Developmental aspects of event-related potentials

Reduction in right lateralized N2 error response to stroke order violations in poor Chinese word spellers: A study on event-related potential markers for Chinese reading and spelling

Stroke order knowledge is critical for Chinese reading and spelling acquisition. Previous studies have demonstrated enhancements of the N2 and P3 event-related potential (ERP) components at the Pz electrode to stroke order violations of Chinese characters in younger adults. However, it remained unclear whether similar ERP responses could be found in children. The current study investigated the ERP responses to stroke order violations of Chinese characters in children and examined the associations of the ERP responses with children's Chinese reading and spelling performance. A total of 26 Grade 2 Hong Kong Chinese children observed stroke-by-stroke displays of Chinese characters and judged whether the Chinese characters were written in the correct order. The ERP results showed larger anterior N2 and posterior P3 at the midline electrodes to the incorrect strokes than to the correct strokes. In addition, a smaller right lateralized temporal N2 response to the incorrect strokes was found in poor spellers as compared with good spellers of Chinese. The effect of the right lateralized temporal N2 response on reading performance was fully mediated through spelling ability. These results demonstrated increases in the anterior N2 and posterior P3 responses to stroke order violation of Chinese characters in second graders and suggest the right lateralized N2 response as a potential neural marker of Chinese literacy development in children.

Delayed maturation of P2 flash visual evoked potential (VEP) latency in newborns of gestational diabetic mothers

BACKGROUND

The prevalence of gestational diabetes mellitus (GDM) has rapidly increased, yet few prior studies have investigated parameters of early brain development in infants born to gestational diabetic mothers. The present study assessed visual evoked potentials (VEPs) in healthy infants born to gestational diabetic mothers and matched controls.

METHODS

After exclusions, in this prospective study we examined VEPs in 73 neonates between 37 weeks and 41 weeks gestation at birth (n = 37 infants of gestational diabetic mothers). Stroboscopic flashes were presented through closed eyelids during passive electroencephalography (EEG) recording to derive VEP waveforms during natural sleep.

RESULTS

There was a statistically significant moderate correlation between gestational age at birth and P2 latency of the flash VEP where P2 latency significantly decreased with increasing gestational age (Pearson's R(73) = -0.32, p < .01). There was also a significant moderate correlation between postnatal age (hours of life) and P2 latency of the flash VEP where P2 latency significantly decreased with increasing postnatal age (Pearson's R(73) = -0.23, p < .05). When controlling for gestational age at birth, postnatal age, and sex, there was a significant effect of group (GDM-exposed vs. control) on P2 latency of the flash VEP (p < .05). Infants of gestational diabetic mothers had a significantly longer P2 latency (M: 215.29 ± SD: 2.58 ms) than controls (M: 206.41 ± SD: 2.62 ms).

CONCLUSION

Our findings suggest P2 flash VEP latency is a potential measure of cortical maturation and marker of immature development in infants of gestational diabetic mothers.

Posterior brain sensorimotor recruitment for inhibition of delayed responses in children

Inhibitory control, the ability to suppress irrelevant thoughts or actions, is central to cognitive and social development. Protracted maturation of frontal brain networks has been reported as a major restraint for this ability, yet, young children, when motivated, successfully inhibit delayed responses. A better understanding of the age-dependent neural inhibitory mechanism operating during the awaiting-to-respond window in children may elucidate this conundrum. We recorded ERPs from children and parental adults to a visual-spatial working memory task with delayed responses. Cortical activation elicited during the first 1000 ms of the awaiting-to-respond window showed, as predicted by prior studies, early inhibitory effects in prefrontal ERPs (P200, 160-260 ms) associated with top-down attentional-biasing, and later effects in parietal/occipital ERPs (P300, 270-650 ms) associated with selective inhibition of task-irrelevant stimuli/responses and recurrent memory retrieval. Children successfully inhibited delayed responses and performed with a high level of accuracy (often over 90%), although, the prefrontal P200 displayed reduced amplitude and uniformly delayed peak latency, suggesting low efficacy of top-down attentional-biasing. P300, however, with no significant age-contrasts in latency was markedly elevated in children over the occipital/inferior parietal regions, with effects stronger in younger children. These results provide developmental evidence supporting the sensorimotor recruitment model of visual-spatial working memory relying on the occipital/parietal regions of the early maturing dorsal-visual network. The evidence is in line with the concept of age-dependent variability in the recruitment of cognitive inhibitory networks, complementing the former predominant focus on frontal lobes.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Maturation of auditory evoked potentials from 6 to 48 months: prediction to 3 and 4 year language and cognitive abilities

OBJECTIVE

To investigate the maturation of long-latency auditory evoked potentials (LLAEP) from 6 to 48 months in infants with a family history of language impairment (FH+) and control infants (FH-).

