Posterior Electrodes Research Articles

Neural Activity Differentiates Novel and Learned Event Boundaries.

People parse continuous experiences at natural breakpoints called event boundaries, which is important for understanding an environment's causal structure and for responding to uncertainty within it. However, it remains unclear how different forms of uncertainty affect the parsing of continuous experiences and how such uncertainty influences the brain's processing of ongoing events. We exposed human participants of both sexes (N = 34) to a continuous sequence of semantically meaningless images. We generated sequences from random walks through a graph that grouped images into temporal communities. After learning, we asked participants to segment another sequence at natural breakpoints (event boundaries). Participants segmented the sequence at learned transitions between communities, as well as at novel transitions, suggesting that people can segment temporally extended experiences into events based on learned structure as well as prediction error. Greater segmentation at novel boundaries was associated with enhanced parietal scalp electroencephalography (EEG) activity between 250 and 450 ms after the stimulus onset. Multivariate classification of EEG activity showed that novel and learned boundaries evoked distinct patterns of neural activity, particularly theta band power in posterior electrodes. Learning also led to distinct neural representations for stimuli within the temporal communities, while neural activity at learned boundary nodes showed predictive evidence for the adjacent community. The data show that people segment experiences at both learned and novel boundaries and suggest that learned event boundaries trigger retrieval of information about the upcoming community that could underlie anticipation of the next event in a sequence.

ComBat models for harmonization of resting-state EEG features in multisite studies

ObjectivePooling multisite resting-state electroencephalography (rsEEG) datasets may introduce bias due to batch effects (i.e., cross-site differences in the rsEEG related to scanner/sample characteristics). The Combining Batches (ComBat) models, introduced for microarray expression and adapted for neuroimaging, can control for batch effects while preserving the variability of biological covariates. We aim to evaluate four ComBat harmonization methods in a pooled sample from five independent rsEEG datasets of young and old adults. MethodsRsEEG signals (n = 374) were automatically preprocessed. Oscillatory and aperiodic rsEEG features were extracted in sensor space. Features were harmonized using neuroCombat (standard ComBat used in neuroimaging), neuroHarmonize (variant with nonlinear adjustment of covariates), OPNested-GMM (variant based on Gaussian Mixture Models to fit bimodal feature distributions), and HarmonizR (variant based on resampling to handle missing feature values). Relationships between rsEEG features and age were explored before and after harmonizing batch effects. ResultsBatch effects were identified in rsEEG features. All ComBat methods reduced batch effects and features’ dispersion; HarmonizR and OPNested-GMM ComBat achieved the greatest performance. Harmonized Beta power, individual Alpha peak frequency, Aperiodic exponent, and offset in posterior electrodes showed significant relations with age. All ComBat models maintained the direction of observed relationships while increasing the effect size. ConclusionsComBat models, particularly HarmonizeR and OPNested-GMM ComBat, effectively control for batch effects in rsEEG spectral features. SignificanceThis workflow can be used in multisite studies to harmonize batch effects in sensor-space rsEEG spectral features while preserving biological associations.

Memorization-Based Training and Testing Paradigm for Robust Vocal Identity Recognition in Expressive Speech Using Event-Related Potentials Analysis.

Recognizing familiar speakers from vocal streams is a fundamental aspect of human verbal communication. However, it remains unclear how listeners can still discern the speaker's identity in expressive speech. This study develops a memorization-based individual speaker identity recognition approach and an accompanying electroencephalogram (EEG) data analysis pipeline, which monitors how listeners recognize familiar speakers and tell unfamiliar ones apart. EEG data captures online cognitive processes during new versus old speaker distinction based on voice, offering a real-time measure of brain activity, overcoming limits of reaction times and accuracy measurements. The paradigm comprises three steps: listeners establish associations between three voices and their names (training); listeners indicate the name corresponding to a voice from three candidates (checking); listeners distinguish between three old and three new speaker voices in a two-alternative forced-choice task (testing). The speech prosody in testing was either confident or doubtful. EEG data were collected using a 64-channel EEG system, followed by preprocessing and imported into RStudio for ERP and statistical analysis and MATLAB for brain topography. Results showed an enlarged late positive component (LPC) was elicited in the old-talker compared to the new-talker condition in the 400-850 ms window in the Pz and other wider range of electrodes in both prosodies. Yet, the old/new effect was robust in central and posterior electrodes for doubtful prosody perception, whereas the anterior, central, and posterior electrodes are for confident prosody condition. This study proposes that this experiment design can serve as a reference for investigating speaker-specific cue-binding effects in various scenarios (e.g., anaphoric expression) and pathologies in patients like phonagnosia.

