Dual-task repetition alters event-related brain potentials and task performance

ObjectiveWe examined the modulation of event-related brain potentials (ERPs) and the accuracy of sensori-motor coordination on short-term repetition of the concurrent performance of a somatosensory discrimination (oddball) task and a visuo-motor tracking task.MethodsThe subjects concurrently performed visuomotor tracking and somatosensory oddball tasks. In the dual-task condition, the subjects performed the visuomotor tracking and somatosensory oddball tasks concurrently for about an hour. In the oddball-only condition, they performed just the oddball task for the same period.ResultsTracking performance improved with task repetition. The amplitude of the P300 elicited by somatosensory stimulation in the oddball-only condition decreased significantly with task repetition, whereas in the dual-task condition, it showed a complex pattern of change. The earlier responses were decreased in amplitude in the dual-task condition compared to the oddball-only condition, and gradually decreased with task repetition in both conditions.ConclusionsDynamic changes in ERPs and task performance with dual-task repetition support the idea that dual-task repetition produces changes in resource allocation following the automation of stimulus processing in addition to so-called habituation.SignificanceThis study also provides evidence for use of ERP amplitudes as physiological indices of functionally different types of resources.     

Electrophysiological correlates of retrieval processing: effects of consistent versus inconsistent retrieval demands

Studies employing event-related potentials (ERPs) during tests of recognition memory have reported differences in neural activity elicited by new test items according to the specific demands of the retrieval task, such as retrieving studied words versus pictures. The present study investigated whether differential processing of new items is possible when retrieval demands vary unpredictably on a trial-by-trial basis. In separate study-test phases, subjects encoded lists of intermixed words and pictures, and undertook retrieval tests with words as test items. Each test item was preceded by a task cue that signaled whether subjects were to attempt to retrieve a word or a picture from the study list. In the "blocked"condition, the targeted study material remained constant throughout the test, whereas in the "mixed"condition, the targeted material varied unpredictably across trials. New-item ERPs were more positive-going when words rather than pictures were targeted in the "blocked" condition, replicating previous findings, but this effect was absent in the "mixed"condition. The findings are consistent with the hypothesis that differential processing of retrieval cues depends upon the adoption of different task sets ("retrieval orientations" that develop over multiple trials and cannot be adjusted merely in response to an instructional cue. Unlike the new-item ERPs, ERPs elicited by the task cues in the mixed condition differed according to targeted material, but only on trials when there was a switch between target material. The implications of these findings for understanding the different retrieval strategies engaged when retrieval demands are consistent versus inconsistent are discussed.     

Greater sensitivity of the P300 component to bimodal stimulation in an event-related potentials oddball task

ObjectiveStudies that explore neurophysiological correlates of psychiatric disorders have commonly used event-related potentials during a visual or an auditory oddball task with the main results being changes in the P300 component. In the present study, a bimodal oddball design with synchronized pairs of audio–visual stimuli was used to further improve the clinical sensitivity of the P300.MethodsTwo groups of healthy participants, one consisting of students displaying anxious–depressive tendencies and the other of control students, completed visual, auditory and two kinds of audio–visual oddball task (one using emotional stimuli and the other using geometrical figures and simple sounds), in which they had to detect deviant rare stimuli among more frequently presented standard stimuli as quickly as possible. Behavioral performance and P300 data were analyzed.ResultsThe subjects with anxious and depressive tendencies had lower P300 amplitudes than controls, but only in the bimodal tasks.ConclusionsAlthough the two groups differed in their levels of anxiety and depression, only the bimodal tasks were able to identify these differences.SignificancesThese results suggest that a bimodal oddball design should be used in future studies to increase the sensitivity of P300 differences for differentiating between healthy participants and those with clinical symptoms.     

