The gradient of spatial auditory attention in free field: An event-related potential study

Young adult subjects attended selectively to brief noise bursts delivered in free field via a horizontal array of seven loudspeakers spaced apart by 9° of angle. Frequent “standard” stimuli (90%) and infrequent “target/deviant” stimuli (10%) of increased bandwidth were delivered at a fast rate in a random sequence equiprobably from each speaker. In separate runs, the subjects’ task was to selectively attend to the leftmost, center, or rightmost speaker and to press a button to the infrequent “target” stimuli occurring at the designated spatial location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sound source, thus providing support for gradient models of auditory spatial attention. Furthermore, the ERP data suggested that the spatial focusing of attention was achieved in two distinct stages, with an early more broadly tuned filtering of inputs occurring over the first 80–200 msec after stimulus onset, followed by a more narrowly focused selection of attended-location deviants that began at around 250 msec and closely resembled the behavioral gradient of target detections.     

Early selective-attention effect on evoked potential reinterpreted

In a dichotic listening situation stimuli were presented one at a time and at random to either ear of the subject at constant inter-stimulus intervals of 800 msec. The subject's task was to detect and count occasional slightly different stimuli in one ear. In Experiment 1, these ‘signal’ stimuli were slightly louder, and in Experiment 2 they had a slightly higher pitch, than the much more frequent, ‘standard’, stimuli. In both experiments signals occured randomly at either ear. Separate evoked potentials from three different locations were recorded for each of the four kinds of stimuli (attended signals, unattended signals, attended standards, unattended standards). Contrary to Hillyard et al. (1973), no early (N₁ component) evoked-potential enhancement was observed to stimuli to the attended ear as compared with those to the unattended ear, but there was a later negative shift superimposed on potentials elicited by the former stimuli. This negative shift was considered identical to the N₁ enhancement of Hillyard and his colleagues which in the present study was forced, by the longer inter-stimulus interval used, to demonstrate temporal dissociation with the N₁ component. The ‘Hillyard effect’ was, consequently, explained as being caused by a superimposition of a CNV kind of negative shift on the evoked potential to the attended stimuli rather than by a growth of the ‘real’ N₁ component of the evoked potential.     

跨感觉通路ERP注意成分的研究

采用提高了非注意纯度的“跨通路延迟反应”实验模式,研究跨通路注意的事件相关电位（ＥＲＰ）成分,以注意ＥＲＰ减去非注意ＥＲＰ的早期差异负波（Ｎｄ１）为主要分析对象。被试者为１２名青年正常人。结果发现：①听觉偏差刺激、视觉标准与偏差刺激皆在其特异性感觉区域的头皮部位,观察到注意引起Ｎ１波幅增大的现象。Ｎｄ１的起始时间与注意Ｎ１相同,而早于非注意Ｎ１,支持注意的早期选择学说;②听觉与视觉偏差刺激产生的Ｎｄ１最大峰分布在它们各自的初级感觉投射区,而标准刺激诱发的Ｎｄ１最大峰却分布于额部,表明跨通路选择性注意对偏差刺激的加工部位主要是通路特异性的,而对标准刺激的加工部位则主要是通路上的。作者据此针对选择性注意中长期争论问题进一步提出,注意的选择性发生时程的早晚可因刺激条件而异,信息过滤器的位置具有可塑性。     

Semantic Processing of Foveally and Parafoveally Presented Words in a Lexical Decision Task

Using a lexical decision task in which two primes appeared simultaneously in the visual field for 150 msec followed by a target word, two experiments examined semantic priming from attended and unattended primes as a function of both the separation between the primes in the visual field and the prime-target stimulus-onset asynchrony (SOA). In the first experiment significant priming effects were found for both the attended and unattended prime words, though the effect was much greater for the attended words. In addition, and also for both attention conditions, priming showed a tendency to increase with increasing eccentricity (2.3°, 3.3°, and 4.3°) between the prime words in the visual field at the long (550 and 850 msec) but not at the short (250 msec) prime-target SOA. In the second experiment the prime stimuli were either two words (W-W) or one word and five Xs (W-X). We manipulated the degree of eccentricity (2° and 3.6°) between the prime stimuli and used a prime-target SOA of 850 msec. Again significant priming was found for both the attended and unattended words but only the W-W condition showed a decrement in priming as a function of the separation between the primes; this decrement came to produce negative priming for the unattended word at the narrow (2°) separation. These results are discussed in relation to the semantic processing of parafoveal words and the inhibitory effects of focused attention.     

