not a standard tone stimulus was presented and the subject was required to react to the target tone. Our results show that the passive sequence and the single-tone paradigm yielded similar P300 waveform to those obtained from the active task. Separate age/ERP component latency and amplitude linear regression were computed. A significant negative correlation between age and P3 latency was found. The event-related potential P3 wave shows consistent and significant age-related changes in human cerebral function, regardless of the methodology used. These findings suggest that the passive and single-tone paradigms can be a useful way to elicit the P3 ERP component.

Normal aging and odor intensity effects on the olfactory event-related potential

Olfactory event-related potentials (OERPs) were recorded in 14 young and 14 older adults, with odor strength of isoamyl acetate manipulated to assess olfactory stimulus intensity. Young participants produced significantly larger N1/P2, N2/P3 amplitudes and shorter N1, P2 and N2 latencies than older participants. Medium- and high-odor concentrations elicited significantly shorter P2 and N2 latencies than the lowest concentration for both age groups. Odor concentration appears to affect the speed of olfactory stimulus information processing regardless of age.

Visual P300 latency predicts treatment response to modafinil in patients with narcolepsy

OBJECTIVE

To evaluate the hypothesis that visual P300 latency (VL) predicts treatment response to modafinil (a new wake-promoting agent) in patients with narcolepsy.

METHODS

DESIGN

Comparison of responders and non-responders in a double-blind randomized placebo-controlled trial.

SETTING

Private practice referral sleep disorders center.

PATIENTS

Twenty one patients with narcolepsy (ages 17-65 years).

INTERVENTIONS

Auditory and visual P300 testing using 31 evenly spaced scalp electrodes, and baseline polysomnograms and objective and subjective tests of daytime sleepiness, followed by modafinil treatment for 9 weeks. Polysomnograms and tests of sleepiness were then repeated.

MAIN OUTCOME MEASURE

The Maintenance of Wakefulness Test (MWT). Response defined as a final MWT > 7.3min (normative sample mean - 3 SD), plus an increase > 1SD based on normative sample (3.6 min) over baseline MWT.

RESULTS

Non-responders had longer age-adjusted 31-electrode mean VL (448.4 ms vs. 410.8 ms, P = 0.024), and larger auditory P300 amplitude, with no topographical P300 differences. Non-responders and responders did not differ on any other baseline clinical variable. Using a cut-off of 0.5 SE from normal regression constant, shorter age-adjusted VL predicted modafinil response, with specificity of 0.71 and sensitivity of 0.86.

CONCLUSIONS

VL predicts treatment response to modafinil in patients with narcolepsy.

Age-related changes in the brain electrical correlates of response control

OBJECTIVES

Previously, a quantification method was validated which, on a single case basis, allows one to assess the NoGo-anteriorisation (NGA) of the positive area of long latency event-related potential (ERP) fields elicited by a cued continuous performance test (CPT). The NGA was shown to be associated with right frontal activity. The present study was conducted to investigate the influence of age and gender on this topographical index of cognitive response control.

METHODS

Thirty-seven healthy controls were investigated with 21-channel recordings during the execution of a cued CPT, and ERPs of the Go and NoGo condition were obtained. The location of the positive area centroids in a P300 range and the NGA were calculated and related to age and gender by means of correlation analysis and t tests.

RESULTS

The centroid locations of the brain electrical activity during the NoGo- and the Go-condition of the CPT, were both located in more anterior brain regions with increasing age (P<0.01 and P<0.1, respectively); the NGA, however, was not correlated with the subject's age. Latencies and amplitudes of the Go- and NoGo-centroids were not correlated with age. No gender differences were found.

CONCLUSIONS

The study showed that age is a source of variance for the positive area centroid locations in this Go-NoGo paradigm. The NGA, on the other hand, was robust to age and gender effects. The result is interpreted as a sign of an increasing contribution of frontal brain areas to cognitive response control during lifespan. The finding is consistent with the age-related topographical changes described in acoustic oddball-paradigms and, therefore, appears to be a general topographical ERP effect.

