Age-related changes in cognitive ERPs of attenuation

Summary 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.This research was supported, in part, by NASA #NAG9-413 and by Neuromedical Technologies, Inc. The fine EEG technical support of Ms. Shelley Sutter is appreciated, as well as the editorial comments of Ms. Pamela Leitzell.     

Evaluation of auditory, visual and olfactory event-related potentials for comparing interspersed- and single-stimulus paradigms

Background

An interspersed-stimulus paradigm (ISP) for event-related potential (ERP) recordings in which different sensory modality stimuli are presented within the same test session was developed to minimize recording time and facilitate modality comparison. The present study compared the ISP with a single-stimulus paradigm (SSP), using auditory, visual, and olfactory stimuli.

Method

Normal participants (n = 16) were assessed on two independent test occasions to obtain data on inter-paradigm and test-retest reliability. Peak amplitude/latency and area measures were obtained for the N1, P2 and P3 peaks for each paradigm.

Results

Except for larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP, no significant differences in amplitudes or latencies were found between the two paradigms. Correlation coefficients between paradigms were generally fairly high (amplitude mean r = 0.76; latency r = 0.42). Test-retest reliability within paradigms for amplitudes (ISP r = 0.70; SSP r = 0.68) and latencies (ISP r = 0.44; SSP r = 0.42) was similar across paradigms.

Conclusion

The findings suggest that the ISP, compared to the SSP, produces, in general, highly comparable auditory, visual, and olfactory peak amplitudes and latencies, and comparable reliability estimates, even though the ISP takes much less time to record (25 vs. 50 min). The larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP may be attributable to a less predictable stimulus environment. Thus, this method enables systematic comparisons of ERP peaks across sensory modalities while reducing testing time. Practical implications are discussed.     

Time-course of trigeminal versus olfactory stimulation: Evidence from chemosensory evoked potentials

Habituation of responses to chemosensory signals has been explored in many ways. Strong habituation and adaptation processes can be observed at the various levels of processing. For example, with repeated exposure, amplitudes of chemosensory event-related potentials (ERP) decrease over time. However, long-term habituation has not been investigated so far and investigations of differences in habituation between trigeminal and olfactory ERPs are very rare. The present study investigated habituation over a period of approximately 80 min for two olfactory and one trigeminal stimulus, respectively. Habituation was examined analyzing the N1 and P2 amplitudes and latencies of chemosensory ERPs and intensity ratings. It was shown that amplitudes of both components – and intensity ratings – decreased from the first to the last block. Concerning ERP latencies no effects of habituation were seen. Amplitudes of trigeminal ERPs diminished faster than amplitudes of olfactory ERPs, indicating that the habituation of trigeminal ERPs is stronger than habituation of olfactory ERPs. Amplitudes of trigeminal ERPs were generally higher than amplitudes of olfactory ERPs, as it has been shown in various studies before. The results reflect relatively selective central changes in response to chemosensory stimuli over time.     

The influence of stimulus duration on odor perception.

Although different parameters are known to alter the shape of olfactory event related potentials (ERP), ERP parameters are generally thought to be independent from stimulus duration. Evidence from recent studies investigating trigeminal ERP indicates that this may not be true. Aim of the present study was to investigate the relationship of stimulus duration and ERP. A total of 20 young healthy subjects participated. Subjects were investigated on 5 occasions on 5 different days. ERP were recorded to olfactory stimuli of two different concentrations and 3 different durations (100 ms, 200 ms, 300 ms). In two sessions olfactory ERP to PEA were recorded, in another two sessions H2S was applied. During the same sessions, intensity ratings were recorded. In the fifth session, subjects were asked to rate the duration of H2S stimuli and PEA stimuli. Whereas at weak stimulus concentrations no effect of stimulus duration could be observed, there was a clear effect of "duration" in ERP amplitudes following stimuli with higher concentrations: the longer the stimulus duration the larger the ERP amplitudes. No effect was found on ERP latencies. With regard to intensity ratings, strong stimuli and longer lasting stimuli lead to higher ratings. Similarly, ratings of stimulus duration were dependent from stimulus concentration and stimulus duration. Results of the present study showed that similar to trigeminal ERP, information about stimulus duration is encoded in olfactory ERP, mainly in amplitudes.     

