Modality shift effects mimic multisensory interactions: an event-related potential study

A frequent approach to study interactions of the auditory and the visual system is to measure event-related potentials (ERPs) to auditory, visual, and auditory-visual stimuli (A, V, AV). A nonzero result of the AV ? (A + V) comparison indicates that the sensory systems interact at a specific processing stage. Two possible biases weaken the conclusions drawn by this approach: first, subtracting two ERPs from one requires that A, V, and AV do not share any common activity. We have shown before (Gondan and Röder in Brain Res 1073–1074:389–397, 2006) that the problem of common activity can be avoided using an additional tactile stimulus (T) and evaluating the ERP difference (T + TAV) ? (TA + TV). A second possible confound is the modality shift effect (MSE): for example, the auditory N1 is increased if an auditory stimulus follows a visual stimulus, whereas it is smaller if the modality is unchanged (ipsimodal stimulus). Bimodal stimuli might be affected less by MSEs because at least one component always matches the preceding trial. Consequently, an apparent amplitude modulation of the N1 would be observed in AV. We tested the influence of MSEs on auditory-visual interactions by comparing the results of AV ? (A + V) using (a) all stimuli and using (b) only ipsimodal stimuli. (a) and (b) differed around 150 ms, this indicates that AV ? (A + V) is indeed affected by the MSE. We then formally and empirically demonstrate that (T + TAV) ? (TA + TV) is robust against possible biases due to the MSE.     

An event-related potential study of supramodal attentional control and crossmodal attention effects

We conducted two audiovisual experiments to determine whether event-related potential (ERP) components elicited by attention-directing cues reflect supramodal attentional control. Symbolic visual cues were used to direct attention prior to auditory targets in Experiment 1, and symbolic auditory cues were used to direct attention prior to visual targets in Experiment 2. Different patterns of cue ERPs were found in the two experiments. A frontal negativity called the ADAN was absent in Experiment 2, which indicates that this component does not reflect supramodal attentional control. A posterior positivity called the LDAP was observed in both experiments but was focused more posteriorly over the occipital scalp in Experiment 2. This component appears to reflect multiple processes, including visual processes involved in location marking and target preparation as well as supramodal processes involved in attentional control.     

基于ERP和稳态诱发电位的听觉和触觉整合研究

目的通过记录与分析单一听觉、单一触觉和混合听触觉条件下的头皮脑电信号,探究一种研究大脑听觉和触觉整合现象的分析方法,为研究听觉和触觉整合的神经机制提供基础。方法首先构建听觉和触觉双模态刺激的头皮脑电记录系统,通过采集13例正常受试者在单一模态和混合模态条件下的头皮脑电信号,分别比较不同条件下听觉和触觉事件相关动作电位(event-related potential,ERP)与稳态诱发电位(steady-state evoked potential,SSEP)的差异。结果听觉和触觉整合的ERP信号峰值比单一听觉和单一触觉条件下的幅值更强,脑电响应的潜伏期显著提前,并且混合模态下的稳态诱发电位的能量显著高于单一模态。结论事件相关动作电位信号峰值的潜伏期与幅值以及稳态响应的能量可作为衡量听觉和触觉整合的参数指标,对听觉和触觉整合的研究具有参考意义。     

Involuntary attention impairment in early Parkinson's disease: an event-related potential study

Dopaminergic nigro-striatal depletion interferes with the detection of novel stimuli. This suggests that Parkinson's disease (PD) may generate from the initial stages a failure in involuntary attention (IA), which can be studied through the distraction potential, composed by the mismatch negativity (MMN), the P3a and the reorientation negativity (RON). This study analyzed IA using event-related potentials (ERPs) in patients with early PD with and without dopaminergic replacement therapy. Twenty-five medicated, and 17 non-medicated patients with early PD were studied, as well as 20 healthy control subjects. All subjects performed an auditory distraction task while a digital EEG was being recorded. The distraction potential was obtained by averaging methodology. Each wave was analyzed with a Repeated Measures ANOVA test. The MMN was obtained in all subjects and no significant differences in mean amplitude were found among the groups. There was a main effect of group for the amplitude of P3a (F(2,59) = 4.8, p = 0.01, ? = 0.411), with a significant lower amplitude in the medicated group compared to the control group (MD = −1.03, p = 0.003). RON also showed a main effect of group (F(2,59) = 4.8, p = 0.01, ? = 0.467), with significantly lower amplitudes in non-medicated patients with respect to both the control and medicated groups (MD = 1.19, p = 0.01, MD = 1.27, p = 0.005, respectively). There were no significant differences in the latencies of any of the waves among the groups. The main finding of this study was the reduction in the IA in early PD. Reorientation of attention (RON) showed a dopaminergic modulation in these patients. These results represent the basis for future in depth studies on the involvement of IA in executive impairments in PD.     