Changes in high-order interaction measures of synergy and redundancy during non-ordinary states of consciousness induced by meditation, hypnosis, and auto-induced cognitive trance

High-order interactions are required across brain regions to accomplish specific cognitive functions. These functional interdependencies are reflected by synergistic information that can be obtained by combining the information from all the sources considered and redundant information (i.e., common information provided by all the sources). However, electroencephalogram (EEG) functional connectivity is limited to pairwise interactions thereby precluding the estimation of high-order interactions. In this multicentric study, we used measures of synergistic and redundant information to study in parallel the high-order interactions between five EEG electrodes during three non-ordinary states of consciousness (NSCs): Rajyoga meditation (RM), hypnosis, and auto-induced cognitive trance (AICT). We analyzed EEG data from 22 long-term Rajyoga meditators, nine volunteers undergoing hypnosis, and 21 practitioners of AICT. We here report the within-group changes in synergy and redundancy for each NSC in comparison with their respective baseline. During RM, synergy increased at the whole brain level in the delta and theta bands. Redundancy decreased in frontal, right central, and posterior electrodes in delta, and frontal, central, and posterior electrodes in beta1 and beta2 bands. During hypnosis, synergy decreased in mid-frontal, temporal, and mid-centro-parietal electrodes in the delta band. The decrease was also observed in the beta2 band in the left frontal and right parietal electrodes. During AICT, synergy decreased in delta and theta bands in left-frontal, right-frontocentral, and posterior electrodes. The decrease was also observed at the whole brain level in the alpha band. However, redundancy changes during hypnosis and AICT were not significant. The subjective reports of absorption and dissociation during hypnosis and AICT, as well as the mystical experience questionnaires during AICT, showed no correlation with the high-order measures. The proposed study is the first exploratory attempt to utilize the concepts of synergy and redundancy in NSCs. The differences in synergy and redundancy during different NSCs warrant further studies to relate the extracted measures with the phenomenology of the NSCs.

Family lexicon: Using language models to encode memories of personally familiar and famous people and places in the brain.

Knowledge about personally familiar people and places is extremely rich and varied, involving pieces of semantic information connected in unpredictable ways through past autobiographical memories. In this work, we investigate whether we can capture brain processing of personally familiar people and places using subject-specific memories, after transforming them into vectorial semantic representations using language models. First, we asked participants to provide us with the names of the closest people and places in their lives. Then we collected open-ended answers to a questionnaire, aimed at capturing various facets of declarative knowledge. We collected EEG data from the same participants while they were reading the names and subsequently mentally visualizing their referents. As a control set of stimuli, we also recorded evoked responses to a matched set of famous people and places. We then created original semantic representations for the individual entities using language models. For personally familiar entities, we used the text of the answers to the questionnaire. For famous entities, we employed their Wikipedia page, which reflects shared declarative knowledge about them. Through whole-scalp time-resolved and searchlight encoding analyses, we found that we could capture how the brain processes one's closest people and places using person-specific answers to questionnaires, as well as famous entities. Overall encoding performance was significant in a large time window (200-800ms). Using spatio-temporal EEG searchlight, we found that we could predict brain responses significantly better than chance earlier (200-500ms) in bilateral temporo-parietal electrodes and later (500-700ms) in frontal and posterior central electrodes. We also found that XLM, a contextualized (or large) language model, provided superior encoding scores when compared with a simpler static language model as word2vec. Overall, these results indicate that language models can capture subject-specific semantic representations as they are processed in the human brain, by exploiting small-scale distributional lexical data.