Expectation decreases brain susceptibility to fearful stimuli: ERP evidence from a modified emotion evaluation task

Expectation decreased the susceptibility to fearful stimuli in prior studies using distracting tasks. The present study tests whether expectation remains effective in decreasing this susceptibility, when subjects focus attention on emotional properties. Event-related potentials were recorded for fearful and neutral faces, while subjects performed a modified emotion evaluation task during unpredictable and predictable conditions. Behavioral data showed faster response latencies during predictable versus unpredictable conditions. ERP data showed prolonged peak latencies in N1 (80–130 ms) and larger amplitudes in P2 (130–180 ms) and N200-300 components, for unpredictable fearful versus neutral faces. Conversely, all these components showed similar responses to predictable fearful and neutral faces. Source analysis suggested that medial temporal lobe mediated ERPs elicited by unpredictable fearful faces, while ventromedial prefrontal cortex mediated those elicited by predictable fearful faces, in the 130–180 ms interval. Thus, we propose emotional expectation as a cognitive regulation strategy that reliably dampens human susceptibility to fearful stimuli.     

Stability of Pathway-Hemisphere Differences in the Auditory Event-Related Potential (ERP) to Monaural Stimulation

The evidence for ERP manifestations of contralateral dominance in the auditory pathways is not entirely compelling. The effect when found has involved either latency or amplitude of a variety of components obtained from averaged or subtraction waveforms. Also, the effect appears to have as much to do with hemisphere as pathway differences. The objectives of this experiment were to establish whether a specific ERP peak reflected contralateral dominance, to assess its long-term stability, and to clarify the apparent pathway-hemisphere interactions which result from monaural stimulation. Ten male subjects were tested on 6 occasions (generally weekly intervals). On each occasion, 76 monaural tones were presented while EEG was recorded at C₂, P₂, T₃, and T₄ referred to linked earlobes. P70, N120, and P200 peak amplitudes and latencies and N1–P2 amplitudes were examined. N120 amplitudes proved to be larger at the temporal site contralateral to the ear stimulated. This contralateral dominance effect was observed on all 6 occasions for right ear stimuli and on all but one occasion for left ear stimuli. N1–P2 amplitudes less reliably reflected contralateral dominance because possible hemisphere effects appeared with this measure. Methodological issues related to assessment of ERP contralateral dominance and to the variety of effects seen in the literature are discussed. The data are examined with reference to neurophysiological substrates thought to underlie auditory ERPs. Finally, the utility of a stable ERP phenomenon in assessing drug or pathology effects is evaluated.     

Effects of stimulus repetitions on the event-related potential of humans and rats.

The present study compared the effects of repeated stimulus presentations on the event-related potential (ERP) of humans and rats. Both species were presented with a total of 100 auditory stimuli, divided into four blocks of 25 stimuli. By means of wavelet denoising, single-trial ERPs were established in both humans and rats. The auditory ERPs were characterized by the presence of two positive and two negative waves in both humans and rats, albeit with different latencies in the two species (P1, N1, P2, and N2). The results showed decreased amplitudes within blocks for the N1, P2, and N2 components in humans and for the N1 and P2 components in rats. Decreased amplitudes across blocks were found for the N2 component in humans and for the P2 and N2 components in rats. In both humans and rats, response decrements within a block were thus most prominent for the early ERP components, whereas the changes across blocks were most prominent for the later components. These results suggest a correspondence of the ERP correlates of elemental stimulus processing between humans and rats. It is further suggested that the observed amplitude reductions may reflect habituation and/or recovery cycle processes.     

