Two- and three-stimuli auditory oddball ERP tasks and neuropsychological measures in aging

Daily biofeedback to modulate heart rate oscillations affects structural volume in hippocampal subregions targeted by the locus coeruleus in older adults but not younger adults

Using data from a clinical trial, we tested the hypothesis that daily sessions modulating heart rate oscillations affect older adults' volume of a region-of-interest (ROI) comprised of adjacent hippocampal subregions with relatively strong locus coeruleus (LC) noradrenergic input. Younger and older adults were randomly assigned to one of two daily biofeedback practices for 5 weeks: (1) engage in slow-paced breathing to increase the amplitude of oscillations in heart rate at their breathing frequency (Osc+); (2) engage in self-selected strategies to decrease heart rate oscillations (Osc-). The interventions did not significantly affect younger adults' hippocampal volume. Among older adults, the two conditions affected volume in the LC-targeted hippocampal ROI differentially as reflected in a significant condition × time-point interaction on ROI volume. These condition differences were driven by opposing changes in the two conditions (increased volume in Osc+ and decreased volume in Osc-) and were mediated by the degree of heart rate oscillation during training sessions.

Daily biofeedback to modulate heart rate oscillations affects structural volume in hippocampal subregions targeted by the locus coeruleus in older adults but not younger adults

Using data from a clinical trial, we tested the hypothesis that daily sessions modulating heart rate oscillations affect older adults' volume of a region-of-interest (ROI) comprised of adjacent hippocampal subregions with relatively strong locus coeruleus (LC) noradrenergic input. Younger and older adults were randomly assigned to one of two daily biofeedback practices for 5 weeks: 1) engage in slow-paced breathing to increase the amplitude of oscillations in heart rate at their breathing frequency (Osc+); 2) engage in self-selected strategies to decrease heart rate oscillations (Osc-). The interventions did not significantly affect younger adults' hippocampal volume. Among older adults, the two conditions affected volume in the LC-targeted hippocampal ROI differentially as reflected in a significant condition x time-point interaction on ROI volume. These condition differences were driven by opposing changes in the two conditions (increased volume in Osc+ and decreased volume in Osc-) and were mediated by the degree of heart rate oscillation during training sessions.

Effects of exploring a novel environment on memory across the lifespan

Exploration of a novel environment has been shown to promote memory formation in healthy adults. Studies in animals have suggested that such novelty-induced memory boosts are mediated by hippocampal dopamine. The dopaminergic system is known to develop and deteriorate over the lifespan, but so far, the effects of novelty on memory across the lifespan have not yet been investigated. In the current study, we had children, adolescents, younger, and older adults (n = 439) explore novel and previously familiarized virtual environments to pinpoint the effects of spatial novelty on declarative memory in humans across different age groups. After exploration, words were presented while participants performed a deep or shallow encoding task. Incidental memory was quantified in a surprise test. Results showed that participants in the deep encoding condition remembered more words than those in the shallow condition, while novelty did not influence this effect. Interestingly, however, children, adolescents and younger adults benefitted from exploring a novel compared to a familiar environment as evidenced by better word recall, while these effects were absent in older adults. Our findings suggest that the beneficial effects of novelty on memory follow the deterioration of neural pathways involved in novelty-related processes across the lifespan.

The reliability of P300 and the influence of age, gender and education variables in a 50 years and older normative sample

OBJECTIVES

The present study aims to investigate the effects of age, gender, and level of education on P300 in a healthy population, aged 50 years and over; and determine the reliability metrics for different conditions and measurement methods.

METHOD

Auditory and visual oddball recordings of 171 healthy adults were investigated. A fully automated preprocessing was applied to elicit ERP P300. Maximum peak amplitude, latency and mean amplitudes were measured. Data were stratified by age, gender, and education to determine group-level differences by using repeat measures of ANOVA. The internal consistency of P300 was calculated by a split-half method using odd-even segments. Test-retest reliability was assessed by calculating the intraclass correlation coefficient (ICC).

RESULTS

Maximum peak P300 amplitudes were higher in the 50-64 years age group compared to the >65 years age group; and females showed increased P300 amplitudes compared to males. P300 measures showed fair to good internal consistency and poor to good test-retest reliability.

CONCLUSION

Age and gender should be taken into account when designing ERP studies with elderly individuals. P300 showed good internal consistency in general, between gender groups and age groups. Long-term test-retest reliability was lower but acceptable. These findings can be interpreted as the strength of P300 by being an objective and reliable method independent of cultural differences. Here we underline several factors that may affect P300 measures and discuss other possible factors that should be standardized for P300 to be used in clinical settings.

Dynamics of the "Cognitive" Brain Wave P3b at Rest for Alzheimer Dementia Prediction in Mild Cognitive Impairment