METHODS

LLAEPs of seventeen FH+ infants were compared to 28 FH- infants at 6, 9, 12, 16, 24, 36 and 48 months. Participants received a passive oddball paradigm using fast- and slow-rate non-linguistic auditory stimuli and at 36 and 48 months completed a battery of standardized language and cognitive tests.

RESULTS

Overall, the morphology of LLAEP responses differed for fast- versus slow-rate stimuli. Significant age-related changes in latency and amplitude were observed. Group differences, favoring FH- infants, in the rate of maturation of LLAEPs were found. Responses to fast-rate stimuli predicted language abilities at 36 and 48 months of age.

CONCLUSIONS

The development of LLAEP in FH+ children is modulated by differences in the rate of maturation as well as variations in temporal processing abilities.

SIGNIFICANCE

These findings provide evidence for the role of non-linguistic auditory processes in early language development and illustrate the utility of using a perceptual-processing skills model to further our understanding of the precursors of language development and impairment.

Developmental gender differences in the synchronization of auditory event-related oscillations

OBJECTIVES

The aim of the present study was to explore the neurophysiologic origins of gender differences in auditory processing mechanisms of 7-10 year-old children by means of event-related oscillations. It was tested if the developmental changes in synchronization and magnitude of oscillations in different processing conditions depended on gender.

METHODS

Eighteen girls and 18 boys aged 7-10 years were pair wise matched for age and were divided into two age groups. Auditory event-related potentials (ERPs) were recorded in passive, sensorimotor and working memory conditions. Phase-locking and single-trial magnitude of ERPs were analyzed in the delta (0.5-4 Hz), theta (4-7 Hz), slow (7-10 Hz), and fast (10-14 Hz) alpha frequency bands to test the effects of gender, age, and processing condition.

RESULTS

The phase-locking of auditory delta, theta, and slow alpha oscillations increased with development only in girls, independently of task processing. Only for the theta phase-locking was this effect additionally affected by the motor-related task. No changes in the magnitude of oscillations accompanied these gender differences in synchronization except for parietal delta responses that also increased with development only in girls.

CONCLUSIONS

The results demonstrate that gender differences in auditory ERPs basically originate from a stronger functional synchronization of oscillatory responses generated during stimulus processing.

SIGNIFICANCE

The study provides evidence that the functional maturation of oscillatory auditory networks reflected by a progressive developmental increase of synchronization, is accelerated in girls relative to boys between 7 and 10 years of age.

The P300 event-related potential and its possible role as an endophenotype for studying substance use disorders: a review

The concept of endophenotypes has gained popularity in recent years. This is because of the potential that endophenotypes provide of measuring objective trait markers that are simpler to access and assess than complex behavioral disease phenotypes themselves. The simplicity, ease of measurement and the putative links to the etiology of the disease in the study of an endophenotype has the potential promise of unraveling the genetic basis of the disease in question. Of the various proposed endophenotypes, the P300 component of the event-related potential has been used in studies on alcoholism, schizophrenia and externalizing disorders. The current state of knowledge regarding the concept of endophenotypes, P300 and the validity of P300 as an endophenotype with special reference to substance use disorders is discussed in this review. The implications of the above are discussed.

Gender-specific development of auditory information processing in children: an ERP study

OBJECTIVES

The aim of the present study was to evaluate the effects of gender on sensory and cognitive information processing in children by analyzing auditory event-related potentials (ERPs). The major questions were: (1) do ERPs differ between girls and boys aged 7-10years, (2) do gender differences in ERPs depend on the development with age, on task-processing demands, and on the development of neuroelectric networks as reflected by the spontaneous EEG?

METHODS

Thirty-six healthy children (18 girls and 18 boys) were divided in two age groups (7- to 8- and 9- to 10-year-old). Boys and girls were pairwise matched for age. Auditory ERPs were analyzed in a passive listening condition (PLC), a simple reaction task (SRT) and a serial learning reaction task (SLRT), in which memory and sensorimotor processes were varied in a balanced way. Cognitive performance, reaction times (RTs), and the spontaneous electroencephalogram (EEG) were also measured.

