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

Age effects on central nervous system activity reflected in the olfactory event-related potential. Evidence for decline in middle age

A series of studies in this laboratory using the olfactory event-related potential (OERP) have examined the underlying central nervous system activity associated with age-related changes in olfactory functioning. Early (sensory) components of the OERP showed reduced amplitude and longer latency in elderly subjects, with larger effects in males. Amplitudes are already decreased in middle age. The late cognitive component, P3, showed a longer latency as well as a decreased amplitude in the elderly, with effect sizes for age significantly larger for the late component than for the early components. We report here the significantly longer latency, particularly for the P3, in middle-aged persons, suggesting age-related slowing of olfactory information processing as early as the 50s. Results suggest that the elderly brain, and indeed, the middle-aged brain shows smaller responses to odors, is less able to allocate attentional resources and slows in its olfactory cognitive processing. The OERP is a potent reflection of these changes.

Improvement predictors in obsessive-compulsive disorder. An event-related potential study

The treatment of patients with obsessive-compulsive disorder gives variable and unpredictable results. Numerous clinical features have been investigated as potential predictors of medication response but without consistent results. Preliminary findings have shown that some impairments of pre-treatment event-related potentials (ERPs) could be associated with future treatment outcome (Morault et al., 1997). The present study aimed to confirm the relationships between ERPs and treatment efficacy with larger sample sizes. ERP components were elicited during a verbal auditory 'oddball' paradigm and were recorded in 21 unmedicated patients compared to 21 control subjects. After a pharmacological treatment, the disorder improved in 12 patients. Pre-treatment ERP data were retrospectively compared between treatment responders, non-responders and control subjects. Patients who were to respond favorably to treatment had significantly reduced N2 amplitude and shorter N2 and P3 latencies compared to non-responders and control subjects. In contrast, no difference was shown between non-responders and control subjects. Our findings provide evidence for abnormalities of ERPs which could be considered as potential predictors of treatment response in patients with OCD. These results need to be tested in a prospective protocol.

Electrophysiological changes in children with learning and attentional abnormalities as a function of age: event-related potentials to an "oddball" paradigm

This study investigated age-related electrophysiological differences between children diagnosed with Learning Disabilities (LD), Attention Deficit Hyperactivity Disorder (ADHD), LD-ADHD and Conduct Disorder, using Event-Related Potentials recorded during a two-tone discrimination test. Although age-related (N1 and N2 amplitude), as well as diagnostic group-related (P3 latency and amplitude) ERP changes were found, there was no significant interaction between the diagnostic groups and age grouping. We conclude that: 1) Electrophysiological abnormalities in LD and ADHD do not significantly change with age during childhood. This study does not, therefore, support a hypothesis of age-related brain abnormalities in LD and ADHD. 2) Significant group differences for P3 latency and amplitude were found between normal children and the LD groups (LD and LD-ADHD), but not between normal children and those with ADHD alone, suggesting that main correlates of P3 abnormalities in these children are "processing" and not attentional problems.

EEG theta and frontal alpha oscillations during auditory processing change with aging

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

Aging-related changes in processing of non-target and target stimuli during an auditory oddball task

A total of 73 healthy subjects aged 20-86 years performed an auditory 'oddball' task. The age-dependence of N1 and P2 elicited by non-target stimuli, of N2 and P3 elicited by target stimuli and of N2a and N2b components (target minus non-target difference waves) was investigated across 20 electrodes to detect any aging-related changes in the psychophysiological processing of such stimuli during the task. Aging-related differences in within-task changes in non-target ERPs were also investigated. In non-target ERPs, it was found that P2 amplitude at Fz increased linearly with advancing age and the analysis of within-task changes indicated that P2 amplitude decreased during the task in young subjects at Pz, but remained unchanged in middle-aged and elderly subjects. These results suggest the existence of aging-related inhibitory deficits that may hinder the disengagement of attentional resources from irrelevant stimuli during the task. In the target ERPs, the latencies of N2 and P3 increased linearly at Fz, Cz and Pz. The increases in N2 were mainly due to linear increases in N2b latency at Fz, Cz and Pz, indicating that the aging-related slowing begins at controlled memory comparison of non-target/target stimuli. P3 amplitude presented a more uniform scalp distribution in middle-aged and in elderly subjects and pnly decreased significantly with advancing age in men, which may explain the divergent results in the literature on aging-related changes of P3 amplitude.

Event-related potentials (P300) in primary headache in childhood and adolescence

There is strong evidence for a loss of habituation during cognitive processing in migraine as measured by P300 and contingent negative variation in adults. Event-related potentials evoked by an oddball paradigm have not yet been studied in children and adolescents suffering from different primary headache types. We recorded visually evoked event-related potentials (two consecutive trials, 200 stimuli each) in 48 children and adolescents suffering from migraine without or with aura, from episodic tension-type headache, and from ergotamine-induced headache and analyzed the latencies, amplitudes, and reaction times. No statistically significant differences were noted between all headache types and healthy controls analyzing the averaged parameters for the whole measurement. However, a highly significant loss of cortical habituation as measured by P300 amplitude and latency could be observed in migraine without and with aura by analyzing the first and the second trial of measurement separately. This phenomenon increased with age and could not be seen in healthy controls, or patients with tension-type headache or ergotamine-induced headache. Our data suggest a specific cognitive processing in migraine even in children and adolescents. Measurement of the habituation effect in P300 latency and amplitude provides a specific method to differentiate between primary headache types in childhood and adolescence.

ERPs, semantic processing and age

ERPs (N400, LPC and CNV) were elicited in two sets of subjects grouped according to age (young vs. elderly) using a word-pair category matching paradigm. Each prime consisted of a Japanese noun (constructed from two to four characters of the Hiragana) followed by one Chinese character (Kanji) as the target, this latter representing one of five semantic categories. There were two equally probable target conditions: match or mismatch. Each target was preceded by a prime, either belonging to, or not belonging to, the same semantic category. The subjects were required to respond with a specified button press to the given target according to the condition. We found RTs to be longer in the elderly subjects and under the mismatch condition. N400 amplitude was reduced in the elderly subjects under the mismatch condition and there was no difference between match and mismatch response, which were similar in amplitude to that under match condition for the young subjects. In addition, the CNV amplitudes were larger in the elderly subjects. These results suggested that functional changes in semantic processing through aging (larger semantic networks and diffuse semantic activation) were the cause of this N400 reduction, attributing a subsidiary role to attentional disturbance. We also discuss the importance of taking age-related changes into consideration in clinical studies.