Interhemispheric transfer time correlates with white matter integrity of the corpus callosum in healthy older adults

The corpus callosum (CC) has been identified as an important structure in the context of cognitive aging (Fling et al., 2011). Interhemispheric transfer time (IHTT) is regularly used in order to estimate interhemispheric integration enabled by the CC (Marzi, 2010; Nowicka and Tacikowski, 2011). However, only little is known with regards to the relationship between IHTT and the structural properties of the CC with only few studies with specific samples and methods available (Whitford et al., 2011). Thus, the present study aimed at investigating this relationship applying an event-related potentials (ERP) based approach of estimating IHTT as well as diffusion weighted imaging (DWI) with fractional anisotropy (FA) as an indicator of white matter integrity (WMI) of the genu, corpus and splenium of the CC. 56 healthy older adults performed a Dimond Task while ERPs were recorded and underwent DWI scanning. IHTT derived from posterior electrode sites correlated significantly with FA of the splenium (r = −0.286*, p = .03) but not the corpus (r = −0.187, p = .08) or genu (r = −0.189, p = .18). The present results support the notion that IHTT is related to WMI of the posterior CC. It may be concluded that ERP based IHTT is a suitable indicator of CC structure and function, however, likely specific to the interhemispheric transfer of visual information. Future studies may wish to confirm these findings in a more divers sample further exploring the precise interrelation between IHTT and structural or functional properties of the CC.

Dynamic alpha power modulations and slow negative potentials track natural shifts of spatio-temporal attention.

Alpha power modulations and slow negative potentials have previously been associated with anticipatory processes in spatial and temporal top-down attention. In typical experimental designs, however, neural responses triggered by transient stimulus onsets can interfere with attention-driven activity patterns and our interpretation of such. Here, we investigated these signatures of spatio-temporal attention in a dynamic paradigm free from potentially confounding stimulus-driven activity using electroencephalography. Participants attended the cued side of a bilateral stimulus rotation and mentally counted how often one of two remembered sample orientations (i.e., the target) was displayed while ignoring the uncued side and non-target orientation. Afterwards, participants performed a delayed match-to-sample task, in which they indicated if the orientation of a probe stimulus matched the corresponding sample orientation (previously target or non-target). We observed dynamic alpha power reductions and slow negative waves around task-relevant points in space and time (i.e., onset of the target orientation in the cued hemifield) over posterior electrodes contralateral to the locus of attention. In contrast to static alpha power lateralization, these dynamic signatures correlated with subsequent memory performance (primarily detriments for matching probes of the non-target orientation), suggesting a preferential allocation of attention to task-relevant locations and time points at the expense of reduced resources and impaired performance for information outside the current focus of attention. Our findings suggest that humans can naturally and dynamically focus their attention at relevant points in space and time and that such spatio-temporal attention shifts can be reflected by dynamic alpha power modulations and slow negative potentials.

Safety of the Radiofrequency Balloon for Pulmonary Vein Isolation: A Focus on Lesion Metric Analysis of Posterior Electrodes.