RESULTS

Cognitive performance improved earlier in girls than boys, whereas response speed was not affected by gender. Independent of processing demands, ERP components within 300ms after stimulation (N1, P2, N2 and P3) increased with development only in the group of girls. For later components, the developmental speeding of the parietal P3b component to task-relevant stimuli also tended to be more expressed in girls than boys, whereas a late frontal negative wave N400-700 was shorter in the girls than boys from the two age groups. Likewise, independently of age, the spontaneous EEG manifested a larger theta activity in girls than boys.

CONCLUSIONS

Developmental changes of basic auditory processing mechanisms strongly depend on gender in children between 7 and 10years by being faster in girls. This gender-specific development of early ERP components is not modulated by processing demands, cannot be attributed to a faster cognitive maturation of girls, nor can it be explained with the gender-specific maturation of background neuroelectric networks. Rather, it reflects an accelerated functional activation of auditory processing networks in girls. Interestingly, the cognitive development was also faster in girls, but it occurred earlier than the functional activation of auditory processing networks.

SIGNIFICANCE

This study provides evidence for accelerated neuroelectric (as reflected by spontaneous EEG), neurofunctional (as reflected by auditory ERPs), and neurocognitive (as reflected by learning performance) development in 7- to 10-year-old girls than boys.

Growth status related to brain responses, nutrition, home environment, and behavior in infants and toddlers

To investigate whether growth status in infants and toddlers affects processes involved in speech perception and discrimination, cortical event-related potentials (ERPs) to consonant-vowel syllables were recorded from 48 healthy babies: 26 low in growth status (LGS, < 25 th percentile in growth measures) and from 22 normal in growth status (NGS, 25t--75 th percentile in growth measures). Food records indicated no significant differences in the amounts of various nutrients consumed in the two groups, but LGS babies consumed slightly more of most nutrients than NGS babies. In response to speech stimuli (either /pa/ or /ba/ presented with 20 and 80% randomized occurrence), brain ERPs showed two prominent post-stimulus components: a large positive wave peaking at about 484 msec and a negative but positive going slow wave (SW) between 867 and 1199 msec. Principal components analysis followed by promax rotation revealed four additional important components. Maximum peak and latency values-for these components showed that NGS and LGS babies differed from one another on all measures in either amplitude, latency, or both. Comparing the two groups of babies, only the LGS group demonstrated a deficit in the phonetic discrimination of speech sounds. The growth deficiencies of the LGS group could not be attributed to the lack of an adequate diet. These negative findings are present in babies generally considered to be healthy (lowest 10-25% in growth measures). This underscores the need for research examining in more detail the relationship between growth status and cognitive growth.

Development of MEG sleep patterns and magnetic auditory evoked responses during early infancy

OBJECTIVE

To follow the development of MEG sleep patterns and auditory evoked responses (AERs) during the first six months of life.

METHODS

The subjects were 18 neonates, born at conceptional age (CA) 36-42 weeks, following uncomplicated pregnancies. During each session, several 10-min MEG recordings were acquired in the presence of auditory stimulation. The recordings were classified into three distinct MEG patterns-low amplitude irregular; high-amplitude slow; and mixed-based largely on MEG amplitude and frequency. Averaged AERs were computed for the entire recording and for each MEG pattern within the recording. The results were based on analysis of 61 recording sessions of the 10 subjects who yielded three or more sessions of usable data.

RESULTS

Developmental changes in the MEG sleep patterns were most pronounced at the earliest ages. By CA 48 weeks the patterns had progressed to a more mature form, characterized by the prevalence of delta wave sleep, absence of discontinuity, and development of spindling and higher amplitude delta rhythms. In contrast to the MEG patterns, the AERs did not change markedly during the first 8 weeks (CA 40-48 weeks) and showed a simple morphology, consisting of a prominent deflection at 250 ms (P250m) and a more diffuse one at around 750 ms (N750m). During the period CA 48-54 weeks, however, a relatively abrupt transition occurred to a more complex morphology, characterized by a double peak with peak latencies 150ms (P150m) and 350 ms (P350m). Beyond this period the AERs continued to evolve, showing biphasic complexes and the emergence of late components arising from outside the auditory cortex.