An event-related brain potential study of auditory attention in cochlear implant users

ObjectiveCochlear implants (CIs) provide access to the auditory world for deaf individuals. We investigated whether CIs enforce attentional alterations of auditory cortical processing in post-lingually deafened CI users compared to normal-hearing (NH) controls.MethodsEvent-related potentials (ERPs) were recorded in 40 post-lingually deafened CI users and in a group of 40 NH controls using an auditory three-stimulus oddball task, which included frequent standard tones (Standards) and infrequent deviant tones (Targets), as well as infrequently occurring unique sounds (Novels). Participants were exposed twice to the three-stimulus oddball task, once under the instruction to ignore the stimuli (ignore condition), and once under the instruction to respond to infrequently occurring deviant tones (attend condition).ResultsThe allocation of attention to auditory oddball stimuli exerted stronger effects on N1 amplitudes at posterior electrodes in response to Standards and to Targets in CI users than in NH controls. Other ERP amplitudes showed similar attentional modulations in both groups (P2 in response to Standards, N2 in response to Targets and Novels, P3 in response to Targets). We also observed a statistical trend for an attenuated attentional modulation of Novelty P3 amplitudes in CI users compared to NH controls.ConclusionsERP correlates of enhanced CI-mediated auditory attention are confined to the latency range of the auditory N1, suggesting that enhanced attentional modulation during auditory stimulus discrimination occurs primarily in associative auditory cortices of CI users.SignificanceThe present ERP data support the hypothesis of attentional alterations of auditory cortical processing in CI users. These findings may be of clinical relevance for the CI rehabilitation.     

Thirty-site P300 scalp distribution, amplitude variance across sites, and amplitude in detection of deceptive concealment of multiple guilty items

Previous tests of P300 in deception detection have focused mainly on amplitude analysis. Since countermeasures for such tests have been reported, we looked here at other possible variables as deception indices: P300 scalp distribution and amplitude variance, both across 30 sites. We were also concerned, for the first time, in testing for recognition of more than one guilty item in a mock crime scenario. There were three groups: (1) two-probe group, two of six items were guilty knowledge (GK) items; (2) three-probe group, three of six items were GK items; (3) control group, zero of six items were GK items. In group analyses, in the two-probe group, P300s for lies were significantly greater than P300s for truthful responses. There were significant interactions of condition (Lie vs Truth) by site, suggesting different scalp profiles for deceptive versus truthful responding. Amplitude variance across sites was also greater in Lie than in Truth blocks. These results did not obtain in the three-probe and control groups. In terms of amplitude variances in probe conditions across groups, two-probe group was larger than three-probe and control groups. Regarding individual diagnostics, the variance method yielded a greater-than-chance detection rate of 71% versus 28% false positives. Regarding amplitude at multiple nonfrontal sites, 71% of guilty subjects were detected versus 14% false positives. Grier's (1971) A' indices of various test discrimination efficiencies varied from .76 to .87. Results of the present study suggested further investigation of the variance method as a diagnostic tool for lie detection.     

Event-related potential changes due to early-onset Parkinson’s disease in parkin (PARK2) gene mutation carriers and non-carriers

ObjectiveTo investigate cognitive functions in non-demented patients with early-onset Parkinson's disease (PD), and to compare PARK2 gene mutation carriers and non-carriers by means of event-related brain potentials (ERPs).MethodsThe participants comprised patients with early-onset PD (EOPD) and healthy controls (HC). Patients with EOPD were divided into two groups as carriers of known pathogenic variants of PARK2 gene (EOPD-PC) and non-carriers of genes involved in familial PD (EOPD-NC). ERP data were collected during auditory oddball and visual continuous performance test (CPT).ResultsBoth EOPD groups (EOPD-PC and EOPD-NC) displayed reduced and delayed P3 in response to oddball target and CPT NoGo. CPT Go P3 was reduced in EOPD-NC but not in EOPD-PC. Oddball target N1 was reduced and P2 was enhanced in both EOPD-PC and EOPD-NC. In both cognitive tasks, RTs were prolonged and accuracy was lower in EOPD-PC and EOPD-NC.ConclusionsWe found several EOPD-related neurophysiologic changes, implying impairments in cognitive functions. Pairwise comparisons between EOPD-PC and EOPD-NC revealed no significant ERP marker.SignificanceIn this study, the confounding effect of normative aging was somewhat excluded compared with many previous studies. In contrast with the many oddball studies in non-demented PD, we clearly observed reduced and prolonged P3 in early-onset PD. Our NoGo P3 findings also contribute to the limited ERP research concerning response inhibition.     

