Event-related Brain Potentials Amplitudes Research Articles

Tonal and syllabic encoding in overt Cantonese Chinese speech production: An ERP study.

This study was conducted to investigate how syllables and lexical tones are processed in Cantonese speech production using the picture-word interference task with concurrent recording of event-related brain potentials (ERPs). Cantonese-speaking participants were asked to name aloud individually presented pictures and ignore an accompanying auditory word distractor. The target and distractor either shared the same word-initial syllable with the same tone (Tonal-Syllable related), the same word-initial syllable without the same tone (Atonal-Syllable related), the same tone only (Tone alone related), or were phonologically unrelated. Participants' naming responses were faster, relative to an unrelated control, when the target and distractor shared the same tonal- or atonal-syllable but null effect was found in the Tone alone related condition. The mean ERP amplitudes (per each 100-ms time window) were subjected to stimulus-locked (i.e., time-locked to stimulus onset) and response-locked (i.e., time-locked to response onset) analyses. Significant differences between related and unrelated ERP waves were similarly observed in both Tonal-Syllable related and Atonal-Syllable related conditions in the time window of 400-500 ms post-stimulus. However, distinct ERP effects were observed in these two phonological conditions within the 500-ms pre-response period. In addition, null effects were found in the Tone alone related condition in both stimulus-locked and response-locked analyses. These results suggest that in Cantonese spoken word production, the atonal syllable of the target is retrieved first and then associated with the target lexical tone, consistent with the view that tone has an important role to play at a late stage of phonological encoding in tonal language production.

The effect of landmark visualization in mobile maps on brain activity during navigation: A virtual reality study

The frequent use of GPS-based navigation assistance is found to negatively affect spatial learning. Displaying landmarks effectively while providing wayfinding instructions on such services could facilitate spatial learning because landmarks help navigators to structure and learn an environment by serving as cognitive anchors. However, simply adding landmarks on mobile maps may tax additional cognitive resources and thus adversely affect cognitive load in mobile map users during navigation. To address this potential issue, we set up the present study experimentally to investigate how the number of landmarks (i.e., 3 vs. 5 vs. 7 landmarks), displayed on a mobile map one at a time at intersections during turn-by-turn instructions, affects spatial learning, cognitive load, and visuospatial encoding during map consultation in a virtual urban environment. Spatial learning of the environment was measured using a landmark recognition test, a route direction test, and Judgements of Relative Directions (JRDs). Cognitive load and visuospatial encoding were assessed using electroencephalography (EEG) by analyzing power modulations in distinct frequency bands as well as peak amplitudes of event-related brain potentials (ERPs). Behavioral results demonstrate that landmark and route learning improve when the number of landmarks shown on a mobile map increases from three to five, but that there is no further benefit in spatial learning when depicting seven landmarks. EEG analyses show that relative theta power at fronto-central leads and P3 amplitudes at parieto-occipital leads increase in the seven-landmark condition compared to the three- and five-landmark conditions, likely indicating an increase in cognitive load in the seven-landmark condition. Visuospatial encoding indicated by greater theta ERS and alpha ERD at occipital leads with a greater number of landmarks on mobile maps. We conclude that the number of landmarks visualized when following a route can support spatial learning during map-assisted navigation but with a potential boundary—visualizing landmarks on maps benefits users’ spatial learning only when the number of visualized landmarks shown does not exceed users’ cognitive capacity. These results shed more light on neuronal correlates underlying cognitive load and visuospatial encoding during spatial learning in map-assisted navigation. Our findings also contribute to the design of neuro-adaptive landmark visualization for mobile navigation aids that aim to adapt to users’ cognitive load to optimize their spatial learning in real time.

