P3a Amplitude Research Articles

Does working memory protect against auditory distraction in older adults?

BackgroundPast research indicates that when younger adults are engaged in a visual working memory task, they are less distracted by novel auditory stimuli than when engaged in a visual task that does not require working memory. The current study aimed to determine whether working memory affords the same protection to older adults.MethodWe examined behavioral and EEG responses in 16 younger and 16 older adults to distractor sounds when the listeners performed two visual tasks; one that required working memory (W1) and the other that did not (W0). Auditory distractors were presented in an oddball paradigm, participants were exposed to either standard tones (600 Hz: 80%) or various novel environmental sounds (20%).ResultsIt was found that: 1) when presented with novel vs standard sounds, older adults had faster correct response times in the W1 visual task than in the W0 task, indicating that they were less distracted by the novel sound; there was no difference in error rates. Younger adults did not show a task effect for correct response times but made slightly more errors when a novel sound was presented in the W1 task compared to the W0 task. 2) In older adults (but not the younger adults), the amplitude of N1 was smaller in the W1 condition compared to the W0 condition. 3) The working memory manipulation had no effect on MMN amplitude in older adults. 4) For the W1 compared to W0 task, the amplitude of P3a was attenuated for the older adults but not for the younger adults.ConclusionsThese results suggest that during the working memory manipulation older adults were able to engage working memory to reduce the processing of task-irrelevant sounds.

Interaction of Background Noise and Auditory Hallucinations on Phonemic Mismatch Negativity (MMN) and P3a Processing in Schizophrenia.

Auditory hallucinations (AHs) are among the cardinal symptoms of schizophrenia (SZ). During the presence of AHs aberrant activity of auditory cortices have been observed, including hyperactivation during AHs alone and hypoactivation when AHs are accompanied by a concurrent external auditory competitor. Mismatch negativity (MMN) and P3a are common ERPs of interest within the study of SZ as they are robustly reduced in the chronic phase of the illness. The present study aimed to explore whether background noise altered the auditory MMN and P3a in those with SZ and treatment-resistant AHs.MethodsMMN and P3a were assessed in 12 hallucinating patients (HPs), 11 non-hallucinating patients (NPs) and 9 healthy controls (HCs) within an auditory oddball paradigm. Standard (P = 0.85) and deviant (P = 0.15) stimuli were presented during three noise conditions: silence (SL), traffic noise (TN), and wide-band white noise (WN).ResultsHPs showed significantly greater deficits in MMN amplitude relative to NPs in all background noise conditions, though predominantly at central electrodes. Conversely, both NPs and HPs exhibited significant deficits in P3a amplitude relative to HCs under the SL condition only.SignificanceThese findings suggest that the presence of AHs may specifically impair the MMN, while the P3a appears to be more generally impaired in SZ. That MMN amplitudes are specifically reduced for HPs during background noise conditions suggests HPs may have a harder time detecting changes in phonemic sounds during situations with external traffic or “real-world” noise compared to NPs.

Hierarchical Pathways from Sensory Processing to Cognitive, Clinical, and Functional Impairments in Schizophrenia.

Cognitive impairment is a hallmark of schizophrenia and a robust predictor of functional outcomes. Impairments are found in all phases of the illness and are only moderately attenuated by currently approved therapeutics. Neurophysiological indices of sensory discrimination (ie, mismatch negativity (MMN) and P3a amplitudes) and gamma-band auditory steady-state response (ASSR; power and phase locking) are translational biomarkers widely used in the development of novel therapeutics for neuropsychiatric disorders. It is unclear whether laboratory-based EEG measures add explanatory power to well-established models that use only cognitive, clinical, and functional outcome measures. Moreover, it is unclear if measures of sensory discrimination and gamma-band ASSR uniquely contribute to putative causal pathways linking sensory discrimination, neurocognition, negative symptoms, and functional outcomes in schizophrenia. To answer these questions, hierarchical associations among sensory processing, neurocognition, clinical symptoms, and functional outcomes were assessed via structural equation modeling in a large sample of schizophrenia patients (n = 695) and healthy comparison subjects (n = 503). The results showed that the neurophysiologic indices of sensory discrimination and gamma-band ASSR both significantly contribute to and yield unique hierarchical, "bottom-up" effects on neurocognition, symptoms, and functioning. Measures of sensory discrimination showed direct effects on neurocognition and negative symptoms, while gamma-band ASSR had a direct effect on neurocognition in patients. Continued investigation of the neural mechanisms underlying abnormal networks of MMN/P3a and gamma-band ASSR is needed to clarify the pathophysiology of schizophrenia and the development of novel therapeutic interventions.

