Posterior P1 Research Articles

The effect of mental abacus calculation training on form recognition of children: an ERP study

Objective To explore the influence of mental abacus calculation(MAC) training on children's form recognition. Methods 28 children (14 children with MAC training and 14 children with non-MAC traning) were investigated by using event-related potential(ERP) technology.The event-related potentials were recorded when subjects were in the different form shape recognition. Results (1) The amplitudes of the posterior P1 evoked by the children with MAC training((9.59±3.58)μV) were significantly greater than that of the children without MAC training ((7.06±2.84)μV) (P<0.05). (2) The amplitudes of right temporal-posterior N170 of children with MAC((-9.83±2.97) μV) were markedly less than that of children with non-MAC((-12.45±2.51) μV)(P<0.05). (3) The amplitudes of prefrontal P3 of children with MAC((7.65±2.25)μV) were remarkably greater than that of children with non-MAC((4.89±3.35)μV)(P<0.05). Conclusion The brain function of form recognition in children is influenced by mental abacus calculation training. Key words: Mental abacus calculation training; Form recognition; Event-related potential; Children

Psychophysical and Neural Evidence for Emotion-Enhanced Perceptual Vividness

Highly emotional events are associated with vivid "flashbulb" memories. Here we examine whether the flashbulb metaphor characterizes a previously unknown emotion-enhanced vividness (EEV) during initial perceptual experience. Using a magnitude estimation procedure, human observers estimated the relative magnitude of visual noise overlaid on scenes. After controlling for computational metrics of objective visual salience, emotional salience was associated with decreased noise, or heightened perceptual vividness, demonstrating EEV, which predicted later memory vividness. Event-related potentials revealed a posterior P2 component at ∼200 ms that was associated with both increased emotional salience and decreased objective noise levels, consistent with EEV. Blood oxygenation level-dependent response in the lateral occipital complex (LOC), insula, and amygdala predicted online EEV. The LOC and insula represented complimentary influences on EEV, with the amygdala statistically mediating both. These findings indicate that the metaphorical vivid light surrounding emotional memories is embodied directly in perceptual cortices during initial experience, supported by cortico-limbic interactions.

Quantification of Mitral Valve Anatomy by Three-Dimensional Transesophageal Echocardiography in Mitral Valve Prolapse Predicts Surgical Anatomy and the Complexity of Mitral Valve Repair

Three-dimensional (3D) transesophageal echocardiography (TEE) is more accurate than two-dimensional (2D) TEE in the qualitative assessment of mitral valve (MV) prolapse (MVP). However, the accuracy of 3D TEE in quantifying MV anatomy is less well studied, and its clinical relevance for MV repair is unknown. The number of prolapsed segments, leaflet heights, and annular dimensions were assessed using 2D and 3D TEE and compared with surgical measurements in 50 patients (mean age, 61 ± 11 years) who underwent MV repair for mainly advanced MVP. Three-dimensional TEE was more accurate (92%-100%) than 2D TEE (80%-96%) in identifying prolapsed segments. Three-dimensional TEE and intraoperative measurements of leaflet height did not differ significantly, while 2D TEE significantly overestimated the height of the posterior segment P1 and the anterior segment A2. Three-dimensional TEE quantitative MV measurements were related to surgical technique: patients with more complex MVP (one vs two to four vs five or more prolapsed segments) showed progressive enlargement of annular anteroposterior (31 ± 5 vs 34 ± 4 vs 37 ± 6 mm, respectively, P = .02) and commissural diameters (40 ± 6 vs 44 ± 5 vs 50 ± 10 mm, respectively, P = .04) and needed increasingly complex MV repair with larger annuloplasty bands (60 ± 13 vs 67 ± 9 vs 72 ± 10 mm, P = .02) and more neochordae (7 ± 3 vs 12 ± 5 vs 26 ± 6, P < .01). Measurements of MV anatomy on 3D TEE are accurate compared with surgical measurements. Quantitative MV characteristics, as assessed by 3D TEE, determined the complexity of MV repair.