Investigation of the optimal time interval between task-irrelevant auditory probes for evaluating mental workload in the shortest possible time

Event-related brain potentials (ERPs) elicited by auditory stimuli unrelated to a current visual-cognitive task (i.e., task-irrelevant auditory probes) can be used to evaluate the level of mental workload. Towards the evaluation of workload in the shortest possible time, the present study with a multiple-stimulus paradigm (Takeda and Kimura, 2014, Int. J. Psychophysiol.) examined whether manipulating time intervals between probes could improve the temporal resolution in evaluating workload. Probes were presented in four interval conditions as a combination of two mean interval lengths [long (600 ms) vs. short (300 ms)] and two interval variabilities [variable (five levels) vs. fixed], while participants were performing a driving game at slow and fast speeds (i.e., imposing low and high workload, respectively). For each interval condition, the minimum data length required to obtain a significant difference in the amplitude of ERPs (i.e., auditory N1 and P2) between the slow and fast driving tasks was estimated. The N1 difference was significant in all four interval conditions but the required minimum data lengths to observe this difference did not greatly differ across the interval conditions (about 60–90 s). The P2 difference was significant only in the long-variable condition and the required minimum data length was about 120 s. These results suggest that, at least with a multiple-stimulus paradigm, manipulations of time intervals between probes did not greatly improve the temporal resolution in evaluating mental workload; at present, long-variable intervals would be optimal for evaluating mental workload in detail.

Effects of Supplementation With Iron Syrup or Iron-Containing Multiple Micronutrient Powders on Neural Indices of Cognitive Functioning in Bangladeshi Children

ObjectivesMicronutrients, especially iron, play a critical role in the developing infant brain. Yet, the causal effects of iron supplementation on neurocognitive functioning in a low-income anemic population of children have not been examined. This study sought to evaluate the effects of supplementation with iron syrup and iron-containing multiple micronutrient powders (MNPs) in Bangladeshi children on habituation to familiar sounds, a marker for healthy memory development, using auditory event-related brain potentials (ERPs). MethodsThis study was nested within the Benefits and Risks of Iron Supplementation in Children (BRISC) trial, a double blinded double dummy randomized controlled trial (RCT). At 8 months of age, 3300 children were randomized to receive 3 months of 1) iron syrup + placebo MNPs, or 2) MNPs (containing iron, retinol, zinc, and Vitamin C) + placebo iron syrup, or 3) placebo iron syrup and placebo MNPs. ERPs in response to an auditory roving oddball paradigm were measured in a random subset of 441 children at 3 months post-intervention (11 months of age) and 595 children after a further 9 months follow-up (20 months of age). ERP measures indexing aspects of habituation included the [deviant minus standard] difference waveform amplitude, N2 waveform amplitude, and the difference in deviant-evoked ERP amplitudes between the first and second half of the paradigm. Intention-to-treat analyses on ERP outcomes using linear models were used at 11 and 20 months of age separately. ResultsBaseline characteristics were balanced between treatment groups. Overall prevalence of anemia was 43.7% and iron deficiency was 28.4%. Intention-to-treat analyses indicated no significant treatment effects of iron or MNPs on the difference waveform amplitude at 11 months of age [mean difference (MD, 95% CI) iron vs placebo 0.24 (–1.03, 1.51); MNP vs placebo 0.59 (–0.70, 1.88)] and 20 months of age [(MD, 95% CI) iron vs placebo 0.50 (–0.62, 1.63); MNP vs placebo 0.24 (–0.89, 1.38)]. There were no differences by treatment arm for the other ERP measures. ConclusionsResults from a rigorous prospectively powered sub-study of an RCT in an iron deficient population indicated no significant effects of supplementation with iron or MNPs on neural indices of habituation. Funding SourcesNHMRC and The University of Melbourne.

Changes in attentional resources during the acquisition of laparoscopic surgical skills.