Event-related brain potentials reflect predictive coding of anticipated economic change

Research has demonstrated the importance of economic forecasts for financial decisions at the aggregate economic level. However, little is known about the psychological and neurophysiological mechanisms that economic forecasts activate at the level of individual decision-making. In the present study, we used event-related brain potentials (ERPs) to test the hypothesis that economic forecasts influence individuals’ internal model of the economy and their subsequent decision behavior. Using a simple economic decision-making game, the Balloon Analogue of Risk Task (BART) and predictive messages about possible economic changes in the game before each block, we test the idea that brain potentials time-locked to decision outcomes can vary as a function of exposure to economic forecasts. Behavioural results indicate that economic forecasts influenced the amount of risk that participants were willing to take. Analyses of brain potentials indicated parametric increases of the N1, P2, P3a, and P3b amplitudes as a function of the level of risk in subsequent inflation steps in the BART. Mismatches between economic forecasts and decision outcomes in the BART (i.e., reward prediction errors) were reflected in the amplitude of the P2, P3a, and P3b, suggesting increased attentional processing of unexpected outcomes. These electrophysiological results corroborate the idea that economic messages may indeed influence people’s beliefs about the economy and bias their subsequent financial decision-making. Our findings present a first important step in the development of a low-level neurophysiological model that may help to explain the self-fulfilling prophecy effect of economic news in the larger economy.

Trajectories of Mismatch Negativity and P3a Amplitude Development From Ages 9 to 16 Years in Children With Risk Factors for Schizophrenia

BackgroundMismatch negativity (MMN) and P3a amplitude reductions are robust abnormalities of sensory information processing in schizophrenia, but they are variably present in different profiles of risk (family history vs. clinical high risk) for the disorder. This study aimed to determine whether these abnormalities characterize children presenting replicated risk factors for schizophrenia, using longitudinal assessment over the ages of 9–16 years in children with multiple replicated antecedents of schizophrenia (ASz) and with family history of schizophrenia (FHx), relative to typically developing (TD) peers. MethodsA total of 105 children (52 female) sampled from the community were assessed at ages 9–12 years and approximately 2 and 4 years later. Linear mixed models were fitted to MMN and P3a peak amplitudes and latencies, with intercept and slope estimates from 32 ASz and 28 FHx children compared with those of 45 TD peers. ResultsIn ASz relative to TD children, MMN amplitude initially increased and then prominently decreased during adolescence. Both ASz and FHx children had greater P3a amplitude than TD children at 11 years, which decreased with age, in contrast to P3a amplitude increasing during adolescence in TD youths. MMN abnormalities were specific to ASz children who continued to present symptoms during follow-up. ConclusionsAge-dependent MMN and P3a abnormalities demarcate adolescent development of ASz and FHx from TD children, with auditory change detection abnormalities specific to ASz children with continuing symptoms and attention-orienting abnormalities characterizing both ASz and FHx risk profiles. Follow-up is required to determine whether these abnormalities index vulnerability for schizophrenia or an illness nonspecific developmental delay.