Decoding ability makes waves in reading: Deficient interactions between attention and phonological analysis in developmental dyslexia

Whilst there is general consensus that phonological processing is deficient in developmental dyslexia, recent research also implicates visuo-attentional contributions. Capitalising on the P3a wave of event-related potentials as an index of attentional capture, we tested dyslexic and normal readers on a novel variant of a visual oddball task to examine the interplay of orthographic-phonological integration and attentional engagement. Targets were animal words (10% occurrence). Amongst nontarget stimuli were two critical conditions: pseudohomophones of targets (10%) and control pseudohomophones (of fillers; 10%). Pseudohomophones of targets (but not control pseudohomophones) elicited a large P3 wave in normal readers only, revealing a lack of attentional engagement with these phonologically salient stimuli in dyslexic participants. Critically, both groups showed similar early phonological discrimination as indexed by posterior P2 modulations. Furthermore, phonological engagement, as indexed by P3a differences between pseudohomophone conditions, correlated with several measures of reading. Meanwhile, an analogous experiment using coloured shapes instead of orthographic stimuli failed to show group differences between experimental modulations in the P2 or P3 ranges. Overall, our results show that, whilst automatic aspects of phonological processing appear intact in developmental dyslexia, the breakdown in pseudoword reading occurs at a later stage, when attention is oriented to orthographic-phonological information.

Perceptual load, voluntary attention, and aging: An event-related potential study

The locus of attentional selection is known to vary with perceptual load (Lavie et al., 2004). Under voluntary attention, perceptual load modulates selective visual processing at an early cortical stage, as reflected in the posterior P1 and N1 components of the event-related potentials (ERPs). Adult aging also affects both behavioral and ERP signs of attentional selection. However, it is not known whether perceptual load modulates this relationship. Accordingly, in the present study ERPs were recorded in a voluntary attention task. Young and old participants were asked to discriminate the direction of a target line embedded within a display of four lines that appeared in the left or right visual field. Participants responded faster and more accurately to valid relative to invalid trials and to low-load relative to high-load condition. Older participants responded more slowly and with lower accuracy than young participants in all conditions. The amplitudes of the posterior contralateral P1 and N1 components in valid trials were larger than that in invalid trials in all conditions. N1 amplitude was larger under the high load condition than that in the low load condition. Moreover, in the high perceptual load condition, the old group had a larger N1 than the young group at contralateral sites. The findings suggest that under voluntary attention, perceptual load and aging modulates attentional selection at an early but not the earliest stage, during the N1 (120–200ms) time range. Increased N1 amplitude in older adults may reflect increased demands on target discrimination in high perceptual load.

Audiovisual temporal discrimination is less efficient with aging

We investigated the crossmodal temporal discrimination deficit characterizing older adults and its event-related potential (electroencephalogram) correlates using an audiovisual temporal order judgment task. Audiovisual stimuli were presented at stimulus onset asynchronies (SOA) of 70 or 270 ms. Older were less accurate than younger adults with an SOA of 270 ms but not 70 ms. With an SOA of 270 ms only, older adults had smaller posterior P1 and frontocentral N1 amplitudes for visual stimuli in auditory-visual trials and auditory stimuli in visual-auditory trials, respectively. These results suggest a deficit in cross-sensory processing with aging reflected at the behavioural and neural level, and suggest an impairment in switching between modalities even when the inputs are separated by long temporal intervals.