BackgroundIncreasing familiarity and practice might free up mental resources during laparoscopic surgical skills training. The aim of the study was to track changes in mental resource allocation during acquisition of laparoscopic surgical skills.MethodsMedical students with no previous experience in laparoscopic surgery took part in a 5-week laparoscopic training curriculum. At the beginning and end of the training period, one of the training tasks was combined with a secondary auditory detection task that required pressing a foot switch for defined target tones, creating a dual-task situation. During execution of the two concurrent tasks, continuous electroencephalographic measurements were made, with special attention to the P300 component, an index of mental resources. Accuracy and reaction times of the secondary task were determined.ResultsAll 14 participants successfully completed the training curriculum. Target times for successful completion of individual tasks decreased significantly during training sessions (P <0.001 for all tasks). Comparing results before and after training showed a significant decrease in event-related brain potential amplitude at the parietal electrode cluster (P300 component, W = 67, P = 0.026), but there were no differences in accuracy (percentage correct responses: W = 48, P = 0.518) or reaction times (W = 42, P = 0.850) in the auditory detection task.ConclusionThe P300 decrease in the secondary task over training demonstrated a shift of mental resources to the primary task: the surgical exercise. This indicates that, with more practice, mental resources are freed up for additional tasks.

Electrophysiological dynamics of visuocortical processing in hoarding disorder.

Individuals with hoarding disorder (HD) typically perform worse than peers on neuropsychological tasks involving visual perception. Functional neuroimaging shows diffusely increased activity in the visual cortex, consistent with inefficient visual processing in HD. The temporal locus of these inefficiencies in HD is unknown. This study examined the temporal unfolding of visual event-related brain potentials (ERPs) to help better define the neurophysiological mechanisms underlying visual dysfunction in HD. Thirty-three individuals with HD and 35 healthy controls (HC) were assessed using a 64-channel EEG during a modified flanker task. Permutation-controlled analyses were conducted to detect group differences in visual evoked ERPs on a millisecond-to-millisecond basis. Bayesian ANCOVAs and linear regressions that included hoarding and age were conducted to identify the best-fit model for the identified VEPs, compared to a null model that included depression and anxiety severity. Three temporal regions (175ms, 270ms, and 440ms), showed differences in amplitude between HD and HC and were consistent with ERP components N1, P1/N2, and a late negative slow wave (LNSW), respectively. After controlling for depression and anxiety, HD demonstrated an enhanced ERP amplitude at N1 and an attenuated amplitude in LNSW compared to HC but did not show differences at P1/N2. For the N1 and LNSW, there was also a primary effect of the interaction between hoarding and age. This study indicates that altered visuocortical reactivity in HD first occurs at the level of visuocortical processing after 170ms, indicating alterations of middle and later, but not early, processing in occipitotemporal visual cortex.

Neural Processes Underlying Nonword Rhyme Differentiate Eventual Stuttering Persistence and Recovery.

Purpose Phonological skills have been associated with developmental stuttering. The current study aimed to determine whether the neural processes underlying phonology, specifically for nonword rhyming, differentiated stuttering persistence and recovery. Method Twenty-six children who stutter (CWS) and 18 children who do not stutter, aged 5 years, completed an auditory nonword rhyming task. Event-related brain potentials were elicited by prime, rhyming, and nonrhyming targets. CWS were followed longitudinally to determine eventual persistence (n = 14) or recovery (n = 12). This is a retrospective analysis of data acquired when all CWS presented as stuttering. Results CWS who eventually recovered and children who do not stutter exhibited the expected rhyme effect, with larger event-related brain potential amplitudes elicited by nonrhyme targets compared to rhyme targets. In contrast, CWS who eventually persisted exhibited a reverse rhyme effect, with larger responses to rhyme than nonrhyme targets. Conclusions These findings suggest that CWS who eventually persisted are not receiving the same benefit of phonological priming as CWS who eventually recovered for complex nonword rhyming tasks. These results indicate divergent patterns of phonological processing in young CWS who eventually persisted, especially for difficult tasks with limited semantic context, and suggest that the age of 5 years may be an important developmental period for phonology in CWS. Supplemental Material https://doi.org/10.23641/asha.12682874.