Feature processing during high-rate auditory selective attention

Auditory event-related brain potentials (ERPs) and reaction times were, analyzed in a selective attention task in which subjects attended to tone pips presented at high rates-Xinterstimulua intervals [ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 252–350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110–120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feaure conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.     

Lexical recognition of embedded unattended words: Some implications for reading processes

Two questions were addressed by these experiments. Firstly, do unattended words influence attended words only when they appear in isolation and thereby may attract attention, or are they influential even when embedded amongst ineffective material? Secondly, can the influence of an unattended display be increased by increasing the number of potentially effective words. By having observers give category names to attended words at the same time as masked unattended words appeared in a column to the right of fixation, experiment 1 found that a single word was effective even when embedded, and that an increasing effect was not observed with a display with a 50 msec duration. There was some evidence of a linear increase in the size of the effect with a 200 msec display, but evidence from experiment 2 suggests that subjects may have been aware of the unattended words when they were exposed for this duration. The results were discussed in relation to a model of eye-fixation control during reading which postulates that unattended words gain lexical recognition when they are semantically related to the attended activity. This lexical recognition may then serve to mark interesting locations in the text and attract future eye-fixations.     

Time course and task dependence of emotion effects in word processing

The emotional content of stimuli influences cognitive performance. In two experiments, we investigated the time course and mechanisms of emotional influences on visual word processing in various tasks by recording event-related brain potentials (ERPs). The stimuli were verbs of positive, negative, and neutral valence. In Experiment 1, where lexical decisions had to be performed on single verbs, both positive and negative verbs were processed more quickly than neutral verbs and elicited a distinct ERP component, starting around 370 msec. In Experiment 2, the verbs were embedded in a semantic context provided by single nouns. Likewise, structural, lexical, and semantic decisions for positive verbs were accelerated, and an ERP effect with a scalp distribution comparable to that in Experiment 1 now started about 200 msec earlier. These effects may signal an automatic allocation of attentional resources to emotionally arousing words, since they were not modulated by different task demands. In contrast, a later ERP effect of emotion was restricted to lexical and semantic decisions and, thus, appears to indicate more elaborated, task-dependent processing of emotional words.     

The effects of attention and task-relevance on the processing of syntactic violations during listening to two concurrent speech streams

The notion of automatic syntactic analysis received support from some event-related potential (ERP) studies. However, none of these studies tested syntax processing in the presence of a concurrent speech stream. Here we present two concurrent continuous speech streams, manipulating two variables potentially affecting speech processing in a fully crossed design: attention (focused vs. divided) and task (lexical – detecting numerals vs. syntactical – detecting syntactic violations). ERPs elicited by syntactic violations and numerals as targets were compared with those for distractors (task-relevant events in the unattended speech stream) and attended and unattended task-irrelevant events. As was expected, only target numerals elicited the N2b and P3 components. The amplitudes of these components did not significantly differ between focused and divided attention. Both task-relevant and task-irrelevant syntactic violations elicited the N400 ERP component within the attended but not in the unattended speech stream. P600 was only elicited by target syntactic violations. These results provide no support for the notion of automatic syntactic analysis. Rather, it appears that task-relevance is a prerequisite of P600 elicitation, implying that in-depth syntactic analysis occurs only for attended speech under everyday listening situations.     