CONCLUSIONS

Over the age range of this study the MEG sleep patterns and AER developed in succession, rather than concurrently; i.e. development of the sleep patterns was most rapid during the first 8 weeks (CA 40-48 weeks) while major development of the AERs commenced after this time.

SIGNIFICANCE

This finding suggests that the brain must achieve a certain level of overall maturity, reflected in the character of the MEG sleep patterns at CA 48 weeks, before the cortex enters a phase of significant functional development, reflected in the more rapid evolution of the AER after CA 48 weeks. The results of this study affirm the efficacy of MEG for spatiotemporal characterization of neonatal brain activity.

Brain Event-Related Potentials (ERPs) Measured at Birth Predict Later Language Development in Children with and Without Familial Risk for Dyslexia

We report associations between brain event-related potentials (ERPs) measured from newborns with and without familial risk for dyslexia and these same children's later language and verbal memory skills at 2.5, 3.5, and 5 years of age. ERPs to synthetic consonant-vowel syllables (/ba/, /da/, /ga/; presented equiprobably with 3,910-7,285 msec interstimulus intervals) were recorded from 26 newborns at risk for familial dyslexia and 23 control infants participating in the Jyväskylä Longitudinal Study of Dyslexia. The correlation and regression analyses showed that the at-risk type of response pattern at birth (a slower shift in polarity from positivity to negativity in responses to /ga/ at 540-630 msec) in the right hemisphere was related to significantly poorer receptive language skills across both groups at the age of 2.5 years. The similar ERP pattern in the left hemisphere was associated with poorer verbal memory skills at the age of 5 years. These results demonstrate that ERPs of newborns may be valid predictors of later language and neurocognitive outcomes.

Effects of auditory distraction on electrophysiological brain activity and performance in children aged 8-13 years

Distractibility was investigated in three age groups of children (8-9, 10-11, and 12-13 years) with event-related brain potentials (ERPs) and performance measures in a forced-choice visual task. Distraction was reflected by increased reaction times (RTs) and decreased performance accuracy in the visual discrimination task following presentation of unexpected novel sounds. The amplitude of the late portion of the P3a elicited by novel sounds was largest for the youngest group and showed a centrally dominant scalp distribution and smallest for the oldest group with a frontal scalp distribution. A frontally dominant late negativity (LN) that was largest in the youngest group followed the P3a. Correlation between the RT increase caused by the distracting novel sounds and the amplitude of the LN elicited by these sounds suggested that the LN is associated with the degree of attention engaged by the distracting sounds.

Event related potentials during attention tasks in VLBW children with and without attention deficit disorder

OBJECTIVE

Children born prematurely have a higher incidence of attention deficit disorder with or without hyperactivity. We have used visual event related potentials to study possible brain dysfunctions that could explain this higher incidence.

METHODS

Very low birth weight (VLBW) children with and without AD/HD and term born children with and without AD/HD, were matched for IQ, age and socio-economic status (n=41, mean age 104 months). A visual oddball paradigm, consisting of target and non-target stimuli, was used with analysis of response times, error scores, N200, P300 and a P500 component.

RESULTS

AD/HD children responded slower (F (1,38)=11.20, p<0.002); more varied (F (1,38)=21.77, p<0.000) and made more commission and omission errors (Kruskal-Wallis p<0.000). Non-target N200 was increased in amplitude (F (1.39)=4.01, p=0.05) with a wide anterior topography in children with AD/HD. The late positivity (P500) was decreased over central leads in children with AD/HD during the non-target stimuli (F (3,75)=3.00, p<0.036). No differences could be found in latency, amplitude or topography between VLBW children with AD/HD and term born children with AD/HD.

CONCLUSIONS

Prematurity does not induce specific attentional brain dysfunction or maturation delays in stimulus processing during cognitive tasks. Other factors should be investigated to explain the higher incidence of AD/HD in VLBW children.

Newborn infants can organize the auditory world

The perceptual world of neonates is usually regarded as not yet being fully organized in terms of objects in the same way as it is for adults. Using a recently developed method based on electric brain responses, we found that, similarly to adults, newborn infants segregate concurrent streams of sound, allowing them to organize the auditory input according to the existing sound source. The segregation of concurrent sound streams is a crucial step in the path leading to the identification of objects in the environment. Its presence in newborn infants shows that the basic abilities required for the development of conceptual objects are available already at the time of birth.