Congruency of intervening events and self-induced action influence prediction of final results

Predicting self-induced stimuli is easier than predicting externally produced ones and the amplitude of event-related brain potentials (ERP) elicited by self-induced stimuli is smaller than that elicited by externally produced ones. Previous studies reported that these phenomena occurred strong when stimuli were presented immediately after self-induced action. To be able to adapt to changes, however, it is necessary to predict not only an event that follows a self-induced action but also a subsequent final result. We investigated whether congruency among self-induced actions, intervening events, and final results influences the processing of final results. The congruency of an intervening event with self-induced action was task-irrelevant information for the required response to a final result. The results showed that the P1 amplitude elicited by the final result (i.e., somatosensory stimulus) when an intervening event was congruent with self-induced action was smaller than other elicited amplitudes. This suggests that the congruency of an intervening event and self-induced action may facilitate prediction of a final result, even when this congruency is irrelevant to the ongoing task.

Depression and Fatigue in Patients With Multiple Sclerosis Have No Influence on the Parameters of Cognitive Evoked Potentials.

The purpose of this study was to examine if depression and fatigue affect event-related brain potentials (ERPs) in patients with relapsing-remitting multiple sclerosis, and to assess the significance of ERP as an indicator of cognitive impairment. A total of 81 relapsing-remitting multiple sclerosis patients and 32 healthy control subjects participated in the study. Cognitive functions were evaluated using a standard PASAT, the symbol digit modality test, and ERP. The degrees of depressive symptomatology and fatigue were assessed with Beck Depression Inventory, the Fatigue Severity Scale, and the Fatigue Impact Scale. Fatigue and depression had a negative effect on the cognitive functions examined by neuropsychological tests. Depression and fatigue did not influence ERP amplitude and latency findings. Depression level was negatively correlated with symbol digit modality test score (r = -0.135, P < 0.05). Fatigue level was negatively correlated with the results for PASAT A (r = -0.225, P < 0.05) and PASAT B (r = -0.342, P < 0.01). Reaction time was positively associated with depression (r = 0.246, P = 0.01) and fatigue (r = 0.281, P = 0.01). Depression and fatigue have no effect on ERP amplitude and latency, so they cannot participate in risk assessment for the development of cognitive impairment in patients with relapsing-remitting multiple sclerosis.

Electrophysiological Processes on Motor Imagery Mediate the Association Between Increased Gray Matter Volume and Cognition in Amnestic Mild Cognitive Impairment.

Motor imagery is considered as an ideal window to observe neural processes of action representations. Behavioral evidence has indicated an alteration of motor imagery in amnestic mild cognitive impairment (aMCI). However, it still remains unclear on the altered neurophysiological processing mechanism of motor imagery and whether this mechanism links the abnormal biological basis of motor imagery with impaired cognition in aMCI. This study was to investigate the altered neurophysiological processing mechanism of motor imagery and to examine the relationships between this knowledge and the altered structural basis of motor imagery with impaired cognition in aMCI. A hand mental rotation paradigm was used to manipulate the processing of motor imagery while event-related brain potentials (ERPs) were recorded and gray matter (GM) voxel-based morphometry was performed in 20 aMCI and 29 healthy controls. Compared with controls, aMCI exhibited lower ERP amplitudes in parietal cortex and higher ERP amplitudes in frontal cortex during motor imagery. In addition, aMCI showed reduced GM volumes in cerebellum posterior lobe, insula and hippocampus/parahippocampal gyrus, and increased GM volumes in middle cingulate gyrus and superior frontal gyrus. Most importantly, increased ERP amplitude significantly mediated the association between increased GM and cognition. This study provided a novel evidence for the relationships between the electrophysiological processing mechanism and structural basis of motor imagery with impaired cognition in aMCI. It suggests that improving neural activity by stimulating the frontal lobe can potentially contribute to acquire motor imagery skills for neurological rehabilitation in aMCI subjects.

Changes in laser-evoked potentials during hypnotic analgesia for chronic pain: a pilot study.