Effects of rhyme and spelling patterns on auditory word ERPs depend on selective attention to phonology

ERP responses to spoken words are sensitive to both rhyming effects and effects of associated spelling patterns. Are such effects automatically elicited by spoken words or dependent on selectively attending to phonology? To address this question, ERP responses to spoken word pairs were investigated under two equally demanding listening tasks that directed selective attention either to sub-syllabic phonology (i.e., rhyme judgments) or to melodies embedded within the words. ERPs elicited when participants selectively attended to phonology demonstrated a rhyming effect that was concurrent with online stimulus encoding and an orthographic effect that emerged later. ERP responses to the same stimuli presented under melodic focus, however, showed no evidence of sensitivity to rhyme or spelling patterns. Results reveal limitations to the automaticity of such ERP effects, suggesting that rhyme effects may depend, at least to some degree, on allocation of attention to phonology, which may in turn activate task-incidental orthographic information.     

The role of selective attention in visual awareness of stimulus features: Electrophysiological studies

Attention and awareness are closely related, but the nature of their relationship is unclear. The present study explores the timing and temporal evolution of their interaction with event-related potentials. The participants attended to specific conjunctions of spatial frequency and orientation in masked (unaware) and unmasked (aware) visual stimuli. A correlate of awareness appeared 100-200 msec from stimulus onset similarly to both attended and unattended features. Selection negativity (SN), a correlate of attentional selection, emerged in response to both masked and unmasked stimuli after 200 msec. This double dissociation between correlates of awareness and SN suggests that the electrophysiological processes associated with feature-based attentional selection and visual awareness of features can be dissociated from each other at early stages of processing. In a passive task, requiring no attention to the stimuli, early electrophysiological responses (before 200 msec) related to awareness were attenuated, suggesting that focal attention modulates visual awareness earlier than does selective feature-based attention.     

Iconic gestures prime related concepts: An ERP study

To assess priming by iconic gestures, we recorded EEG (at 29 scalp sites) in two experiments while adults watched short, soundless videos of spontaneously produced, cospeech iconic gestures followed by related or unrelated probe words. In Experiment 1, participants classified the relatedness between gestures and words. In Experiment 2, they attended to stimuli, and performed an incidental recognition memory test on words presented during the EEG recording session. Event-related potentials (ERPs) time-locked to the onset of probe words were measured, along with response latencies and word recognition rates. Although word relatedness did not affect reaction times or recognition rates, contextually related probe words elicited less-negative ERPs than did unrelated ones between 300 and 500 msec after stimulus onset (N400) in both experiments. These findings demonstrate sensitivity to semantic relations between iconic gestures and words in brain activity engendered during word comprehension.     

Selective attention to multidimensional auditory stimuli

Event-related brain potentials (ERPs) elicited by multidimensional auditory stimuli were recorded from the scalp in a selective-attention task. Subjects listened to tone pips varying orthogonally between two levels each of pitch, location, and duration and responded to longer duration target stimuli having specific values of pitch and location. The discriminability of the pitch and location attributes was varied between groups. By examining the ERPs to tones that shared pitch and/or locational cues with the designated target, we inferred interrelationships among the processing of these attributes. In all groups, stimuli that failed to match the target tone in an easily discriminable cue elicited only transitory ERP signs of selective processing. Tones sharing the "easy" but not the "hard" cue with the target elicited ERPs that indicated more extensive processing, but not as extensive as stimuli sharing both cues. In addition, reaction times and ERP latencies to the designated targets were not influenced by variations in the discriminability of pitch and location. This pattern of results is consistent with parallel, self-terminating models and holistic models of processing and contradicts models specifying either serial or exhaustive parallel processing of these dimensions. Both the parallel, self-terminating models and the holistic models provide a generalized mechanism for hierarchical stimulus selections that achieve an economy of processing, an underlying goal of classic, multiple-stage theories of selective attention.     