Differential effects of normal aging on sources of standard N1, target N1 and target P300 auditory event-related brain potentials revealed by low resolution electromagnetic tomography (LORETA)

The P300 event-related potential (ERP) is considered to be closely related to cognitive processes. In normal aging, P300 scalp latencies increase, parietal P300 scalp amplitudes decrease and the scalp potential field shifts to a relatively more frontal distribution. Based on ERPs recorded in 172 normal healthy subjects aged between 20 and 88 years in an auditory oddball paradigm, the effects of age on the electrical activity in the brain corresponding to N1 and P300 components were estimated by means of low resolution electromagnetic tomography (LORETA). This distributed approach directly computes a unique 3-dimensional electrical source distribution by assuming that neighbouring neurons are simultaneously and synchronously active. N1 LORETA generators, located predominantly in both auditory cortices and also symmetrically in prefrontal areas, increased with advancing age for standards but remained stable for targets. P300 LORETA generators, located symmetrically in the prefrontal cortex, in the parieto-occipital junction and in the inferior parietal cortex (supramarginal gyrus) and medially in the superior parietal cortex, were differentially affected by age. While age did not affect parieto-occipital sources, superior parietal and right prefrontal sources decreased pronouncedly. Thus, in normal aging, P300 current density decreased in regions were a fronto-parietal network for sustained attention was localized.

Age and stage dependency of P300 latency alterations in non-demented Parkinson's disease patients without therapy

Acoustic P300 was recorded from Fz, Cz and Pz by means of an 'odd-ball' paradigm in 44 non-demented de novo Parkinson's disease patients (PD) or PD patients under treatment withdrawal, and in 31 age-matched normal subjects, to evaluate whether a P300 latency increase was present in PD patients. The influence of age and disease stage on latency was successively verified by subgrouping PD patients according to different age ('young' and 'old') and disease stage ('early' or 'advanced'). PD patient data were compared to data of normal subjects subgrouped into 'young' and 'old' or, to eliminate the age-dependent shift of latency, this latter was adjusted to 60 years in all the examined subjects. A significant increase of latency has been found in Fz and Cz in the 'old' group of PD patients (n = 23) but not in the 'young' group (n = 21) utilising both methods. Moreover, a significant latency increase was also present in Fz and Cz in the group of 'advanced' PD patients (n = 8), but not in the group of 'early' PD patients (n = 36) utilising age-adjusted measurements. When the 'early' PD patient group was divided into 'young' (n = 20) and 'old' (n = 16), the 'early old' group displayed significantly increased latencies in Fz compared with normal subjects. Abnormal P300 latencies were observed, at least in one electrode, by analysing the raw data, in 5.0% of the 'early young', 43.7% of the 'early old' and up to 62.7% of the 'advanced' patients. Fz represented the site in which abnormal P300 latencies were most often observed. Moreover, in the total group of PD patients, the P300 delay was significant only on the frontal (Fz) site when compared with normal subjects. The reported findings were interpreted as if PD produces a sort of 'accelerated effect of age' on the cognitive functions, presumably produced by a mechanism different from that producing motor impairment since no clear correlation could be detected between P300 latency and motor score. The frontal impairment of P300 is in line with previous neuropsychological findings obtained in these patients. Considering that about 30% of PD patients develop dementia during their disease progression, a border-line or abnormal P300 latency observed at disease onset may represent a predictive marker of this evolution.

P300 clinical utility and control of variability

The P300 event-related brain potential (ERP) has been used to study normal aging as well as patient populations with a variety of neurologic and psychiatric disorders. The P300 has demonstrated reasonable success as a means to assess disturbances in cognitive function, and its clinical utility has been enhanced by the identification of factors that contribute to the variability of ERP measurements. In this article, the neuropsychological theory of P300 is reviewed, ways in which this brain potential can be used as a measure of cognitive efficiency are defined, and methodologic issues that must be considered for successful clinical ERP applications are outlined. This approach is then extended to specific recommendations concerning the technical and practical aspects of P300 recording, so that a well-defined normative database can be developed for evaluating individual patients. When appropriate procedures are used, the P300 can provide a highly useful means to quantify human cognitive capability.

P300 latency and age: a quadratic regression explains their relationship from age 5 to 85

The use of P300 latency to demonstrate cognitive dysfunction is important. P300 latency decreases with age in children and then increases with age in adults. It has been debated whether the relationship between age and P300 latency is linear or quadratic. If the relationship is linear, then at least two regression equations in opposite directions are required for children and for adults, and perhaps a third for the elderly. This is a report of data from an age-stratified sample of 97 normal individuals ages 5 through 85. The best regression equation is quadratic, using log transformed age, with accurate projection of 95% confidence limits for P300 latency by age. This quadratic regression simplifies the application of P300 latency across the life-span in the management of disorders affecting cognition, such as Traumatic Brain Injury, Attention Deficit-Hyperactivity Disorder, and Obstructive Sleep Apnea.

Developmental changes in P1 and N1 central auditory responses elicited by consonant-vowel syllables

Normal maturation and functioning of the central auditory system affects the development of speech perception and oral language capabilities. This study examined maturation of central auditory pathways as reflected by age-related changes in the P1/N1 components of the auditory evoked potential (AEP). A synthesized consonant-vowel syllable (ba) was used to elicit cortical AEPs in 86 normal children ranging in age from 6 to 15 years and ten normal adults. Distinct age-related changes were observed in the morphology of the AEP waveform. The adult response consists of a prominent negativity (N1) at about 100 ms, preceded by a smaller P1 component at about 50 ms. In contrast, the child response is characterized by a large P1 response at about 100 ms. This wave decreases significantly in latency and amplitude up to about 20 years of age. In children, P1 is followed by a broad negativity at about 200 ms which we term N1b. Many subjects (especially older children) also show an earlier negativity (N1a). Both N1a and N1b latencies decrease significantly with age. Amplitudes of N1a and N1b do not show significant age-related changes. All children have the N1b; however, the frequency of occurrence of N1a increases with age. Data indicate that the child P1 develops systematically into the adult response; however, the relationship of N1a and N1b to the adult N1 is unclear. These results indicate that maturational changes in the central auditory system are complex and extend well into the second decade of life.