Altered resting-state thalamo-occipital functional connectivity is associated with cognition in isolated rapid eye movement sleep behavior disorder

ObjectiveIsolated rapid eye movement sleep behavior disorder (iRBD) patients are at risk of cognitive impairments, however the underlying mechanism is still unclear. This study aimed to evaluate thalamo-cortical functional connectivity (FC) using resting-state functional magnetic resonance imaging (fMRI) and its correlation with cognitive dysfunction in patients with iRBD.MethodsA total 37 polysomnographies (PSGs) confirmed iRBD patients and 15 age-sex matched controls underwent resting-state fMRI and comprehensive neuropsychological assessment. Thalamo-cortical FC was evaluated by using seed-to voxel analysis and was compared between the iRBD and controls. Correlation between the average value of significant clusters and cognitive function scores in iRBD were calculated.ResultsCompared to the control subjects, patients with iRBD patients showed cognitive decline in word list recognition (p = 0.016), and constructional recall (p = 0.044). The FC analysis showed increased FC between the left thalamus and occipital regions including the right cuneal cortex, left fusiform gyrus and lingual gyrus (cluster level p < 0.05, corrected for false discovery rate). The averaged thalamo-fusiform FC value positively correlated with word list recognition after adjusting for age and sex (adjusted r = 0.347, p = 0.041).ConclusionThalamic resting state FC is altered in iRBD patients and is associated with the cognitive function. Enhancement of the thalamo-occipital FC may reflect a compensatory mechanism for cognitive impairment in iRBD.     

DBH −1021C>T and COMT Val108/158Met genotype are not associated with the P300 ERP in an auditory oddball task

ObjectiveThe amplitude and latency of the P300 may be associated by variations in dopaminergic genes. The current study was conducted to determine whether functional variants of the catechol-O-methyltransferase (COMT) and dopamine beta-hydroxylase (DBH) gene were associated with P300 amplitude and latency in an auditory oddball task.MethodsThe P300 ERP was assessed by a two-tone auditory oddball paradigm in a large sample of 320 healthy volunteers. The Val108/158Met polymorphism (rs4680) of the COMT gene and the ?1021C>T polymorphism (rs1611115) of the DBH gene were genotyped. P300 amplitude and latency were compared across genotype groups using analysis of variance.ResultsThere were no differences in demographic characteristics in subjects for genotypic subgroups. No genotype associations were observed for the P300 amplitude and latency on frontal, central and parietal electrode positions.ConclusionsCOMT Val108/158Met and DBH ?1021C>T polymorphisms do not show evidence of association with characteristics of the P300 ERP in an auditory oddball paradigm in healthy volunteers.SignificanceWe failed to find evidence for the association between dopaminergic enzymatic polymorphisms and the P300 ERP in healthy volunteers, in the largest study undertaken to date.     

Frontal attentional responses to food size are abnormal in obese subjects: An electroencephalographic study

ObjectiveAre obese subjects characterized by a reduction of attentional cortical responses to the enlargement of food or body images?MethodsElectroencephalographic data were recorded in 19 obese and 15 normal-weight adults during an “oddball” paradigm. The subjects were given frequent (70%) and rare (30%) stimuli depicting faces (FACE), food (FOOD), and landscapes (CONTROL), and clicked the mouse after the rare stimuli. These stimuli depicted the same frequent stimuli graphically dilated by 25% along the horizontal axis. Bioelectrical impedance indexed subjects’ body fat percentage. Cortical attentional responses were probed by the difference between positive event-related potentials peaking around 400–500 ms post-stimulus for the rare minus frequent stimuli (P300). Low resolution electromagnetic source tomography (LORETA) estimated P300 sources.ResultsIn the FOOD condition, the amplitude of medial prefrontal P300 sources (Brodmann area 9) was lower in the obese than normal-weight subjects, and there was a negative correlation between the body fat percentage and the amplitude of these sources in all subjects as a single group.ConclusionsThese results disclose that prefrontal attentional processes to food size are abnormal in obese subjects.SignificanceThe present study motivates future research evaluating the effects of cognitive rehabilitation in obese subjects.     

