Grade-related changes in event-related potentials (ERPs) in primary school children: Differences between two reading tasks

Abstract

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during word reading in a group of children who were followed over three consecutive years, starting at Grade 1. The first task required the child to read repeatedly presented words; the second task consisted of a series of different words, with each word being presented only once. All ERP components showed changes in amplitude as a function of grade: P240, N530, the parietal N150, and SW all decreased, whereas the temporal N360 and SW both increased. In addition, SW changed from no asymmetry to larger positivity over the right site, whereas N360 changed from symmetric amplitudes to larger amplitudes over the left hemisphere with grade. Single word presentations were associated with smaller SW activity and larger N530 and N360 amplitudes than were repeated word presentations. It was also found that proficient readers showed larger SW and N360 asymmetries and shorter vocal response times than did less proficient readers. In addition, a positive relationship was found between reading performance and ERP amplitudes over the left temporal hemisphere at Grades 2 and 3, particularly in the single word reading task. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in learning to read.     

Delayed P3 event-related potentials (ERPs) in thalamic hemorrhage.

Delayed P3 ERPs were recorded with an acoustic oddball paradigm in 5 patients affected by unilateral thalamic hemorrhage. P3 latencies in these 5 patients were above the normal mean latency of age-matched controls +2/+3 S.D.s. The P3 delay was persistent in serial follow-ups at 6 months from stroke. Normal P3 latencies were instead recorded in 4 patients with paramedian hemorrhage not involving or only partially involving the thalamus.     

Alterations in event-related potentials (ERPs) of MPTP-treated monkeys

Using an auditory 'oddball' paradigm and classical conditioning, we have studied auditory evoked potentials (AEPs) and P300-like potentials in monkeys pre- and post-MPTP treatment. Free-field acoustic stimuli were 500 Hz and 4000 Hz tones, which were designated as the 'frequent' and 'rare' conditions, respectively. The 4000 Hz stimuli were reinforced with mild somatosensory electrical stimulation. During the first few weeks following 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) administration, all monkeys gradually developed a parkinsonian syndrome, which partially, but not completely improved within 30-40 days in 2 animals. The amplitudes of the AEP were initially significantly decreased, but progressively returned to pretreatment magnitudes in the 2 monkeys which partially recovered. P300-like potentials were initially abolished in all animals; however, 30-40 days later P300 spontaneously re-emerged in the same 2 monkeys. Latencies of both of these signals were unaffected by MPTP. Acute administration of dopamine precursor during the first phase of neurotoxicity partially and temporarily improved depressed AEP amplitudes, but did not restore absent P300-like potentials. The relevance of these results for Parkinson's disease is discussed.     

Delayed P3 event-related potentials (ERPs) in thalamic hemorrhage

Delayed P3 ERPs were recorded with an acoustic oddball paradigm in 5 patients affected by unilateral thalamic hemorrhage. P3 latencies in these 5 patients were above the normal mean latency of age-matched controls +2/ +3 S.D.s. The P3 delay was persistent in serial follow-ups at 6 months from stroke. Normal P3 latencies were instead recorded in 4 patients with paramedian hemorrhage not involving or only partially involving the thalamus.     

Age-related changes in event-related potentials in visual discrimination tasks

Visual event-related potentials and reaction times in physical and semantic discrimination tasks were studied in 29 normal subjects between the ages of 21 and 74 years. The NA, N2 and P3 components of the evoked potential, and simple and GO/NOGO reaction times were observed in both kinds of discrimination. Significant age-related slowing of the GO/NOGO reaction time was observed only in the semantic discrimination task. The N2 and P3 latencies elicited by both the physical and semantic stimuli were significantly and positively correlated with age, although there was no significant correlation between the NA latency and age. The interpeak latency between N2 and P3 showed no age-related changes. The decline of cognitive information processing with advancing age was evident from the classification of a perceived event as reflected by the N2 component.     

Event-related brain potentials (ERPs) in schizophrenia for tonal and phonetic oddball tasks.