Development and topography of auditory event-related potentials (ERPs): mismatch and processing negativity in individuals 8-22 years of age

How do event-related potentials (ERPs) reflecting auditory processing develop across adolescence? Such development was described for five ERP components in four groups of 11 healthy participants with mean ages of 10, 14, 17, and 21 years. Data from 19 sites during diffuse (passive) and focused (discrimination) attention in a three-tone oddball were analyzed to see how ERP loci varied with age for tone type, attention condition, and for four types of difference waves reflecting nontarget and target comparisons. Age interacted with site for most components. P1 loci sensitive to rare tones moved posteriorly and N1 loci lost their right bias in early puberty. The P2 loci did not move anterior to Cz until adulthood. N2 amplitude, sensitive to attention condition, developed a frontal focus by 17 years. Right-biased P3 loci moved to the midline with focused attention similarly in all age groups. Difference waves developed in three stages: In 10-year-old participants, early deflections (< 150 ms) were diffusely distributed; in midadolescent participants, the main frontal negative component (150-300 ms) became well formed and lost an earlier right bias; and for participants 17 years old and older, the late positive complex developed a right bias in target-derived waves. Latency decreases for early frontal components were marked in participants 10-14 years old and for later posterior components in participants 14-17 years old. Major developments appeared at the onset of adolescence in early stimulus selection processes and during adolescence in the differential use of this information (N2- and P3-like latencies).

Developmental changes in the event-related EEG theta response and P300

Event-related potentials (ERPs) from 50 children (6-11 years) and 10 adults were elicited by auditory passive, and by rare target and frequent non-target stimuli, and analyzed in the time and frequency domains. The latency of the maximal theta response (or the theta frequency component of the ERP) was evaluated with respect to age and scalp topography effects. The major findings were: (1) The latency of the maximal theta response decreased with increasing age in children, although for each stimulus type and location adults had shorter latencies than the children. (2) The developmental time course of latency reduction depended on the electrode location, with the most prominent reduction occurring at 8 years at Cz, and no differences between children groups obtained for the frontal site. (3) Maximal theta response latency was strongly associated with the latency of the late parietal P400-700 (P3b) component in children. The results suggest that the developmental latency decrease in P300 processes originate from a decrease in the preceding theta-related processes and may reflect a speeding of cognitive stimulus evaluation.

Estimate of physiological variability of peak latency in single sweep P300

Among single sweep records of event-related potentials (ERPs), the peak latency of P300, which is one of the most prominent positive peaks in the ERP obtained in the oddball paradigm, may vary depending on the conditions of the subject. In the analysis of characteristics of the variability in the peak latency, it is important to know to what extent the variability of the measured peak latency (measured variability) is actually caused by physiological factors (physiological variability). In our previous study, a method was developed for judging whether the physiological variability really exists or not, and if it does exist, the developed method extracts the physiological variability from the measured variability based on a limited number of single sweep records. In the present study, based on the P300 waveforms which were detected by blinded visual inspection of the ERP data obtained by an auditory oddball paradigm from 12 healthy adults, the physiological variability was shown to exist with a confidence level of 95% for all subjects. Furthermore, its interval estimate was calculated by subtracting noise variability from the measured variability with a confidence level of 80%, and it was found to range from 17 to 57 ms for all subjects.

Age-related changes in cognitive ERPs of attenuation

This investigation explored developmental changes in passive and effortful components of ERPs associated with a visual attention task in children, adolescents, and adults. The task was a 'go-go' version of a continuous performance task, coupled with a passive attending phase in which the subjects merely watched the stimuli of the task. The three age groups featured a constellation of ERP components that shared the same general morphological appearance and distribution, but differences were seen with respect to latencies and amplitudes. Consistent with other studies, there was an inverse relationship with respect to age and peak latencies of the major passive and effortful components. With respect to peak amplitudes, however, the most impressive changes with age were observed in the passive processing components. For example, the P150 and P250 components presented greater amplitudes in children, whereas the N200 component presented its greatest amplitude in adults. While passive in the sense that their appearances were independent of the 'decision-making' process, these components were found to be upwardly adjustable by effort. The late positive component was found to be a combination of a passive P350 and an effortful P450. The P350 component was judged to be largely passive in character as it was well developed in subjects of all age groups when passively attending to the visual stimuli. There was no marked amplitude difference between the child and adult P450 components, but the components peaked in amplitude later in the children. Finally, the children's ERPs featured a distinct frontal negativity (FN) that was present in the Passive phase, but greatly enhanced during the Effortful phase. This study, as have many others, showed that there are reliable developmental changes in the components of visual ERPs. Therefore, the characteristics of the various components of cognitive ERPs may be effective markers of neurodevelopmental status, especially of those neuronal systems vital to attentional processing and effort regulation.

Olfactory event-related potentials: older males demonstrate the greatest deficits

Olfactory event-related potentials (OERPs) were recorded monopolarly at the Fz, Cz, and Pz electrode sites in 16 young adults (8M/8F) and 16 older adults (8M/8F) with inter-stimulus intervals (ISI) of 45, 60 and 90 s using amyl acetate as the odorant stimulus. N1, P2, and N2 peak amplitudes and latencies were measured. Young participants demonstrated significantly shorter peak latencies than older participants. Older males demonstrated significantly smaller peak amplitudes than the other participant groups. Peak amplitudes also increased with longer ISIs for older males. The OERP is compared to traditional olfactory psychophysical testing.

The impact of age-related changes in event-related P300 potentials on detecting early cognitive dysfunction

Event-related P300 potentials that closely reflect cognitive brain functions show significant age-related latency prolongations. This aging-P300 interaction can best be approximated by third-order polynomial regressions. To delineate the clinical impact this special kind of regression function may have on detecting early cognitive dysfunction, we applied visual P300 potential data of healthy subjects (n = 344; age range, 18-98 years) to nondemented patients with either (i) chronic liver disease (n = 104; age range, 19-74 years) or (ii) cerebral arteriosclerosis (n = 80; age range, 38-80 years). As compared with linear regressions, third-order polynomial regressions for the age-related changes in P300 potential latencies showed a smaller latency increase during middle age, with an accelerating latency prolongation from age 60 onward. In patients with liver cirrhosis, third-order polynomial regressions yielded a rate of abnormal P300 potential latencies exceeding that of linear regressions absolutely by 17-21%, and relatively by 67-71%. Although the rate of P300 abnormalities was much lower in the CAD patients with either regression model, the relative increase in P300 abnormalities due to third-order polynomial regressions was 40-112.5%. In conclusion, normal data for the latencies of P300 potentials based on third-order polynomial regressions result in a higher sensitivity of P300 potentials for detecting early cognitive dysfunction. This gain in diagnostically important information is not offset by a loss in specificity, and may depend on the kind as well as stage of the disease, the age distribution of the patients and the degree of the P300 potential abnormalities.