Hypnotic analgesia is one of the most effective nonpharmacological methods for pain control. Hypnosis and distraction of attention from pain might share similar mechanisms by which brain responses to painful stimulation could be similarly reduced in both states. There is ample evidence for the efficacy of clinical hypnosis as a psychological intervention in the treatment of acute or chronic pain. Results are conflicting, however, with some studies showing an increase, others a reduction, and others still no change in the amplitude of event-related brain potentials during hypnosis as compared to control conditions. Here we compared the effects of clinical hypnosis to simple distraction of attention during recording of laser-evoked potentials (LEPs) in patients with chronic pain. The dominant hand in ten patients with chronic pain was tested with LEPs during: (I) resting state; (II) clinical hypnosis, and (III) distraction of attention. Nociceptive responses elicited by LEPs were graded on a numerical rating scale (NRS), and the change in N2-P2 complex amplitude during the three experimental conditions was analyzed. N2-P2 amplitudes were significantly decreased during the hypnotic state as compared to the resting state and distraction of attention. Hypnosis is a modified state of consciousness that may differ from mental relaxation or distraction of attention from pain. A reduction in N2-P2 amplitude may result from the modulation of diverse brain networks, particularly the frontolimbic pathways, which could modify noxious stimuli input processing during hypnotic analgesia. Our findings indicate that several different brain mechanisms may act together in hypnosis and distraction of attention during pain processing and that clinical hypnosis may provide a useful non-invasive pain relief therapy.

Event Related Brain Potentials (ERP) Could Not Assess the Risk of Cognitive Impairment in Relapse-Remitting Multiple Sclerosis (RRMS)

Objectives: The first objective of our study was to determine differences between groups of patients receiving disease modifying therapy (DMTs) (INFβ-1a and INFβ-1b), patients without DMTs and a control group, in terms of neuropsychological tests and event-related brain potentials (ERP). The second objective was to determine factors that may serve to assess the risk of cognitive impairment in patients with relapsing remitting multiple sclerosis (RRMS). Methods: A total of 81 RRMS patients (mean age 41.09 ± 8.71 years old, 51 women, mean disease duration 133.05 ± 76.56 months) and 32 healthy controls participated in the study. Cognitive functions were evaluated using a standard PASAT-3, the symbol digit modality test (SDMT) and ERP. Results: There were statistically significant differences between the mean values for parietal (Pz) (p ≤ 0.05) and central (Cz) latency (p<0.05) between the four groups of study participants. RRMS increased the risk of cognitive impairment approximately 3.5 fold. Each year of age raised the risk of cognitive impairment by 6.0%. Each unit increase in level of education reduced the risk of cognitive impairment approximately 2.5 fold. Increase in reaction time (RT) Cz by 1 ms elevated the risk of cognitive impairment by 0.5%. Conclusions: There were statistically significant differences between the mean values of Pz and Cz latency between the four groups of study participants. Factors that may be used to assess the risk of developing cognitive impairment in patients with RRMS include age, education level, and RT Cz. However, ERP (latency and amplitude) did not independently assess the risk of cognitive impairment in RRMS patients.

70. Laser-evoked potentials (LEPs) in chronic pain conditions during hypnotic analgesia

Hypnotic analgesia represents one of the most effective nonpharmacological methods for pain control. Hypnosis and distraction from pain might share similar mechanisms, implying that brain responses to painful stimulation should be similarly reduced in both situations. Literature data are conflicting, showing increase, reduction or no change in Event-Related Brain Potentials amplitudes during hypnosis compared to control conditions. Here we investigate effects of hypnosis and distraction during laser-evoked potentials (LEPs) in patients with chronic painful diseases. 9 patients with chronic pain were studied with LEPs on the dominant hand during resting state, medium and deep hypnosis (techniques for analgesia), and focused attention on article reading. Pain induced by LEPs was assessed with Numerical Rating Scale (NRS) and we analyzed N2/P2 complex amplitude change during the three conditions. Patients under hypnosis showed significant N2/P2 amplitudes decrease compared to resting state and distraction. Hypnosis is a physiological modified state of consciousness that may differ either from mental relaxation or distraction from pain. N2/P2 amplitude reduction may depend on different brain networks activation, in particular frontolimbic pathways, which could modify noxious stimuli input processing during hypnotic analgesia. Our results indicate that different brain mechanisms might act in hypnosis and distraction during pain processing.

