A lifespan comparison of the reliability,test‐retest stability,and signal‐to‐noise ratio of event‐related potentials assessed during performance monitoring

The reliability, stability, and signal‐to‐noise ratio (SNR) of event‐related potentials (ERPs) were investigated in children, adolescents, younger adults, and older adults in performance monitoring tasks. P2, N2, P3, and P2‐N2 peak‐to‐peak amplitude showed high odd‐even split reliabilities in all age groups, ranging from.70 to.90. Multigroup analyses showed that test‐retest stabilities (across 2 weeks) of ERP amplitudes did not differ among the four age groups. In contrast, relative to adolescents and younger adults, SNRs were lower in children and older adults, with higher noise levels in children and lower signal power in older adults. We conclude that age differences in the SNR of stimulus‐locked ERPs can be successfully compensated by the averaging procedure with about 40 trials in the average. However, age differences in baseline noise and split‐half reliability should be considered when comparing age groups in single trial measures or time‐varying processes with ERPs.     

A simultaneous ERP/fMRI investigation of the P300 aging effect

One of the most reliable psychophysiological markers of aging is a linear decrease in the amplitude of the P300 potential, accompanied by a more frontal topographical orientation, but the precise neural origins of these differences have yet to be explored. We acquired simultaneous electroencephalogram (EEG)/functional magnetic resonance imaging (fMRI) recordings from 14 older and 15 younger adults who performed a 3-stimulus visual oddball task designed to elicit P3a and P3b components. As in previous reports, older adults had significantly reduced P3a/P3b amplitudes over parietal electrodes but larger amplitudes over frontal scalp with no between-group differences in accuracy or reaction time. Electroencephalogram/functional magnetic resonance imaging fusion revealed that the P3a age effects were driven by increased activation of left inferior frontal and cingulate cortex and decreased activation of inferior parietal cortex in the older group. P3b differences were driven by increased activation of left temporal regions, right hippocampus, and right dorsolateral prefrontal cortex in the older group. Our results support the proposal that the age-related P300 anterior shift arises from an increased reliance on prefrontal structures to support target and distractor processing.     

Behavioural and electrophysiological effects of visual paired associate context manipulations during encoding and recognition in younger adults,older adults and older cognitively declined adults

The current study examined the EEG of young, old and old declined adults performing a visual paired associate task. In order to examine the effects of encoding context and stimulus repetition, target pairs were presented on either detailed or white backgrounds and were repeatedly presented during both early and late phases of encoding. Results indicated an increase in P300 amplitude in the right parietal cortex from early to late stages of encoding in older declined adults, whereas both younger adults and older controls showed a reduction in P300 amplitude in this same area from early to late phase encoding. In the right hemisphere, stimuli encoded with a white background had larger P300 amplitudes than stimuli presented with a detailed background; however, in the left hemisphere, in the later stages of encoding, stimuli presented with a detailed background had larger amplitudes than stimuli presented with a white background. Behaviourally, there was better memory for congruent stimuli reinstated with a detailed background, but this finding was for older controls only. During recognition, there was a general trend for congruent stimuli to elicit a larger amplitude response than incongruent stimuli, suggesting a distinct effect of context reinstatement on underlying patterns of physiological responding. However, behavioural data suggest that older declined adults showed no memory benefits associated with context reinstatement. When compared with older declined adults, younger adults had larger P100 amplitude responses to stimuli presented during recognition, and overall, younger adults had faster recognition reaction times than older control and older declined adults. Further analysis of repetition effects and context-based hemispheric asymmetry may prove informative in identifying declining memory performance in the elderly, potentially before it becomes manifested behaviourally.     

The effects of age on the neural correlates of feedback processing in a naturalistic gambling game

We examined age‐related differences in the spatiotemporal distribution of event‐related brain potentials (ERPs) related to feedback processing in a virtual blackjack game. The behavioral data revealed that older adults were less risk seeking than younger adults both within and across trials. Age‐related differences were observed in the amplitude of several ERP components (P2‐FN‐P3a, P3a, slow wave activity) related to feedback processing. These components were localized to the anterior and posterior cingulate, the occipital cortex, and the inferior and medial frontal cortices. The effects of aging on the ERPs ranged from 200–2,000 ms after feedback onset. Our findings indicate that aging affects the activity of a distributed neural network that underpins processing the valence and motivational significance of feedback related to risky decisions.     