Cognitive potentials in children with learning disabilities

A group of 16 children, aged from 8 to 14 years, with learning disabilities, were studied by means of a series of conventional and sensitized audiological tests, including recording of the late cognitive electrical responses (P300). They had no otolaryngological or neurological complaints but expressive language disorders (difficulties in speaking and/or writing), receptive language disorders (difficulties in reading and text comprehension), and lack of concentration and/or restlessness. Their audiograms, speech discrimination and immitance tests were normal. The P300 responses, as compared with those found in 20 normal controls within the same age group, occurred at significantly longer latency periods.

Temporal prominence of auditory evoked potentials (N1 wave) in 4-8-year-old children

Cortical auditory evoked potentials (N1 wave) were studied in 24 adults (12 men, 12 women) and 20 children (12 boys, 8 girls; age: 4-8 years). In adults, this wave was recorded with maximal amplitude at frontocentral sites, peaking at about 100 ms poststimulation, whereas in children the auditory response displayed maximal amplitude at the midtemporal sites, with a positive wave at about 100 ms and a large negative wave at approximately 170 ms. Moreover, the modulatory effects of intensity on N1 amplitude were prominent at frontocentral sites in adults and at temporal sites in children. Frontocentral negative response was also recorded in children but was smaller in amplitude and longer in peak latency (around 140 ms) than in adults; responses were of greater amplitude at the frontal site than at the vertex before 6 years of age, whereas the reverse was more often found after this age. These data suggest great differences with age in the neural generators contributing to auditory evoked potentials recorded in the N1 latency range.

Age-related prefrontal alterations during auditory memory

Event-related potentials were recorded from young and elderly subjects while they performed a modified auditory Sternberg memory task. Aging was associated with a decrease in frontal activation, suggesting that prefrontal alterations may be central to age-related impairments in auditory working memory. Young subjects showed significant serial position effects electrophysiologically, while elderly subjects showed no recency effects for P3 latency and no serial position effects for N4 and SFN amplitude. This finding, in combination with increased false alarm rates in the elderly, suggest that the two group of subjects employed different cortico-limbic circuits to perform the task.

Steady-state auditory evoked responses to pulsed frequency modulations in children

This study investigated steady-state auditory evoked responses to pulsed frequency modulations (FM) of a continuous tone in normal children ranging in age from 6 to 12 years. We examined variations in response amplitude and phase as a function of age, recording site, and FM pulse duration. The surface topography of these evoked potentials suggested a relatively broad distribution with maximal responses observed at frontal electrode sites, smaller responses from parietal leads and the smallest responses were evident at the temporal lobe placements. Response parameters varied significantly as a function of pulse duration. Fifty milliseconds pulses elicited responses that were on average 20% larger than 100 ms FM pulses. Mean phase differences suggested that responses to the 100 ms pulses also lagged behind responses to the 50 ms pulses by the equivalent of 20 ms. There were no significant age-related variations in response amplitude. Phase varied with age only in response to the 50 ms FM pulses. The findings indicated that steady-state responses are sensitive to temporal parameters of frequency change present in pulsed modulations. The possibility is raised that this paradigm may be clinically useful in detecting dysfunction of specialized auditory mechanisms involved in frequency modulation analysis.

The association between P300 and age from preadolescence to early adulthood

The present study examined the latency and amplitude of P300 in a large sample of subjects between 11 and 21 years old. The P300 components of the visual event-related potential showed consistent and significant age-related changes. Peak amplitude was found to diminish with increasing age, whereas peak latency decreased. Our data indicate that a linear relationship best explains the association between age and P300 amplitude and latency. The changes in P300 amplitude and latency across the different ages are likely to reflect developmental changes in mental processing that are not due to a decrease in general cortical reactivity with increasing age or the result of subject noncompliance.

Age-related changes in child and adolescent event-related potential component morphology, amplitude and latency to standard and target stimuli in an auditory oddball task

Previous studies of auditory event-related potentials (ERPs) to an oddball task in children and adolescents focus on responses to target stimuli and provide little detail of age-related changes to standard stimuli. In this study, age-related changes in behavioural responding and ERP component morphology, amplitude and latency to standard and target stimuli were examined. Auditory ERPs to an oddball task were recorded from the midline sites (Fz, Cz and Pz) of 50 subjects aged 8 to 17 years 11 months. Behavioural results indicate a decrease in reaction time and errors of commission with age. To standard tones, N2 amplitude and N1 latency showed a linear decrease with age while an increase with age was found for P2 amplitude. For target tones, N1 and N2 amplitude and N1, N2 and P3 latency showed a linear decrease with age and P2 and P3 amplitude showed a linear increase with age. Age-related changes in the morphology of the ERP elicited by standard tones (especially the N2 and P2 components), as well as concurrent morphological changes in standard and target tones, are discussed.

Ceruletide improves event-related potential indicators of cognitive processing in young but not in elderly humans

The effect of intravenously administered ceruletide, a cholecystokinin (CCK) analogue, on neurophysiologic signs of stimulus processing was tested in 16 young (19-28 years) and 16 aged (70-86 years) healthy subjects. Placebo or 2.5 micrograms ceruletide was infused within 30 minutes according to a double-blind within-subject crossover design. Thereafter, auditory event-related brain potential (AERP) responses to stimuli of an "oddball" task (including the random presentation of frequent standard tones and rare target tones) were recorded. Amplitudes of the P2, P3, and SW components of the AERP were reduced in aged subjects (p < 0.05, p < 0.001, and p < 0.01, respectively), and latencies (from stimulus onset) of the N2 and P3 components were prolonged (p < 0.05 and p < 0.01, respectively). Together, these changes indicate impaired cognitive processing capabilities in aged compared with young subjects. Ceruletide enhanced P3 and also the subsequent slow-wave (SW) component that occurs 500 to 700 ms poststimulus in young subjects (p < 0.05 and p < 0.001, respectively). The peptide did not at all affect AERPs in the elderly subjects. Results demonstrate the capability of ceruletide after systemic administration to enhance central nervous system indicators of cognitive processing such as P3 and SW in young subjects. However, despite the clear effect of the CCK analogue in young subjects, it remained ineffective in the group of aged subjects and, thus, failed to compensate for the decline in AERP signs of working memory functioning in the elderly subjects.