P3 event-related brain potential reflects allocation and use of central processing capacity in language production

Allocation and use of central processing capacity have been associated with the P3 event-related brain potential amplitude in a large variety of non-linguistic tasks. However, little is known about the P3 in spoken language production. Moreover, the few studies that are available report opposing P3 effects when task complexity is manipulated. We investigated allocation and use of central processing capacity in a spoken phrase production task: Participants switched every second trial between describing pictures using noun phrases with one adjective (size only; simple condition, e.g., “the big desk”) or two adjectives (size and color; complex condition, e.g., “the big red desk”). Capacity allocation was manipulated by complexity, and capacity use by switching. Response time (RT) was longer for complex than for simple trials. Moreover, complexity and switching interacted: RTs were longer on switch than on repeat trials for simple phrases but shorter on switch than on repeat trials for complex phrases. P3 amplitude increased with complexity. Moreover, complexity and switching interacted: The complexity effect was larger on the switch trials than on the repeat trials. These results provide evidence that the allocation and use of central processing capacity in language production are differentially reflected in the P3 amplitude.

Electrophysiological assessment of driving pleasure and difficulty using a task-irrelevant probe technique

The amplitude of event-related brain potentials (ERPs) elicited by task-irrelevant auditory probes decreases when more attentional resources are allocated to a visual task. This task-irrelevant probe technique is considered to be useful in assessing the degree of interest in a visual task, as well as task difficulty. The present study examined the amplitude of the N1 and P2 components elicited by task-irrelevant auditory probes during a driving task in a simulated environment. The analysis of ERPs showed that the N1 amplitude decreased when participants drove on the road course that had more frequent and sharper curves, whereas the P2 amplitude decreased when the road contained sharper curves, irrespective of curve frequency. Subjective ratings of driving pleasure and difficulty showed the same variation patterns as the N1 and P2 amplitudes, respectively. These results suggest that use of the task-irrelevant probe technique can assess the degree of driving pleasure and difficulty separately.

A preliminary investigation into the neural basis of the production effect.

Items that are produced (e.g., read aloud) during encoding typically are better remembered than items that are not produced (e.g., read silently). This "production effect" has been explained by distinctiveness: Produced items have more distinct features than nonproduced items, leading to enhanced retrieval. The goal of the current study was to use electroencephalography (EEG) to examine the neural basis of the production effect. During study, participants were presented with words that they were required to read silently, read aloud, or sing while EEG data were recorded. Subsequent memory performance was tested using a yes/no recognition test. Analysis focused on the event-related brain potentials (ERPs) evoked by the encoding instruction cue for each instruction condition. Our data revealed enhanced memory performance for produced items and a greater P300 ERP amplitude for instructions to sing or read aloud compared with instructions to read silently. Our results demonstrate that the amplitude of the P300 is modulated by at least 1 aspect of production, vocalization (singing/reading aloud relative to reading silently), and are consistent with the distinctiveness account of the production effect. The ERP methodology is a viable tool for investigating the production effect. (PsycINFO Database Record

Data of ERPs and spectral alpha power when attention is engaged on visual or verbal/auditory imagery.

This article provides data from statistical analysis of event-related brain potentials (ERPs) and spectral power from 20 participants during three attentional conditions. Specifically, P1, N1 and P300 amplitude of ERP were compared when participant׳s attention was oriented to an external task, to a visual imagery and to an inner speech. The spectral power from alpha band was also compared in these three attentional conditions. These data are related to the research article where sensory processing of external information was compared during these three conditions entitled “Orienting attention to visual or verbal/auditory imagery differentially impairs the processing of visual stimuli” (Villena-Gonzalez et al., 2016) [1].

