Event-related Potential Experiment Research Articles

Material differences of auditory source retrieval: Evidence from event-related potential studies

Two event-related potential experiments were conducted to investigate the temporal and the spatial distributions of the old/new effects for the item recognition task and the auditory source retrieval task using picture and Chinese character as stimuli respectively. Stimuli were presented on the center of the screen with their names read out either by female or by male voice simultaneously during the study hase and then two tests were performed separately. One test task was to differentiate the old items from the new ones, and the other task was to judge the items read out by a certain voice during the study phase as targets and other ones as non-targets. The results showed that the old/new effect of the auditory source retrieval task was more sustained over time than that of the item recognition task in both experiments, and the spatial distribution of the former effect was wider than that of the latter one. Both experiments recorded reliable old/new effect over the prefrontal cortex during the source retrieval task. However, there existed some differences of the old/new effect for the auditory source retrieval task between picture and Chinese character, and LORETA source analysis indicated that the differences might be rooted in the temporal lobe. These findings demonstrate that the relevancy of the old/new effects between the item recognition task and the auditory source retrieval task supports the dual-process model; the spatial and the temporal distributions of the old/new effect elicited by the auditory source retrieval task are regulated by both the feature of the experimental material and the perceptual attribute of the voice.

Inconspicuous anchoring effects generated by false information

The impact of false information on numerical judgments was examined on young normal subjects by an event-related potential (ERP) experiment. To imitate the judgments in real world, we ensured the subjects acknowledged of the target task. The behavioral results found that both uncertain information and false information assimilated the final estimates: higher after higher anchors and lower after lower anchors; and false information caused a weaker anchoring bias than uncertain information. ERP results provided further electrophysiological evidence for the mechanism of anchoring. In the early phrase, it was an accessibility-dominated process in which two kinds of anchors elicited an N300 component related to the accessibility of anchors propositions. The knowledge relevant to targets joined the process in the late phrase, which caused a larger amplitude of late positive component (LPC) for implausible lower anchors than that for plausible higher anchors. Source analysis showed that medial frontal gyrus, whose activity was suggested to signal the need of adjustment, was more reliable to explain the LPC elicited by implausible lower anchors. Therefore, we suggest that accessibility is facilitated when the external anchor is consistent with the world knowledge, and adjustment is initiated when the external anchor is inconsistent.

Electrophysiological correlates of adjustment process in anchoring effects

Anchoring is a judgmental bias that final judgments are assimilated toward the starting point of the judge's deliberations. The anchoring-and-adjustment heuristic holds that anchoring bias is caused by insufficient adjustment. With the manipulation of some subjective factors, previous research found that anchoring is an effortful process. However, there is little evidence supporting that the effortful process is an adjustment process. In the present work, number accuracy was introduced as an objective factor which involves in an adjustment process. An event-related brain potential (ERP) experiment on young normal subjects examined the impact of number accuracy on anchoring processes responding to anchors which were generated by subjects themselves. A dot-image paradigm was firstly employed to explore anchoring effects. Behavioral results found less accurate anchors which determined a coarser mental scale diminished the anchoring biases responding to self-generated anchors. A positive deflection at 250–800 ms after target onset can be taken as a direct electrophysiological evidence of the adjustment process, whose amplitude was more positive on more accurate anchors condition. The present results further support that people adjust upwards or downwards on a mental scale from the self-generated anchor, which is consistent with the adjustment heuristics.

Brain responses to agreement violations of Chinese grammatical aspect

Grammatical aspect captures ways in which a language uses grammatical markers to describe the temporal structure of an event. An event-related potential experiment was conducted to investigate event-related potential correlates of agreement violations of Chinese grammatical aspect. Participants read sentences containing either aspect agreement violations, semantic violations, or no violations. Semantic violations elicited an N400, whereas aspectual violations elicited a 200-400 ms posterior and left central negativity, followed by a P600, instead of left anterior negativity or N400, suggesting that left anterior negativities may not reflect a general, rule-governed, syntactically compositional process, and that grammatical aspect processing is at least not completely semantically driven. The negativity mostly reflects a failure to bind aspect markers or the detection of aspectual errors.