Effects of interstimulus interval on auditory event-related potentials in congenitally blind and normally sighted humans.

To test the hypothesis of auditory compensation after early visual deprivation, congenitally blind and sighted adults performed an auditory discrimination task. They had to detect a rare target tone among frequent standard tones. Stimuli were presented with different interstimulus intervals (ISIs) (200, 1000, 2000 ms) and the auditory-event related potentials to all tones and reaction times to targets were recorded. Increasing ISIs resulted in an increasing amplitude of the vertex response (N1-P2) in both groups, but this amplitude recovery was more pronounced in the blind. Furthermore, targets elicited larger and more posteriorly distributed N2 responses in the blind than in the sighted. Since target detection times were shorter in the blind as well, these findings imply compensatory adaptations within the auditory modality in humans blind from birth.     

Neural activities of tactile cross-modal working memory in humans: an event-related potential study

In the present study, we examined the neural mechanisms underlying cross-modal working memory by analyzing scalp-recorded event-related potentials (ERPs) from normal human subjects performing tactile-tactile unimodal or tactile-auditory cross-modal delay tasks that consisted of stimulus-1 (S-1, tactile), interval (delay), and stimulus-2 (S-2, tactile or auditory). We hypothesized that there would be sequentially discrete task-correlated changes in ERPs representing neural processes of tactile working memory, and in addition, significant differences would be observed in ERPs between the unimodal task and the cross-modal task. In comparison to the ERP components in the unimodal task, two late positive ERP components (LPC-1 and LPC-2) evoked by the tactile S-1 in the delay of the cross-modal task were enhanced by expectation of the associated auditory S-2 presented at the end of the delay. Such enhancement might represent neural activities involved in cross-modal association between the tactile stimulus and the auditory stimulus. Later in the delay, a late negative component (LNC) was observed. The amplitude of LNC depended on information retained during the delay, and when the same information was retained, this amplitude was not influenced by modality or location of S-2 (auditory S-2 through headphones, or tactile S-2 on the left index finger). LNC might represent the neural activity involved in working memory. The above results suggest that the sequential ERP changes in the present study represent temporally distinguishable neural processes, such as the cross-modal association and cross-modal working memory.     

Interactions between proximity and similarity grouping: an event-related brain potential study in humans

The current work examined neural substrates underlying interactions between two types of Gestalt grouping by recording event-related brain potentials (ERPs). Subjects were presented with stimulus arrays in which local circles and squares were grouped into columns or rows. The cues dominating grouping (proximity and similarity) were either congruent or incongruent. Subjects responded faster to the identification of orientations of perceptual groups based on proximity than similarity cues. Responses were slowed by incongruent cues and this effect was larger in the similarity than proximity conditions. Proximity grouping generated enhanced positivity over the posterior occipital cortex between 100 and 140 ms relative to similarity grouping. Relative to congruent grouping cues, incongruent cues elicited enlarged positivity over the temporal-parietal areas between 180 and 220 ms only in the similarity condition, but generated smaller P3 amplitudes with longer latencies in both proximity and similarity conditions. The results provide ERP indices of the dominance of proximity over shape similarity in guiding perceptual grouping when two grouping principles are present in stimulus displays.     