Auditory hallucinations and the P3a: Attention-switching to speech in schizophrenia

Background

In line with emerging research strategies focusing on specific symptoms rather than global syndromes in psychiatric disorders, we examined the functional neural correlates of auditory verbal hallucinations (AHs) in schizophrenia. Recent neuroimaging and behavioural evidence suggest altered early cognitive processes may be seen in patients with AH as a result of limited processing resources.

Methods

The P3a subcomponent of the P300, an event-related potential (ERP) index of early attention switching, was assessed in 12 hallucinating patients (HP), 12 non-hallucinating patients (NP) and 12 healthy controls (HC) within a passive two-tone auditory oddball paradigm using vowel phonemes. P3a amplitudes and latencies were measured in response to across-phoneme changes. Following P3a acquisition, patients indicated the duration, intensity and clarity of their auditory hallucinations during recording.

Results

Hallucinating patients exhibited smaller P3a amplitudes than non-hallucinating patients and healthy controls. In HPs, P3a amplitude was negatively correlated with AH trait scores.

Significance

These findings suggest that AHs are associated with impaired processing of speech as evidenced by altered P3a amplitudes to vowel phonemes. This finding may be due to limited cognitive resources available for incoming external stimuli due to a usurping of finite resources by AHs. The P3a may be a useful non-invasive tool for probing relationships between hallucinatory and neural states within schizophrenia and the manner in which auditory processing is altered in these afflicted patients.     

Amplitude reduction in visual event-related potentials as a function of sleep deprivation

Eight adult males were subjected to 40 hours of total sleep deprivation (TSD). Reaction time in a visual task and electroncephalographam (C3) were evaluated every 2 hours. One second of EEG before the stimuli was Fourier-transformed, and 750 ms after target and nontarget stimuli were averaged and visual event-related potentials (ERP) were obtained. Factorial analysis identified time windows that showed significant amplitude reduction and longer latencies with TSD: (1) 140 to 288 ms (P180-N242-P281); (2) 288 to 413 ms and 601 to 749 ms (N382; P718) and; (3) 531 to 601 ms (N500). Effect was strongest for N382 and P718, the amplitudes of which dropped to 20% of original size. The entire waveform recovered initial amplitudes and latencies after recovery sleep except for P718 latency. Waveforms within similar time intervals have been associated with attentional gating, sensory discrimination, target selection, uncertainty and decision processes. Amplitudes of the visual ERP were inversely correlated with hours of TSD, reaction time, and absolute power of the prestimulus EEG. Present results clearly show changes in fundamental neurophysiologic mechanisms as a result of TSD, indicating variability and reduction of the alertness mechanisms and changes in thalamocortical gating affecting attention, discrimination and decision-making.     

Correlations between ERP parameters and intelligence: a reconsideration

The present study investigated differences in ERP parameters related to intelligence. For that purpose 74 individuals (Intelligence: M=107; S.D.=12; range 73-135), of average creativity passively listened to two tones and performed two auditory, and two visual oddball tasks while their EEG was recorded. The approximate entropy parameters, peak latencies and amplitudes were determined. The correlation coefficients indicated that in the attended conditions, the more intelligent individuals showed more regular ERP waveforms than less intelligent individuals. It was further found that less intelligent individuals showed increased P300 latencies and reduced amplitudes. The differences were explained with a more specific engagement of neural networks in more intelligent individuals.     