An ERP developmental study of repetition priming by auditory novel stimuli

Event-related potentials were recorded from participants 5-7, 9-11, 14-16, and 22-28 years old during an auditory novelty oddball task. In this task, stimuli about which the participant is not instructed (i.e., novel or uncategorized) typically elicit a more frontally oriented P3 scalp topography (novelty P3). In contrast, stimuli to which the participant must respond (i.e., target or precategorized) elicit a P3 with a more posterior scalp topography. Repetition of identical novel stimuli led to a similar reduction in novelty P3 amplitude for all age groups. Moreover, with repetition the shift in scalp topography of the novelty P3 to a more parietally oriented distribution was similar in children and adults. A second component, the P3(2) (assumed to be an analog of the P3b), exhibited a repetition priming effect in both the adults and the youngest children. The fact that age-related differences induced by novel repetition were small and not systematic indicates that the processing of novel information is similar across a wide age range.

Multichannel auditory event-related brain potentials: effects of normal aging on the scalp distribution of N1, P2, N2 and P300 latencies and amplitudes

Event-related potentials (ERPs) were recorded at 17 leads in an auditory oddball paradigm in 172 normal healthy subjects aged between 20 and 88 years. With advancing age, N1 latency increased parietally (0.12 ms/year), P2 latency increased frontally (0.34 ms/ year) and N2 and P300 latencies increased all over the scalp (0.37 ms/year for N2; 0.92 ms/year for P300). P300 latency/age relationship was curvilinear with accelerated latency increase in elderlies (0.35 ms/year for subjects below 60 years; versus 2.03 ms/year for subjects above 60 years). With advancing age, standard tone ERP amplitudes were enhanced frontally (0.03 microV/year for N1; 0.07 microV/year for P2), N2 amplitudes were attenuated frontally (0.11 microV/year) and P300 amplitudes were attenuated parietally (0.15 microV/year). Multichannel analysis demonstrated that ERP latencies and amplitudes depended on electrode location. Standard tone ERP latencies changed their topographic distribution with age, whereas target tone ERP latencies did not. While N1 amplitude distribution was unaffected by age, P2, N2 and P300 topography changed significantly with age: P2 topography to a more frontal distribution and increased 'global field power'; N2 topography to a more parietal distribution: P300 topography to a more frontal and more equipotential distribution Thus, specific age effects on different ERP components were confirmed.

The effect of stimulus-response incompatibility on P3 latency depends on the task but not on age

To help identify the loci of age-related slowing of cognitive processing, the effects of stimulus-response (S-R) incompatibility and stimulus degradation on P3 latency and reaction time (RT) were assessed in ten young and ten elderly women. Subjects saw the words right, left, RIGHT, or LEFT in tasks which required responses to (1) the meaning of the word (WORD) (2) its case (CASE) and (3) both (CASE/WORD). Each task was tested with regular and degraded stimuli. On half the trials, the stimulus and response were incompatible. Although RTs and P3s of elderly subjects were slower, especially RTs in CASE/WORD, stimulus degradation and S-R incompatibility did not differentially affect the two groups, suggesting that cognitive processing of older subjects is not especially prolonged in perceptual and response-related stages. For both groups RTs and P3s were task dependent and were prolonged by degradation and S-R incompatibility. Incompatibility delayed RTs in WORD and CASE/WORD but P3s in WORD only. Thus, young and elderly subjects show qualitatively similar psychophysiological and behavioral indicators of processing speed.

Topographical analyses of attention disorders of childhood

Cognitive ERPs and EEG spectral differences were compared in three groups of children: nonreferred controls, those with a dominant hyperactivity/impulsivity factor (ADHD-Im), and those with a dominant inattentive factor (ADHD-Ia). The results from the ERP analyses indicated that the P250, P350, and P500 components differed between the groups. The most marked differences were seen with respect to the amplitude of the P500 components. In addition, the topographic foci of the P500 components for the CON and ADHD-Im groups were symmetrical, but the ADHD-Ia group featured P250 and P350 components that were biased away from the right hemisphere. Nevertheless, the P500 was found to be an effective discriminator between the groups. The combined spectral and ERP results suggest that the attention disordered children have difficulty adjusting their level of physiological arousal, and are defective with respect to controlled (or effortful) processing.

Topography of auditory evoked long-latency potentials in children with severe language impairment: the T complex

Topographic maps of the late auditory evoked potentials (AEP) were studied in a group of 20 children, aged 9-15 years, with severe language impairment (LI) and an age-matched control (C) group of 20 normal children. The stimulus was a pure tone at 500 Hz with a duration of 100 ms and a rise and fall time of 20 ms. The intensity was 75 dB HL. Six test sequences of 50 stimuli at an interval of 1.0 s were presented to the left and right ear separately. Grand average maps of all the children in the LI and the C group, separately, were calculated and showed a bilateral negativity over the temporal areas, corresponding to the negative peak of the T complex (Tb) at a latency of about 150 ms. The amplitudes were larger contralateral to the stimulated ear in both groups. A difference map between the two grand average maps showed topographic differences at temporal sites. However, the T complex could not be identified in 7 LI children and 1 C child. In the remaining subjects with a T complex the topographic pattern was similar in the two groups but with lower amplitudes and significantly longer latencies in the LI group. The presence and latency of the positive peak of the T complex (Ta) was also examined, showing significant between-group differences. The value of Tb, in diagnosing language impairment, was tested by means of a scoring system and with statistical mapping. The diagnostic sensitivity of Tb latency, amplitude and topography in selecting the LI children was 90% to 40% with a specificity of 80% to 95%. The results indicate slower and deviating processing in the central auditory pathways of LI children. The variation in results between children, with missing components or prolonged latencies in the majority, but not all, of the LI children, may be explained by different pathophysiological causes of their language impairment. The more pronounced deviations of the T complex compared with the vertex-recorded NI may also indicate a specific role of the T complex-related cortical activity in language impairment.

Topography of auditory evoked long-latency potentials in children with severe language impairment: the P2 and N2 components

OBJECTIVE

To establish objective neurophysiological correlates of a central auditory processing disorder in impaired language development. The study focused on the differences in latency, amplitude, and topography of the auditory evoked long-latency components, P2 and N2, and the potential diagnostic value of these parameters.

DESIGN

Topographic maps of the late auditory evoked potentials (AEPs) were obtained in a group of 20 children, aged 9 to 15 yr, with severe language impairment (LI) and in a control (C) group of 20 normal children. Stimulus was a pure tone at 500 Hz with a duration of 100 msec and a rise and fall time of 20 msec. The intensity was 75 dB HL. Six test sequences of 50 stimuli an interval of 1.0 sec were presented to the left and to the right ear separately. The AEPs were recorded and analyzed with the Bio-Logic Brain Atlas III program.