BACKGROUND: Prior studies using simple target detection ("oddball") tasks with pure tones have reported asymmetric reduction of the P3 event-related potential (ERP). This study investigated the time course and topography of ERPs recorded during both tonal and phonetic oddball tasks. METHODS: Event-related potentials of 66 patients (14 unmedicated) diagnosed with schizophrenia (n = 46) or schizoaffective disorder (n = 20) and 32 healthy adults were recorded from 30 scalp electrodes during two oddball tasks using consonant-vowel syllables or complex tones. Overlapping ERP components were identified and measured by covariance-based principal components analysis. RESULTS: Schizophrenic patients showed marked, task-independent reductions of early negative potentials (N1, N2) but not reduced P3 amplitude or abnormal P3 asymmetry. Task-related hemispheric asymmetries of the N2/P3 complex were similar in healthy adults and schizophrenic patients. Poorer task performance in patients was related to ERP amplitudes, but could not account for reductions of early negativities. CONCLUSIONS: The findings suggest that both patients and control subjects activated lateralized cortical networks required for pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination. Task-independent reductions of negativities between 80 and 280 msec after stimulus onset suggest a deficit of automatic stimulus classification in schizophrenia, which may be partly compensated by later effortful processing.     

Predictive validity of event-related potentials (ERPs) in relation to the directed forgetting effects.

OBJECTIVE: A directed forgetting paradigm (word method) was used to assess the relationships between the event-related potentials (ERPs) recorded during the study phase and the subsequent forgetting effects. METHODS: In the study phase 100 words were presented each followed by either an instruction to remember (R) or to forget (F). Then these 100 words, together with another 100 new words, were presented and subjects had to perform an old/new decision task. The forgetting effect was considered as the difference between the rate of R- and F-words correctly recognised. Based on this difference, the whole sample was divided into two 10-subject groups with high and low forgetting effect. RESULTS: From 300 to 600 msec post-instruction differences in ERPs between R and F instructions were similar in both groups. In contrast, in the 100-300 msec epoch, ERP differences only appeared in the high-effect group and consisted of an enhanced positive activity elicited by F instruction at frontal and prefrontal areas and a larger positivity associated to R instruction at parietal area. CONCLUSIONS: The findings suggest that the processing of the word is kept on stand-by until the instruction is provided. Instruction to remember would reactivate this processing, which would mainly involve the parietal area, whereas instruction to forget appears to trigger frontal and prefrontal mechanisms trying to inhibit such processing.     

Attentive and preattentive processing in narcolepsy as revealed by event-related potentials (ERPs)

Narcolepsy is a neurological disorder, characterised by excessive daytime sleepiness, sleep attacks, cataplexy and abnormal manifestations of rapid eye movement sleep. Recent studies suggest that neuropsychological impairments in narcolepsy may include memory and attention deficits due to a monoaminergic or cholinergic transmitter dysfunction. To explore the nature of cognitive problems, the P300 and mismatch negativity (MMN) event-related potentials were investigated in narcoleptic patients and matched controls. Narcoleptics showed significantly increased P300 amplitudes relative to controls, especially at frontal recording sites. While control subjects exhibited typically larger MMN over the right than the left hemisphere, in particular at frontal and central electrodes, narcoleptics did not show this asymmetry. These results are interpreted as possible alterations in cognitive preattentive and attentive processing associated with altered functioning of the prefrontal cortex in narcolepsy.     

Do event-related potentials (ERPs) reflect right hemisphere's processing of semantics?

To test the right hemisphere's functional difference in relation to semantically related vs. semantically unrelated linguistic tasks we investigated 25 young right-handed healthy adults. A S1-S2 design was used. At S1 one word was presented binaurally, at S2 two words dichotically. S1-S2 was composed of sentence-like (syntagmatic) and nonsentence-like (paradigmatic) word sequences with and without semantic relations. As control trials we used pure tones and modulated noise. The EEG was recorded over frontal, central and temporoparietal areas of both hemispheres. Referring to semantics it could be shown only that semantic relations between words increased the amount of recalled words. Additionally, ERPs reflected: modes of presentation (binaural vs. dichotic) processing of different linguistic categories (e.g., syntagmatic vs. paradigmatic) and frontocentrally focused neuronal processes of both hemispheres before language production.     

Modulation of event-related potentials (ERPs) by word repetition in a task with inconsistent mapping between repetition and response.