刺激放置朝向对返回抑制的影响:一项ERPs研究

返回抑制(inhibition of return, IOR)是指个体对出现在先前提示位置上的刺激反应更慢的现象。尽管大量ERPs研究发现呈现在线索化和非线索化位置上的靶刺激诱发的ERPs在250-300ms处存在一个稳定的差异(Nd250),但这一差异的方向却并不一致。本研究采用事件相关电位技术(Event-related Potentials, ERPs),结合经典的线索-靶子范式,考察刺激放置的朝向是否会影响到IOR中Nd250效应的极性。结果显示虽然刺激放置朝向并未有影响到Nd250的极性,却对早期P1成分的线索化效应的地形图分布有着显著的影响。这表明1）过往ERPs研究中的Nd250效应极性的不一致并非源于刺激放置朝向的作用;2）刺激的放置朝向会导致早期线索化效应(P1)在地形分布上出现差异。     

ERP Correlates of Directed Forgetting Effects in Direct and Indirect Memory Tests

Directed forgetting effects on direct (recognition) and indirect (categorisation) memory tests were analysed using electrophysiological (ERPs) and behavioural (RT and accuracy) measures. These effects were evaluated in relation to the two main hypotheses traditionally proposed to explain them (i.e. the differential rehearsal and inhibition hypotheses). In the study phase, 100 words were presented, each followed by either a remember (R) or a forget (F) instruction. In the test phase, half of the subjects performed a recognition task (old vs new words) and the other half did a categorisation task (concrete vs abstract words). In the study phase, ERPs following Rinstruction differed from those elicited by F-instruction, being more positive in the first 400 msec post-stimulus and becoming less positive from 400 to 800 msec. In the test phase, the effects of the forgetting manipulation were quite clear in the recognition test, affecting both ERP (from 200 to 300 and from 500 to 700 msec) and behavioural measures, but these effects did not appear in the categorisation test. The old/new effects were reflected in the behavioural measures corresponding to both tests, but with the ERP measures they appeared only in the recognition task from 500 to 700 msec. The lack of directed forgetting effects in the indirect test is in line with the differential rehearsal hypothesis. However, the forgetting manipulation produced a short-latency effect (200-300 msec) in the ERPs obtained in the recognition test that is difficult to explain based on that hypothesis. This finding suggests the existence of inhibitory mechanisms, although operating only when conscious access to the previous learning episode is required.     

Directed attention prolongs the perceived duration of a brief stimulus

Stelmach, Herdman, and McNeil (1994) suggested recently that the perceived duration for attended stimuli is shorter than that for unattended ones. In contrast, the attenuation hypothesis (Thomas & Weaver, 1975) suggests the reverse relation between directed attention and perceived duration. We conducted six experiments to test the validity of the two contradictory hypotheses. In all the experiments, attention was directed to one of two possible stimulus sources. Experiments 1 and 2 employed stimulus durations from 70 to 270 msec. A stimulus appeared in either the visual or the auditory modality. Stimuli in the attended modality were rated as longer than stimuli in the unattended modality. Experiment 3 replicated this finding using a different psychophysical procedure. Experiments 4-6 showed that the finding applies not only to stimuli from different sensory modalities but also to stimuli appearing at different locations within the visual field. The results of all six experiments support the assumption that directed attention prolongs the perceived duration of a stimulus.     

An Event-Related Potential Study of Item Recognition Memory in Children and Adults

The purpose of this study was to contrast children's event-related potentials (ERPs) with those of adults in an item recognition memory task. Four-year-old children and adults were presented with pictorial images, one half of which had been previously shown, and were asked to indicate whether each picture had been seen before. In both samples, an old-new effect was found in the ERP, namely that responses to correctly recognized old pictures elicited more positive-going ERPs than responses to correctly rejected new pictures. However, there were differences between adults' and children's ERPs with respect to the asymmetric scalp distribution and the time course of the old-new difference. In adults, the ERP differences between old and new pictures were bilateral, whereas in children the differences had a tendency to be stronger over the right hemisphere. In addition, children's ERP effects for correct discrimination between old and new pictures began around 400 to 500 msec later than it did in adults. The similarities and differences between the child and adult findings are discussed in terms of developmental changes in cognitive abilities that may be mirrored through corresponding changes in ERPs.     