Alzheimer's disease (AD) is the most common cause of dementia that involves a progressive and irrevocable decline in cognitive abilities and social behavior, thus annihilating the patient's autonomy. The theoretical assumption that disease-modifying drugs are most effective in the early stages hopefully in the prodromal stage called mild cognitive impairment (MCI) urgently pushes toward the identification of robust and individualized markers of cognitive decline to establish an early pharmacological intervention. This requires the combination of well-established neural mechanisms and the development of increasingly sensitive methodologies. Among the neurophysiological markers of attention and cognition, one of the sub-components of the 'cognitive brain wave' P300 recordable in an odd-ball paradigm -namely the P3b- is extensively regarded as a sensitive indicator of cognitive performance. Several studies have reliably shown that changes in the amplitude and latency of the P3b are strongly related to cognitive decline and aging both healthy and pathological. Here, we used a P3b spatial filter to enhance the electroencephalographic (EEG) characteristics underlying 175 subjects divided into 135 MCI subjects, 20 elderly controls (EC), and 20 young volunteers (Y). The Y group served to extract the P3b spatial filter from EEG data, which was later applied to the other groups during resting conditions with eyes open and without being asked to perform any task. The group of 135 MCI subjects could be divided into two subgroups at the end of a month follow-up: 75 with stable MCI (MCI-S, not converted to AD), 60 converted to AD (MCI-C). The P3b spatial filter was built by means of a signal processing method called Functional Source Separation (FSS), which increases signal-to-noise ratio by using a weighted sum of all EEG recording channels rather than relying on a single, or a small sub-set, of channels. A clear difference was observed for the P3b dynamics at rest between groups. Moreover, a machine learning approach showed that P3b at rest could correctly distinguish MCI from EC (80.6% accuracy) and MCI-S from MCI-C (74.1% accuracy), with an accuracy as high as 93.8% in discriminating between MCI-C and EC. Finally, a comparison of the Bayes factor revealed that the group differences among MCI-S and MCI-C were 138 times more likely to be detected using the P3b dynamics compared with the best performing single electrode (Pz) approach. In conclusion, we propose that P3b as measured through spatial filters can be safely regarded as a simple and sensitive marker to predict the conversion from an MCI to AD status eventually combined with other non-neurophysiological biomarkers for a more precise definition of dementia having neuropathological Alzheimer characteristics.

Age-related differences in bottom-up and top-down attention: Insights from EEG and MEG

Attention operates through top‐down and bottom‐up processes, and a balance between these processes is crucial for daily tasks. Imperilling such balance could explain ageing‐associated attentional problems such as exacerbated distractibility. In this study, we aimed to characterize this enhanced distractibility by investigating the impact of ageing upon event‐related components associated with top‐down and bottom‐up attentional processes. MEG and EEG data were acquired from 14 older and 14 younger healthy adults while performing a task that conjointly evaluates top‐down and bottom‐up attention. Event‐related components were analysed on sensor and source levels. In comparison with the younger group, the older mainly displayed (1) reduced target anticipation processes (reduced CMV), (2) increased early target processing (larger P50 but smaller N1) and (3) increased processing of early distracting sounds (larger N1 but reduced P3a), followed by a (4) prolonged reorientation towards the main task (larger RON). Taken together, our results suggest that the enhanced distractibility in ageing could stem from top‐down deficits, in particular from reduced inhibitory and reorientation processes.

Validation of DE50-MD dogs as a model for the brain phenotype of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD), a fatal musculoskeletal disease, is associated with neurodevelopmental disorders and cognitive impairment caused by brain dystrophin deficiency. Dog models of DMD represent key translational tools to study dystrophin biology and to develop novel therapeutics. However, characterisation of dystrophin expression and function in the canine brain is lacking. We studied the DE50-MD canine model of DMD that has a missense mutation in the donor splice site of exon 50. Using a battery of cognitive tests, we detected a neurocognitive phenotype in DE50-MD dogs, including reduced attention, problem solving and exploration of novel objects. Through a combination of capillary immunoelectrophoresis, immunolabelling, quantitative PCR and RNAScope in situ hybridisation, we show that regional dystrophin expression in the adult canine brain reflects that of humans, and that the DE50-MD dog lacks full-length dystrophin (Dp427) protein expression but retains expression of the two shorter brain-expressed isoforms, Dp140 and Dp71. Thus, the DE50-MD dog is a translationally relevant pre-clinical model to study the consequences of Dp427 deficiency in the brain and to develop therapeutic strategies for the neurological sequelae of DMD.

Summary: The DE50-MD canine model of Duchenne muscular dystrophy (DMD) shows cognitive and brain biochemical changes secondary to dystrophin deficiency in the brain, and is a relevant pre-clinical model to develop therapies for DMD.

Investigating the Relationships of P3b with Negative Symptoms and Neurocognition in Subjects with Chronic Schizophrenia

Neurocognitive deficits and negative symptoms (NS) have a pivotal role in subjects with schizophrenia (SCZ) due to their impact on patients' functioning in everyday life and their influence on goal-directed behavior and decision-making. P3b is considered an optimal electrophysiological candidate biomarker of neurocognitive impairment for its association with the allocation of attentional resources to task-relevant stimuli, an important factor for efficient decision-making, as well as for motivation-related processes. Furthermore, associations between P3b deficits and NS have been reported. The current research aims to fill the lack of studies investigating, in the same subjects, the associations of P3b with multiple cognitive domains and the expressive and motivation-related domains of NS, evaluated with state-of-the-art instruments. One hundred and fourteen SCZ and 63 healthy controls (HCs) were included in the study. P3b amplitude was significantly reduced and P3b latency prolonged in SCZ as compared to HCs. In SCZ, a positive correlation was found between P3b latency and age and between P3b amplitude and the Attention-vigilance domain, while no significant correlations were found between P3b and the two NS domains. Our results indicate that the effortful allocation of attention to task-relevant stimuli, an important component of decision-making, is compromised in SCZ, independently of motivation deficits or other NS.

Internal consistency reliability of the P300 to novelty in infants: The influence of trial number and data loss due to artifacts

The P300 is an event-related potential component that reflects attention to motivationally salient stimuli and may be a promising tool to examine individual differences in cognitive-affective processing very early in development. However, the psychometric properties of the P300 in infancy are unknown, a fact that limits the component's utility as an individual difference measure in developmental research. To address this gap, 38 infants completed an auditory three-stimulus oddball task that included frequent standard, infrequent deviant, and novel stimuli. We quantified the P300 at a single electrode site and at region of interest (ROI) and examined the internal consistency reliability of the component, both via split-half reliability and as a function of trial number. Results indicated that the P300 to standard, deviant, and novel stimuli fell within moderate to high internal consistency reliability thresholds, and that scoring the component at an ROI led to slightly higher estimates of reliability. However, the percentage of data loss due to artifacts increased across the course of the task, suggesting that including more trials will not necessarily improve the reliability of the P300. Together, these results suggest that robust and reliable measurement of the P300 will require designing tasks that minimize trial number and maximize infant tolerability.