Effect of oxygen enrichment on the flame stability and emissions during biogas combustion: An experimental study

In this paper, a biogas composition consisting of methane and carbon dioxide mixture in a pilot-scale model burner has been enriched with oxygen and the combustion characteristics including combustion stability and emission behaviour have been experimentally investigated. CH4 and CO2 gases have been burned as premixed and the blowout and flashback values of the mixture have been determined. Experiments have been performed at constant equivalence ratio (0.7) and the number of swirl (s = 1) at 3 kW thermal power. To examine the combustion stability, the external acoustic forced condition has been applied with two loudspeakers. Experimental results shown that the highest flame stability has been achieved in the 24% oxygen enrichment rate. The flame extinction occurred at 530 Pa amplitude of 21% oxygen enrichment ratio, although it fluctuated at the dynamic pressure amplitude of 775 Pa at the 24% oxygen enrichment ratio continued to burn. As the enrichment rate was increased to 28%, at the dynamic pressure of 1213 Pa and forced under 175 Hz frequency condition the flashback occurred at the flame. While the oxygen rate increased to 28% it has been observed that a decrease in stability compared to the 24% oxygen rate. Experimental results show that the emissions of CO are 2247 ppm at 21%, 372 ppm at 24% and 10 ppm at 28%. At the same oxygen enrichment rates, the values of NOx are 16 ppm, 1 ppm and 58 ppm, respectively. The decreasing has been observed in NOx emissions up to 24% oxygen enrichment rate.

Electrophysiological correlates of attentional monitoring during a complex driving simulation task

Starting from the evidence that complex tasks (e.g., driving) require lots of cognitive resources, this research aims at assessing the change of attentional electrophysiological correlates during an oddball task performed while driving a simulator.Twenty-four participants drove along six courses on a moped simulator, preceded by a baseline condition (i.e., watching a video clip of one driving course). Throughout the task, an auditory passive multi-feature oddball with both traffic-related and unrelated stimuli was presented, and the EEG activity was recorded along with driving performance indexes.The main results point out that, as participants learn to drive safely, more attentional resources are available to process the deviant oddball stimuli, as shown by the increase in the amplitude of mismatch negativity (deviant pure tones) and P3a (traffic-related sounds) in the second block of driving. We interpreted these effects as dependent on stimuli complexity and salience.

Prestimulus alpha and beta contributions to equiprobable Go/NoGo processing in healthy ageing

The immediately-prestimulus electroencephalographic (EEG) brain state influences subsequent event-related processing, dynamically impacting event-related potential (ERP) and behavioural outcomes. Both EEG and ERPs are known to undergo age-related change, yet few have investigated the consistency in their dynamic interrelations in the context of ageing. The present investigation assessed the impact of prestimulus alpha and beta brain states in 20 young (18–26 years) and 20 gender-matched healthy older (59–75 years) adults who completed an equiprobable auditory Go/NoGo paradigm. Prestimulus alpha and beta band amplitudes in their prominent band topographies were separately used to derive Go and NoGo ERPs at 10 ascending levels of prestimulus activity, and ERP components were derived for these levels using Principal Components Analysis. Prestimulus alpha directly modulated Go/NoGo P3a amplitudes across the groups, while beta inversely modulated the young (cf. older) adult NoGo N1–1, each supporting and extending limited prior research. Several novel effects were also uncovered, most notably an inverse relationship between prestimulus alpha and reaction time. Prestimulus alpha and beta were confirmed as significant determinants of the processing outcomes in this task, and the complex pattern of results provides a normative map in healthy ageing.

The preattentive change detection in preschool children with attention deficit hyperactivity disorder: a mismatch negativity study.

To investigate the preattentive change detection in preschool children with attention deficit hyperactivity disorder (ADHD), we compared the mismatch negativity (MMN) and P3a of event-related potentials (ERPs) between preschool ADHD and normal children using three-stimulus oddball paradigm. Analyzing MMN and P3a components, we found that MMN elicited by deviants and P3a elicited by novelty were significantly reduced in patients than in controls. In addition, the P3a amplitude was positive correlated to IQ and negatively correlated to hyperactivity, antagonistic defiance and conduct problems in Swanson, Nolan, and Pelham IV Rating Scale, parent version. These data provided new neurophysiological evidence for the dysfunction of preattentive change detection and attentional shift in ADHD children.