ERPs were recorded during 5 blocks of a continuous recognition memory task. In each block words were shown twice, separated by an average of 6 intervening items, and the task was to respond discriminatively on the basis of whether each word was appearing in that block for the first (first presentations) or the second (second presentations) time. In blocks 2-5, half of the words had also been shown in the immediately preceding block, and half were new to the experiment. Subjects were slower and less accurate at identifying first presentations of words that had appeared in the preceding block, as compared to first presentations of entirely new words. In the latency ranges of the N400 and late positive components, ERPs to words that had previously been presented were more positive-going than were ERPs to new words. These 'across-block' ERP repetition effects were qualitatively very similar to, and additive with, those evoked by words repeated within a block. These findings suggest that the effects of word repetition on ERPs are not dependent on an invariant mapping between repetition and response and are not a consequence of facilitated decision/response processing for repeated items.     

Longitudinal increases in reward-related neural activity in early adolescence: Evidence from event-related potentials (ERPs)

Adolescence is frequently described as a developmental period characterized by increased sensitivity to rewards. However, previous research on age-related changes in the neural response to gains and losses have produced mixed results, with only some studies reporting potentiated neural responses during adolescence. The current study examined the ERP responses to gains and losses during a simple monetary reward (i.e., Doors) task in a large and longitudinal sample of 248 adolescent females assessed at two time points, separated by two years. At baseline, when the sample was 8- to 14-years-old, age related to larger (i.e., more positive) ERP responses to both gains and losses; moreover, age-related effects were stronger in relation to gains than losses. Overall, the amplitude of the ERP response to gains, but not losses, significantly increased from baseline to follow-up; however, this effect was moderated by age, such that reward-related ERPs only increased longitudinally among the younger participants. At the follow-up assessment, ERP responses to gains and losses were equally related to age. Collectively, these within- and between-subjects findings suggest a relatively specific developmental increase in reward-related neural activity during late childhood and early adolescence.     

Strategic retrieval and retrieval orientation in reality monitoring studied by event-related potentials (ERPs)

Reality monitoring requires the differentiation between perceived and imagined events or between our own actions and the actions of others. The role of control processes in reality monitoring is yet not fully understood. In the current event-related potential (ERP) study, we investigated such control processes in the form of retrieval orientation and strategic retrieval of nontarget information. At study, complete or incomplete object words were presented in sentences. Participants had to identify the words as the subject of the sentence (perceive condition) or had to complete them upon presentation of a word fragment (self-generate condition). The participants' memory accuracy was better for generated items than for perceived items, as tested in a subsequent memory exclusion task. Comparison of ERPs to new items between the two test conditions (i.e. assessing retrieval orientation) showed more positive ERPs when generated object names were targeted. Retrieval orientation also modulated the early midfrontal old/new effect: Items of the self-generate condition elicited this effect irrespective of their target/nontarget status, while in response to the less well remembered items of the perceive condition it was only found when these items were defined as targets. Target retrieval (as reflected in the left-parietal old/new effect) occurred in both test conditions, but nontarget retrieval was observed only for generated items (when perceived items were targeted). Current findings indicate that retrieval orientation can modulate familiarity-related processes. The selective occurrence of nontarget retrieval for generated items corroborates the concept that the ease with which nontarget information can be accessed promotes nontarget retrieval.     

Visual event-related potential changes at two different tasks in nondemented Parkinson's disease.

A visual oddball paradigm and an S1-S2 paradigm were employed to evoke event-related potentials (ERPs) in 38 nondemented Parkinson's disease (PD) patients and 24 healthy elderly subjects. Delayed N200 and reduced P300 amplitude in the whole PD sample were only found in the S1-S2 paradigm. Delayed N200 and reaction time in PD with short duration of illness were found only after the S1-S2 paradigm, which might be an early sign of cognitive changes in PD. This is the first study to apply an S1-S2 paradigm for a visual P300 test in PD and proved the value of this paradigm for detecting minor cognitive abnormalities. ERP changes were correlated with clinical features. Reduced P300 amplitude for the S1-S2 paradigm was significantly correlated with WAIS-R scores and gait disturbance. The correlation between P300 amplitude and clinical scores has rarely been discussed before. P300 latency during the oddball paradigm in PD was influenced by age at test, age at onset, and duration of illness. This may explain why P300 results in nondemented PD have varied among previous authors.     