The Appraisal Approach to Aging and Emotion: An Integrative Theoretical Framework

To advance our understanding of how emotional experience changes across the adult life span, we propose an integrative theoretical framework: the appraisal approach to aging and emotion (AAAE). AAAE posits that (a) age-related cognitive, motivational, and physical changes fundamentally change the appraisal system in certain ways, and that (b) older adults often deploy appraisal processes in different ways relative to their younger counterparts. As such, we hypothesize that these age-related changes to the appraisal process underlie the finding that older and younger adults tend to experience different emotions. In this paper we integrate findings from the aging literature with appraisal theory, grounding AAAE in theoretical and empirical work relevant to the relationship between aging and appraisal processes. Using our theoretical framework, it is possible to identify critical points of investigation for aging and emotion researchers to further develop our understanding of the proximal-level determinants of age differences in emotion.

Pre-attentive Visual Processing in Alzheimer's Disease: An Event-related Potential Study

INTRODUCTION

While identifying Alzheimer's Disease (AD) in its early stages is crucial, traditional neuropsychological tests tend to lack sensitivity and specificity for its diagnosis. Neuropsychological studies have reported visual processing deficits of AD, and event-related potentials (ERPs) are suitable to investigate pre-attentive processing with superior temporal resolution.

OBJECTIVE

This study aimed to investigate visual attentional characteristics of adults with AD, from pre-attentive to attentive processing, using a visual oddball task and ERPs.

METHODS

Cognitively normal elderly controls (CN) and patients with probable AD (AD) were recruited. Participants performed a three-stimulus visual oddball task and were asked to press a designated button in response to the target stimuli. The amplitudes of 4 ERPs were analyzed. Mismatchnegativity (vMMN) was analyzed around the parieto-occipital and temporo-occipital regions. P3a was analyzed around the fronto-central regions, whereas P3b was analyzed around the centro-parietal regions.

RESULTS

Late vMMN amplitudes of the AD group were significantly smaller than those of the CN group, while early vMMN amplitudes were comparable. Compared to the CN group, P3a amplitudes of the AD group were significantly smaller for the infrequent deviant stimuli, but the amplitudes for the standard stimuli were comparable. Lastly, the AD group had significantly smaller P3b amplitudes for the target stimuli compared to the CN group.

CONCLUSION

Our findings imply that AD patients exhibit pre-attentive visual processing deficits, known to affect later higher-order brain functions. In a clinical setting, the visual oddball paradigm could be used to provide helpful diagnostic information since pre-attentive ERPs can be induced by passive exposure to infrequent stimuli.

Temporal Dynamics of Visually Induced Motion Perception and Neural Evidence of Alterations in the Motion Perception Process in an Immersive Virtual Reality Environment

Even though reciprocal inhibitory vestibular interactions following visual stimulation have been understood as sensory-reweighting mechanisms to stabilize motion perception; this hypothesis has not been thoroughly investigated with temporal dynamic measurements. Recently, virtual reality technology has been implemented in different medical domains. However, exposure in virtual reality environments can cause discomfort, including nausea or headache, due to visual-vestibular conflicts. We speculated that self-motion perception could be altered by accelerative visual motion stimulation in the virtual reality situation because of the absence of vestibular signals (visual-vestibular sensory conflict), which could result in the sickness. The current study investigated spatio-temporal profiles for motion perception using immersive virtual reality. We demonstrated alterations in neural dynamics under the sensory mismatch condition (accelerative visual motion stimulation) and in participants with high levels of sickness after driving simulation. Additionally, an event-related potentials study revealed that the high-sickness group presented with higher P3 amplitudes in sensory mismatch conditions, suggesting that it would be a substantial demand of cognitive resources for motion perception on sensory mismatch conditions.

Neural correlates of auditory sensory memory dynamics in the aging brain

The auditory system allows us to monitor background environmental sound patterns and recognize deviations that may indicate opportunities or threats. The mismatch negativity and P3a potentials have generators in the auditory and inferior frontal cortex and index expected sound patterns (standards) and any aberrations (deviants). The mismatch negativity and P3a waveforms show increased positivity for consecutive standards and deviants preceded by more standards. We hypothesized attenuated repetition effects in older participants, potentially because of differences in prefrontal functions. Young (23 ± 5 years) and older (75 ± 5 years) adults were tested in 2 oddball paradigms with pitch or location deviants. Significant repetition effects were observed in the young standard and deviant waveforms at multiple time windows. Except the earliest time window (30-100 ms), repetition effects were absent in the older group. Repetition effects were significant at frontal but not temporal lobe sites and did not differ among pitch and location deviants. However, P3a repetition was evident in both ages. Findings suggest age differences in the dynamic updating of sensory memory for background sound patterns.

Mental workload of young and older adults gauged with ERPs and spectral power during N-Back task performance

Mental workload has been shown to correlate with alpha and theta band power but only few EEG studies focused on the relation between these bands and Event Related Potentials (ERPs), more specifically the P300 component. We report on an EEG study on mental workload where not only young but also older adults performed an N-Back task. Participants watched a sequence of visual pictures and indicated whether the current picture was the same as the one shown N pictures before. We considered N = 4 difficulty levels and analyzed the relation between these and P300 amplitude and theta and alpha band power, and also examined the effect of age, level of education, work activities, and task accuracy. Our results revealed a decrease in P300 amplitude and alpha band activity for higher difficulty levels for young adults in the parietal region. However, for older adults, fatigue played a more important role than we could anticipate as the alpha band power increased for the highest task difficulty level, and since performance accuracy also decreased, it could even be a sign of task disengagement. Beside alpha band, theta band activity showed a positive correlation with task difficulty level for both young and older adults. Additionally, we found higher P300 amplitudes for young adults compared to older adults, in line with their higher performance accuracies and lower reaction times. In conclusion, we showed that P300 amplitude and alpha and theta bands power provide complementary information for judging mental workload during N-Back performance for young and older subjects and for detecting mental fatigue and task disengagement.