Intermodal spatial attention differs between vision and audition: an event-related potential analysis

Subjects were required to attend to a combination of stimulus modality (vision or audition) and location (left or right). Intermodal attention was measured by comparing event-related potentials (ERPs) to visual and auditory stimuli when the modality was relevant or irrelevant, while intramodal (spatial) attention was measured by comparing ERPs to visual and auditory stimuli presented at relevant and irrelevant spatial locations. Intramodal spatial attention was expressed differently in visual and auditory ERPs. When vision was relevant, spatial attention showed a contralateral enhancement of posterior N1 and P2 components and enhancement of parietal P3. When audition was relevant, spatial attention showed a biphasic fronto-central negativity, starting after around 100 ms. The same effects were also present in ERPs to stimuli that were presented in the irrelevant modality. Thus, spatial attention was not completely modality specific. Intermodal attention effects were also expressed differently in vision and audition. Taken together, the obtained ERP patterns of the present study show that stimulus attributes such as modality and location are processed differently in vision and audition.     

Cross-modal links in endogenous spatial attention are mediated by common external locations: evidence from event-related brain potentials

Recent behavioural and event-related potential (ERP) studies reported cross-modal links in spatial attention between vision, audition and touch. Such links could reflect differences in hemispheric-activation levels associated with spatial attention to one side, or more abstract spatial reference-frames mediating selectivity across modalities. To distinguish these hypotheses, ERPs were recorded to lateral tactile stimuli, plus visual (experiment 1) or auditory stimuli (experiment 2), while participants attended to the left or right hand to detect infrequent tactile targets, and ignored other modalities. In separate blocks, hands were either in a crossed or uncrossed posture. With uncrossed hands, visual stimuli on the tactually attended side elicited enhanced N1 and P2 components at occipital sites, and an enhanced negativity at midline electrodes, reflecting cross-modal links in spatial attention from touch to vision. Auditory stimuli at tactually attended locations elicited an enhanced negativity overlapping with the N1 component, reflecting cross-modal links from touch to audition. An analogous pattern of results arose for crossed hands, with tactile attention enhancing auditory or visual responses on the side where the attended hand now lay (i.e. in the opposite visual or auditory hemifield to that enhanced by attending the same hand when uncrossed). This suggests that cross-modal attentional links are not determined by hemispheric projections, but by common external locations. Unexpectedly, somatosensory ERPs were strongly affected by hand posture in both experiments, with attentional effects delayed and smaller for crossed hands. This may reflect the combined influence of anatomical and external spatial codes within the tactile modality, while cross-modal links depend only on the latter codes. Electronic Publication     

An event-related brain potential study of cross-modal links in spatial attention between vision and touch

Event-related potential (ERP) evidence for the existence of cross-modal links in endogenous spatial attention between vision and touch was obtained in an experiment where participants had to detect tactile or visual targets on the attended side and to ignore the irrelevant modality and stimuli on the unattended side. For visual ERPs, attentional modulations of occipital P1 and N1 components were present when attention was directed both within vision and within touch, indicating that links in spatial attention from touch to vision can affect early stages of visual processing. For somatosensory ERPs, attentional negativities starting around 140 ms poststimulus were present at midline and lateral central electrodes when touch was relevant. No attentional somatosensory ERP modulations were present when vision was relevant and tactile stimuli could be entirely ignored. However, in another task condition where responses were also required to infrequent tactile targets regardless of their location, visual-spatial attention modulated somatosensory ERPs. Unlike vision, touch apparently can be decoupled from attentional orienting within another modality unless it is potentially relevant.     

Auditory and somatosensory event-related brain potentials in early blind humans

Previous event-related potential (ERP) studies have suggested a possible participation of the visual cortex of the blind in auditory processing. In the present study, somatosensory and auditory ERPs of blind and sighted subjects were recorded when subjects were instructed to attend to stimuli of one modality and to ignore those of the other. Both modalities were stimulated with frequent (standard) and infrequent (deviant) stimuli, which differed from one another in their spatial locus of origin. In the sighted, deviant stimuli of the attended modality elicited N2 type of deflections (auditory N2b and somatosensory N250) over the lateral scalp areas. In contrast, in the blind, these ERP components were centroposteriorly distributed, suggesting an involvement of posterior brain areas in auditory and somatosensory stimulus discrimination. In addition, the mismatch negativity, elicited by deviant auditory stimuli even when the somatosensory stimuli were attended, was larger in the blind than in the sighted. This appears to indicate enhanced automatic processing of auditory stimulus changes in the blind. Thus, the present data suggest several compensatory changes in both auditory and somatosensory modalities after the onset of early visual deprivation.     