Physical activity and working memory in healthy older adults: An ERP study

This study examined the effects of physical activity on working memory in older adults using both behavioral and neuroelectric measures. Older adults were assigned to either a higher or lower physical activity group, and event‐related potentials were recorded during assessments of a modified Sternberg task. The results indicated that older adults in the higher physical activity group exhibited shorter response times, independent of the working memory load. Enhanced P3 and N1 amplitudes and a decreased P3 latency were observed in the higher physical activity group. These findings suggested that physical activity facilitates working memory by allocating more attentional resources and increasing the efficiency of evaluating the stimulus during the retrieval phase as well as engaging more attentional resources for the early discriminative processes during the encoding phase of a working memory task.     

Event-related potentials and comorbidity in alcohol-dependent adult males

The present study examined event-related potentials (ERPs) elicited by a visual discrimination task in a community sample of adult males with a lifetime diagnosis of alcohol dependence. Study participants were subtyped by the presence of additional comorbid disorders (antisocial personality, depression, and drug abuse or dependence). In all groups of alcohol-dependent subjects, even those without any additional comorbid disorders, P3 amplitude differed from that of a comparison group. Alcohol-dependent subjects with a diagnosis of illicit drug abuse or dependence, especially if they had antisocial personality as well, had the smallest amplitude responses. The amplitude profile of the P3 across the parietal electrodes used as active sites was flattened among alcoholic subjects, with P3 amplitude disproportionately reduced at the midline. Among alcoholic subjects with a lifetime diagnosis of depression, the flattened amplitude profile was due to elevated mean amplitude of the P3 at lateral leads, especially P4, relative to the comparison group. Alterations in ERP responses appear to be a general characteristic of alcoholism in men, although the presence of other comorbid disorders, particularly drug abuse or dependence together with antisocial personality, results in the greatest reductions in P3 amplitude.     

Age-related frontoparietal changes during the control of bottom-up and top-down attention: an ERP study

We investigated age-related changes in frontal and parietal scalp event-related potential (ERP) activity during bottom-up and top-down attention. Younger and older participants were presented with arrays constructed to induce either automatic “pop-out” (bottom-up) or effortful “search” (top-down) behavior. Reaction times (RTs) increased and accuracy decreased with age, with a greater age-related decline in accuracy for the search than for the pop-out condition. The latency of the P300 elicited by the visual search array was shorter in both conditions in the younger than in the older adults. Pop-out target detection was associated with greater activity at parietal than at prefrontal locations in younger participants and with a more equipotential prefrontal-parietal distribution in older adults. Search target detection was associated with greater activity at prefrontal than at parietal locations in older relative to younger participants. Thus, aging was associated with a more prefrontal P300 scalp distribution during the control of bottom-up and top-down attention. Early latency extrastriate potentials were enhanced and N2-posterior-contralateral (N2pc) was reduced in the older group, supporting the idea that the frontal enhancements may be due to a compensation for disinhibition and distraction in the older adults. Taken together these findings provide evidence that younger and older adults recruit different frontal-parietal networks during top-down and bottom-up attention, with older adults increasing their recruitment of a more frontally distributed network in both of these types of attention. This work is in accord with previous neuroimaging findings suggesting that older adults recruit more frontal activity in the service of a variety of tasks than younger adults.     

Olfactory, auditory, and visual ERPs from single trials: no evidence for habituation.

Event-related potentials (ERPs) using olfactory, auditory, and visual stimuli were recorded from young adults to assess possible component habituation across single trials among modalities. A single-stimulus ERP paradigm was used that employed a 10-min inter-stimulus interval (ISI) to minimize possible sensory adaptation and three stimulus trials for each modality to assess initial habituation effects. The present findings were: (1) P3 amplitude does not habituate appreciably over the initial three trials but may increase from the first to second trial. (2) ERPs from a single-stimulus paradigm with a very long ISI produce significantly correlated component amplitudes for the olfactory, auditory, and visual modalities. (3) P3 amplitude from olfactory stimuli demonstrated scalp topography similar to that for auditory and visual ERPs. These findings suggest that the single-stimulus task using a long ISI produces highly comparable and stable P3 components from olfactory, auditory, and visual stimuli. Application of single-stimulus paradigm to olfactory ERP methods is supported.     