听觉失匹配负波反映自动加工──感觉道间选择性注意时的新证据

为考察听觉失匹配负波是否反映自动加工,实验改进了视觉和听觉刺激同时呈现的感觉道间选择性注意实验模式,更好地控制了非注意听觉条件。结果发现,在注意与非注意听觉条件下,听觉偏离刺激均诱发出失匹配负波;注意听觉刺激时１４０－１８０ｍｓ的偏离相关负波与非注意时该时程负波的平均波幅之间无显著差异,而注意时１８０－２２０ｍｓ的偏离相关负波的平均波幅大于非注意时同一时程之负波;非注意听觉时失匹配负波的平均波幅和峰潜伏期不受视觉道任务难度的影响,该结果为听觉失匹配负波反映自动加工的观点提供了进一步证据。     

Reading between the lines: Event-related brain potentials during natural sentence processing

Event-related potentials (ERPs) were recorded from subjects as they silently read 160 different seven-word sentences, presented one word at a time. Each sentence was in itself a natural, meaningful phrase. Substantial intersubject variability was observed in the ERP waveshapes following the words. More than half of the subjects generated P3 components to word stimuli, but those who did showed similar responses to repeated control presentations of a single word. In addition, it was found that all but the first word in the sentence elicited an ERP with a significant left-greater-than-right asymmetry in the late positivity over temporo-parietal regions. The ERPs to the last words were associated with more late positivity than those to the preceding words. One quarter of the sentences, at random, ended with a word printed in a typeface that was different from that of the preceding words. This infrequent change in typeface elicited a complex ERP having three consistent late positive components.     

Differences in the neural mechanisms of selective attention in children from different socioeconomic backgrounds: an event‐related brain potential study

Previous research indicates that children from lower socioeconomic backgrounds show deficits in aspects of attention, including a reduced ability to filter irrelevant information and to suppress prepotent responses. However, less is known about the neural mechanisms of group differences in attention, which could reveal the stages of processing at which attention deficits arise. The present study examined this question using an event‐related brain potential (ERP) measure of selective auditory attention. Thirty‐two children aged from 3 to 8 years participated in the study. Children were cued to attend selectively to one of two simultaneously presented narrative stories. The stories differed in location (left/right speaker), narration voice (male/female), and content. ERPs were recorded to linguistic and non‐linguistic probe stimuli embedded in the attended and unattended stories. Children whose mothers had lower levels of educational attainment (no college experience) showed reduced effects of selective attention on neural processing relative to children whose mothers had higher levels of educational attainment (at least some college). These differences occurred by 100 milliseconds after probe onset. Furthermore, the differences were related specifically to a reduced ability to filter irrelevant information (i.e. to suppress the response to sounds in the unattended channel) among children whose mothers had lower levels of education. These data provide direct evidence for differences in the earliest stages of processing within neural systems mediating selective attention in children from different socioeconomic backgrounds. Results are discussed in the context of intervention programs aimed at improving attention and self‐regulation abilities in children at‐risk for school failure.     

Revisiting the global-dominance phenomenon outside the focus of attention

Previous research has demonstrated global dominance for attended and unattended stimuli. In this paper, this phenomenon is shown to be restricted to small compound stimuli. As a first step, local dominance was obtained with large (8 deg in height) attended stimuli when a single stimulus was displayed. Next, dominance in attended and unattended stimuli was investigated by displaying two large compound stimuli, one surrounded by a square (attended compound stimulus), the other one enclosed in a circle (unattended compound stimulus). The way attention was directed to the attended stimulus was varied. No dominance was observed when subjects were instructed to process the stimulus appearing in the square (experiment 2). However, when a rapid-onset cue pre-directed attention to the attended stimulus, local dominance emerged for attended, but not for unattended stimuli (experiment 3). This latter result was obtained whether or not subjects were more experienced at local than global processing (experiment 4). The implications of the results for the locus of processing dominance are discussed.