RESULTS

In the topographic maps, a focus of positive potential corresponding to P2 (FP2) and a focus of negative potential corresponding to N2 (FN2) were seen in the majority of children, with a similar distribution in the two groups. The latencies of P2 and N2 were significantly longer in the LI group than in the C group, P2 showing the most pronounced difference. The amplitudes of FP2 and FN2 were lower in the LI group. The diagnostic value of the P2 and N2 latency, amplitude, and topography in identifying the LI subjects, was estimated by means of a scoring system. With all three parameters together, the sensitivity was calculated to be 80% and the specificity 80%. Statistical mapping of the latency interval of 135 to 305 msec showed z maps with regions of > or = 3 SD in 14 subjects in the LI group and eight subjects in the C group.

CONCLUSIONS

The deviations in the LI group indicate slower processing in central auditory pathways rather than differences in location and orientation of generators. The deviating topography seen in some LI subjects may reflect the various sites and extent of cerebral dysfunction. The results also support the idea of different generators for the P2 and N2 components. Topographic evaluation of long-latency AEPs may become a diagnostic tool in language disorders. The scoring system is a potential model in the establishment of individual diagnostic variables.

Meta-analysis of P300 normative aging studies

The theoretical and empirical backgrounds for the utility of the P300 event-related potential (ERP) as a measure of cognitive aging are summarized. P300 latency data from 32 different normative aging studies are then reviewed and assessed with meta-analytic procedures. Evaluation of moderator variables indicates that sample characteristics, stimulus factors, and task conditions contribute significantly to the "normal" change in peak latency that occurs with aging. These findings are critiqued in the context of previous reports, and implications are outlined for future applications of ERPs to normative aging. It is concluded that P300 latency can provide useful information about cognitive aging but that specific variables must be considered to obtain more precise results.

Topographical analysis of adolescent affective disorders

This study evaluated the EEG spectral content and the components of the cognitive ERPs evoked by a visual sustained-selective attention task from adolescents diagnosed as having an affective disorder and those who did not (nonreferred controls, CON) to determine if there were different electrophysiological profiles associated with major subtypes of affective disorders; i.e., Dysthymic Disorder (DysD) and Cyclothymic Disorder (CycD). Distinctive ERP and EEG profiles were found to be associated with the DysD and CycD groups. While both groups of depressives presented diminished P3b amplitudes, the DysD group showed a relatively greater suppression over the right temporal regions, whereas the CycD group exhibited relatively greater suppression over the left temporal region. In addition, there were differences with respect to the earlier components associated with information processing. For instance, the P1 was found deficient in the DysD group as compared to the other groups, whereas the N2 component was deficient in the CycD groups as compared to CON and DysD groups. In contrast to these amplitude differences, no significant latency differences were seen with respect to any component elicited by this paradigm. With respect to the EEG spectra, the CON group showed greater relative power in the Beta range than either the CycD or the DysD group, with the depressives featuring more midline frontal Theta activity. Characteristically, both depressant groups showed a greater anterior distribution of Alpha activity. In addition, the foci of the various spectral bands for the DysD subjects were shifted away from the right hemisphere as was the case for the P3b. Overall, the profiles suggested that those who fit the diagnostic classification of DysD have deficit function in right post-Rolandic zones, along with anomalous frontal function. It was also suggested that there may be a core disturbance of physiological arousal in unipolar depression. The CycD subjects, on the other hand, featured no hemispheric bias with respect to the P3b components or spectral foci, but did not show similar features of being cortically "hypoaroused" so that actively depressed adolescent CycD subjects did share certain physiological features with unipolar subjects.

Topography of auditory and visual P300 in normal adults

Auditory and visual P300 recordings were performed on 40 normal, right-handed individuals from age 16 through 65, using 31 evenly spaced scalp electrodes. Amplitude at the P300 peak and latency to this peak at each electrode site were measured. Age was significantly correlated with the 31-electrode mean for auditory and visual P300 amplitudes and auditory and visual P300 latencies. The younger age group (16-40) had shorter auditory and visual P300 latencies than the older group (41-65). Visual P300 amplitudes were of an overall larger magnitude than auditory P300 amplitudes. There were no other differences in P300 amplitudes or latencies by gender, modality, or side of scalp, and no significant topographical differences in P300 amplitudes or latencies by gender, age-group, modality, or side of scalp. Radial current density maps on group-averaged auditory and visual P300 waveforms at the group mean P300 latency at Cz, showed a right centroparietal sink surrounded by sources. This suggests a major right centroparietal P300 generator. Except for the change in P300 amplitudes with age, and the direction of the change in P300 latencies with age, these data on adults are similar to our previous description of P300 topography in normal children. Description of the normal topography of the P300, and demonstration of the lack of topographic differences by gender, age group, modality, or side of scalp, may facilitate the meaningful examination of P300 topography in cognitive disorders. Such an examination might lead to better diagnostic tools and more appropriate treatment of cognitive disorders in adults.

Topography of auditory evoked cortical potentials in children with severe language impairment: the N1 component

Topographic maps of late auditory evoked potentials (AEPs) were obtained in a group of 20 children, aged 9-15 years, with severe language impairment (LI) and an age-matched control (C) group of 20 normal children. The study was focused on differences in the latency, amplitude and topography of the N1 component between the two groups and the potential diagnostic value of these variables. The stimulus was a pure tone at 500 Hz with a duration of 100 msec and a rise and fall time of 20 msec. The intensity was 75 dB HL. Six test sequences of 50 stimuli at an interval of 1.0 sec were presented to the left and right ear separately. The AEPs were recorded and analyzed with the Bio-Logic Brain Atlas III program. In the topographic maps a focus corresponding to N1 (FN1) was seen in 15 subjects after left-ear stimulation and in 17 subjects after right-ear stimulation in the LI group. In the C group FN1 was identified in all 20 subjects after left-ear stimulation and in 19 subjects after right-ear stimulation. The position of FN1 was in front of the interaural line and with a dominance on the side contralateral to the ear stimulated in both groups. Among the subjects with an FN1, 6 in the LI group and 4 in the C group had deviating topography. Non-focal maps were seen in 5 LI subjects and 1 C subject. The latencies of N1 were longer in the LI group and there was no decrease in latency with age. There were no differences in FN1 amplitudes between groups. The prolonged latencies in the LI subjects compared to the C subjects may be explained by a slower processing in central auditory pathways and the lack of decrease in latencies with age in the LI subjects might indicate that the disturbance persists and is not a pure delay of maturation. The diagnostic sensitivity of N1 latency, amplitude and topography, in selecting the LI subjects, was 40% with a specificity of 90%. Statistical mapping of a time epoch of 70-140 msec and corresponding to FN1 in the map showed regions of > or = 3 S.D. in 10 LI and 2 C subjects, which corresponds to a sensitivity of 50% and a specificity of 90%. The variability of results within the LI group may reflect different pathophysiological factors underlying the language impairment. In conclusion, topographic evaluation of auditory long-latency potentials may become a diagnostic tool in speech and language disorders.