O10.2. DEFICIENT VISUAL ODDBALL STIMULUS PROCESSING PREDICTS PSYCHOSIS ONSET: RESULTS FROM THE NORTH AMERICAN PRODROME LONGITUDINAL STUDY

BackgroundClinical outcomes vary among young people with the psychosis risk syndrome (PRS), with approximately 20% of individuals progressing to a psychotic disorder over 2–3 years and 30% achieving clinical remission. The identification of neurophysiological abnormalities associated with schizophrenia that predate and predict psychosis onset may enhance the accuracy of clinical outcome prediction in the PRS and help elucidate the pathogenic mechanisms of psychosis onset. Auditory P300 event-related potential (ERP) component amplitude reductions are well established in schizophrenia and reflect early attention-mediated information processing deficits. Recent studies employing auditory oddball tasks have shown that P300 amplitude deficits in PRS individuals are associated with later clinical outcomes, including both conversion to full-blown psychosis and remission from the at-risk state. The present study examined whether these effects extend to P300 in the visual modality using visual oddball task data collected as part of the North American Prodrome Longitudinal Study. Specifically, we evaluated whether visual P300 amplitudes are reduced in the PRS and predict future clinical outcomes.Methods540 individuals meeting PRS criteria and 229 healthy individuals completed baseline EEG recording during a visual oddball task. Visual P300 subcomponents were measured in response to two stimulus types: (1) infrequent target stimuli, reflecting top-down allocation of attention (target P3b), and (2) infrequent non-target novel distractor stimuli, reflecting bottom-up orienting of attention (novelty P3a). P300 amplitudes of PRS participants who converted to psychosis (n=70) were compared with those of PRS non-converters who were followed clinically for 24 months and continued to be symptomatic (n=131) or fully remitted from the PRS (n=87).ResultsGroup comparison effects did not differ by stimulus type. Visual P300 amplitudes were not significantly reduced in the PRS group relative to healthy individuals (p=.25). However, baseline target P3b and novelty P3a amplitudes were reduced in PRS individuals who later converted to psychosis relative to all PRS non-converters, including those who remitted (p=.006, d=.44) and those who remained symptomatic (p=.015, d=.37), as well as healthy individuals (p=.001, d=.44). Baseline P300 amplitudes were similar among healthy controls, PRS remitters, and PRS individuals who remained symptomatic (ps>.45). Moreover, visual P300 amplitudes differentiated future psychosis converters after accounting for PRS symptom severity. Finally, both target P3b and novelty P3a amplitudes predicted the time to psychosis onset in PRS participants (p=.03 and p=.02, respectively), such that more deficient P300 amplitudes were associated with shorter time to conversion.DiscussionBaseline visual P300 amplitudes were reduced in future PRS converters relative to non-converters, with effect sizes comparable to those reported in previous auditory P300 studies of the PRS. Results implicate visual P300 as a neurophysiological vulnerability marker that predicts clinical outcomes among PRS individuals, including future transition to psychosis. Accordingly, together with prior auditory P300 studies, results suggest that P300 may have the potential to contribute to personalized early intervention in the PRS by distinguishing individuals with the greatest risk for psychotic illness, who require the most aggressive treatment, from those who may need minimal intervention.

MMN and P3a are Correlated With Symptom Severity in Early-Phase Psychosis

Deficits in the EEG-derived mismatch negativity (MMN) have been robustly observed in people with schizophrenia (SZ). The subsequent auditory P3a is also reduced in SZ. However, while reduced MMN and P3a amplitudes are reliably reported in chronic SZ, it is unclear under what conditions reductions are reported in early-phase psychosis (EPP). The primary objective of this study was to determine whether MMN and P3a are attenuated in EPP and whether these reductions are associated with symptom profiles.

P3a amplitude is related to conclusion specificity during category-based induction.