Effects of aging on P300 between late young-age and early middle-age adulthood: an electroencephalogram event-related potential study

The aim of this study was to identify age-related changes of P300 peak amplitude and P300 latency between closely separated nonsenile age groups (late young-aged adults and early middle-aged adults) and to investigate whether or not P300 has the potential to be used as a measure of cognitive aging even among nonsenile age groups. Twenty-eight adults (25-55 years old) completed an event-related potential oddball task. The elicitation of both P300 peak amplitude and P300 latency indicated age-related changes of P300. The results of the study showed that the P300 target peak amplitude was significantly larger in late young age compared with early middle age and that P300 target latency was also significantly delayed in early middle age compared with late young age. The results of this work contribute toward research efforts on a consensus on how aging affects event-related potential and/or P300. The main conclusions are that there exist significant age-related P300 changes even between closely separated, relatively younger, and nonsenile age groups, and that P300 has the potential to be used as a measure for cognitive aging even in nonsenile adults.

Lack of progressive reduction in P3 amplitude after the first-episode of schizophrenia: A 6-year follow-up study

P3 event-related potential may track the course of neurophysiological pathology in schizophrenia. Reduction in the amplitude of the auditory P3 is a widely replicated finding, already present at the first psychotic episode, in schizophrenia. Whether a progressive deficit is present in auditory P3 in schizophrenia over the course of illness is yet to be clarified. Previous longitudinal studies did not report any change in P3 over time in schizophrenia. However, these studies have been inconclusive, because of their relatively short follow-up periods, lack of follow-up data on controls, and assessment of patients already at the chronic stages of schizophrenia. Auditory P3 potentials, elicited by an oddball paradigm, were assessed in 14 patients with first-episode schizophrenia and 22 healthy controls at baseline and at the 6-year follow-up. P3 amplitudes were smaller in patients with first-episode schizophrenia than in controls. Importantly, over the 6-year interval, the P3 amplitudes were reduced in controls, but they did not change in patients. The lack of P3 reduction over time in patients with schizophrenia might be explained by the maximal reduction in P3 already at baseline or by the alleviation of P3 reduction over time.

Auditory perception in the aging brain: the role of inhibition and facilitation in early processing

Aging affects the interplay between peripheral and cortical auditory processing. Previous studies have demonstrated that older adults are less able to regulate afferent sensory information and are more sensitive to distracting information. Using auditory event-related potentials we investigated the role of cortical inhibition on auditory and audiovisual processing in younger and older adults. Across puretone, auditory and audiovisual speech paradigms older adults showed a consistent pattern of inhibitory deficits, manifested as increased P50 and/or N1 amplitudes and an absent or significantly reduced N2. Older adults were still able to use congruent visual articulatory information to aid auditory processing but appeared to require greater neural effort to resolve conflicts generated by incongruent visual information. In combination, the results provide support for the Inhibitory Deficit Hypothesis of aging. They extend previous findings into the audiovisual domain and highlight older adults' ability to benefit from congruent visual information during speech processing.

Combined frontal and parietal P300 amplitudes indicate compensated cognitive processing across the lifespan

In the present study the frontal and parietal P300, elicited in an auditory oddball paradigm were investigated in a large sample of healthy participants (N = 1572), aged 6–87. According to the concepts of the compensation-related utilization of neural circuits hypothesis (CRUNCH) it was hypothesized that the developmental trajectories of the frontal P300 would reach a maximum in amplitude at an older age than the amplitude of the parietal P300 amplitude. In addition, the amplitude of the frontal P300 was expected to increase with aging in adulthood in contrast to a decline in amplitude of the parietal P300 amplitude. Using curve-fitting methods, a comparison was made between the developmental trajectories of the amplitudes of the frontal and parietal P300. It was found that the developmental trajectories of frontal and parietal P300 amplitudes differed significantly across the lifespan. During adulthood, the amplitude of the parietal P300 declines with age, whereas both the frontal P300 amplitude and behavioral performance remain unaffected. A lifespan trajectory of combined frontal and parietal P300 amplitudes was found to closely resemble the lifespan trajectory of behavioral performance. Our results can be understood within the concepts of CRUNCH. That is, to compensate for declining neural resources, older participants recruit additional neural resources of prefrontal origin and consequently preserve a stable behavioral performance. Though, a direct relation between amplitude of the frontal P300 and compensatory mechanisms cannot yet be claimed.

P300 development across the lifespan: a systematic review and meta-analysis

Background

The P300 component of the event-related potential is a large positive waveform that can be extracted from the ongoing electroencephalogram using a two-stimuli oddball paradigm, and has been associated with cognitive information processing (e.g. memory, attention, executive function). This paper reviews the development of the auditory P300 across the lifespan.

Methodology/Principal Findings

A systematic review and meta-analysis on the P300 was performed including 75 studies (n = 2,811). Scopus was searched for studies using healthy subjects and that reported means of P300 latency and amplitude measured at Pz and mean age. These findings were validated in an independent, existing cross-sectional dataset including 1,572 participants from ages 6–87. Curve-fitting procedures were applied to obtain a model of P300 development across the lifespan. In both studies logarithmic Gaussian models fitted the latency and amplitude data best. The P300 latency and amplitude follow a maturational path from childhood to adolescence, resulting in a period that marks a plateau, after which degenerative effects begin. We were able to determine ages that mark a maximum (in P300 amplitude) or trough (in P300 latency) segregating maturational from degenerative stages. We found these points of deflection occurred at different ages.