Word and picture processing in children: an event-related potential study

In an investigation of the N400 component, event-related potentials (ERPs) elicited by 4 types of word stimuli (real words, pseudowords, random letter strings, and false fonts) and 3 types of picture stimuli (real pictures, pseudopictures, and picture parts) presented in separate lists were recorded from 10- and 11-year-old children. All types of word stimuli elicited an anteriorly distributed negativity peaking at about 400 msec (antN400). Words and pseudowords elicited similar ERPs, whereas ERPs to letter strings differed from those to both pseudowords and false fonts. All types of picture stimuli elicited dual anterior negativities (N350 and N430). Real pictures and pseudopictures elicited similar ERPs, whereas pseudopictures and picture parts elicited asymmetrical processing. The results are discussed in terms of increased sensitivity to and dependence on context in children.

Electric brain responses obtained from newborn infants to changes in duration in complex harmonic tones

Event-related brain potentials of 10 full-term newborns in response to duration changes in complex, harmonic tones known to elicit prominent mismatch negativity (MMN) response in adults were investigated. Here we report that duration changes elicited prominent MMN responses in a 11 newborns tested. In contrast, MMN has been reported in as little as 50% of the infants in some previous studies using other sound attributes. When the infant MMN latency was compared with that obtained from adults, and 4- as well as 8-year-old children, it was found that the MMN latency was a bit later in newborns than in older age groups. This result is consistent with previous findings. The MMN amplitude, however, was surprisingly large in infants compared to older children.

Neurodevelopmental patterns of visual P3b in association with familial risk for alcohol dependence and childhood diagnosis

BACKGROUND

The P3b component of the event-related potential (ERP) has frequently been reported to be reduced in children and adolescents at high risk for developing alcoholism relative to control children and adolescents without familial loading for alcohol dependence. P300 amplitude changes during development for all children. Previously it has been shown that high-risk offspring display a pattern in which the amplitude is lower at age 8 with a smaller rate of change during adolescence.

METHODS

Admixture analysis was applied to data obtained for those children and adolescents having five or more annual assessments of ERPs to determine if multiple P3b growth patterns exist. The P3b amplitude patterns obtained were related to risk status, concurrent presence of childhood psychopathology (internalizing or externalizing), and age of onset to develop a diagnosis.

RESULTS

A pattern characterized by lower P3b amplitude at study entry and a slower rate of change during child and adolescent development (pattern 3) was most often associated with high-risk status in boys and high-risk status in combination with the presence of a childhood diagnosis in girls. Pattern 3 was significantly related to the overall presence of childhood psychopathology (internalizing or externalizing) and to the presence of an Axis I diagnosis at young adult follow-up.

CONCLUSIONS

The developmental pattern previously described for offspring at high risk for developing alcoholism because of their familial/genetic background was confirmed. Admixture analysis has refined this observation and suggests that among all children and adolescents tested, three developmental patterns can be identified, one of which is most often seen in association with male high-risk children and adolescents.

Event-related potential features indexing central auditory discrimination by newborns

Behavioral research has produced little evidence on sound feature discrimination in neonates. Sensory processes underlying sound perception can be studied using the mismatch negativity (MMN) component of auditory event-related potentials (ERPs), which is not contingent on conscious perception and response. Thus, MMN is suitable for studying newborns, who are difficult to obtain behavioral responses from. The present study thus utilized spectrally rich sounds, known to elicit the most replicable MMN in adults, to investigate newborns' preattentive analysis of sound duration and frequency changes. An attempt was also made to control for the obligatory ERP effects on the MMN. Three-partial harmonic tones were presented in Duration and in Frequency oddball conditions to 55 newborns. In the other two, Equiprobable duration and Equiprobable frequency, conditions frequency and duration deviants of the oddball paradigms were presented with equal probabilities among sounds of other durations and frequencies. MMN was elicited in 81% of newborns in Frequency oddball condition and in 78% of newborns in Duration oddball condition. No significant amplitude differences between the duration and frequency MMNs were found, but MMN latency was delayed in Duration condition. The obligatory components seemed to contribute significantly to the deviant-standard difference in Duration but not in Frequency condition. The majority of neonates appear to possess effective sound frequency and duration discrimination mechanisms. Their preattentive sound discrimination is facilitated by spectrally rich sound content. The present findings support a change-detection nature of MMN in neonates; however, sound duration-related obligatory effects need to be taken into account in infant MMN studies.