Category-based induction involves the generalization of a novel property (conclusion property) to a new category (conclusion category), based on the knowledge that a category exemplar (premise category) has the respective novel property. Previous studies have shown that conclusion specificity (i.e., specific [S] or generic categories [G]) influences category-based induction. However, the timing of brain activity underlying this effect is not well known, especially with controlling the similarities of premise and conclusion categories between S and G arguments. In this study, the event-related potential (ERP) responses to category-based induction between S and G arguments were compared under both congruent (+, premise and conclusion categories are related) and incongruent (-, premise and conclusion categories are unrelated) arguments; additionally, the similarities of premise and conclusion categories between S and G arguments were controlled. The results showed that replicating this effect, S+ arguments have increased “strong” response rates compared to G+ arguments, suggesting that category-based induction is contingent on factors beyond matched similarities. Moreover, S arguments have more liberal inductive decision thresholds than G arguments, which suggest that conclusion specificity affects the inductive decision reflected by inductive decision thresholds. Furthermore, G+ arguments elicit greater P3a amplitudes than S+ arguments, which suggest greater attention resources allocation to the review of decisions for G+ arguments than that for S+ arguments. Taken together, the conclusion specificity effect during semantic category-based induction can be revealed by “strong” response rates, inductive decision thresholds, and P3a component after controlling the premise-conclusion similarity, providing evidence that category-based induction rely on more than simple similarity judgment and conclusion specificity would affect category-based induction.

Altered P3a Modulations to Emotional Faces in Male Patients With Chronic Schizophrenia.

Existing evidence suggests that patients with schizophrenia may have a deficit in processing facial expressions. However, the neural basis of this processing deficit remains unclear. A total of 20 men diagnosed with chronic schizophrenia and 13 age- and sex-matched controls participated in the study. We investigated visual N170 and P3a components evoked in response to fearful, happy, and sad faces during an emotion discrimination task. Compared with control subjects, patients showed significantly smaller N170 amplitudes bilaterally (P = .04). We found no significant main effect of emotion of the presented faces (fearful, happy, or sad) on N170 amplitude. Patients showed significantly smaller P3a amplitudes in response to fearful (P = .01) and happy (P = .02) faces, but no significant between-group differences were observed for sad faces (P = .22). Moreover, we found no significant P3a modulation effect in response to emotional faces in patients with schizophrenia. Our results suggest that altered P3a modulations to emotional faces may be associated with emotion recognition deficits in patients with schizophrenia.

Symmetrical electrophysiological brain responses to unilateral and bilateral auditory stimuli suggest disrupted spatial processing in schizophrenia

Research has found auditory spatial processing deficits in patients with schizophrenia (SCZ), but no study has examined SCZ patients’ auditory spatial processing at both pre-attentional and attentional stages. To address this gap, we investigated schizophrenics’ brain responses to sounds originating from different locations (right, left, and bilateral sources). The event-related potentials (ERPs) of 25 chronic schizophrenic patients and 25 healthy subjects were compared. Mismatch negativity (MMN) in response to frequency and duration deviants was assessed. Two P3 components (P3a and P3b) were elicited via a frequency discrimination task, and MMN and P3 were recorded through separate monaural and dichotic stimulation paradigms. Our results corroborated the previously published finding that MMN, P3a, and P3b amplitudes are reduced in SCZ patients, but they showed no significant effect of stimulus location on either MMN or P3. These results indicated similarity between the SCZ patients and healthy individuals as regards patterns of ERP responses to stimuli that come from different directions. No evidence of auditory hemispatial bias in the SCZ patients was found, supporting the existence of non-lateralized spatial processing deficits in such patients and suggesting compensatory changes in the hemispheric laterality of patients’ brains.