Conclusions/Significance

It is hypothesized that latency and amplitude index different aspects of brain maturation. The P300 latency possibly indexes neural speed or brain efficiency. The P300 amplitude might index neural power or cognitive resources, which increase with maturation.

Abnormal salience network in normal aging and in amnestic mild cognitive impairment and Alzheimer's disease

The salience network (SN) serves to identify salient stimuli and to switch between the central executive network (CEN) and the default-mode network (DMN), both of which are impaired in Alzheimer's disease (AD)/amnestic mild cognitive impairment (aMCI). We hypothesized that both the structural and functional organization of the SN and functional interactions between the SN and CEN/DMN are altered in normal aging and in AD/aMCI. Gray matter volume (GMV) and resting-state functional connectivity (FC) were analyzed from healthy younger (HYC) to older controls (HOC) and from HOC to aMCI and AD patients. All the SN components showed significant differences in the GMV, intranetwork FC, and internetwork FC between the HYC and HOC. Most of the SN components showed differences in the GMV between the HOC and AD and between the aMCI and AD. Compared with the HOC, AD patients exhibited significant differences in intra- and internetwork FCs of the SN, whereas aMCI patients demonstrated differences in internetwork FC of the SN. Most of the GMVs and internetwork FCs of the SN and part of the intranetwork FC of the SN were correlated with cognitive differences in older subjects. Our findings suggested that structural and functional impairments of the SN may occur as early as in normal aging and that functional disconnection between the SN and CEN/ DMN may also be associated with both normal aging and disease progression.

Asymmetry in stimulus and response conflict processing across the adult lifespan: ERP and EMG evidence

Several studies have shown that conflict processing improves from childhood to adulthood and declines from adulthood to old age. However the neural mechanisms underlying this lifespan asymmetry were previously unexplored. We combined event-related potentials (ERPs) and electromyography (EMG) to examine lifespan changes in stimulus and response conflict processing using a modified Stroop task. We used a Stroop task that a priori dissociated stimulus and response conflict. Delayed P3b latency and increased amplitude revealed that middle age adults have a deficit in stimulus processing. Additionally a sustained P3a across frontal and central electrodes occurred only in middle age adults indicating the recruitment of frontal activity. Conversely, decreased lateralized readiness potential (LRP) amplitude and increased EMG activity in the incorrect hand in adolescents reveal protracted development of response processing into late adolescence. The N450, a measure of conflict processing, was found to be sensitive to both stimulus and response conflict. Altogether these results provide evidence for asymmetrical differences in stimulus and response conflict processing across adolescence, young adulthood and middle age.

Age-related decrease in functional connectivity of the right fronto-insular cortex with the central executive and default-mode networks in adults from young to middle age

The right fronto-insular cortex (rFIC) is a core node of the salience network (SN) and plays a critical role in switching between the central executive network (CEN) and the default-mode network (DMN), an important function in cognitive processing. In the present study, we tested the hypothesis that the functional connectivity (FC) between the rFIC and the CEN and DMN may decrease with age in adults from youth to middle age given that the intra- and inter-network FCs of the three networks decline in aged people. We performed voxel-wise FC analysis based on resting state functional MRI data (171 subjects; 17-62 years of age) to investigate whether the FCs of the rFIC are associated with age in normal adults. We found age-related decreases in the positive FCs between the rFIC and the CEN and in the negative FCs between the rFIC and the DMN with and without atrophy correction. These findings suggest that the connection of the rFIC with the CEN and DMN is degraded even in middle-aged adults, which may influence the role of the rFIC in effectively switching between the CEN and DMN and may further affect cognitive function in these subjects.

Behavioural correlates of the P3b event-related potential in school-age children

The latency and amplitude of the P3b component of event-related potentials (ERPs) have been related to behavioural performance on several attention and memory tasks in adult populations. However, the extent to which these results apply to children is unknown. This study examined the neurobehavioral correlates of the P3b component in a longitudinal sample of school-age children from Arctic Québec. Children (N=110; mean age=11.3years) were assessed on an ERP auditory oddball paradigm and a neurobehavioral evaluation targeting several aspects of cognition, including the Stewart Extended Continuous Performance Test (E-CPT), California Verbal Learning Test (CVLT), Stroop Color-Word Interference Test, and five subtests from the Wechsler Intelligence Scale for Children-Fourth edition (WISC-IV). P3b latency was positively related to reaction time measures and negatively associated with performance on the WISC-IV Digit Span Forward subtest. Amplitude of the P3b was associated with shorter completion time on the Stroop test and better delayed recognition memory performance among children who did not use semantic strategies on the CVLT. Profile analyses revealed no difference in scalp distribution of the P3b according to performance on these tests. The results are consistent with previous studies with older participants and suggest that, despite age-related differences in waveform and scalp distribution, the P3b component relates to similar neurocognitive processes in children and adults.

Age-related changes in early novelty processing as measured by ERPs

This study investigated age-related changes in the early processing of novel visual stimuli using ERPs. Well-matched old (n=30), middle-aged (n=30), and young (n=32) subjects were presented standard, target/rare, and perceptually novel visual stimuli under Attend and Ignore conditions. Our results suggest that the anterior P2 component indexes the motivational salience of a stimulus as determined by either task relevance or novelty. Its enhancement by focused attention does not decrease with age. Its responsiveness to novel stimuli is particularly striking in older adults. The age-related increase in the anterior P2 to novel visual stimuli does not appear to be due to impaired inhibitory control associated with aging. Rather, the enhanced anterior P2 to novel stimuli in older adults may be linked to age-related changes in the process of matching unusual visual stimuli to stored representations, which is indexed by the temporally overlapping anterior N2 component whose amplitude substantially decreases with age.