Early stages (P100) of face perception in humans as measured with event-related potentials (ERPs)

Summary. According to current ERP literature, face specific activity is reflected by a negative component over the inferior occipito-temporal cortex between 140 and 180 ms after stimulus onset (N170). A recently published study (Liu et al., 2002) using magnetoencephalography (MEG) clearly indicated that a face-selective component can be observed at 100 ms (M100) which is about 70 ms earlier than reported in most previous studies. Here we report these early differences at 107 ms between the ERPs of faces and buildings over the occipito-temporal cortex using electroencephalography. To exclude contrast differences as the main factor for this P100 differences we replicated this study using pictures of faces and scrambled faces. Both studies indicated that face processing starts already at ∼100 ms with an initial stage which can be measured not only with MEG but also with ERPs.     

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 Jyv?skyl? 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.     

Statistical detection of between-group differences in event-related potentials.

OBJECTIVE: Many event-related potential (ERP) situations do not fulfill the multivariate statistics requirement of more cases than measurements. Five simulation studies were carried to select a sensitive test for comparing two independent groups of ERPs. METHODS: Simulated signal and noise waveforms were generated using different combinations of parameters: cases or replications per group, correlation between data points, number of points, signal-to-noise ratio (S/N), etc. The false alarm (FA) rate of each method was assessed and their sensitivity compared over sets of 2000 simulated experiments per condition. RESULTS: Study 1 identified the 'Projection onto Centroids Difference Vectors' (PCDV) method of Haig and Gordon (Brain Topogr 1995;8:67) as very good, but its FA rate was erratic under several conditions. The following studies served to shape the implementation parameters of a version of PCDV, termed PCDVp, that assesses significance through random permutations of the case labels. The final form is very sensitive. For instance, with two groups of 48 trials of 30-point EEG-like waveforms, its power for alpha=0.05 is about 50% at S/N 1.0 and 90% at S/N 1.5 (amplitude). CONCLUSION: PCDVp requires no a priori knowledge and is sensitive to detect differences between independent sets of waveforms, topographies or spatio-temporal data.     

Midlatency auditory event-related potentials in mice: comparison to midlatency auditory ERPs in humans

Midlatency event-related potentials (ERPs) reflect early stages in processing of modality specific information. In humans, the auditory midlatency ERPs most investigated are the P1, N1 and P2. Abnormalities of these ERPs in neuropsychiatric disorders such as schizophrenia point to deficits in information processing at early stages. Investigations of corresponding ERPs in mice might thus permit to elucidate the molecular biology of such abnormalities. We conducted studies in mice and humans in order to establish the correspondence of midlatency ERPs in mice to the human P1, N1 and P2. We investigated their so-called recovery function-i.e. their systematic amplitude changes as a function of varying stimulus onset asynchrony (SOA). Furthermore, we explored effects of specific genetic alterations (ERK1 gene deletion Gdi1 gene deletion) on this measure. In mice, P1-like activity showed a significant recovery not present in human data. In contrast, N1-like and P2-like activity in mice demonstrated similar recovery functions as the corresponding ERPs in human subjects and could be best fitted by the same function. In addition, ERK1 gene knockout mice showed a significantly different N1 recovery function compared to wild-type mice, possibly related to enhanced memory functions in these mice. Our results indicate that midlatency ERPs in mice share some, but not all, characteristics with the human P1, N1 and P2. As in humans, N1 recovery may provide an assessment of auditory sensory memory function. Investigations of these ERPs in mice may thus permit to elucidate the abnormalities underlying deficient generation of these ERPs in neuropsychiatric disorders.     

The development of lateral event-related potentials (ERPs) related to word naming: a four year longitudinal study

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during a word naming task. Subjects were a group of children that were followed over four consecutive years starting at Kindergarten. ERP waveforms contained a sequence of positive and negative components (N150, P240, N360, N530 and SW). All components, except N150, showed changes in amplitude as a function of age, whereas SW, N360 and N150 also changed in hemispheric distribution. In addition, a relationship was found between reading performance and ERP amplitudes over the right parietal hemisphere in young children, and over the left temporal hemisphere in older children. Proficient readers showed larger (more negative) parietal N530 amplitudes than less proficient readers, especially when stimuli were degraded words. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in early and advanced stages of reading, that might possibly be related to visual word recognition.