When Chinese semantics meets failed syntax

Previous event-related potential studies in Indo-European languages reported a surprising finding that failed syntactic category processing appears to block lexical-semantic integration, suggesting a functional primacy of syntax over semantics. An event-related potential experiment was conducted to test whether there is such primacy in Chinese sentence reading, using sentences containing either semantic only violations, combined syntactic category and semantic violations, or no violations. Semantic only violations elicited a centro-parietal negativity and combined violations a broadly distributed, but centro-parietally focused negativity, both in the 300-500 ms window and followed by a P600, suggesting that semantic integration proceeds even when syntactic category processing fails. Thus, there is no functional primacy of syntactic category over semantic processes during Chinese sentence reading.

Event-related Potential Evidence on the Influence of Accentuation in Spoken Discourse Comprehension in Chinese

In an event-related potential experiment with Chinese discourses as material, we investigated how and when accentuation influences spoken discourse comprehension in relation to the different information states of the critical words. These words could either provide new or old information. It was shown that variation of accentuation influenced the amplitude of the N400, with a larger amplitude for accented than for deaccented words. In addition, there was an interaction between accentuation and information state. The N400 amplitude difference between accented and deaccented new information was smaller than that between accented and deaccented old information. The results demonstrate that, during spoken discourse comprehension, listeners rapidly extract the semantic consequences of accentuation in relation to the previous discourse context. Moreover, our results show that the N400 amplitude can be larger for correct (new, accented words) than incorrect (new, deaccented words) information. This, we argue, proves that the N400 does not react to semantic anomaly per se, but rather to semantic integration load, which is higher for new information.

ERP correlates of the development of orthographical and phonological processing during Chinese sentence reading

An event-related potential (ERP) experiment was conducted to investigate the development of orthographic and phonological processing during Chinese sentence reading between school children and adult readers. Participants were visually presented with sentences, word-by-word, and were asked to judge whether the sentences were semantically acceptable. The crucial manipulation was on the sentence-final two-character compound words, which were either correct or incorrect. For the incorrect compounds, the second characters of the base words were replaced by homophonic or orthographically similar characters. ERP results showed that, across participant groups, the peak of P200 appeared earlier for the homophonic condition than for the orthographic and the baseline conditions. Importantly, for both child and adult readers, relative to the baseline, both orthographic mismatch in the homophonic condition and phonological mismatch in the orthographic condition elicited N400 effects. While for adults these effects appeared to be equal in size, the peak of the N400 component appeared earlier for orthographic mismatch than for phonological mismatch. For children the N400 effect was larger for orthographic mismatch than for phonological mismatch. The N400 component was also more negative for children than for adults in the homophonic condition, and its peak appeared later for children than for adults in the homophonic and the baseline conditions. Moreover, the offset of the N400 effects appeared earlier for adults than for children and for orthographic mismatch than for phonological mismatch. These findings suggest that both Chinese adult readers and school children rely more on orthographic information than on phonological information to access lexical semantics in reading Chinese sentences. However, the differential effects between orthography and phonology may have different ERP manifestations in adults and children.

Is task switching nothing but cue priming? Evidence from ERPs

Recent findings suggesting that switch costs in the task-cuing paradigm are largely attributable to a change in the task-indicating cue have been interpreted in terms of a priming model of task-switch costs (Logan & Bundesen, 2003). According to this explanation, participants do not actually switch task sets, but merely use a cue-stimulus compound to disambiguate competing response tendencies associated with bivalent stimuli. Here, we report an event-related potential (ERP) experiment that provides evidence against this notion. In a paradigm with a 2:1 mapping between cues and tasks, we show that cue-switch and task-switch effects are dissociable on a neurophysiological level, indicating that task switching is more than a switch in the task-indicating cue. Moreover, a systematic analysis of the ERPs during the cue-stimulus interval suggests that updating processes can run in advance, before the stimulus is presented.