Comparison of endogenous event-related potentials in attend and non-attend conditions: latency changes with normal aging

OBJECTIVE

Endogenous event-related potential (ERP) components have been observed under both attend and non-attend conditions, but it appears that at least some of the attend and non-attend components are functionally and topographically distinct. Also, under active task conditions, motivational and attentional variations may modulate the amplitude of the ERP. These various effects of attention on the ERP can complicate comparisons of the ERPs of normal subjects with the ERPs of clinical subjects, who may have reduced attentional capabilities. The experiment reported here sought to develop a non-task paradigm that reliably produces the same ERP components typically seen under task conditions.

METHODS

Using rare auditory stimuli that were discrepant from the frequent stimuli both in frequency and intensity, stimuli were presented under non-attend instructions and under instruction to count the rare stimuli. The ERPs in these two conditions were compared with ERPs in a standard oddball paradigm which used stimulus parameters comparable to those of most previous experiments on ERPs in aging. Fifty subjects, ranging in age from 20 to 77, participated.

RESULTS

The ERPs to the DISCREPANT oddball stimuli under non-task conditions were similar in scalp distribution to the ERPs to the same stimuli in the ATTEND condition and to the ERPs in the STANDARD/ATTEND condition. Furthermore, there were no significant differences in the age-related increase in ERP latencies among the DISCREPANT/IGNORE, the DISCREPANT/ATTEND, and the STANDARD/ATTEND conditions.

CONCLUSION

The results indicate that increases in ERP latencies with aging can be assessed in the absence of task requirements, and that the paradigm described here may prove useful in investigating cognitive processing speed in clinical populations.

Effects of age on working memory: an event-related potential study

The effects of age on behavioural performance and event-related potentials recorded during a working memory task using digits presented either acoustically or visually, were studied in 37 healthy subjects with an age range from 19 to 71 years. With increasing age, psychological tests showed a progressive decline in visuo-spatial performance and both auditory and visual reaction times (RT) increased. There were multiple and varying effects of age on both early and late ERP components. For both auditory and visual responses, increasing age was associated with an increased amplitude of early positive waves (auditory P100 and visual P145) and, in the oldest subjects, significant delays of the major late positive waves. Other changes were modality-specific with a progressive shift of amplitude maxima in the early negative waves of the visual ERPs (from an N190 peak maximal at Pz in the young, to an N270 peak maximal at Cz in the older subjects) and an altered amplitude distribution of late potentials (after the P250 wave) in the auditory responses. The age at which ERP changes occurred varied-significant latency prolongations and increases in the amplitude of the major frontal positive waves occurred only in the oldest subjects, whereas a redistribution of late auditory ERPs also occurred in the intermediate age group. There was no interaction between age and increasing memory load, suggesting that there is no specific effect of age on memory scanning in this age range for these levels of task difficulty. Thus, although performance in working memory was apparently unaffected by age, as judged by behavioural parameters (apart from slowing of the reaction times), ERPs revealed significant changes in both early and late electrical brain processes associated with working memory as age increases. These changes which were not symptomatically manifest and only revealed by sensitive tests, may represent subtle dysfunction of working memory (or associated processes) which does not prevent the successful completion of our task, compensatory mechanisms (which are essential to successfully complete the task), or a combination of both age-induced dysfunction and compensatory mechanisms.

The Effects of Age on Late Components of the ERP and Reaction Time

The effects of age on late component (N100, P200, N200, and P300) event-related potentials (ERP) and reaction time (RT) were investigated in 50 normal subjects, 18 to 70 years of age. A conventional auditory oddball paradigm was employed. An equal number of subjects, as well as an equal number of males and females, were examined in each decade. There were no significant associations found between ERP amplitude and age. A significant positive correlation was found between age and N200/P300 latency. There were no significant effects of age on RT in the overall group. However, females had slower RT and decreased P200 and N200 amplitude as compared with males. Moreover, males had significant correlations between N200 latency and RT, whereas females showed significant correlations between P300 amplitude and RT. ERP/RT effects should be further explicated between gender, as well as across age.