A comparison of saccade evoked potentials recorded during reading and tracking tasks

The influence of visual processing demands on saccade-triggered evoked potentials was investigated at P3, P4 and Oz recording sites during reading and tracking tasks. To maximize the physical similarities between tasks, subjects tracked a series of lights that flashed in a stereotypic reading pattern behind a page of text; eye movements recorded during reading initiated the light sequence. In the first experiment, a significant decrease observed in the latency of the major positive peak recorded from Oz during tracking was attributed to the smaller amplitude of tracking, relative to reading, saccades. To confirm this interpretation, the experiment was repeated with modification to the light display. As anticipated, equating saccade amplitudes across tasks eliminated waveform differences in the second experiment. Although peak latencies and amplitudes were not influenced reliably by visual processing demands, tracking potentials exhibited a negative DC shift relative to reading waveforms that was significant at 174 msec at the Oz site. These data suggest that the saccade-triggered evoked potential components generally are insensitive to task differences within the visual modality when visual configuration and eye movement parameters are controlled.     

Event-related potentials in autistic and healthy children on an auditory choice reaction time task

Event-related potentials (ERPs) were recorded from midline (Fz, Cz, Pz) and lateral sites (F3, F4, P3, P4) in autistic children (n = 7) and age-matched controls (n = 9) on an auditory choice reaction time task. Subjects were asked to press a button to an infrequent target (500 Hz, P = 0.14) and to ignore higher pitched infrequent (2000 Hz, P = 0.14) and frequent (1000 Hz) non-targets. Autistic subjects made twice as many errors of omission as controls and showed a higher criterion (beta) for targets. Maximum ERP peak amplitudes showed a more varied scalp distribution in the autistic group. N1 latencies were consistently shorter in the autistic group and in 3 subjects the target P3 latencies were markedly longer than for the controls. Compared to controls, the N1 amplitude of the autistic response was larger to the rare stimuli (particularly to non-targets). The amplitude of the P3 component was smaller in the autistic group (particularly to the target). The stimuli were also presented in a passive condition requiring no response. After subtraction of the waveform obtained in the passive condition from that obtained in the active condition or subtraction of the waveform elicited by the rare non-target from that elicited by the target, N1 target amplitude was larger in control than in autistic children. Autistic subjects showed more early negativity to the rare non-target at left frontal and a larger P3 to the target at right parietal sites. ERPs of autistic children are more responsive to stimulus features (e.g. high/rare non-target tone) and less responsive to their associations or meaningfulness (e.g. target P3). Attention-related ERPs of autistic children show signs of precocious (right dominance for P3) and delayed development (P3 not maximal at parietal sites).     

A cross-sectional examination of age and physical activity on performance and event-related brain potentials in a task switching paradigm.

Younger and older physically active and sedentary adults participated in a task switching paradigm in which they performed a task repeatedly or switched between two different tasks, while measures of response speed, response accuracy, P3 amplitude, and P3 latency were recorded. Overall, response times were faster and midline P3 amplitudes were larger for the active than for the sedentary participants. P3 latencies discriminated between active and sedentary individuals on trials in which multiple task sets were maintained in memory and task switches occurred unpredictably but not in blocks of trials in which a single task was repeatedly performed. Results are discussed in terms of the specificity and generality of physical activity effects on cognition.     

Methylphenidate's effects on paired-associate learning and event-related potentials of young adults

The effects of methylphenidate (0.3 mg/kg) on young adults' paired-associate learning (PAL) of consonant–vowel–consonant (CVC) pairs and concomitant event-related potentials were assessed. The stimulant elevated mood and heart rate but did not affect PAL performance. For the first CVC, there were amplitude increases with learning for P3b at Pz, P2 at midline sites, and for a negative slow wave at Cz. For the second CVC, P3b and positive slow wave amplitude declined with learning. Increases in P3b amplitude to the first CVC were attributed to increments in stimulus meaningfulness. Decreases in P3b amplitude to the second CVC were interpreted as resulting from fewer disconfirmed expectations of feedback. The negative slow wave following the first CVC was viewed as a contingent negative variation. Methylphenidate increased parietal P3b amplitude for CVC 2, averaged over learning phases.     