ERPs reveal comparable syntactic sentence processing in native and non-native readers of English

L2 syntactic processing has been primarily investigated in the context of syntactic anomaly detection, but only sparsely with syntactic ambiguity. In the field of event-related potentials (ERPs) syntactic anomaly detection and syntactic ambiguity resolution is linked to the P600. The current ERP experiment examined L2 syntactic processing in highly proficient L1 Spanish-L2 English readers who had acquired English informally around the age of 5 years. Temporary syntactic ambiguity (induced by verb subcategorization information) was tested as a language-specific phenomenon of L2, while syntactic anomaly resulted from phrase structure constraints that are similar in L1 and L2. Participants judged whether a sentence was syntactically acceptable or not. Native readers of English showed a P600 in the temporary syntactically ambiguous and syntactically anomalous sentences. A comparable picture emerged in the non-native readers of English. Both critical syntactic conditions elicited a P600, however, the distribution and latency of the P600 varied in the syntactic anomaly condition. The results clearly show that early acquisition of L2 syntactic knowledge leads to comparable online sensitivity towards temporal syntactic ambiguity and syntactic anomaly in early and highly proficient non-native readers of English and native readers of English.

Orthographic and phonological processing in Chinese dyslexic children: An ERP study on sentence reading

An event-related potential (ERP) experiment was conducted to explore the differences between Chinese-speaking dyslexic children and normal school children in orthographic and phonological processing during Chinese sentence reading. Participants were visually presented with sentences, word-by-word and were asked to judge whether the sentences were semantically acceptable. The crucial manipulation was on the sentence-final two-character compound words, which were either correct or incorrect. For the incorrect compounds, the second characters of the base words were replaced by homophonic or orthographically similar characters. It was found that, for the normal controls, the orthographic and phonological mismatches elicited more negative ERP responses, relative to the baseline, over a relatively long time course (including the time windows for P200 and N400) at the central-posterior scalp regions. In contrast, the dyslexic children in general showed no differences between experimental conditions for P200 and N400, although the more detailed time course analyses did reveal some weak effects for the N400 component between experimental conditions. In addition, the mean amplitude of N400 in the homophonic condition was less negative-going for the dyslexics than for the controls. These findings suggest that Chinese dyslexic children have deficits in processing orthographic and phonological information conveyed by characters and, compared with normal children, they rely more on phonological information to access lexical semantics in sentence reading.

ERP correlates of familiarity and recollection processes in visual associative recognition

Associative recognition memory often is thought to rely primarily on recollection processes, but opinions differ regarding the possible contribution of familiarity. The current experiments capitalized on hypothesized event-related potential (ERP) measures of familiarity and recollection to assess the contribution of each process to associative recognition. In two ERP experiments, participants studied pairs of fractals and were later tested on their ability to recognize the studied pairs. Early (100–175 ms) visual ERP components were sensitive to the novelty of individual fractals, but later components hypothesized to be indicative of familiarity and recollection were sensitive to the novelty of the association between fractals. These relationships suggest that accurate memory for visual associations may be dependent on both familiarity and recollection processes.

To Predict or Not to Predict: Influences of Task and Strategy on the Processing of Semantic Relations

We report a series of event-related potential experiments designed to dissociate the functionally distinct processes involved in the comprehension of highly restricted lexical-semantic relations (antonyms). We sought to differentiate between influences of semantic relatedness (which are independent of the experimental setting) and processes related to predictability (which differ as a function of the experimental environment). To this end, we conducted three ERP studies contrasting the processing of antonym relations (black-white) with that of related (black-yellow) and unrelated (black-nice) word pairs. Whereas the lexical-semantic manipulation was kept constant across experiments, the experimental environment and the task demands varied: Experiment 1 presented the word pairs in a sentence context of the form The opposite of X is Y and used a sensicality judgment. Experiment 2 used a word pair presentation mode and a lexical decision task. Experiment 3 also examined word pairs, but with an antonymy judgment task. All three experiments revealed a graded N400 response (unrelated > related > antonyms), thus supporting the assumption that semantic associations are processed automatically. In addition, the experiments revealed that, in highly constrained task environments, the N400 gradation occurs simultaneously with a P300 effect for the antonym condition, thus leading to the superficial impression of an extremely "reduced" N400 for antonym pairs. Comparisons across experiments and participant groups revealed that the P300 effect is not only a function of stimulus constraints (i.e., sentence context) and experimental task, but that it is also crucially influenced by individual processing strategies used to achieve successful task performance.