Syntactic processing with aging: an event-related potential study

To assess age-related changes in simple syntactic processing with normal aging, event-related brain potentials (ERPs) elicited by grammatical number violations as individuals read sentences for comprehension were analyzed. Violations were found to elicit a P600 of equal amplitude and latency regardless of an individual's age. Instead, advancing age was associated with a change in the scalp distribution of the P600 effect, being less asymmetric and more frontal (though still with a parietal maximum) in older than younger adults. Our results thus show that the brain's response to simple syntactic violations, unlike those reported for simple binary categorizations and simple semantic violations, is neither slowed nor diminished in amplitude by age. At the same time, the brain's processing of these grammatical number violations did engage at least somewhat different brain regions as a function of age, suggesting a qualitative change rather than any simple quantitative change in speed of processing.     

Age-related changes in brain responses to personally known faces: an event-related potential (ERP) study in humans

Midlife period has not been investigated so far regarding associations between brain responses and spared abilities for face processing. This study examines the effects of midlife aging on behavioural performance and event-related potentials (ERPs) during the perception of personally known faces. Ten middle-aged adults (aged 45-60) and 12 young adults (aged 20-30) performed a visual discrimination task based on the detection of modified eye colours. We found that this task was performed as accurately by middle-aged as by young adults. However, midlife aging is associated with specific ERP latency delays and important changes in scalp ERP distribution. These results -interpreted according to a compensation hypothesis- provide enlightening indications showing that, compared to young adults, the changes in brain activities observed in middle-aged adults may contribute to their maintained behavioural performance.     

An event-related potential study on exposure therapy for patients suffering from spider phobia

The present event-related potential (ERP) study investigated electrocortical changes related to cognitive behavior therapy (CBT) in spider phobic females. Forty-five patients and twenty non-phobic women were presented with phobia-relevant, generally fear-inducing, disgust-inducing and affectively neutral pictures in a first EEG session. Phobic patients were randomly assigned to either a therapy (TG) or a waiting-list (WG) group. EEG measurement was repeated after CBT or a waiting period. ERPs were extracted in the time windows 340-500 ms (P300), 550-770 ms (late positive potential (LPP), early LPP) and 800-1500 ms (late LPP). Relative to controls, untreated phobics showed enhanced amplitudes of P300 and early LPP in response to spider pictures. This most likely reflects the emotional significance of the phobic stimulus, which automatically draws attention. The therapy effect consisted of a significant enhancement of late LPP amplitudes in response to spider pictures. Results are discussed in terms of reduced attentional avoidance.     

Age-related changes in cognitive conflict processing: an event-related potential study

Cognitive tasks involving conflicting stimuli and responses are associated with an early age-related decline in performance. Conflict and conflict-induced interference can be stimulus- or response-related. In classical stimulus-response compatibility tasks, such as the Stroop task, the event-related potential (ERP) usually reveals a greater negativity on incongruent versus congruent trials which has often been linked with conflict processing. However, it is unclear whether this negativity is related to stimulus- or response-related conflict, thus rendering the meaning of age-related changes inconclusive. In the present study, a modified Stroop task was used to focus on stimulus-related interference processes while excluding response-related interference. Since we intended to study work-relevant effects ERPs and performance were determined in young (about 30 years old) and middle-aged (about 50 years old) healthy subjects (total n = 80). In the ERP, a broad negativity developed after incongruent versus congruent stimuli between 350 and 650 ms. An age-related increase of the latency and amplitude of this negativity was observed. These results indicate age-related alterations in the processing of conflicting stimuli already in middle age.     