Previous clinical studies on pulmonary vein isolation (PVI) with radiofrequency balloons (RFB) reported safe and effective procedures for a 20 s RF delivery via posterior electrodes. Recent recommendations from the manufacturer suggest reducing the application time to 15 s on the posterior wall (PW) when facing the esophagus region. Here, we retrospectively assess whether 15 s of RF delivery time on posterior electrodes is safe while still ensuring lesion metrics of sufficient quality. This retrospective study included 133 patients with paroxysmal and persistent atrial fibrillation who underwent PVI using an RFB (Heliostar, Biosense Webster, Inc., Irvine, CA, USA) at two European centers. The ablation protocol was set for an RF duration of 20 s/60 s for the posterior/anterior electrodes. A multielectrode temperature probe was systematically used. In the case of an esophageal temperature rise (ETR) above 42 °C (ETR+), an endoscopic evaluation was performed. All posterior electrode lesion metric dynamics (temperature (T) and impedance (Z)) were collected from the RFB generator and analyzed offline. In total, 2435 posterior electrode applications were analyzed. With an RF delivery of 19.8 (19.7-19.8) s, the median impedance drop was 18.4 (12.2-25.2) Ω, while the temperature rise was 11.1 (7.1-14.9) °C. Accordingly, impedance (84.6 (79.3-90.2) Ω) and temperature plateaus (38 (35.3-41.1) °C) were reached at 13.9 (10.6-16) s and 16.4 (12.6-18.5) s, respectively. Overall, 99.6% and 95.8% of electrodes reached 90% (16.6 Ω) and 95% (17.5 Ω) of their impedance drops within 15 s of RF delivery, while 97.2% and 92.8% achieved 90% (34.2 °C) and 95% (36.1 °C) of their temperature rise to reach the plateaus within 15 s of RF delivery. An ETR >42 °C occurred in 37 (30.1%) patients after 17.7 ± 2.3 s of RF delivery. In the ETR+ group, the impedance drop and temperature rise on the posterior electrodes were higher compared to patients where ETR was <42 °C. Two asymptomatic thermal esophageal injuries were observed. In conclusion, 15 s of RF delivery on the posterior electrodes provides a good balance between safety, with no esophageal temperature rise, and efficacy with high-profile lesion metrics.

Differential effects of intra-modal and cross-modal reward value on perception: ERP evidence.

In natural environments objects comprise multiple features from the same or different sensory modalities but it is not known how perception of an object is affected by the value associations of its constituent parts. The present study compares intra- and cross-modal value-driven effects on behavioral and electrophysiological correlates of perception. Human participants first learned the reward associations of visual and auditory cues. Subsequently, they performed a visual discrimination task in the presence of previously rewarded, task-irrelevant visual or auditory cues (intra- and cross-modal cues, respectively). During the conditioning phase, when reward associations were learned and reward cues were the target of the task, high value stimuli of both modalities enhanced the electrophysiological correlates of sensory processing in posterior electrodes. During the post-conditioning phase, when reward delivery was halted and previously rewarded stimuli were task-irrelevant, cross-modal value significantly enhanced the behavioral measures of visual sensitivity, whereas intra-modal value produced only an insignificant decrement. Analysis of the simultaneously recorded event-related potentials (ERPs) of posterior electrodes revealed similar findings. We found an early (90-120 ms) suppression of ERPs evoked by high-value, intra-modal stimuli. Cross-modal stimuli led to a later value-driven modulation, with an enhancement of response positivity for high- compared to low-value stimuli starting at the N1 window (180-250 ms) and extending to the P3 (300-600 ms) responses. These results indicate that sensory processing of a compound stimulus comprising a visual target and task-irrelevant visual or auditory cues is modulated by the reward value of both sensory modalities, but such modulations rely on distinct underlying mechanisms.

Active search signatures in a free-viewing task exploiting concurrent EEG and eye movements recordings.

Tasks we often perform in our everyday lives, such as reading or looking for a friend in the crowd, are seemingly straightforward but they actually require the orchestrated activity of several cognitive processes. Free-viewing visual search requires a plan to move our gaze on the different items, identifying them, and deciding on whether to continue with the search. Little is known about the electrophysiological signatures of these processes in free-viewing because there are technical challenges associated with eye movement artefacts. Here, we aimed to study how category information, as well as ecologically relevant variables such as the task performed, influence brain activity in a free-viewing paradigm. Participants were asked to observe/search from an array of faces and objects embedded in random noise. We concurrently recorded electroencephalogram and eye movements and applied a deconvolution analysis approach to estimate the contribution of the different elements embedded in the task. Consistent with classical fixed-gaze experiments and a handful of free-viewing studies, we found a robust categorical effect around 150 ms in occipital and occipitotemporal electrodes. We also report a task effect, more negative in posterior central electrodes in visual search compared with exploration, starting at around 80 ms. We also found significant effects of trial progression and an interaction with the task effect. Overall, these results generalise the characterisation of early visual face processing to a wider range of experiments and show how a suitable analysis approach allows to discern among multiple neural contributions to the signal, preserving key attributes of real-world tasks.