Electrocortical responses to ecologically relevant visual stimuli among professional drivers with and without cardiovascular disease

Electrocortical responses were assessed using two simulated aspects of visual signals encountered in traffic: the Glare Pressor Test (GPT) and Event-Related Potential Avoidance Task (ERPAT) among four groups of male professional drivers: 12 with ischemic heart disease (IHD), 12 hypertensives, 10 borderline hypertensives, 34 who were apparently healthy and 23 nonprofessional driver healthy control subjects. The blood pressure (BP) responses immediately after the ERPAT were also measured. There was a significant between groups effect for the amplitude of the target N2 component in the ERPAT (p = 0.02), with the lowest means among the drivers with IHD and the highest among those with hypertension. Drivers with IHD also showed the highest diastolic BP reactivity to the ERPAT. Significantly more than the expected number of drivers with IHD failed to recover alpha activity after the first glare impulse of the GPT. Professional drivers who failed to recover baseline levels of alpha activity after the GPT showed a significantly smaller N2 amplitude compared to those who recovered (p = 0.01). There was a positive correlation between abundance of alpha activity at rest with P300 amplitude (p = 0.02). An inverse relation was found between number of work hours behind the wheel and the amplitude of the target P300 (p = 0.04). Results are interpreted in light of recent advances concerning integrative mechanisms of defence versus vigilance response patterns. The findings in this study justify further applications of these psychophysiologic methods to assess the relationship between simulated signals of the work environment and mechanisms of cardiac risk in this occupational group.

Age, color processing and meaningfulness: an event-related potential study

The effects of aging on event-related potentials (ERPs) and reaction time (RT) performance were investigated in a task that combined color discrimination and lexical decision. The stimuli were either words or non-words, presented either in the relevant or in the irrelevant color. RT responses were required to words in the relevant color. Stimuli appeared in the relevant color elicited attention-related ERP components (anterior positivity, selection negativity and N2b). The latency values of the attention-related ERP components and the RT were longer in the older group, indicating the slowing down of attentional processes in the elderly. In the older group the late positivity to stimuli in the relevant color was absent over the posterior locations. Unlike in the older group, in the younger subjects the words appeared in the irrelevant color elicited a central negative wave in the 400 ms range. These results are considered as a capacity limitation in the elderly in processing of the stimulus characteristics beyond to the actual stimulus-response contingencies.

Event-related potential P3 change in mild Parkinson's disease

The purpose was to determine if unmedicated, mildly affected patients with Parkinson's disease exhibited abnormality in the P3 component of the event-related potential, and whether such abnormality differed between younger and older patients. The study evaluated 10 younger (mean age = 43.7 years) and 10 older (mean age = 64.4 years) unmedicated patient volunteers diagnosed with idiopathic PD during the past 4 years and equal numbers of age-, gender-, and education-matched controls. The auditory oddball P3 was recorded, and P3 peak amplitude, peak latency, and the component score derived from principal components analysis were analysed. Neuropsychological measures focusing on frontal lobe and memory function were obtained. Although patients did not show neuropsychological deficits, they had significantly enlarged P3 amplitude measured at Cz (p < 0.01) or Pz (p < 0.01). The P3 amplitude abnormality among patients was not affected by age. Patient P3 latency was not prolonged. The results indicate that P3 amplitude may more sensitive than neuropsychological measures for detecting subtle brain dysfunction occurring early in PD. This measure has possible utility for detecting and tracking early disease. It is hypothesized that enlarged P3 amplitude reflects abnormality in use of attentional resources to compensate for brain dysfunction.

ERP responses to target and nontarget visual stimuli in alcoholics from VA and community treatment programs

This study had three aims: 1) to cross-validate previously reported findings that sober alcoholics compared to nonalcoholic peers have reduced ERP P300 amplitudes to visual target stimuli at the Pz electrode; 2) to test the hypothesis that alcoholics from VA Hospital treatment programs will manifest more ERP indications of brain dysfunction than peer alcoholics from community treatment programs (paralleling our neuropsychological findings in these samples); and 3) to explore differences among the groups in ERP responses to the little-studied nontarget stimuli. Nineteen VA alcoholics, 32 community alcoholics, and 24 peer community controls were given a visual "oddball" stimulus task. The total group of alcoholics had significantly lower P300 amplitudes than controls for target stimuli at the Pz electrode but VA and community alcoholic subgroups did not differ. There were no latency differences between or among the groups. On the nontarget stimuli, alcoholics had significantly higher P100 and lower N100 amplitudes than the controls at all three scored electrodes (Fz, Cz, and Pz). We conclude that cross-validation of reduced P300 amplitudes at Pz in sober alcoholics was obtained but that differences in severity of brain dysfunction, at least as measured by neuropsychological test performance, cannot account for alcoholics' ERP changes relative to controls. Finally, our data suggest that ERP changes to nontarget visual stimuli should be investigated in addition to the more traditional ERP measures to target stimuli.

Topography of auditory and visual P300 in normal children

Auditory and visual P300 recordings were performed on 39 normal, right-handed individuals from age 6 through 15, using 31 evenly spaced scalp electrodes. Amplitude at the P300 peak and latency to this peak at each electrode site were measured. Age was significantly correlated with the 31-electrode mean for auditory and visual P300 latencies, but not for amplitudes. The younger age group (6-10) had longer auditory and visual P300 latencies than the older age group. Visual P300 amplitudes were of an overall larger magnitude than auditory amplitudes. There were no other differences including significant topographical differences in P300 amplitudes or latencies by gender, age group, modality, or side of scalp. Radial current density maps on group-averaged auditory and visual P300 waveforms at the group mean P300 latency at Cz, showed a right centroparietal sink surrounded by sources. This suggests a major right centroparietal P300 generator. Description of the normal topography of the P300, and demonstration of the lack of topographic differences by gender, age group, modality, or side of scalp, may facilitate the meaningful examination of P300 topography in cognitive disorders. Such an examination might lead to better diagnostic tools and more appropriate treatment of cognitive disorders in children.