Topographic distribution and developmental timecourse of auditory event-related potentials in two subtypes of attention-deficit hyperactivity disorder

The effect of age on the topographic distribution of auditory event-related potentials (ERPs) recorded during a two-tone discrimination, or oddball, task was examined in two subtypes of attention deficit/hyperactivity disorder (AD/HD) as defined by the most recent diagnostic manual, DSM-IV. EEG was recorded at 17 sites from AD/HD predominantly inattentive type (n=50) and AD/HD combined type (n=50) subjects aged from 8 to 17 years 11 months. ERP components were quantified at each site. Results revealed topographic differences from controls (n=50) that were common to both subtypes (e.g. target and standard P2 amplitude, and standard P2 latency) or unique to a particular subtype of AD/HD (Inattentive type: target N1, N2, P3b and standard N2 amplitude, target P2 latency; Combined type: target N1, P2, N2 and P3b amplitude, target N2 and standard N1 latency). These group differences showed different age effects. The across-region results revealed differing patterns of abnormal component development for each subtype, indicating a qualitative difference in information processing stage deficits in each of these AD/HD subtypes.

Developmental delay in P300 production in children at high risk for developing alcohol-related disorders

BACKGROUND

Reduction of P300 amplitude in children and adolescents at high risk for developing alcoholism has frequently been reported. It has been hypothesized that this reduction represents a developmental delay in reaching age-appropriate levels in P300 amplitude. Using latent growth analysis of longitudinal data obtained at yearly intervals, this study seeks to define normal growth, and determine if the pattern seen in high-risk children differs from that obtained in normal low-risk controls.

METHODS

A total of 156 children from either high or low-risk families have been assessed multiple times (two-thirds more than 4 times) using both a clinical assessment (K-SADS) and ERP evaluation performed on the same day. A total of 635 separate assessments were available for modeling.

RESULTS

Quadratic growth curves revealed a slower rate of change in P300 amplitude in high-risk than low-risk males. High-risk girls showed reduced visual P300 amplitude only when the presence of a K-SADS diagnosis was considered. No differences were seen for P300 latency.

CONCLUSIONS

This study confirms the hypothesis that when reduction of P300 amplitude is seen in males at high risk for developing alcoholism, it is due to a developmental delay.

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.

Alpha response system in children: changes with age

Evoked and event-related brain potentials (Eps, ERPs) may be regarded as originating from the reorganization of the spontaneous EEG rhythms (Başar, 1980). Until now, no data is available about the development of the evoked frequency components in EPs and ERPs of children. The main objective of the present research was to study the alpha response system in 6-11-year-old children. We suggested that the ability to reorganize the alpha activity and produce repeatable alpha patterns after external stimulation might undergo developmental changes that could reflect certain changes in information processing with increasing age from childhood to adulthood. Fifty 6-11-year-old children divided into five age groups, and 10 young adults were studied in a passive and an odd-ball condition. Alpha responses in the auditory EPs and non-target ERPs at Fz, Cz and Pz were analyzed. The magnitude and phase-locking with stimulus of single alpha responses were evaluated in the first 300 ms of the post-stimulus epoch. An original method was applied to assess quantitatively the repeatability (phase-locking) of the evoked alpha oscillations. The magnitude and the phase-locking to stimulus were analyzed with respect to their dependence on the age and topography factors. Our main results show that the alpha responses in 6-11-year-old children are different from those in adults: (1) Adults had significantly lower amplitude and stronger phase-locking than children; (2) Adults had maximal alpha amplitudes and phase-locking over the vertex, whereas children displayed maximal responses over the parietal site; (3) The phase-locking of eldest (10-11-year-old) children was as strong as in adults. Whereas no difference existed between groups of children in alpha response amplitudes, a significant increase in phase-locking from 6 to 11 years was observed. Concerning the obtained results we suggest that (1) Alpha response system is functionally involved in 6-11-year-old children, though its development is not complete at the age of 11, the upper limit of our sample (2) With regard to their differential developmental time-courses, the magnitude and the phase-locking parameters might be suggested to relate to different functional aspects of the alpha response system. The applied original method makes it possible to analyze the phase-locking to stimulus (or phase-reordering) separately and independently from the amplitude (enhancement) of the frequency responses, thus providing for a deeper examination of the evoked frequency components.