Triboelectric current generation in InP

Energy harvesting is an area that presents the greatest potential for powering wireless low-energy electronics. Development of semiconductor-based energy harvesting is of interest. Herein we focus on studying two different energy harvesting mechanisms in indium phosphide. Piezoelectric harvesting was checked by bending vertical InP nanowires with conductive atomic force microscope (AFM) probe and simultaneously detecting current passing through the probe. No current pulses were observed that we associate with surface trapping of piezoinduced carriers. Triboelectric generation was studied by creating frictional contact between AFM tip and metal-dielectric-semiconductor (MIS) interface formed by InP layer covered with native oxide. Current peaks of 320 pA amplitude corresponding to the current density around 2.3 kA/m2 were observed under sliding reciprocating motion of the tip during AFM scanning. Achieved current density was higher than in polymer- and silicon-based triboelectric structures. The open-circuit voltage value exceeded 15 mV and the output electric power was 35 W/m2.

Design, fabrication, and optical characterization of one-dimensional photonic crystals based on porous silicon assisted by in-situ photoacoustics

We present a methodology to fabricate one-dimensional porous silicon (PSi) photonic crystals in the visible range by controlled etching and monitored by photoacoustics. Photoacoustic can record in-situ information about changes in the optical path and chemical reaction as well as in temperature, refractive index, and roughness during porous layers formation. Radiometry imaging can determine the carrier distribution of c-Si substrate that is a fundamental parameter to obtain high-quality PSi films. An electrochemical cell was calibrated through a series of single PSi layers that allows knowing the PA amplitude period, porosity, and roughness as a function of the current density. Optical properties of single layers were determined using the reflectance response in the UV-Vis range to solve the inverse problem through genetic algorithms. PhC structures were designed using the transfer matrix method and effective media approximation.Based on the growth kinetics of PSi single layers, those structures were fabricated by electrochemical etching monitored and controlled by in-situ photoacoustics.

Association Between P300 Responses to Auditory Oddball Stimuli and Clinical Outcomes in the Psychosis Risk Syndrome

In most patients, a prodromal period precedes the onset of schizophrenia. Although clinical criteria for identifying the psychosis risk syndrome (PRS) show promising predictive validity, assessment of neurophysiologic abnormalities in at-risk individuals may improve clinical prediction and clarify the pathogenesis of schizophrenia. To determine whether P300 event-related potential amplitude, which is deficient in schizophrenia, is reduced in the PRS and associated with clinical outcomes. Auditory P300 data were collected as part of the multisite, case-control North American Prodrome Longitudinal Study (NAPLS-2) at 8 university-based outpatient programs. Participants included 552 individuals meeting PRS criteria and 236 healthy controls with P300 data. Auditory P300 data of participants at risk who converted to psychosis (n = 73) were compared with those of nonconverters who were followed up for 24 months and continued to be symptomatic (n = 135) or remitted from the PRS (n = 90). Data were collected from May 27, 2009, to September 17, 2014, and were analyzed from December 3, 2015, to May 1, 2019. Baseline electroencephalography was recorded during an auditory oddball task. Two P300 subcomponents were measured: P3b, elicited by infrequent target stimuli, and P3a, elicited by infrequent nontarget novel stimuli. This study included 788 participants. The PRS group (n = 552) included 236 females (42.8%) (mean [SD] age, 19.21 [4.38] years), and the healthy control group (n = 236) included 111 females (47.0%) (mean [SD] age, 20.44 [4.73] years). Target P3b and novelty P3a amplitudes were reduced in at-risk individuals vs healthy controls (d = 0.37). Target P3b, but not novelty P3a, was significantly reduced in psychosis converters vs nonconverters (d = 0.26), and smaller target P3b amplitude was associated with a shorter time to psychosis onset in at-risk individuals (hazard ratio, 1.45; 95% CI, 1.04-2.00; P = .03). Participants with the PRS who remitted had baseline target P3b amplitudes that were similar to those of healthy controls and greater than those of converters (d = 0.51) and at-risk individuals who remained symptomatic (d = 0.41). In this study, deficits in P300 amplitude appeared to precede psychosis onset. Target P3b amplitudes, in particular, may be sensitive to clinical outcomes in the PRS, including both conversion to psychosis and clinical remission. Auditory target P3b amplitude shows promise as a putative prognostic biomarker of clinical outcome in the PRS.