Adaptation to Frequent Conflict in the Eriksen Flanker Task

We examined adaptation to frequent conflict in a flanker task using event-related potentials (ERPs). A prominent model of cognitive control suggests the fronto-central N2 as an indicator of conflict monitoring. Based on this model we predicted (1) an increased N2 amplitude for incompatible compared to compatible stimuli and (2) that this difference in N2 amplitude would be less pronounced under conditions of frequent conflict (high cognitive control). In this model, adaptation to frequent conflict is implemented as modulation of early visual processing. Traditionally, variations in processing selectivity in the flanker task have been related to a zoom lens model of visual attention. Therefore, we further predicted (3) effects of conflict frequency on early visual ERP components of the event-related potential, and (4) generalization of conflict adaptation due to increased conflict frequency in the flanker task to other visuospatial tasks, intermixed within flanker task trials. Frequent conflict was associated with reduced flanker interference in response times (RTs) and error rate. Consistent with the literature, amplitude of the fronto-central N2 was larger and latency of the central P3 longer for incompatible stimuli. Both effects were smaller when conflict was frequent, supporting the notion of fronto-central N2 as indicator of conflict monitoring. Neither amplitude nor latency of the posterior P1, as index of early visual processing, was modulated by conflict frequency. Additionally, conflict frequency in the flanker task did not affect the pattern of RTs in a probe task. In sum, our results suggest that conflict adaptation operates in a task-specific manner and does not necessarily alter early information processing, that is, the spatial focus of visual attention.

The different effect of negative emotion induced by background music on verbal and spatial working memory: evidence from ERP study

Objective To investigate the different effect of negative emotion induced by background music on verbal and spatial working memory. Methods Fifteen participants were exposed in relaxing or horrible background music and did the working memory task. After each emotional condition, the 9-point Self Assessment Manikin scale was registered. n-back paradigm was employed as WM task and the WM task contained two different types, the verbal WM and spatial WM. In the same time,The ERPs during each emotional condition was recorded,and the anterior LPC and posterior P300 were analyzed. Results The valence,arousal and dominance were 5.40±0.91,3.93 ±0.79 and 5.33 ± 1.29 in relaxing condition,while the same dimensionalities in negative condition were 2.00 ± 0.75,6.47 ± 0.99 and 2.33 ± 0.89. The self reported data showed that horrible background music induced the negative emotional state, which were observed from the decrease of valence (t(14)= 15. 902, P ＜0.01) and dominance (t(14) =6.708, P＜0.01) while the increase of arousal (t (14)=9.906, P＜0.01). The ERP data showed,there was a main effect in emotion with anterior LPC (F (1.14)= 7.37, P ＜ 0.01) and in both verbal and spatial WM,the amplitude of LPC were reduced in negative emotional condition. However, there was an interaction of emotion and type on amplitude of P300 (F (1.14)= 11.25, P ＜ 0.01), selective influence of negative emotion in spatial WM were seen (F (1.14)= 12.43, P＜0.01). Conclusion The WM was influenced by negative emotion induced by negative background music ,and the spatial WM was more vulnerable to negative emotion. Key words: Event related potential; Music; Negative emotional state; Working memory

LGL Can Partition the Cortex of One-Cell Caenorhabditis elegans Embryos into Two Domains

Many metazoan cell types are polarized by asymmetric partitioning of the conserved PAR (PAR-3/PAR-6/PKC-3) complex. Cortical domains containing this PAR complex are counterbalanced by opposing domains of varying composition. The tumor-suppressor protein LGL facilitates asymmetric localization of cell fate determinants, in part through modulating the activity of the PAR complex. However, the mechanisms by which LGL acts to maintain a cortical domain remain unclear. Here we identify Caenorhabditis elegans LGL in a biochemical complex with PAR proteins, which localize to the anterior cortex. But LGL itself localizes to the posterior cortex. We show that increasing the amounts of LGL can restrict localization of the PAR complex to an anterior cortical domain, even in the absence of PAR-2. Importantly, LGL must be phosphorylated on conserved residues to exert this function. LGL and the PAR complex can maintain two cortical domains that are sufficient to partition cell fate determinants. Our data suggest a mechanism of "mutual elimination" in which an LGL phosphorylation cycle regulates association of the PAR complex with the cortex: binding of LGL to the PAR complex at the interface of the two domains stimulates its phosphorylation by PKC-3, and the whole complex leaves the cortex.