The effect of age on event-related potentials (ERP) associated with face naming and with the tip-of-the-tongue (TOT) state

This study examined the effects of aging on the ERP components associated with the different processing stages in a face naming task. Two hundred photographs were presented to 13 young and 10 elderly adults, who had to press a button and then to say the name aloud (KNOW condition), or "Can't remember" if they were experiencing a tip-of-the-tongue state (TOT condition). Young adults showed larger ERP amplitudes in KNOW than in TOT in the 550-750 and 1550-2000ms intervals, but the older adults did not show any such differences. The older adults showed a specific lengthening in ERP latencies from 250ms onwards, and smaller mean amplitudes in the 550-750ms interval in the KNOW category and in the 750-1000ms interval in both categories, and a wider and more frontalized scalp topographical distribution of the ERP amplitudes than the young adults. The results may indicate activation of compensatory mechanisms in elderly adults.

P300 amplitude age reductions are not caused by latency jitter

Studies of the event-related potentials (ERPs) P3a/P3b have given insights into age effects on cognitive processes in the brain, and it has been established that latency increases and amplitude decreases with age. However, if latency jitter, that is, variation in single trial latencies, is larger in elderly than in younger participants, this may create an artificial age-amplitude correlation. The aim of this article is to test whether correction for latency jitter affects the P3a/P3b age correlations. One hundred thirty-three healthy adults (20-88 years old) went through a 3-stimuli visual oddball paradigm. Latency jitter was corrected by use of a Maximum Likelihood Estimation method. The results showed that corrections for latency jitter did not significantly affect the correlations between P3a/P3b and age. It is concluded that previous reports of amplitude reduction as a function of age seem to be valid regardless of whether latency jitter correction has been applied.

Compensatory neural activity distinguishes different patterns of normal cognitive aging

Most cognitive neuroscientific research exploring the nature of age-associated compensatory mechanisms has compared old adults (high vs. average performers) to young adults (not split by performance), leaving ambiguous whether findings are truly age-related or reflect differences between high and average performers throughout the life span. Here, we examined differences in neural activity (as measured by ERPs) that were generated by high vs. average performing old, middle-age, and young adults while processing novel and target events to investigate the following three questions: (1) Are differences between cognitively high and average performing subjects in the allocation of processing resources (as indexed by P3 amplitude) specific to old subjects, or found throughout the adult life span? (2) Are differences between cognitively high and average performing subjects in speed of processing (as indexed by target P3 latency) of similar magnitude throughout the adult life span? (3) Where along the information processing stream does the compensatory neural activity attributed to cognitively high performing old subjects begin to take place? Our results suggest that high performing old adults successfully manage the task by a compensatory neural mechanism associated with the modulation of controlled processing and the allocation of more resources, whereas high performing younger subjects execute the task more efficiently with fewer resources. Differences between cognitively high and average performers in processing speed increase with age. Middle-age seems to be a critical stage in which substantial differences in neural activity between high and average performers emerge. These findings provide strong evidence for different patterns of age-related changes in the processing of salient environmental stimuli, with cognitive status serving as a key mediating variable.

Cognitive function, P3a/P3b brain potentials, and cortical thickness in aging

The purpose of the study was to assess the relationship between the P3a/P3b brain potentials, cortical thickness, and cognitive function in aging. Thirty-five younger and 37 older healthy participants completed a visual three-stimuli oddball ERP (event-related potential)-paradigm, a battery of neuropsychological tests, and MRI scans. Groups with short vs. long latency, and low vs. high amplitude, were compared on a point by point basis across the entire cortical mantle. In the young, thickness was only weakly related to P3. In the elderly, P3a amplitude effects were found in parietal areas, the temporoparietal junction, and parts of the posterior cingulate cortex. P3b latency was especially related to cortical thickness in large frontal regions. Path models with the whole sample pooled together were constructed, demonstrating that cortical thickness in the temporoparietal cortex predicted P3a amplitude, which in turn predicted executive function, and that thickness in orbitofrontal cortex predicted P3b latency, which in turn predicted fluid function. When age was included in the model, the relationship between P3 and cognitive function vanished, while the relationship between regional cortical thickness and P3 remained. It is concluded that thickness in specific cortical areas correlates with scalp recorded P3a/P3b in elderly, and that these relationships differentially mediate higher cognitive function.

The development of visual P3a and P3b

The relationship of visual P3a and P3b to age and neuropsychological performance was investigated in 26 healthy children (6.8-15.8 years) and 129 adult volunteers (20.0-88.8 years). Within the sample of children, an effect of age on midline topography was observed, with higher frontal amplitudes in the youngest compared to the oldest children. Increasing age was associated with lower P3a and P3b amplitude and shorter P3b latency at Fz. Performance on neuropsychological tests (matrix reasoning from WASI, digit span from WAIS, word order and hand movement from Kaufman) was only weakly associated with measures of P3a and P3b. The analyses were then repeated with the full life-span sample (n = 155). It was found that for P3a, amplitude decreased and latency increased with age. For P3b, the pattern was more complex, with a nonlinear amplitude reduction and no latency change with age. It appears that the development of P3a in children represents the start of processes that later continue in the adult life-span, but that the automatic processes indexed by P3a seems to mature earlier than the controlled processes reflected by P3b. Finally, it was demonstrated that the relationships between neuropsychological test scores (matrix reasoning, digit span) and P3 parameters were complex, following a mix of linear and nonlinear patterns. It is suggested that the neuropsychological significance of the different P3a and P3b parameters may change from childhood to the adult life-span.