Early cognitive components of somatosensory event-related potentials

Somatosensory event-related potentials (ERPs) were recorded during a selective attention task involving electrical stimuli delivered to index fingers or the left and right median nerves at the wrist. In 11 healthy, young subjects, ERPs were recorded from 6 scalp locations while they mentally counted the electrical stimuli designated as target. Sequential ERP events measured included N20 (negativity at 20 ms), P30, P45, N60, P100, N140, P180, and P400. Analysis of amplitude data indicated modifications of both early and late ERP events with selective attention. While electrical stimulation at the wrist yielded early ERP amplitudes that were larger overall and latencies that were generally shorter, the selection attention effects did not differ on the basis of site of stimulation. The early ERP selective attention effects had differing scalp topography, with the P30/P45 effect of maximal over postcentral gyrus and N60 effect maximal over prerolandic gyrus. The data further elucidate the temporal features and spatial distribution of somatosensory ERP processes involved in attentional activity.     

Event-related potentials as asymmetry indices of lateralized cognitive processes during music and verbal tasks

The present study replicates and extends earlier findings by using event-related potentials (ERPs) as a means of providing information about differential hemispheric engagement in cognitive processing. ERPs were recorded from T3, T4, T5 and T6 in response to task-irrelevant tone pips superimposed on white noise, on music and on verbal passages, which are thought to differentially activate the two hemispheres. The latencies and amplitudes of three peaks (N1, P2 and N2) were obtained in 37 women. Task-related ERP asymmetries were found only for the peak amplitude of N2 recorded at posterior-temporal scalp areas, whereas at the anterior-temporal recording, there were no interactional effects. The hemisphere assumed to be most engaged in task processing showed a smaller N2 peak amplitude to tone pips at the posterior-temporal scalp area than the hypothesized unengaged hemisphere. A result common to the three peaks in the ERP was that peak latencies were longer in the music than in the noise condition. Finally, the posterior-temporal areas produced longer N2 peak latencies in verbal and even more in music conditions compared to white noise conditions. No differences in latencies were found between hemispheres during the ongoing cognitive tasks.     

Heritability of event-related brain potentials in families with a history of alcoholism.

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism.     

P300 Development from Auditory Stimuli

Event-related potentials (ERPs) were elicited with an auditory discrimination paradigm in 20 adult subjects. The amplitude and latency of the N1, P2, N2, and P3 (P300) components were measured from each two-trial average and successively after each two-trial block were added to the ERP average. The dual trial-to-trial analysis generally demonstrated consistent component amplitudes and latencies across trials. The successive average analysis found that component amplitudes decreased significantly while their latencies remained relatively constant as additional trials were incorporated into the average. The results suggest that ERP component latencies are stable, while amplitudes decrease with increased numbers of trials. The implications for the application of P3 in the assessment of individual differences are discussed.     

Modulation of Brain Activities by Hierarchical Processing: A High-Density ERP Study

The present study investigated how attention to global or local levels of hierarchical patterns modulates brain activities by recording high-density event-related brain potentials (ERPs) evoked by hierarchical stimuli. 120-channel recordings of ERPs were obtained from subjects while they detected targets at global or local levels of hierarchical stimuli displayed in the left or the right visual field. We found that attention to local stimulus features enhanced posterior PI and N2 components, with the N2 enhancement showing a left hemisphere predominance regardless of stimulus positions. Difference was also seen in the distribution of the frontal P2. Reaction times were slowed when global and local levels of stimuli were incompatible, and an interference effect was observed on anterior N2 amplitudes and latencies. Three-dimensional current distributions showed common sources over the posterior cortex between 80-230 ms and a contralateral frontal source between 300-400 ms for global and local conditions. However, an additional ipsilateral frontal focus between 230-350 ms was found specially for local processing. The results corroborate the findings of previous ERP studies, and suggest that the frontal lobe is particularly important for the selective processing of local parts of a global structure.     