Brain theta response predicts P300 latency in children

The present study assessed the relationship between stimulus-induced electroencephalographic (EEG) theta activity (4-7 Hz) and the endogenous component P300 of auditory event-related potentials (ERPs) using a developmental model. ERPs were recorded from 50 children (6-11 years old) for oddball target and frequent non-target stimuli and analysed in the time and frequency domains. The latency of the maximal theta response of the digitally filtered (4-7 Hz) ERPs was evaluated with respect to age and scalp topography effects. The maximal theta response latency at Cz and Pz decreased with increasing age and entirely predicted the developmental latency reduction of the parietal P400-700 (P3b) component in children.

Developmental changes in the alpha response system

Evoked and event-related brain potentials (ERPs) may be regarded as originating from the reorganization of the spontaneous EEG rhythms. The main objective of the present research was to study the alpha responses in 6-11 year old children to determine whether the ability to reorganize alpha activity after external stimulation demonstrates developmental changes that could reflect variations in information processing with increased age. A total of 50 children aged 6-11 years, divided into 5 age groups, and 10 young adults were assessed in a passive and an oddball condition. Alpha responses in the passive and non-target ERPs at Fz, Cz and Pz were analyzed to assess quantitatively the repeatability (phase-locking) of the evoked alpha oscillations. The alpha responses in 6-11 year old children were different from those in adults: (1) adults had significantly lower amplitude and stronger phase-locking than children; (2) adults had maximal alpha amplitudes and phase-locking over the vertex, whereas children displayed maximal responses over the parietal site; (3) the phase-locking of eldest (10-11 year old) children was as strong as in adults. These findings indicate that the alpha response system is functionally involved in 6-11 year old children, though its development is not complete at the age of 11, and the magnitude and the phase-locking parameters may relate to different functional aspects of the alpha response system. Thus, younger children do produce alpha responses during information processing, but are not able to engage this system as strongly as older children and adults.

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.

Topography of auditory evoked long-latency potentials in normal children, with particular reference to the N1 component

Topographic maps of late auditory evoked potentials were obtained with the Brain Atlas III system in 34 healthy, normal hearing children aged 8-16 years. The stimulus was a 100 msec, 500 Hz tone burst, presented separately to the left and right ears, at 75 dB HL. The resulting auditory evoked potentials showed a prominent N1, after about 100 msec, and a topographic map with a corresponding fronto-lateral focus designated as the focus of N1 (FN1). Foci with varying positions and amplitudes were identified in 33 of 34 subjects after left ear stimulation and in 29 of 32 subjects after right ear stimulation. The topography showed a high degree of stability in most subjects, with the position of the negative "peak" of FN1 in front of the interaural line and with a dominance contralateral to the ear stimulated. There was a significant decrease in the latency of N1 with increasing age. FN1 tended to change position with age and some differences from adults were also observed. In conclusion, a distinct topographic pattern of the N1 component of the late auditory evoked potentials was seen in the majority of children. It remains to be established to what extent this method may be clinically useful for disclosing functional disturbances in the central auditory pathways.

EEG, auditory evoked potentials and evoked rhythmicities in three-year-old children

According to our working hypothesis, the resonance properties of the brain systems play an important role in internal brain communications (e.g., Başar, 1992; Başar, Başar-Eroglu, Demiralp & Schürmann, 1992). It was assumed that evoked potentials (EPs) reflect brain resonance properties, showing enhancement, time and frequency-locking during the poststimulus period. All these phenomena might be referred to the spontaneous (intrinsic) EEG rhythms according to the excitability rule and the related concept of brain system response susceptibility: a brain system could react to internal or external stimuli producing those rhythms or frequency components, which have already been present in intrinsic or spontaneous activity (Başar, 1980). In order to test the hypothesis of response susceptibility, in the present paper we used an natural model--3-year-old children--to investigate how brain systems respond to external stimulation if their spontaneous rhythms are different in comparison to the spontaneous EEG rhythms in adults. For that purpose we used a combined time and frequency domain approach. The spectral characteristics of the spontaneous EEGs as well as the frequency components of auditory EPs elicited under identical auditory stimulation in 3-year-old children and adults aged 20-22 years were compared. Our observations support the hypothesis for response susceptibility; if in a given frequency channel the spontaneous brain rhythms are missing, they are also absent in the evoked and induced rhythmicities and vice versa: children at 3 years do not create alpha resonance upon sensory stimulation while they do not have developed EEG rhythms in the range of 8-15 Hz. Elicited under identical experimental conditions (auditory stimulation with fixed stimulus parameters) children and adult evoked rhythms differ. It was concluded that the AEPs recorded in 3-year-old children might be regarded mainly as a superposition of rhythmicities in delta and theta ranges. These rhythmicities are prolonged and delayed in comparison to the corresponding rhythms in adults.