Contribution of familiarity and recollection to associative recognition memory: insights from event-related potentials

Within the dual-process perspective of recognition memory, it has been claimed that familiarity is sufficient to support recognition of single items, but recollection is necessary for associative recognition of item pairs. However, there are some reports suggesting that familiarity might support associative recognition judgments when the items form an easy to access bound representation. In contrast, recollection seems to be required for the recognition of bindings that might be flexibly rearranged in novel situations. We investigated whether both forms of binding are mediated by different mechanisms as reflected by a qualitatively different spatiotemporal eventrelated potential (ERP) pattern. In a recognition memory experiment, subjects gave old/new judgments to words learned by focusing either on interitem associations or on size relation of word triplets. Results revealed higher hit rates in the relational condition as compared to the associative condition. In addition, the proportion of triplets from which all three items were remembered was significantly larger in the relational condition suggesting that memory retrieval in this condition relies primarily on bound representations of word triplets. The ERP revealed a late parietal old/new effect for both conditions, with relational processing resulting in a greater effect. In contrast, an early frontal old/new effect was solely present in the associative condition. Taken together, these data provide evidence that familiarity might support associative recognition if the associated components are coherently encoded into a bound representation. Recollection might foster the recognition of relational bindings among items. This indicates that the contribution of familiarity and recollection to associative recognition depends on the kind of binding operations performed on the items rather than on the single versus multiple item distinction.     

Item Priming and Skill Learning in Amnesia

Abstract

This study employed a semantic decision-making task to examine both item priming and skill learning in amnesia, which traditionally have been demonstrated with separate tasks. Fourteen amnesic patients of mixed etiologies and 14 normal control subjects judged whether words represented animate or inanimate objects. One list was presented repeatedly on four continuous blocks of trials, and a new list was presented on the fifth block. For both groups, decision times decreased significantly from Block 1 to Block 5 (indicating skill acquisition) and increased significantly from Block 4 to Block 5 (indicating item-specific learning). The amnesic patients demonstrated a normal rate of skill learning, but a reduced magnitude of item priming. As expected, the amnesics had significantly impaired explicit memory of the implicitly learned items, as measured by recognition accuracy. The results suggest that both implicit and explicit learning of individual items is impaired in amnesia, despite normal semantic skill learning.     

Cognitive effects of topiramate revealed by standardised low-resolution brain electromagnetic tomography (sLORETA) of event-related potentials

ObjectiveTo evaluate the effect of topiramate (TPM) on event-related potentials (ERPs) in patients with epilepsy.MethodsNeuropsychological tests and ERP study using auditory oddball paradigm were conducted before and after treatment with TPM in drug-naive epilepsy patients. To detect target brain regions in which ERP changed during the cognitive task, cortical current densities of ERP components were analysed using standardised low-resolution electromagnetic tomography (sLORETA).ResultsNeuropsychological tests (n = 18 patients) showed that TPM significantly decreased the score in digit span, Corsi block and Controlled Oral Word Association word fluency. Repeated-measures analysis of variance of ERP data (n = 13 patients) revealed that P2 amplitude was significantly increased at Fz electrode following treatment with TPM. Statistical non-parametric map of sLORETA between pre- and post-TPM ERPs revealed that current density of P200 component was significantly reduced by TPM in bilateral parieto-occipital, temporolimbic and dorsolateral right prefrontal regions.ConclusionsOur findings suggest that TPM affects selective brain regions which may be related to cognitive side effects.SignificanceSource localisation of ERPs can be helpful in identifying target brain regions for the cognitive side effects of anti-epileptic drugs.     

Changes in event-related potentials during dual task walking in aging and Parkinson's disease

ObjectiveTo investigate EEG changes during an auditory odd-ball task while walking (dual-task) in young adults, older adults, and patients with Parkinson's disease.Methods11 young adults, 10 older adults, and 10 patients with Parkinson’s disease (PD) performed an auditory oddball task during standing and walking on a treadmill, while wearing a wireless EEG cap. The amplitude and latency of P300 were compared between groups and within conditions using linear mix model analysis. Gait was evaluated using wearable sensors and cognition was assessed using the Color Trail Test.ResultsP300 latency became longer during walking in all groups (p = 0.005). During walking, older adults (p = 0.005) and patients with PD (p = 0.001) showed prolonged P300 latency compared to young adults. Significant task by group interaction was found in P300 amplitude (p = 0.008). Patients with PD demonstrated reduced P300 amplitude during walking compared to standing (p = 0.023). Among all subjects, better motor and cognitive performance correlated with shorter P300 latency (r = 0.457, p = 0.014 and r = 0.431, p = 0.040, respectively).ConclusionsThese findings provide direct evidence of the physiological recruitment of attentional networks during walking and their impact by ageing and disease.SignificanceThis study is the first to report on changes in P300 latency and amplitude during dual-task oddball walking in older adults and patients with PD.     