Adaptive CRT algorithm and electrical synchrony

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): United Hospital Medical Education and Research Committee, United Hospital Foundation. Background We have previously shown that optimization of cardiac resynchronization therapy (CRT) nonresponders using a novel electrical dyssynchrony mapping (EDM) system significantly improves electrical dyssynchrony, left ventricle (LV) size and systolic function. Whether this methodology can improve electrical dyssynchrony (and potentially LV function) in nonresponder patients programmed with the adaptive CRT (aCRT) algorithm is not known. Purpose To quantify electrical dyssynchrony in CRT nonresponders programmed using aCRT and determine if it can be improved using EDM. Methods We studied 97 patients programmed with the aCRT algorithm at multiple device settings with an ECG system of 9 anterior and 9 posterior electrodes. We quantified electrical dyssynchrony using a measure of wavefront fusion, cardiac resynchronization index (CRI), calculated as % change in area under the curve between all combinations of anterior and posterior electrodes as compared to native LBBB (CRT off). CRI results were displayed on an electrical dyssynchrony map (EDM) showing atrial-to-right ventricle-paced intervals (A-RVp) on the y-axis and atrial-to-left ventricle-paced intervals (A-LVp) on the x-axis. Results Figure 1 shows an EDM for a typical patient with CRI values marked at different programmed settings. Figure 2 shows CRI for 58 patients programmed LV-only by aCRT at baseline (red bars) and 39 patients programmed biventricular (BiV) by aCRT at baseline (blue bars). CRI at baseline was significantly (p≤0.001) higher in patients programmed LV-only vs. those programmed BiV. In both groups programming to LV-only at the optimal atrial-ventricular delay (AVD) and to sequential BiV pacing at the optimal ventricular-ventricular delay (VVD) produced significantly and markedly better CRI as compared to CRI at aCRT baseline settings. In the patients programmed by aCRT at baseline to LV-only, BiV VV=0 at standard device setting (SAV 120 ms) had significantly worse CRI than baseline. Conclusions Electrical dyssynchrony as measured by CRI is better in patients programmed aCRT LV-only than those programmed aCRT BiV. CRI can be improved by 20% or more by using EDM to program patients to LV-only pacing at the optimal AVD or to BiV pacing at the optimal VVD. EDM technology offers the possibility of substantially improving electrical synchrony in nonresponder patients programmed with aCRT.

Commonalities between mind wandering and task-set switching: An event-related potential study

Previous research has established that mind wandering does not necessarily disrupt one's task-switching performance. Here we investigated the effects of mind wandering on electrophysiological signatures, measured using event-related potentials (ERPs), during a switching task. In the current study, a final sample of 22 young adults performed a task-switching paradigm while electroencephalography was continuously recorded; mind wandering was assessed via thought probes at the end of each block. Consistent with previous research, we found no significant disruptive effects of mind wandering on task-switching performance. The ERP results showed that at the posterior electrode sites (P3, Pz, and P4), P3 amplitude was higher for mind-wandering switch trials than on-task switch trials, thus opposing the typical pattern of P3 attenuation during periods of mind wandering relative to on-task episodes. Considering that increased P3 amplitude during higher-order switch trials (e.g., response rule switching) may reflect the implementation of new higher-order task sets/rules, the current findings seem to indicate similar executive control processes underlie mind wandering and task-set switching, providing further evidence in favor of a role for switching in mind wandering.

Feedback information transfer in the human brain reflects bistable perception in the absence of report.