When audition alters vision: an event-related potential study of the cross-modal interactions between faces and voices

Ten healthy volunteers took part in this event-related potential (ERP) study aimed at examining the electrophysiological correlates of the cross-modal audio-visual interactions in an identification task. Participants were confronted either to the simultaneous presentation of previously learned faces and voices (audio-visual condition; AV), either to the separate presentation of faces (visual, V) or voices (auditive, A). As expected, an interference effect of audition on vision was observed at a behavioral level, as the bimodal condition was performed more slowly than the visual condition. At the electrophysiological level, the subtraction (AV - (A + V)) gave prominence to three distinct cerebral activities: (1) a central positive/posterior negative wave around 110 ms, (2) a central negative/posterior positive wave around 170 ms, AND (3) a central positive wave around 270 ms. These data suggest that cross-modal cerebral interactions could be independent of behavioral facilitation or interference effects. Moreover, the implication of unimodal and multisensory convergence regions in these results, as suggested by a source localization analysis, is discussed.     

Crossmodal effects of Guqin and piano music on selective attention: An event-related potential study

To compare the effects of music from different cultural environments (Guqin: Chinese music; piano: Western music) on crossmodal selective attention, behavioral and event-related potential (ERP) data in a standard two-stimulus visual oddball task were recorded from Chinese subjects in three conditions: silence, Guqin music or piano music background. Visual task data were then compared with auditory task data collected previously. In contrast with the results of the auditory task, the early (N1) and late (P300) stages exhibited no differences between Guqin and piano backgrounds during the visual task. Taking our previous study and this study together, we can conclude that: although the cultural-familiar music influenced selective attention both in the early and late stages, these effects appeared only within a sensory modality (auditory) but not in cross-sensory modalities (visual). Thus, the musical cultural factor is more obvious in intramodal than in crossmodal selective attention.     

Differential effects of saliency: an event-related brain potential study

The fate of neural stem/progenitor cells (NSCs/NPCs) in vivo lies on the local microenvironment. Whether the denervated hippocampus provides a stimulative role on the survival and differentiation of the anterior subventricular zone (SVZa) progenitors was investigated in the present study. In vivo the SVZa progenitors were transplanted into the denervated hippocampus and the contralateral side, and were found migrating along the subgranular layer. More implanted cells were found survived and differentiated into the Neurofilament 200 (NF-200) or beta-Tubulin-III positive neurons in the denervated than in the normal hippocampus at all points studied. In vitro the extracts from the denervated and normal hippocampus were used to induce differentiation of the SVZa progenitors. More progenitors incubated with the denervated hippocampal extract differentiated significantly into the MAP-2 or AChE positive neurons than those incubated with the normal hippocampal extract (P<0.05). We concluded that the deafferented hippocampus provided proper microenvironment for the survival and neuronal differentiation of neural progenitors.     

Visual search for biological motion: an event-related potential study

To investigate the neural response to detection of biological motion (BM) surrounded by distractors, event-related potentials (ERPs) were recorded. Scrambled motion with the same velocity vector as the BM but randomized initial starting points was used as the distractor. The number of distractors was varied to control the difficulty of the task. The behavioral data showed that the reaction time increased with the number of distractors. Moreover, the ERP results showed that enhanced negativity was elicited at posterior electrodes contralateral to the location of the BM as with the conventional N2pc-like component, which is related to selection of the target. The increment of reaction time indicated that the attentional process is involved in the detection of BM. Furthermore, the ERP waveforms suggest that, even when detection of the target requires form-from-motion processing, similar neural mechanisms to those involved in conventional visual search tasks were employed here.     

Word and picture processing in children: an event-related potential study

In an investigation of the N400 component, event-related potentials (ERPs) elicited by 4 types of word stimuli (real words, pseudowords, random letter strings, and false fonts) and 3 types of picture stimuli (real pictures, pseudopictures, and picture parts) presented in separate lists were recorded from 10- and 11-year-old children. All types of word stimuli elicited an anteriorly distributed negativity peaking at about 400 msec (antN400). Words and pseudowords elicited similar ERPs, whereas ERPs to letter strings differed from those to both pseudowords and false fonts. All types of picture stimuli elicited dual anterior negativities (N350 and N430). Real pictures and pseudopictures elicited similar ERPs, whereas pseudopictures and picture parts elicited asymmetrical processing. The results are discussed in terms of increased sensitivity to and dependence on context in children.