Deficit of long-term memory traces for words in children with cochlear implants

ObjectiveLanguage experience can develop long-term memory traces for speech units in the brain, to ensure efficient processing of speech sounds. However, prelingually deafened children lack sufficient auditory input before cochlear implantation. Whether the experience-dependent long-term memory traces exist in prelingually deafened children with cochlear implants (CIs) remains unclear.MethodsWe presented CI and normal hearing (NH) children with Mandarin Chinese spoken disyllables in an oddball paradigm and recorded event-related potentials. Each disyllable was defined as a meaningful word or a meaningless pseudoword by the tonal information in the second syllable.ResultsThe amplitude of mismatch negativity (MMN) elicited by words was larger than that elicited by pseudowords in NH children. However, this enhancement of the MMN amplitude was not found in CI children. Behavioral results showed later recognition points for words and lower accuracies for speech comprehension in CI children than in NH children. Furthermore, increased theta power for words compared with pseudowords was only found in NH children.ConclusionsOur findings indicate a deficit of long-term memory traces for words in prelingually deafened children with cochlear implants.SignificanceEarly speech input may be crucial to the formation of long-term memory traces for speech units.     

The influence of seizure frequency on anterograde and remote memory in mesial temporal lobe epilepsy

PurposeSeizure frequency, although considered as an important factor in memory impairment in mesial temporal epilepsy (mTLE), is mostly confounded with other clinical variables, making it unclear to what extent recurrent seizures actually interfere with memory. The present study focuses on the influence of seizure frequency, studied as a main variable, on anterograde and remote memory.MethodsSeventy-one patients with unilateral mTLE were divided into two subgroups, as a function of their seizure frequency (monthly versus weekly seizures). Other seizure-related variables were controlled, namely, lateralisation and type of lesion, age at onset, years of ongoing seizures, etiologic factors, and number of AED. A comprehensive neuropsychological examination, including anterograde memory (verbal and non verbal recognition memory and free recall) tasks together with a large range of tests exploring different domains of remote memory, was carried out.ResultsDespite similar results on IQ, executive functions and attention, the low seizure-frequency group performed significantly better than the high seizure-frequency group on anterograde memory tests. Loss of autobiographical episodes and public-events memory, concomitant with spared personal semantic knowledge, was observed in both patient groups compared with healthy subjects. A worsening effect of high seizure frequency was recorded for autobiographical incidents and news-events memory, but unexpectedly, not for memory for famous people.ConclusionThe study of seizure frequency as the main variable leads us to suggest that high seizure frequency, itself, potentiates the effects of mesial temporal lobe damage on episodic memory deficits.     

Dissociation of memory and awareness in young and older adults

Abstract

Young (mean age=23.41 years) and older (mean age=69.41 years) adults studied a list of 80 words. They were tested immediately and 7 days later for both yes/no recognition and for ability to complete fragments such as _E_D_L_M, with words, some of which had been studied previously. The fragment completion task was not described as a memory test and subjects were encouraged to respond to all word fragments. Younger adults scored higher on recognition than older adults but not on fragment completion. These results, similar to those obtained with amnesics, suggest that older adults are impaired on tasks which require a conscious effort to recognize an event but that memory without awareness is unaffected by age.     

Neurophysiological markers of cue reactivity and inhibition subtend a three-month period of complete alcohol abstinence

ObjectiveFinding new tools for conventional management of alcohol disorders is a challenge for psychiatrists. Brain indications related to cognitive functioning could represent such an add-on tool.MethodsForty alcohol-dependent inpatients undertook two cognitive event-related potential (ERP) tasks at the beginning and at the end of a 4-week detoxification program. These comprised a visual oddball task investigating cue reactivity and a Go/No-go task tagging inhibition using oddball P3d and No-go P3d ERP components. Three months after discharge, the patient group (N = 40) was split into two subgroups: patients who remained abstinent during this post-treatment period (90 days; n = 15), and patients who relapsed (mean time: 28.5 ± 26.2 days; n = 25). Pattern changes of both ERP markers (oddball P3d and No-go P3d) during the detoxification were compared to differentiate these populations.ResultsAbstinent patients exhibited similar P3d responses devoted to alcohol cues in Sessions 1 and 2, but an increased No-go P3d devoted to No-go trials in alcohol-related contexts in Session 2 compared to Session 1.ConclusionsSpecific cue-reactivity and inhibitory neurophysiological markers subtend a further three-months of complete abstinence.SignificanceMonitoring these ERP changes during detoxification may provide important clues regarding patients’ future abstinence vs. relapse.     