Targets and non-targets in the aging brain: A go/nogo event-related potential study

This study tested whether older adults show enhanced suppression of inappropriate processing of non-target information, as marked with the nogo-P3 event-related potential (ERP). Healthy younger and older adults were tested on a simple go/nogo task with visually presented numbers. Unlike in most of the previous studies, go and nogo stimuli were matched for frequency and conflict level in order to minimize the impact of task difficulty, probability monitoring, or conflict detection and resolution on the age-related ERP differences. Older adults showed slower go responses but a comparable accuracy to younger controls. The parietal go-P3 latency was also delayed with aging, while the central nogo-P3 was more pronounced in older adults than in younger controls. The amplitude of this component negatively correlated with go-RTs. In line with previous studies, this suggests that a partial response preparation to nogo events is strongly suppressed in older adults, especially faster ones.     

Life-span changes in P3a

The relationship of visual P3a to age was investigated in a life-span sample. The aims of the study were (1) to assess to what extent P3a, relative to P3b, decreases with increasing age; (2) To assess at which recording sites the relationship between P3a and age is strongest; (3) to investigate whether the relationship between P3a and age is best described as linear or nonlinear. One hundred and three well-functioning adults, 20-92 years old, were given a health interview, a battery of neuropsychological tests, and performed a visual three-stimuli oddball ERP task yielding both a P3a and a P3b. P3a and age was moderately correlated, with coefficients reaching.53 (Cz) and -.52 (Pz) for latency and amplitude, respectively. P3b was to a much lesser extent related to age. Generally, the age-P3a relationship was strongest at midline and central electrodes. Finally, the relationship between age and P3a was best described as linear. P3a seems selectively more impaired with age than P3b, but this impairment seems less pronounced at Fz than at Cz and Pz. There is a need for complex theoretical integration of these and previous findings.     

Wavelet Analysis of P3a and P3b

Target/standard discrimination difficulty and the degree of stimulus "novelty" were manipulated systematically in a three-stimulus oddball task to assess how these variables affect target and non-target P300 scalp distributions for visual stimuli. Wavelet transformation (WT) analyses were performed on the non-target (P3a) and target (P3b) ERPs to assay how the underlying electroencephalographic (EEG) activity was affected by both the difficulty and novelty factors. When target/standard discrimination was easy, P300 amplitude was higher for the target than the non-target across all electrode sites, and both demonstrated parietal maximums. In contrast, when target/standard discrimination was difficult, non-target amplitude (P3a) was higher and earlier over the frontal/central electrode sites for both levels of novelty, whereas target amplitude (P3b) was greater parietally and occurred later than the non-target components and was generally unaffected by non-target novelty level. The WT analyses indicated that appreciable theta activity was related to the more novel non-target stimuli; primarily target component delta coefficients were affected by the discrimination difficulty variable. The findings suggest that target/standard discrimination difficulty, rather than stimulus novelty, determines P3a generation for visual stimuli but that the underlying theta oscillations are differentially affected by stimulus novelty. WT analysis methods are discussed along with the theoretical and neurophysiological implications of the findings.     

Task relevance and recognition of concealed information have different influences on electrodermal activity and event‐related brain potentials

This study aimed at differentiating between memory‐ and task‐related processes and their correlates on the electrodermal and electrocortical level during information concealment. Variations of the Guilty Knowledge Test were implemented in two experiments while we measured skin conductance responses (SCRs) and event‐related brain potentials. P300 amplitudes were specifically enhanced for items requiring a deviant behavioral response but they were not sensitive to concealed knowledge. In contrast, N200 amplitudes differed between memorized and irrelevant items in both experiments. SCR measures reflected a combined influence of task relevance and probe recognition, and they provided incremental validity above N200 amplitudes. These results suggest that the P300 mainly reflects task relevance in the given experimental setting whereas the N200 amplitude is sensitive to previously encoded information and potentially linked to response monitoring processes.     