Accessing characters in spoken Chinese disyllables: An ERP study on the resolution of auditory ambiguity

Chinese differs from most Indo-European languages in its phonological, lexical, and syntactic structures. One of its unique properties is the abundance of homophones at the monosyllabic/morphemic level, with the consequence that monosyllabic homophones are all ambiguous in speech perception. Two-morpheme Chinese words can be composed of two high homophone-density morphemes (HH words), two low homophone-density morphemes (LL words), or one high and one low homophone-density morphemes (LH or HL words). The assumption of a simple inhibitory homophone effect is called into question in the case of disyllabic spoken word recognition, in which the recognition of one morpheme is affected by semantic information given by the other. Event-related brain potentials (ERPs) were used to trace on-line competitions among morphemic homophones in accessing Chinese disyllables. Results showing significant differences in ERP amplitude when comparing LL and LH words, but not when comparing LL and HL words, suggested that the first morpheme cannot be accessed without feedback from the second morpheme. Most importantly, analyses of N400 amplitude among different densities showed a converse homophone effect in which LL words, rather than LH or HL words, triggered larger N400. These findings provide strong evidence of a dynamic integration system at work during spoken Chinese disyllable recognition.

Neural oscillatory deficits in schizophrenia predict behavioral and neurocognitive impairments.

Paying attention to visual stimuli is typically accompanied by event-related desynchronizations (ERD) of ongoing alpha (7–14 Hz) activity in visual cortex. The present study used time-frequency based analyses to investigate the role of impaired alpha ERD in visual processing deficits in schizophrenia (Sz). Subjects viewed sinusoidal gratings of high (HSF) and low (LSF) spatial frequency (SF) designed to test functioning of the parvo- vs. magnocellular pathways, respectively. Patients with Sz and healthy controls paid attention selectively to either the LSF or HSF gratings which were presented in random order. Event-related brain potentials (ERPs) were recorded to all stimuli. As in our previous study, it was found that Sz patients were selectively impaired at detecting LSF target stimuli and that ERP amplitudes to LSF stimuli were diminished, both for the early sensory-evoked components and for the attend minus unattend difference component (the Selection Negativity), which is generally regarded as a specific index of feature-selective attention. In the time-frequency domain, the differential ERP deficits to LSF stimuli were echoed in a virtually absent theta-band phase locked response to both unattended and attended LSF stimuli (along with relatively intact theta-band activity for HSF stimuli). In contrast to the theta-band evoked responses which were tightly stimulus locked, stimulus-induced desynchronizations of ongoing alpha activity were not tightly stimulus locked and were apparent only in induced power analyses. Sz patients were significantly impaired in the attention-related modulation of ongoing alpha activity for both HSF and LSF stimuli. These deficits correlated with patients’ behavioral deficits in visual information processing as well as with visually based neurocognitive deficits. These findings suggest an additional, pathway-independent, mechanism by which deficits in early visual processing contribute to overall cognitive impairment in Sz.

Dissociating the Influence of Affective Word Content and Cognitive Processing Demands on the Late Positive Potential.

The late positive potential (LPP) elicited by affective stimuli in the event-related brain potential (ERP) is often assumed to be a member of the P3 family. The present study addresses the relationship of the LPP to the classic P3b in a published data set, using a non-parametric permutation test for topographical comparisons, and residue iteration decomposition to assess the temporal features of the LPP and the P3b by decomposing the ERP into several component clusters according to their latency variability. The experiment orthogonally manipulated arousal and valence of words, which were either read or judged for lexicality. High-arousing and positive valenced words induced a larger LPP than low-arousing and negative valenced words, respectively, and the LDT elicited a larger P3b than reading. The experimental manipulation of arousal, valence, and task yielded main effects without any interactions on ERP amplitude in the LPP/P3b time range. The arousal and valence effects partially differed from the task effect in scalp topography; in addition, whereas the late positive component elicited by affective stimuli, defined as LPP, was stimulus-locked, the late positive component elicited by task demand, defined as P3b, was mainly latency-variable. Therefore LPP and P3b manifest different subcomponents.