Different perceptual sensitivities for Chernoff's face between children and adults

The aim of this study was to investigate the differences between children and adults in recognizing facial expressions of simple line drawings of "Chernoff's face". First, the angles of the eyebrows and mouth of Chernoff's face were changed in a stepwise way with a personal computer, and the emotional response of the subjects was evaluated by a questionnaire. Second, three drawings of non-target stimuli (neutral face, angry face, and wheelchair) and target stimuli were used to elicit event-related potentials (ERPs). Children had higher scores for the facial expressions than adults, and relied much more on the angles of the eyebrows and mouth. The major ERP findings were (1) the latencies of P100 and N170 were significantly longer in children than adults, (2) the amplitudes of P100 were significantly larger in children than adults, but the N170 amplitudes were not significantly different, and (3) a slow negative shift was recorded with a latency of 240-460ms at the posterior-temporal site for angry face compared with neutral face in adults but not in children. These results suggest that the differences in the electrophysiological recognition of facial expressions can be set at 240ms after appearance of the Chernoff's face in adults but not in children.     

Acoustic startle response in young and aging C57BL/6J and CBA/J mice

C57BL/6J (C57) mice demonstrate progressive age-related hearing loss during the first year of life, whereas CBA/J (CBA) mice lose little sensitivity through 18 months of age. The acoustic startle response (ASR) was measured in these strains to determine behavioral correlates of aging with and without presbycusis. The stimuli were tone pips (10-ms duration, 1-ms rise-fall) with frequencies of 4, 8, 12, 16, or 24 kHz at intensities of 70, 80, 90, or 100 dB SPL. ASR "thresholds" (the minimum SPL required to elicit ASRs more than 50% of the time) increased with age, and startle amplitudes became smaller in both strains. However, the changes in these startle parameters were much more pronounced in C57 mice, with middle to high frequencies (12-24 kHz) severely affected. The startle latencies at and above ASR "threshold" increased with age in C57 mice, but did not change in CBA mice. The CBA data indicate that aging, per se, has little effect on ASR parameters; the C57 data show that hearing loss is a cogent factor. However, ASR parameters of C57 mice are altered to a greater extent than expected, on the basis of the elevations of absolute sensory thresholds, particularly for middle frequencies (12-16 kHz). Both peripheral and central mechanisms are proposed to account for the discrepancy.     

Heritability of event-related brain potentials in families with a history of alcoholism

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:383–390, 1999. © 1999 Wiley-Liss, Inc.     

Auditory event-related potentials in poor readers.

Although poor readers (PR) are considered the major group among reading-disabled children, there are not event-related potentials (ERP) studies reported of PR on the subject. In this study, attentional and memory processes were studied in an auditory oddball task in PR and normal controls. ERP to auditory stimuli were recorded in 19 leads of the 10/20 system, using linked earlobes as references, in 20 normal children (10 female) and 20 PR (10 female) of the same age (10-12 years old). Two pure tones (1000 and 3000 Hz) were used in an oddball paradigm. No significant differences were observed in the amplitudes and latencies of N100 between the groups. However, N200 to frequent stimuli and P200 to both frequent and infrequent stimuli were of higher amplitude in poor readers than in normal children. There were no differences between groups in the latency and amplitude of P300. The results suggest that PR use more attentional resources in the components occurring before P300 to both frequent and infrequent stimuli than the normal children, and this finding is particularly marked for PR girls.     

Event-related brain potentials and affective responses to threat in spider/snake-phobic and non-phobic subjects.

We investigated cortical responses and valence/arousal ratings of spider phobic, snake phobic, and healthy subjects while they were processing feared, fear-relevant, emotional neutral, and pleasant stimuli. Results revealed significantly larger amplitudes of late ERP components (P3 and late positive complex, LPC) but not of early components (N1, P2, N2) in phobics when subjects were processing feared stimuli. This fear-associated increase of amplitudes of late ERP components in phobic subjects was maximal at centro-parietal and occipital brain sites. Furthermore, phobics but not controls rated feared stimuli to be more negative and arousing than fear-relevant, emotional neutral, and pleasant stimuli. Since late ERP components and valence/arousal ratings were only significantly increased when phobic subjects but not when healthy controls were processing feared stimuli, the present data suggest that P3 and LPC amplitudes represent useful neural correlates of the emotional significance and meaning of stimuli.