ERP evidence for distinct mechanisms of fast and slow visual perceptual learning

Perceptual learning (PL) occurs not only within the first training session but also between sessions. Once acquired, the learning effects can last for a long time. By examining the time course of learning-associated ERP changes, this study explores whether fast and slow visual PL contribute to long-term preservation. Subjects first participated in a visual task for three training sessions, and were then given one test session six months later. ERP results showed that fast learning effects, as reflected by the decrement of posterior N1 and increment of posterior P2 within session 1, were preserved in session 3 but not in the test session. However, slow learning effects, as reflected by the increment of posterior N1 and decrement of frontal P170 between sessions 1 and 3, were retained completely in the test session. This study indicates that PL induces different changes in the human adult brain during and after active training, and only the delayed changes of brain activity can be preserved for a long period of six months.

Electrophysiological correlates of figure–ground segregation directly reflect perceptual saliency

In a figure identification task, we investigated the influence of different visual cue configurations (spatial frequency, orientation or a combination of both) on the human EEG. Combining psychophysics with ERP and time–frequency analysis, we show that the neural response at about 200 ms reflects perceptual saliency rather than physical cue contrast. Increasing saliency caused (i) a negative shift of the posterior P2 coinciding with a power decrease in the posterior θ-band and (ii) an amplitude and latency increase of the posterior P3. We demonstrate that visual cues interact for a percept that is non-linearly related to the physical figure–ground properties.

Task difficulty modulates electrophysiological correlates of perceptual learning

To investigate the influence of task difficulty on the neural mechanisms of visual perceptual learning, we recorded event-related potentials (ERPs) from human adults while they were trained with either an easy or a difficult orientation discrimination task. The discrimination thresholds of participants trained with the difficult task decreased after training, but thresholds of participants with the easy task did not. More importantly, although posterior N1 reduction and anterior P2 decrement were obtained in both conditions, only the difficult task training showed an enhancement in posterior P1, an increase in N2 and P3, and a broader scalp distribution of posterior N1 attenuation. These differences indicated that the difficult task training affected the early visual processing stage, the later ERP components, and the broader visual cortical regions, respectively. The results in the present study provide direct electrophysiological evidence for task difficulty modulation of perceptual learning-related neuroplasticity.

The electrophysiological correlate of saliency: Evidence from a figure-detection task

Although figure-ground segregation in a natural environment usually relies on multiple cues, we experience a coherent figure without usually noticing the individual single cues. It is still unclear how various cues interact to achieve this unified percept and whether this interaction depends on task demands. Studies investigating the effect of cue combination on the human EEG are still lacking. In the present study, we combined psychophysics, ERP and time–frequency analysis to investigate the interaction of orientation and spatial frequency as visual cues in a figure detection task. The figure was embedded in a matrix of Gabor elements, and we systematically varied figure saliency by changing the underlying cue configuration. We found a strong correlation between the posterior P2 amplitude and the perceived saliency of the figure: the P2 amplitude decreased with increasing saliency. Analogously, the power of the θ-band decreased for more salient figures. At longer latencies, the posterior P3 component was modulated in amplitude and latency, possibly reflecting increased decision confidence at higher saliencies. In conclusion, when the cue composition (e.g. one or two cues) or cue strength is changed in a figure detection task, first differences in the electrophysiological response reflect the perceived saliency and not directly the underlying cue configuration.

Three stages of facial expression processing: ERP study with rapid serial visual presentation

Electrophysiological correlates of the processing facial expressions were investigated in subjects performing the rapid serial visual presentation (RSVP) task. The peak latencies of the event-related potential (ERP) components P1, vertex positive potential (VPP), and N170 were 165, 240, and 240 ms, respectively. The early anterior N100 and posterior P1 amplitudes elicited by fearful faces were larger than those elicited by happy or neutral faces, a finding which is consistent with the presence of a ‘negativity bias.’ The amplitude of the anterior VPP was larger when subjects were processing fearful and happy faces than when they were processing neutral faces; it was similar in response to fearful and happy faces. The late N300 and P300 not only distinguished emotional faces from neutral faces but also differentiated between fearful and happy expressions in lag2. The amplitudes of the N100, VPP, N170, N300, and P300 components and the latency of the P1 component were modulated by attentional resources. Deficient attentional resources resulted in decreased amplitude and increased latency of ERP components. In light of these results, we present a hypothetical model involving three stages of facial expression processing.