The Brain Locus of Interaction between Number and Size: A Combined Functional Magnetic Resonance Imaging and Event-related Potential Study

Whether the human brain is equipped with a special neural substrate for numbers, or rather with a common neural substrate for processing of several types of magnitudes, has been the topic of a long-standing debate. The present study addressed this question by using functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs) together with the size-congruity paradigm, a Stroop-like task in which numerical values and physical sizes were varied independently. In the fMRI experiment, a region-of-interest analysis of the primary motor cortex revealed interference effects in the hemisphere ipsilateral to the response hand, indicating that the stimulus-stimulus conflict between numerical and physical magnitude is not completely resolved until response initiation. This result supports the assumption of distinct comparison mechanisms for physical size and numerical value. In the ERP experiment, the cognitive load was manipulated in order to probe the degree to which information processing is shared across cognitive systems. As in the fMRI experiment, we found that the stimulus-stimulus conflict between numerical and physical magnitude is not completely resolved until response initiation. However, such late interaction was found only in the low cognitive load condition. In contrast, in the high load condition, physical and numerical dimensions interacted only at the comparison stage. We concluded that the processing of magnitude can be subserved by shared or distinct neural substrates, depending on task requirements.

When emotional prosody and semantics dance cheek to cheek: ERP evidence

To communicate emotionally entails that a listener understands a verbal message but also the emotional prosody going along with it. So far the time course and interaction of these emotional ‘channels’ is still poorly understood. The current set of event-related brain potential (ERP) experiments investigated both the interactive time course of emotional prosody with semantics and of emotional prosody independent of emotional semantics using a cross-splicing method. In a probe verification task (Experiment 1) prosodic expectancy violations elicited a positivity, while a combined prosodic–semantic expectancy violation elicited a negativity. Comparable ERP results were obtained in an emotional prosodic categorization task (Experiment 2). The present data support different ERP responses with distinct time courses and topographies elicited as a function of prosodic expectancy and combined prosodic-semantic expectancy during emotional prosodic processing and combined emotional prosody/emotional semantic processing. These differences suggest that the interaction of more than one emotional channel facilitates subtle transitions in an emotional sentence context.

Syntactic Priming in Comprehension

Syntactic priming is the facilitation of processing that occurs when a sentence has the same syntactic form as a preceding sentence. Such priming effects have been less consistently demonstrated in comprehension than in production, and those that have been reported have depended on the repetition of verbs across sentences. In an event-related potential experiment, subjects read target sentences containing reduced-relative clauses. Each was preceded by a sentence that contained the same verb and either a reduced-relative or a main-clause construction. Reduced-relative primes elicited a larger positivity than did main-clause primes. Reduced-relative targets that were preceded by a main-clause prime elicited a greater positivity than the same target sentences following a reduced-relative prime. In addition, syntactic priming effects were dissociated from effects of lexical repetition at the verb.

Role of the Corpus Callosum in Speech Comprehension: Interfacing Syntax and Prosody

The role of the corpus callosum (CC) in the interhemispheric interaction of prosodic and syntactic information during speech comprehension was investigated in patients with lesions in the CC, and in healthy controls. The event-related brain potential experiment examined the effect of prosodic phrase structure on the processing of a verb whose argument structure matched or did not match the prior prosody-induced syntactic structure. While controls showed an N400-like effect for prosodically mismatching verb argument structures, thus indicating a stable interplay between prosody and syntax, patients with lesions in the posterior third of the CC did not show this effect. Because these patients displayed a prosody-independent semantic N400 effect, the present data indicate that the posterior third of the CC is the crucial neuroanatomical structure for the interhemispheric interplay of suprasegmental prosodic information and syntactic information.