The effect of aging on spectral parameters of event-related potentials

Forty-two healthy subjects ranging in age from 20 to 73 were divided into three groups according to age; a young group (20-33 years), a middle-aged group (34-49 years) and older group (50-73 years). Event-related potentials (ERPs) of three groups were recorded in two different experimental conditions that the infrequent stimulus was counted (Test 1) or uncounted (Test 2). ERPs were elicited using infrequent and frequent stimuli as red and green lights respectively. Spectral analysis of ERPs showed that decibel (dB) values of 1-2 and 3-4 Hz in young and middle-aged groups while dB value of 1-2 Hz in older group were significantly decreased in Test 2 compared with Test 1. When the number of subjects displaying amplitude maximum in each frequency band was considered, significant differences were found in 1-2 and 5-7 Hz frequency bands of young and middle-aged groups, but no significant differences were found for older group.

Neurophysiological evaluation of zidovudine in asymptomatic HIV-1 infection: a longitudinal placebo-controlled study

The effect of early antiretroviral medication with zidovudine on neurophysiological functions was evaluated in subjects with asymptomatic HIV-1 infection. Patients were recruited participants of a larger double-blind randomised placebo-controlled treatment trial with zidovudine (Concorde). The main outcome measures included: quantitative electroencephalography (QEEG), auditory event-related potentials (AEP) and pattern-reversal visual evoked potentials (PRVEP), as well as standard clinical, virological and immunological markers. No significant impairment and no difference between treatment groups was found in visual P100 latency and auditory long-latency P3 responses which is in agreement with the absence of neurological and neuropsychological impairment over the study period. Significant treatment effects were revealed by quantitative electroencephalography (QEEG). While the placebo group showed a significant increase in delta and theta slow frequency QEEG activity over the study period, slow wave amplitude remained unchanged in the zidovudine group after a mean follow-up period of 28 months. In summary, the data provide evidence for a low level neuropathological process in asymptomatic HIV-1 infection which can be effectively suppressed by antiretroviral medication.

Cognitive and biological determinants of P300: an integrative review

The P300 event-related brain potential (ERP) is thought to reflect neuroelectric activity related to cognitive processes such as attention allocation and activation of immediate memory. However, recent studies have provided evidence that the P300 also is influenced by biological processes such as fluctuations in the arousal state of subjects. The effects of natural (circadian, ultradian, seasonal, menstrual) and environmentally induced (exercise, fatigue, drugs) state variables on the P300 are reviewed. The findings suggest that these factors contribute to P300 measures and are discussed in terms of their theoretical and applied implications.

Brain electrical activity (quantitative EEG and bit-mapping neurocognitive CNV components), psychometrics and clinical findings in presenile subjects with initial mild cognitive decline or probable Alzheimer-type dementia

Clinical, neuropsychological and neuropsychophysiological data (Q-EEG, ERPs and CNV/RT activity) were obtained from 24 patients who had more or less severe presenile primary cognitive decline without depression, and compared with similar data from 10 age-matched healthy volunteers (mean age, 59.4 years). All of the patients (15 M and 9 F; mean age 59.6 years) were selected according to the DSM III-R, ICD-10 and NINCDS-ADRDA criteria and underwent CT and MRI scanning, in addition to a standard clinical examination, a battery of psychometric tests, spectral EEG, and bit-mapped CNV complex and RT to S2 analyses. Twelve of the 24 patients presented an initial presenile idiopathic cognitive decline (PICD) but did not wholly fulfil the clinical and neuropsychological criteria for primary dementia or for a diagnosis of probable AD; the remaining 12 patients showed characteristic clinical signs and symptoms of a very probable early stage of presenile Alzheimer-type dementia (PAD). ANOVA, correlational and discriminant analyses of the neuropsychological test scores, and the neurophysiological and RT to S2 data revealed 22 highest-ranked between-group discriminant factors (all with a significance level of p < 0.01). The conclusive discriminant analysis retained 13 of these factors as final canonical functions, and these showed a 97% grouping accuracy (33 of the 34 subjects examined); the same percentage of correct classifications was also achieved using only the 15 best indicators in the group of CNV/RT findings. Using both of these sets of highest-ranked discriminators, all of the normal subjects and all of the PAD patients were correctly classified; only 1 PICD patient was misclassified as normal when the first group of 13 factors was used, and another PICD patient was misclassified as PAD using the second group of 15 factors. Our findings suggest that, providing they are correctly performed and interpreted, these non-invasive techniques may be an important tool for identifying incipient stages of presenile Alzheimer-type dementia.

ERP indices of auditory selective attention in aging and Parkinson's disease

In the present study, we compared the performance of normal subjects in three age groups and of medicated Parkinson's disease patients on auditory selective attention processes. Two tone sequences were dichotically presented. Subjects responded to deviant tones in the attended location. Event-related potentials (ERPs) were recorded from nine scalp electrodes. The old group showed significant decline in hit rate, increase in N1 amplitude, and reduction in P3a, P3b, target negativity, and mismatch negativity amplitude. The amplitude and duration of late Nd increased with age, reflecting modulation of both attended and unattended standard ERPs. Although the middle group showed a similar pattern of ERP changes, the effects were generally nonsignificant. The Parkinson's disease group showed little further disruption of behavioral or ERP measures. However, Parkinson's disease affected late Nd in the direction opposite of that of aging, reflecting differential modulation of unattended standard positivity.

Developmental changes in P300 wave elicited during two different experimental conditions

Age-related correlations on auditory event-related potentials were studied using a task-relevant oddball paradigm in 175 normal subjects aged 4-21 years and age-related correlations in the "ignore" condition were studied in 108 normal subjects aged 1-21 years. In the ignore condition, subjects more than 4 years of age were instructed to read a book to divert attention from the auditory stimulus. From 4 to about 17 years of age, the latencies of task-relevant P300 in event-related potentials (ERPs) gradually shortened. In the ignore condition experiment, the P300 latency shortened progressively, but stabilized at about 12 years of age. Whereas P300 in the ignore condition likely corresponds to P3a described previously (passive attention), the conventional P300 wave corresponds to P3b (active attention). The findings indicate a developmental difference between the P3a and P3b potential.