Cognitive status impacts age-related changes in attention to novel and target events in normal adults

In this study, the authors investigated the relationship between the cognitive status of normal adults and age-related changes in attention to novel and target events. Old, middle-age, and young subjects, divided into cognitively high and cognitively average performing groups, viewed repetitive standard stimuli, infrequent target stimuli, and unique novel visual stimuli. Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at different kinds of stimuli served as a measure of visual attention and exploratory activity. Cognitively high performers spent more time viewing novel stimuli than cognitively average performers. The magnitude of the difference between cognitively high and cognitively average performing groups was largest among old subjects. Cognitively average performers had slower and less accurate responses to targets than cognitively high performers. The results provide strong evidence that the link between engagement by novelty and higher cognitive performance increases with age. Moreover, the results support the notion of there being different patterns of normal cognitive aging and the need to identify the factors that influence them.

Increased responsiveness to novelty is associated with successful cognitive aging

The animal literature suggests that exposure to more complex, novel environments promotes neurogenesis and cognitive performance in older animals. Studies in humans indicate that participation in intellectually stimulating activities may serve as a buffer against mental decline and help to sustain cognitive abilities. Here, we show that across old adults, increased responsiveness to novel events (as measured by viewing duration and the size of the P3 event-related potential) is strongly linked to better performance on neuropsychological tests, especially those involving attention/executive functions. Cognitively high performing old adults generate a larger P3 response to visual stimuli than cognitively average performing adults. These results suggest that cognitively high performing adults successfully manage the task by appropriating more resources and that the increased size of their P3 component represents a beneficial compensatory mechanism rather than less efficient processing.

Age-related differences in attention to novelty among cognitively high performing adults

Age-related differences in attention to novel events were studied in well-matched, cognitively high performing old, middle-aged and young subjects. Event-related potentials were recorded during a visual novelty oddball task in which subjects controlled viewing durations that served as a behavioral measure of attentional allocation. All age groups had a larger P3 amplitude and longer viewing duration to novel than to standard stimuli, with no age-related differences in the magnitude of these effects, indicating old individuals were as engaged by the processing of novelty as younger adults. Old subjects had a larger, more anteriorly distributed P3 component to novels and standards. The increased P3 amplitude differs from prior reports of a diminished P3 response with processes, including aging, that have a potentially deleterious impact on the brain. We hypothesise that cognitively high performing old individuals successfully manage the task by relying on additional neural resources and perhaps more effortful frontal activity than their younger counterparts.

The functional and structural significance of the frontal shift in the old/new ERP effect

There is a lack of studies mapping electrophysiological event-related potentials (ERPs) to structural neuroanatomical characteristics. The aim of the present study was to integrate electrophysiological memory-related activity with cortical and hippocampal volume, as well as psychometric memory performance, in a life-span sample. More specifically, we wanted to investigate the functional significance of the often-observed frontal shift of ERP amplitude with increasing age and whether neuroanatomical characteristics can explain this shift. Sixty six healthy participants (20-78 years) went through a neuropsychological examination, MRI scans, and a visual recognition ERP task with verbal stimuli. The results showed that ERPs elicited in the recognition memory task (the old/new effect) correlated significantly with cortical volume, but not with hippocampal volume. Large cortex predicted more differentiated ERP activity and not just larger amplitude in general, implying more distinct and efficient retrieval. Furthermore, ERP amplitude, cortical volume, and hippocampal volume all predicted scores on a composite memory scale. All these relationship were dependent upon the common influence of age. Finally, the participants with the most anterior distribution of activity showed the poorest recognition memory performance. Neither cortical nor hippocampal volume were related to this frontal shift. It is concluded that the distribution of activity along the anterior-posterior axis in a memory paradigm may have functional but not neuroanatomical volumetric correlates. The functional correlates need not be restricted to the older age groups.

Basic information processing of neurotics and stables: An experimental ERP approach to personality and distractibility

The aim of the study was to investigate the effects of level of neuroticism on electrophysiological event-related potentials (ERPs) to different kinds of stimuli. The neuroticism items from the NEO-PI-R were administered to 168 female, right-handed undergraduates between 19 and 29 years of age. 20 highly neurotic and 22 highly stable persons underwent an ERP task that was designed to be a combination of an auditory P3a and a visual P3b oddball task. No significant differences in the P3a and P3b were detected. It is concluded that highly neurotic and highly stable persons do not differ in fast neurocognitive processing of neutral stimuli, and that cognitive differences between the groups may be located at another level in the sequence of information processing stages.

Age-dependent changes in distribution of P3a/P3b amplitude and thickness of the cerebral cortex

With increasing age, the electrophysiological event-related potentials P3a/P3b tend to get a more frontal maximum. The cognitive significance of this so-called frontal shift is not known, but hypotheses have focused on changes in the integrity of the frontal lobes. The aim of the present study was to test how the thickness of the cerebral cortex is related to the frontal shift. Well screened elderly participants went through a visual three-stimuli oddball-task, a battery of neuropsychological tests and magnetic resonance imaging scans. It was found that participants with frontocentral maxima had a thicker cerebral cortex in distinct areas than participants with parietal maxima, both for P3a and for P3b, while the parietal P3b participants had a thicker cortex in the anterior cingulate. This is the first study to demonstrate that age-dependent changes in the scalp distribution of electrophysiological activity are related to differences in thickness of the cerebral cortex.