Audiovisual Events in Sensory Memory

The functional properties of the auditory sensory memory have been extensively studied using the mismatch negativity (MMN) component of the auditory event-related potential (ERP) and its magnetic counterpart recorded using magneto-encephalography (MEG). It has been found that distinct auditory features (such as frequency or intensity) are encoded separately in sensory memory. Nevertheless, the conjunction of these features (auditory “gestalts”) can also be encoded in auditory sensory memory. Here we investigated how auditory and visual features of bimodal events are represented in sensory memory by recording audiovisual MMNs in two different audiovisual oddball paradigms. The results of a first ERP experiment showed that the sensory memory representations of auditory and visual features of audiovisual events lie within the temporal and occipital cortex, respectively, yet with possible interactions between the processing of the unimodal features. In a subsequent MEG experiment, we found some evidence that audiovisual feature conjunctions could also be represented in sensory memory. These results, thus, extend to the audiovisual domain a number of properties of sensory memory already established within the auditory system.

Event-related Potential Signatures of Relational Memory

Various lines of evidence suggest that memory for the relations among arbitrarily paired items acquired prior to testing can influence early processing of a probe stimulus. The event-related potential experiment reported here was designed to explore how early in time memory for a previously established face-scene relationship begins to influence processing of faces, under sequential presentation conditions in which a preview of the scene can promote expectancies about the to-be-presented face. Prior to the current work, the earliest component documented to be sensitive to memory for the relations among arbitrarily paired items was the late positive complex (LPC), but here relational memory effects were evident as early as 270-350 msec after face onset. The latency of these relational memory effects suggests that they may be the precursor to similar effects observed in eye movement behavior. As expected, LPC amplitude was also affected by memory for face-scene relationships, and N400 amplitude reflected some combination of memory for items and memory for the relations among items.

The effects of stress and statistical cues on continuous speech segmentation: An event-related brain potential study

The study of the processes involved in speech segmentation has gained special relevance in recent years by trying to establish what type of information listeners use to segment the speech signal into words. An event-related brain potential experiment was conducted in order to understand how two of these cues (statistical and stress cues) interact. The experiment consisted of the presentation of artificial speech streams in which words were marked either by statistical cues alone, or by a combination of statistical and stress cues. As a baseline, comparison streams were also created with the same syllables but organized in random order. Results showed an N400 component that marks the on-line segmentation of speech into words, and an increased positivity (P2 component) for languages that include both types of cues. Possible implications of these results for the process of speech segmentation are discussed.

Thematic role assignment in patients with Broca's aphasia: Sentence–picture matching electrified

An event-related brain potential experiment was carried out to investigate on-line thematic role assignment during sentence–picture matching in patients with Broca's aphasia. Subjects were presented with a picture that was followed by an auditory sentence. The sentence either matched the picture or mismatched the visual information depicted. Sentences differed in complexity, and ranged from simple active semantically irreversible sentences to passive semantically reversible sentences. ERPs were recorded while subjects were engaged in sentence–picture matching. In addition, reaction time and accuracy were measured. Three groups of subjects were tested: Broca patients ( N = 10), non-aphasic patients with a right hemisphere (RH) lesion ( N = 8), and healthy aged-matched controls ( N = 15). The results of this study showed that, in neurologically unimpaired individuals, thematic role assignment in the context of visual information was an immediate process. This in contrast to patients with Broca's aphasia who demonstrated no signs of on-line sensitivity to the picture–sentence mismatches. The syntactic contribution to the thematic role assignment process seemed to be diminished given the reduction and even absence of P600 effects. Nevertheless, Broca patients showed some off-line behavioral sensitivity to the sentence–picture mismatches. The long response latencies of Broca's aphasics make it likely that off-line response strategies were used.