Right frontal cortex generates reward-related theta-band oscillatory activity

When participants in a gambling game are given feedback as to whether they won or lost the previous bet, a series of stereotypical brain electrical responses can be observed in the electroencephalogram (EEG) and the stimulus-locked Event-Related Potential (ERP). These include the Feedback-Related Mediofrontal Negativity (FRN), a posterior P300, and a feedback-induced increase in power at the theta (4 to 8 Hz) band over frontal scalp. Although the generators of the FRN and P300 have been studied previously, little is known about the generator of feedback-induced theta. We employed a gambling game in which participants chose either high-risk/high-reward or low-risk/low-reward bets to investigate these feedback-related responses. The FRN was not modulated by the riskiness of the bet, but both P300 and feedback-induced theta were of greater amplitude following high- relative to low-risk bets. Using a bilateral multi-source Beamformer approach, we localized the induced theta-band responses following wins and losses to partially overlapping regions in the right medial frontal cortex, possibly including the Anterior Cingulate. Using a dipole-fitting approach, we found that the generators of feedback-induced theta are anatomically distinct from those of the FRN and P300.

Perceptual load interacts with involuntary attention at early processing stages: Event-related potential studies

Perceptual load is known to influence the locus of attentional selection in the brain but through an unknown underlying mechanism. We used event-related potentials (ERPs) to investigate how perceptual load interacts with cue-driven involuntary attention. Perceptual load was manipulated in a line orientation discrimination task in which target location was cued involuntarily by means of peripheral cues. Attentional modulation was observed for P1m (the posterior midline P1 component with peak latency between 108 and 140 ms) with invalid trials eliciting larger P1m than valid trials. This attentional effect on P1m increased as a function of perceptual load, suggesting an early temporal locus for the interaction of perceptual load and involuntary attention. Attentional modulation for the C1 component (peak latency at approximately 80 ms) was also observed, but only for high-load stimuli that were presented intermixed with low-load stimuli. Results suggest that (a) perceptual load affects attentional selection at early processing stages; (b) perceptual load interacts with involuntary attention earlier and with different brain mechanisms relative to voluntary attention; and (c) attentional modulation in the C1 time range is possible under optimal experimental conditions.

Serum vitamin B12, folate, and homocysteine levels and their association with clinical and electrophysiological parameters in multiple sclerosis

Patients with multiple sclerosis (MS) may have low serum vitamin B12 and folate levels and high levels of homocysteine. We aimed to evaluate serum vitamin B12, folate, homocysteine, mean corpuscular volume (MCV), hemoglobin (Hb), and hematocrit (Hct) levels in patients with MS. We examined the relationship between these parameters and age, sex, disease type, age at onset, disease duration, Expanded Disability Status Score, immunoglobulin G (IgG) index, oligoclonal band presence, visual evoked potentials (VEP) and posterior tibial somatosensory evoked potentials (SEP). These parameters were evaluated in 35 patients during an acute attack and compared to data collected from 30 healthy individuals (control subjects). Serum vitamin B12, folate, homocysteine, Hb, and Hct levels and MCV were low in a proportion of patients with MS (20%, 14.3%, 20%, 6.7%, 3.3% and 10% respectively), whereas only vitamin B12 and folate levels were low in only 3.3% of the control subjects. Homocysteine levels were high in 20% of patients with MS but were within normal limits in the control group. Elevated Hct levels were significantly correlated ( p < 0.05) with prolonged posterior tibial SEP P1 and P2 latencies compared to the control subjects. Patients with MS who had prolonged VEP and posterior tibial SEP P1 and P2 latencies also had lower vitamin B12 levels compared to patients with normal latencies. Thus, we found a significant relationship between MS and vitamin B12 deficiency, and also demonstrated a relationship between vitamin B12 deficiency, VEP and posterior tibial SEP in MS.

New insights into name category-related effects: is the Age of Acquisition a possible factor?