Event-related potentials (ERPs) to hemifield presentations of emotional stimuli: differences between depressed patients and healthy adults in P3 amplitude and asymmetry.

Depression may involve dysfunction of right parietotemporal cortex, a region activated during perception of affective stimuli. To further test this hypothesis, event-related brain potentials (ERPs) were measured in a paradigm previously shown to produce ERP asymmetries to affective stimuli over parietal sites in healthy adults. Pictures of patients with dermatological diseases showing disordered or healed facial areas before (negative) or after (neutral) surgical treatment were briefly exposed for 250 ms to either the left or right hemifield. ERPs of 30 unmedicated, unipolar depressed patients and 16 healthy adults, all right-handed, were recorded from 30 electrodes. A principal components analysis extracted factors which closely corresponded to distinctive ERP components previously reported for this task (N1, N2, early P3, late P3, slow wave). Significant effects of emotional content, i.e. enhanced amplitudes to negative than neutral stimuli, were found for early and late P3. Control subjects showed significant hemispheric asymmetries of emotional processing for late P3 (peak latency 460 ms), with the largest emotional content effects over the right parietal region. In striking contrast to control subjects, depressed patients did not show an increase in late P3 for negative compared to neutral stimuli over either hemisphere and had smaller late P3 amplitude than control subjects. Patients did, however, show larger early P3 (peak latency 330 ms) to negative than neutral stimuli. Results suggest intact early discrimination but abnormal late appraisal of affective content in depression, which may arise from selective inhibition of right parietal regions integral for perceiving and evaluating emotional stimuli.     

Shifting visual attention away from fixation is specifically associated with alpha band activity over ipsilateral parietal regions

We studied brain activity during the displacement of attention in a modified visuo‐spatial orienting paradigm. Using a behaviorally relevant no‐shift condition as a control, we asked whether ipsi‐ or contralateral parietal alpha band activity is specifically related to covert shifts of attention. Cue‐related event‐related potentials revealed an attention directing anterior negativity (ADAN) contralateral to the shift of attention and P3 and contingent negative variation waveforms that were enhanced in both shift conditions as compared to the no‐shift task. When attention was shifted away from fixation, alpha band activity over parietal regions ipsilateral to the attended hemifield was enhanced relative to the control condition, albeit with different dynamics in the upper and lower alpha subbands. Contralateral‐to‐attended parietal alpha band activity was indistinguishable from the no‐shift task.     

Age-related effects of novel visual stimuli in a letter-matching task: an event-related potential study

Younger and older participants (n=8 in each age group) performed a letter-matching task, where they had to respond to identical letters (P=0.15). Task-relevant (target and non-target) letters were presented on two corners of an imagery square, while on the other two corners irrelevant letters were presented. In some trials (P=0.05), pictures of visual objects (novels, unrelated to the matching task) were presented. Reaction times were slower and error rates higher for older adults. The amplitude of the N1 event-related potential component was smaller over anterior locations for the older adults. All target stimuli elicited a late positivity over anterior locations for both age groups, but the late positivity (P3b) was absent over posterior scalp for the older adults. For the younger adults, novel stimuli elicited a large negative component (N2(novel)) that was maximal over the central location. No such activity was observed for older adults. Based on the results, processing of novel stimuli is considered to be compromised in the elderly.     

Listening strategy for auditory rhythms modulates neural correlates of expectancy and cognitive processing

A recently described auditory tempo perception paradigm revealed individual differences in perceived stimulus timing for identical stimulus sequences. The current study takes advantage of this paradigm by recording event‐related potentials (ERPs) concurrent with task performance in order to reveal brain responses that reflect individual differences in timing strategy. No strategy‐related differences were observed in sensory encoding of tones, as measured by the P1‐N1‐P2 complex. However, the contingent negative variation (CNV) leading up to the final tone of the sequence varied as a function of strategy, as did a parietal‐maximum late positive component (P3b) that occurred following the final tone. These data suggest that temporal expectancy for and cognitive processing of the final tone of rhythmic sequences underlies differences in strategy during rhythm perception.