Age-differences in verbal recognition memory revealed by ERP

Seventy-four participants (aged 20-82 years) went through a continuous performance recognition memory task with multiple repetitions of words and non-words while ERPs were recorded from the scalp. The old/new ERP effect (the difference in activation to stimuli correctly recognized as old and stimuli correctly recognized as new) for words but not non-words declined with increasing age in a linear pattern, but the relationship between the old/new effect and age varied throughout the ERP time window. Differences in topography between age groups were manifested in a frontal shift in activation for older age groups. Further, the data point to differences in semantic versus non-semantic processing across the adult life span, and it is concluded that specific cognitive memory processes are differentially involved at different ages.

Auditory P3 indexes personality traits and cognitive function in healthy men and women

The relationship of the auditory P3 event-related potential to major personality dimensions and neuropsychological performance was examined in psychiatrically healthy men and women (28 male, 15 female) recruited from the community. An auditory oddball paradigm was used to collect P3 amplitude and latency data. Personality traits were measured with the NEO Five-Factor Inventory. Several Wechsler Adult Intelligence Scale-Revised (WAIS-R) subtests, the Digit Symbol Test, and the Trail Making Test comprised the neuropsychological tests. A multivariate statistical procedure (Partial Least Squares) was used to quantify the relationships between P3 variables and personality and neuropsychological performance variables. P3 amplitude was negatively related to Neuroticism and positively related to Extraversion, Openness, Agreeableness and Conscientiousness. Better neuropsychological performance was associated with greater P3 amplitude and earlier latency. Thus, greater P3 amplitude was associated with less deviant personality scores and better neuropsychological performance in healthy subjects. Earlier P3 latency was also associated with better neuropsychological performance. The physiological significance of these relationships is not yet clear, but these results suggest that neural assemblies indexed by P3 may subserve both elemental cognition and healthy personality function.

Cortical volume and speed-of-processing are complementary in prediction of performance intelligence

The rationale for the present study was to investigate the relationship between cortical volume, the latency of the ERP component P3a (as a measure of speed-of-processing), and performance intelligence (not adjusted for age differences). Seventy-one participants aged 20-88 years underwent a visual 3-stimuli oddball ERP task, an MRI-scan, and intelligence testing. P3a latency and cortical volume shared 9% variance (p<.05) and both were significantly related to performance intelligence (R2=.26 and .40, respectively). The amount of explained variance increased significantly (to R2=.51) when both measures were used as simultaneous predictors. When a path diagram was constructed including age as an exogenous variable, P3a latency and cortical volume both significantly predicted performance intelligence, but were no longer related to one another. The main conclusion from the study is that speed and size are complementary in prediction of performance intelligence, and the theoretical implications are discussed.

Age-related differences in novelty and target processing among cognitively high performing adults

Previous research on age-related changes in ERP components in response to novel and target stimuli has not carefully controlled for differences in level of cognitive status between age groups, which may have contributed to the common findings of increased P3 latency, decreased P3 amplitude, and altered P3 scalp distribution. Here, cognitively high-performing (top third based on published norms) old, middle-aged, and young adults matched for IQ, education, and gender participated in a novelty oddball paradigm. There were no age-associated differences in P3 latency. Older adults had a larger, more anteriorly distributed P3 amplitude to all stimulus types, even repetitive standards, suggesting they may rely on increased resources and effortful frontal activity to successfully process any kind of visual stimulus. However, after controlling for this non-specific age-related processing difference, the amplitude and scalp distribution of the P3 component to novel and target stimuli were comparable across age groups, indicating that for cognitively high functioning elders there may be no age-related differences specific to the processing of novel and target events as indexed by the P3 component.

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.

Effects of auditory stimulus intensity and hearing threshold on the relationship among P300, age, and cognitive function

OBJECTIVE

Although P300 is regarded as cognitive or endogenous, studies have demonstrated that stimulus intensity influences the component. To isolate effects of hearing from cognition, two experiments were designed to compare the effects of variation in stimulus intensities with naturally occurring differences in hearing thresholds.

METHODS

In experiment 1, 18 participants were tested with 5 auditory oddball event-related potential (ERP) paradigms with different intensities. In experiment 2, an auditory oddball ERP task was completed by 3 groups of participants with different hearing thresholds (n=57). P300 was then correlated with block design and matrices from Wechsler's abbreviated scale of intelligence.

RESULTS

At Cz and Pz, manipulation of intensity had less effect on P300 than the observed differences between groups with different hearing thresholds. At Fz, however, the effect of manipulations of stimulus intensity was greater than the effect of naturally occurring differences in hearing thresholds. P300 still correlated in predicted directions with cognitive tests after correcting for the estimated effect of differences in hearing.

CONCLUSIONS

The results indicate that P300 is an index of cognitive function even when the relationship is corrected for perceptual differences, at least at posterior scalp areas.

The relationship between P3 and neuropsychological function in an adult life span sample

The relationship of P3 to age and neuropsychological performance was investigated in a sample of 71 well-functioning adults ranging in age from 21.8 to 94.7 years. ERPs were recorded while the participants performed an auditory two-stimuli oddball task in which the rare tones were to be counted. The Wechsler Abbreviated Scale of Intelligence (WASI) and the digit span subtest from the Wechsler Adult Intelligence Scale-R (WAIS-R) were administered. Regression analyses showed significant, linear effects of age on P3 latency and amplitude. Significant relationships between P3 and neuropsychological measures were found, in that P3 latency correlated moderately in predictable ways with scores on matrices, block design, and digit span. Overall, these relationships are best characterized by a linear function, but a non-linear component is involved in the relationship between P3 latency and fluid tests. Finally, a linear relationship between ERP components and age was found, while a curvilinear relationship was found between age and block design and matrices, respectively. There appears to be either partially different functions or structures underlying performance on these tests, the P3 component and performance on neuropsychological tests, or one must assume some variant of a multiplicative, as opposed to an additive, model of cognition.