Vection Attenuates N400 Event-Related Potentials in a Change-Detection Task.

The illusion of self-motion (vection) can affect human cognitive functioning, but little is known about the attentional mechanisms of this influence. In this study, event-related potentials were recorded, while participants ( N = 23) performed a visual change-detection task in the S1–S2 matching paradigm, which was embedded in a visual stimulation pattern (VSP) that was static or moving. In the condition of moving VSP, participants had additionally to indicate whether they were sensing the illusion of self-motion (vection) or perceiving object-motion (no vection). For moving VSP, there were no differences in response accuracy or reaction times between conditions with vection and conditions without vection. Both for static and moving VSP, a series of event-related potentials time-locked to the onset of S2 was observed. N400 amplitudes from anterior–frontal electrodes were attenuated in conditions with vection as compared with conditions without vection. P3a and P3b amplitudes were also attenuated by vection but only in the subgroup of participants who had a high frequency of reporting vection. This shows that the illusion of self-motion disrupted the magnitude of an electrophysiological correlate of complex conflict detection. The potentials reflecting the direction of attention were not affected, unless individual differences in vection frequency were considered.

ERPs predict symptomatic distress and recovery in sub-acute mild traumatic brain injury

Mild traumatic brain injury (mTBI) can affect high-level executive functioning long after somatic symptoms resolve. We tested if simple EEG responses within an oddball paradigm could capture variance relevant to this clinical problem. The P3a and P3b components reflect bottom-up and top-down processes driving engagement with exogenous stimuli. Since these features are related to primitive decision abilities, abnormal amplitudes following mTBI may account for problems in the ability to exert executive control. Sub-acute (<2 weeks) mTBI participants (N = 38) and healthy controls (N = 24) were assessed at an initial session as well as a two-month follow-up (sessions 1 and 2). We contrasted the initial assessment to a comparison group of participants with chronic symptomatology following brain injury (N = 23). There were no group differences in P3a or P3b amplitudes. Yet in the sub-acute mTBI group, higher symptomatology on the Frontal Systems Behavior scale (FrSBe), a questionnaire validated as measuring symptomatic distress related to frontal lobe injury, correlated with lower P3a in session 1. This relationship was replicated in session 2. These findings were distinct from chronic TBI participants, who instead expressed a relationship between increased FrSBe symptoms and a lower P3b component. In the sub-acute group, P3b amplitudes in the first session correlated with the degree of symptom change between sessions 1 and 2, above and beyond demographic predictors. Controls did not show any relationship between FrSBe symptoms and P3a or P3b. These findings identify symptom-specific alterations in neural systems that vary along the time course of post-concussive symptomatology.

Endogenous Expectations for Sequence Continuation after Auditory Beat Accelerations and Decelerations Revealed by P3a and Induced Beta-Band Responses

People commonly synchronize taps to rhythmic sounds and can continue tapping after the sounds stop, indicating that time intervals between sounds can be internalized. Here, we investigate what happens in the brain after simply listening to auditory beats in order to understand more about the automatic internalization of temporal intervals without tapping. Electroencephalograms were recorded while musicians attended to accelerating, decelerating, or steady click sequences. Evoked responses and induced beta power modulations (13–30 Hz) were examined for one beat following the last physical beat of each sequence (termed the silent beat) and compared to responses obtained during physical beats near the sequence endings. In response to the silent beat, P3a was observed with the largest amplitude occurring after accelerations and the smallest after decelerations. Late beta power modulations were also found after the silent beat, and the magnitude of the beta-power suppressions was significantly correlated with the concurrent P3a amplitudes. In contrast, physical beats elicited P2 responses and early beta suppressions, likely reflecting a combination of stimulus-related processing and temporal prediction. These results suggest that the activities observed after the silent beat were not produced via sustained entrainment after the physical beats, but via automatically-formed expectation for an additional beat. Therefore, beta modulations may be generated endogenously by expectation violation, while P3a amplitudes may relate to strength of expectation, with acceleration endings causing the strongest expectations for sequence continuation.