Dysfunctions of automatic (P300a) and controlled (P300b) processing in Parkinson’s disease

Abstract

P300 Event Related Potentials components (P300a and P300b) were investigated using an auditory oddball paradigm (with abutton press response to target stimuli) in 15 Parkinson’s disease patients and 50 normal controls whilst simultaneously measuring electrodermal activity. Cluster analysis showed that the first 10 target stimuli generated the largest skin conductance responses. The first 10 single-trial ERP epochs were therefore analysed as an ERP sub-average for each individual. The P300a component (associated with the automatic ‘Orienting Reflex’) was expected to be most prevalent in this sub-average (compared with subaverages of subsequent blocks of 10 target stimuliJ. Twenty-nine out of50 normal controls (58%) elicited a P300a in the first 10 target sub-averages compared with only 2 out of 15 Parkinson’s disease subjects (J 3%). The conventional P300b component (associated with controlled processing) was found to be significantly delayed for all sub-averages for the Parkinson’s disease group when compared with controls. These preliminary findings suggest a possible dysfunction in both automatic and controlled processing in this disorder. [Neural Res 1998: 20: 5–10]     

Improvement of encoding and retrieval in normal and pathological aging with word–picture paradigm

Objectives: During the aging process, there is a progressive deficit in the encoding of new information and its retrieval. Different strategies are used in order to maintain, optimize or diminish these deficits in people with and without dementia. One of the classic techniques is paired-associate learning (PAL), which is based on improving the encoding of memories, but it has yet to be used to its full potential in people with dementia. In this study, our aim is to corroborate the importance of PAL tasks as instrumental tools for creating contextual cues, during both the encoding and retrieval phases of memory. Additionally, we aim to identify the most effective form of presenting the related items.

Method: Pairs of stimuli were shown to healthy elderly people and to patients with moderate and mild Alzheimer's disease. The encoding conditions were as follows: word/word, picture/picture, picture/word, and word/picture.

Results: Associative cued recall of the second item in the pair shows that retrieval is higher for the word/picture condition in the two groups of patients with dementia when compared to the other conditions, while word/word is the least effective in all cases.

Conclusion: These results confirm that PAL is an effective tool for creating contextual cues during both the encoding and retrieval phases in people with dementia when the items are presented using the word/picture condition. In this way, the encoding and retrieval deficit can be reduced in these people.     

A 15-day course of donepezil modulates spectral EEG dynamics related to target auditory stimuli in young,healthy adult volunteers

ObjectiveTo identify possible electroencephalographic (EEG) markers of donepezil’s effect on cortical activity in young, healthy adult volunteers at the group level.MethodsThirty subjects were administered a daily dose of either 5 mg donepezil or placebo for 15 days in a double-blind, randomized, cross-over trial. The electroencephalogram during an auditory oddball paradigm was recorded from 58 scalp electrodes. Current source density (CSD) transformations were applied to EEG epochs. The event-related potential (ERP), inter-trial coherence (ITC: the phase consistency of the EEG spectrum) and event-related spectral perturbation (ERSP: the EEG power spectrum relative to the baseline) were calculated for the target (oddball) stimuli.ResultsThe donepezil and placebo conditions differed in terms of the changes in delta/theta/alpha/beta ITC and ERSP in various regions of the scalp (especially the frontal electrodes) but not in terms of latency and amplitude of the P300-ERP component.ConclusionOur results suggest that ITC and ERSP analyses can provide EEG markers of donepezil’s effects in young, healthy, adult volunteers at a group level.SignificanceNovel EEG markers could be useful to assess the therapeutic potential of drug candidates in Alzheimer’s disease in healthy volunteers prior to the initiation of Phase II/III clinical studies in patients.