Visual evoked potentials in term light-for-gestational-age infants and infants of diabetic mothers

The latency and amplitude of the first negative peak of visual evoked potentials (VEP) were evaluated in 52 term infants, investigated within 48 h after birth. Sixteen were light-for-gestational-age (LGA), 16 were appropriate-for-gestational-age (AGA) and 20 were infants of diabetic mothers (IDM). The VEP latency was shorter in LGA infants compared to AGA infants, and it was closely related to the birth weight deviation. The VEP latency was inversely related to gestational age and positively related to head circumference. When corrected for gestational age and head circumference, the VEP latency was not significantly different between the subgroups, nor related to the birth weight deviation, ponderal index or skinfold thickness. Thus, it could be argued that the high conduction velocity in LGA infants is due to stress maturation or alternatively due to the smaller head circumference. The VEP amplitude was higher in LGA infants when compared with AGA infants, and inversely related to the birth weight deviation. No differences were found in VEP latency or VEP amplitude between IDM and AGA infants.

Longitudinal and cross-sectional comparisons of young children's cognitive ERPs and behavior in a picture-matching task: preliminary findings

Event-related brain potentials (ERPs) were recorded from 19 children (6-8 years old at initial testing) performing cognitive tasks in two longitudinal testing sessions administered one year apart. The task used was a modification, using pictorial stimuli, of Posner's (1978) letter-matching experiments. In separate blocks of trials, subjects had to decide whether two sequentially-presented slides were physically identical, shared the same name, or came from the same semantic category. Subjects indicated their choice via a same-different delayed response following the second slide. Behavioral data showed large effects of longitudinal Age reflecting increases in accuracy from Run 1 to Run 2. These effects were corroborated by analyses of cross-sectional Age, suggesting that the performance changes reflected cognitive growth, rather than practice effects. In a similar fashion, both N400 and P700 (classical 'P300') showed reductions in peak latency that appeared to be true age changes, since these latencies shortened as a function of Run of testing as well as cross-sectional Age, and there were no Run by Age interactions. Small sample sizes as well as methodological shortcomings of the current design limit the conclusions that can be drawn from these data. Nevertheless, this study demonstrates the feasibility and usefulness of a cross-sectional/short-term longitudinal design and provides information on the extent and direction of behavioral and ERP changes that can be observed over this limited age range.

Prolonged latencies of the N2 and P3 of the auditory event-related potential in children at risk for schizophrenia. A preliminary report

In previous studies investigating long latency components of the event-related potential (ERP), schizophrenic patients generally showed reduced P3 amplitudes and in some studies prolonged N2 or P3 latencies. As there is a higher risk of offspring of schizophrenics than of mentally healthy parents developing this disease, the present study was intended to clarify whether ERP components (in particular the N2 and P3) differ between these two groups of children. Twelve high-risk and 12 age-matched control children (aged 9-16 years) performed an auditory oddball task in order to assess late ERP components. This task required the subject to covertly count rare target tone pips (P = 0.2) irregularly interspersed among frequent standard tone pips (P = 0.8) in two series of 400 pips. ERPs were recorded from midline electrodes (Fz, Cz, Pz). The results indicated distinctly prolonged N2 and P3 latencies in ERPs to target stimuli in children of schizophrenic patients. These findings suggest a slowed target classification in these children.

Dose-response effects of chronic methylphenidate administration on late event-related potentials in attention deficit disorder

Stimulants, such as methylphenidate, are extensively used in the treatment of attention deficit disorder. In the present study, we used a double-blind placebo-controlled, prospective protocol to evaluate the effects of methylphenidate (MP) (dose 0.1 and 0.33 mg/kg three times daily) on the late event-related potentials, some of which are considered biological attention correlates. Sixteen patients, 6-15 years old, were tested, using an auditory target selection paradigm. The latencies of N200 and amplitudes of P150 increased with MP (p less than 0.01). These effects are in the direction of normal maturational change. The latencies of P300 tended to be shorter in adolescents than in children, and with high MP dose the P300 latencies became even shorter in adolescents but were prolonged in children (p less than 0.05). This pattern of change supports the view that pharmacological interactions with various cerebral phenomena including cognition may be age-specific.