In the search for the neural basis of conscious experience, perception and the cognitive processes associated with reporting perception are typically confounded as neural activity is recorded while participants explicitly report what they experience. Here, we present a novel way to disentangle perception from report using eye movement analysis techniques based on convolutional neural networks and neurodynamical analyses based on information theory. We use a bistable visual stimulus that instantiates two well-known properties of conscious perception: integration and differentiation. At any given moment, observers either perceive the stimulus as one integrated unitary object or as two differentiated objects that are clearly distinct from each other. Using electroencephalography, we show that measures of integration and differentiation based on information theory closely follow participants' perceptual experience of those contents when switches were reported. We observed increased information integration between anterior to posterior electrodes (front to back) prior to a switch to the integrated percept, and higher information differentiation of anterior signals leading up to reporting the differentiated percept. Crucially, information integration was closely linked to perception and even observed in a no-report condition when perceptual transitions were inferred from eye movements alone. In contrast, the link between neural differentiation and perception was observed solely in the active report condition. Our results, therefore, suggest that perception and the processes associated with report require distinct amounts of anterior-posterior network communication and anterior information differentiation. While front-to-back directed information is associated with changes in the content of perception when viewing bistable visual stimuli, regardless of report, frontal information differentiation was absent in the no-report condition and therefore is not directly linked to perception per se.

Listening to familiar music induces continuous inhibition of alpha and low-beta power.

How the brain responds temporally and spectrally when we listen to familiar versus unfamiliar musical sequences remains unclear. This study uses EEG techniques to investigate the continuous electrophysiological changes in the human brain during passive listening to familiar and unfamiliar musical excerpts. EEG activity was recorded in 20 participants while they passively listened to 10 s of classical music, and they were then asked to indicate their self-assessment of familiarity. We analyzed the EEG data in two manners: familiarity based on the within-subject design, i.e., averaging trials for each condition and participant, and familiarity based on the same music excerpt, i.e., averaging trials for each condition and music excerpt. By comparing the familiar condition with the unfamiliar condition and the local baseline, sustained low-beta power (12-16 Hz) suppression was observed in both analyses in fronto-central and left frontal electrodes after 800 ms. However, sustained alpha power (8-12 Hz) decreased in fronto-central and posterior electrodes after 850 ms only in the first type of analysis. Our study indicates that listening to familiar music elicits a late sustained spectral response (inhibition of alpha/low-beta power from 800 ms to 10 s). Moreover, the results showed that alpha suppression reflects increased attention or arousal/engagement due to listening to familiar music; nevertheless, low-beta suppression exhibits the effect of familiarity.NEW & NOTEWORTHY This study differentiates the dynamic temporal-spectral effects during listening to 10 s of familiar music compared with unfamiliar music. This study highlights that listening to familiar music leads to continuous suppression in the alpha and low-beta bands. This suppression starts ∼800 ms after the stimulus onset.

PO-02-009 LEAD REVISION AND OPTIMIZATION OF CRT NONRESPONDERS USING ELECTRICAL DYSSYNCHRONY MAPPING

Identification and treatment of CRT nonresponders who have poor LV lead position is a significant clinical problem. To describe how a new technology for measuring electrical dyssynchrony can be used to identify CRT patients with poor LV lead position and optimize their device programming with or without LV lead revision. An ECG system of 9 anterior/9 posterior leads was used to quantify a novel measure of electrical dyssynchrony called cardiac resynchronization index (CRI), defined as % change in area under the curve between all combinations of anterior and posterior electrodes as compared to native (CRT off). An electrical dyssynchrony map (EDM) was used to graphically display CRI values at multiple different atrial-ventricular delays (AVD) and ventricular-ventricular delays (VVD). Poor LV lead position was defined as optimal CRI (CRIopt) < 90% or need for VVD > -80 ms (LV ahead) to achieve CRIopt. We studied 19 CRT nonresponder patients with poor LV lead position based on EDM criteria. Mean CRI was 31.8±21.5%. LV lead location was anterior (n=8), apical (n=6) and posterior/lateral (n=5). Figure 1 shows an EDM of a patient before and after lead revision. Initial lead was an anterior epicardial lead. CRIopt was at VVD of -90 ms (LV-paced ahead) and EF did not improve with optimization. After placement of a lateral LV lead, VVD optimization of -30 ms resulted in an improvement in EF from 25% to 33%. Fifteen patients were programmed to CRIopt. Four patients were optimized to LV-only pacing at the optimal AVD and 11 were programmed biventricular with mean VVD -61±25 ms (LV-paced ahead). Five of these patients had minimal or no improvement with optimization. and underwent lead revision. Four patients did not have a device setting with a substantially improved CRI and 2 of 4 underwent LV lead revision. All 7 patients with LV lead revision had repeat optimization after lead revision. LV ejection fraction (EF) measured 4-6 months post-optimization improved significantly (p ≤ 0.05) from 29.1 ± 7.1% to 33.5 ± 5.8% in the 17 patients optimized by reprogramming and/or lead revision. EDM is a noninvasive, practical methodology that can be used to identify CRT nonresponder patients with poor LV lead position, determine whether lead revision may be of benefit, and optimize device programming before and/or after lead revision. This clinical approach results in a significant improvement in EF of 4.4%.