BackgroundElectrophysiological, hemodynamic and neuropsychological studies have provided evidence of dissociation in the way words belonging to different semantic categories (e.g., animals, tools, actions) are represented in the brain. The aim of the present study was to investigate whether a word's semantic domain may affect the amplitude and latency of ERP components, independently of any other factor.MethodsEEGs were recorded from 16 volunteers engaged in a lexical decision task (word/non-word discrimination) involving 100 words (flora and fauna names). This task allowed us to evaluate differences in processing between words belonging to different categories (fauna vs. flora) independently of task demands. All stimuli were balanced in terms of length, frequency of occurrence, familiarity and imageability. Low Resolution Electromagnetic Tomography (LORETA) was performed on ERP difference waves of interest.ResultsOur findings showed that the two categories were discriminated as early as 200 ms post-stimulus, with larger responses to flora names over the left occipito-temporal areas, namely BA37 and BA20. Category-related ERP differences were also observed in the amplitudes of the later centro-parietal N400, posterior P300 and anterior LP components. Behavioral responses to words denoting fauna were more accurate than to words denoting flora.ConclusionOverall, it seems that it was easier to access the lexical properties of fauna, probably because of their biologically relevant status. The results are discussed in the light of the possible role played by different factors.

Differences in embryonic pattern formation between Caenorhabditis elegans and its close parthenogenetic relative Diploscapter coronatus

In order to evaluate the evolutionary preservation of developmental programs during nematode embryogenesis, we searched for close relatives of the model system Caenorhabditis elegans with deviant patterns. The parthenogenetically reproducing species Diploscapter coronatus shows prominent differences to C. elegans. While in the 2-cell stage of C. elegans a rotation of the nuclear/centrosome complex is found only in the posterior P1 cell, in D. coronatus cell isolation indicates that rotation takes place in a cell-autonomous manner in both blastomeres, resulting in a linear 4-cell array. In C. elegans, the ABp cell becomes different from its ABa sister via a germline-induced induction. In D. coronatus, AB daughters do not touch the germline but nevertheless execute different fates, suggesting a cell-autonomous mechanism or signaling over distance. Laser ablation experiments revealed that active migration of the EMS cell is required to transform the linearly ordered blastomeres into a 3-dimensional embryo, and the difference can be most easily explained with a heterochronic shift with respect to cell mobility. In D. coronatus, reversal of cleavage polarity in the germline, typical for C. elegans, is absent. This results in four different transient variants of posterior blastomeres which eventually merge into a single pattern prior to the onset of gastrulation. This merging includes primordial germ cell migrations of variable extent toward the gut precursor cell and suggests a specific cell-cell recognition mechanism. Cell distribution in advanced embryos is essentially indistinguishable between both species.

Stage and load effects on ERP topography during verbal and spatial working memory

Frontal-parietal neural networks play a significant role in the functional organization of visual working memory (WM). The relative contribution of material-specific information (e.g., verbal or spatial) on activation of WM circuitry is not fully understood. Process-specific models of WM propose that the activation of WM circuitry is more dependent on the stage of WM than on the type of information being processes. This study investigated the effects of WM information type (verbal, spatial), stage (encoding, maintenance), and load on both the anterior–posterior topography and lateralized scalp distributions of the event-related potential (ERP) P3 amplitude. Seventeen young adults performed verbal and spatial tasks that were equated for stimulus properties and response requirements. Both tasks were presented under 1- and 3-load conditions. The anterior–posterior topography of P3 amplitude at left hemisphere, midline, and right hemisphere scalp locations was affected by the stage of WM and the memory load, but not by the type of information. The encoding stage showed minimal load effects and was associated with a posterior-maximum P3 amplitude distribution. During the maintenance stage, probe letters were presented that were irrelevant to the previously encoded stimuli. Here, higher WM load produced relatively greater frontal and reduced parietal P3 amplitude compared to lower WM load. These anterior–posterior P3 amplitude patterns for encoding and maintenance were similar at left, midline, and right locations. Within the limitations of the study, our results tend to support a process-dependent activation of WM circuits in that P3 amplitude topography only differed as a result of WM stage and load, and not as a result of the type of information (verbal or spatial) presented.