What naturalistic stimuli tell us about pronoun resolution in real-time processing.

Studies on pronoun resolution have mostly utilized short texts consisting of a context and a target sentence. In the current study we presented participants with nine chapters of an audio book while recording their EEG to investigate the real-time resolution of personal and demonstrative pronouns in a more naturalistic setting. The annotation of the features of the pronouns and their antecedents registered a surprising pattern: demonstrative pronouns showed an interpretive preference for subject/agent antecedents, although they are described to have an anti-subject or anti-agent preference. Given the presence of perspectival centers in the audio book, this however confirmed proposals that demonstrative pronouns are sensitive to perspectival centers. The ERP results revealed a biphasic N400-Late Positivity pattern at posterior electrodes for the demonstrative pronoun relative to the personal pronoun, thereby confirming previous findings with highly controlled stimuli. We take the observed N400 for the demonstrative pronoun as an indication for more demanding processing costs that occur due to the relative unexpectedness of this referential expression. The Late Positivity is taken to reflect the consequences of attentional reorientation: since the demonstrative pronoun indicates a possible shift in the discourse structure, it induces updating of the discourse structure. In addition to the biphasic pattern, the data showed an enhanced positivity at frontal electrode sites for the demonstrative pronoun relative to the personal pronoun. We suggest that this frontal positivity reflects self-relevant engagement and identification with the perspective holder. Our study suggests that by using naturalistic stimuli, we get one step closer to understanding the implementation of language processing in the brain during real life language processing.

Transcranial focused ultrasound modulates the emergence of learned helplessness via midline theta modification

BackgroundHelplessness and hopelessness are states closely related to depressive disorders. They ensue following the anticipated absence of valid behavioral options to alleviate an aversive state. One neural structure involved in the detection of such options, is the cingulate cortex (CC), which conveys the evaluation of behavior against the value of its outcome. Accordingly, CC-related EEG measures are thought to correlate to feedback evaluation but also to anxious and conflict-related states, signaling the need for further adaptation to current requirements. Against this background, this study investigated the role of CC functioning in the emergence and prevention of helpless/hopeless states by applying low-intensity transcranial focused ultrasound (litFUS) neuromodulation prior to a learned helplessness task. MethodIn a randomized controlled double blind experimental setup with 55 participants, litFUS was used to inhibit the right lateral prefrontal cortex (lPFC), a region closely connected to CC modulation. Participants were instructed to play 8 games of chess against a computer that was unbeatable to them, while an EEG was recorded. Theta oscillation in midline electrodes, playing performance and self-rate measures on cognitive, affective and physiological parameters were assessed. ResultsThe results show a considerable influence of litFUS neuromodulation of the lPFC on midline theta activity (Fz and Pz electrode position) which in turn correlated to several psychological variables including self-report data on emotion, cognition, and arousal as well as behavioral measures (playing performance). LimitationsDue to the small sample size and sample characteristics, results cannot be generalized to the field of clinical application. A replication of results in larger samples and in context of other sonication parameters is needed to increase the robustness of results and to maximize the efficacy of litFUS application. ConclusionsWe conclude that the development of learned helplessness/hopelessness could be positively influenced in its course by litFUS neuromodulation of the right lPFC. In line with previous results, especially the posterior midline electrode Pz seems to be an interesting target for further research in this field as theta activity at this electrode is correlated to control perception and motivated behavior. To our knowledge, this is the first study to use neuromodulation to monitor and manipulate the development of helplessness in the laboratory.

Anteriolateral versus anterior-posterior electrodes in external cardioversion of atrial fibrillation: A systematic review and meta-analysis of clinical trials.

The efficacy of anteriolateral versus anterior-posterior electrode positions in the success of atrial fibrillation's (AF) electrical cardioversion is unclear. Our aim is to perform a meta-analysis to compare the success rate of both electrode positions.PUBMED, WOS, OVID, and SCOPUS were searched. Inclusion criteria were clinical trials that compared anterior-lateral with anterior-posterior electrodes in external cardioversion of AF. After the full-text screening, 11 trials were included in the analysis. The total number of patients included in the study is 1845. The pooled analysis showed a statistically significant association between anterior-lateral electrode and increased cardioversion rate of AF (odds ratio [OR] = 1.40, 95% confidence interval [CI] = 1.02-1.92, p = .04). Subgroup analysis revealed a statistically significant association between the anterior-lateral electrode and increased cardioversion rate of AF in subgroups of less than five shocks, patients with 60 years old or more and patients with left atrial (LA) diameter >45 mm (OR = 1.72, 95% CI = 1.17-2.54, p = .006), (OR = 1.73, 95% CI = 1.18-2.54, p = .005), and (OR = 1.86, 95% CI = 1.04-3.34, p = .04), respectively. Anteriolateral electrode is more effective than anterior-posterior electrode in external cardioversion of AF, particularly in patients who have received less than 5 shocks, are 60 years old or older and have a LA diameter greater than 45 mm.

Early neural markers for individual difference in mathematical achievement determined from rational number processing

The neural markers for individual differences in mathematical achievement have been studied extensively using magnetic resonance imaging; however, high temporal resolution electrophysiological evidence for individual differences in mathematical achievement require further elucidation. This study evaluated the event-related potential (ERP) when 48 college students with high or low mathematical achievement (HA vs. LA) matched non-symbolic and symbolic rational numbers. Behavioral results indicated that HA students had better performance in the discretized non-symbolic matching, although the two groups showed similar performances in the continuous matching. ERP data revealed that even before non-symbolic stimulus presentation, HA students had greater Bereitschaftspotential (BP) amplitudes over posterior central electrodes. After the presentation of non-symbolic numbers, HA students had larger N1 amplitudes at 160 ms post-stimulus, over left-lateralized parieto-occipital electrodes. After the presentation of symbolic numbers, HA students displayed more profound P1 amplitudes at 100 ms post-stimulus, over left parietal electrodes. Furthermore, larger BP and N1 amplitudes were associated with the shorter reaction times, and larger P1 amplitudes corresponded to lower error rates. The BP effect could indicate preparation processing, and early left-lateralized N1 and P1 effects could reflect the non-symbolic and symbolic number processing along the dorsal neural pathways. These results suggest that the left-lateralized P1 and N1 components elicited by matching non-symbolic and symbolic rational numbers can be considered as neurocognitive markers for individual differences in mathematical achievement.

Bilingualism modulates neural efficiency at rest through alpha reactivity

The aim of the present study was to investigate how resting state EEG rhythms reflect attentional processes and bilingual experience. We compared alpha and beta rhythms for monolingual and bilingual young adults in eyes open and eyes closed conditions using EEG measures of frequency power, reactivity, and coherence. Power shows the amount of brain activity at a given frequency band; reactivity indexes the desynchronization of neuronal activity when individuals open their eyes at rest; and coherence indicates the brain regions that have correlated activity. The results showed that bilinguals had similar alpha power as monolinguals in both resting conditions but less alpha reactivity across the whole scalp. There was also more focused activation for bilinguals expressed as more coherence in posterior electrodes, particularly when eyes were opened to direct attention. For beta, there were no group differences in power or reactivity, but there was higher coherence for monolinguals than bilinguals, a pattern consistent with previous literature showing that beta frequency was related to language learning and native language proficiency. These results are in line with a neural efficiency theory and suggest that bilinguals have a more efficient brain for attentional mechanisms than monolinguals at rest.