Hemispheric asymmetry and pun comprehension: when cowboys have sore calves

Event-related potentials (ERPs) were recorded as healthy participants listened to puns such as "During branding, cowboys have sore calves." To assess hemispheric differences in pun comprehension, visually presented probes that were either highly related (COW), moderately related (LEG), or unrelated, were presented in either the left or right visual half field (LVF/RVF). The sensitivity of each hemisphere to the different meanings evoked by the pun was assessed by ERP relatedness effects with presentation to the LVF and the RVF. In Experiment 1, the inter-stimulus interval between the pun and the onset of the visual probe was 0 ms; in Experiment 2, this value was 500 ms. In Experiment 1, both highly and moderately related probes elicited similar priming effects with RVF presentation. Relative to their unrelated counterparts, related probes elicited less negative ERPs in the N400 interval (300-600 ms post-onset), and more positive ERPs 600-900 ms post-onset, suggesting both meanings of the pun were equally active in the left hemisphere. LVF presentation yielded similar priming effects (less negative N400 and a larger positivity thereafter) for the highly related probes, but no effects for moderately related probes. In Experiment 2, similar N400 priming effects were observed for highly and moderately related probes presented to both visual fields. Compared to unrelated probes 600-900 ms post-onset, related probes elicited a centro-parietal positivity with RVF presentation, but a fronto-polar positivity with LVF presentation. Results suggest that initially, the different meanings evoked by a pun are both active in the left hemisphere, but only the most highly related meaning is active in the right hemisphere. By 500 ms, both meanings are active in both hemispheres.     

Using event-related potentials to examine hemispheric differences in semantic processing

Event-related potentials (ERPs) were used as the dependent measure in a divided visual field study examining the processing of lexically ambiguous words in the cerebral hemispheres. The goal was to determine if the N400 ERP component is sensitive measure of hemispheric differences in semantic processing. ERP waveforms were examined for lateralized target words that were related to either the dominant (MONEY) or subordinate (RIVER) meanings of ambiguous words (BANK). These waveforms were compared to trials where the prime-target pairs were unrelated. Reliable N400s, reflecting a significant difference between related and unrelated trials, were seen when targets were presented to the right visual field/left hemisphere. However, there were no N400s observed for either the dominant or subordinate conditions when targets were presented to the left visual field/right hemisphere.     

Electrodermal responses to attended and nonattended significant stimuli during dichotic listening

Some investigators have found that words previously associated with shock elicit electrodermal responses (EDRs) when presented in the nonattended channel of a dichotic listening task. The present experiment tested for this phenomenon while closely monitoring for shifts in attention to the nonattended channel. College student volunteers verbally shadowed a series of unrelated words presented to the attended channel while words made significant by previous association with shock (and semantically related words) were occasionally presented to the nonattended channel. Three principal findings were obtained. Fist, when EDRs were averaged across all trials and across all subjects, it was found that EDRs were elicited by the significant words presented in the nonattended channel. Second, for the subgroup of subjects that had the significant words presented to the right ear (activating the left cerebral hemisphere), it was found that EDRs were elicited by the significant words presented to the left ear (activating the right cerebral hemisphere), it was found that EDRs were elicited by the significant word seven on trials on which there were no apparent shifts in attention. The results of this study indicate the importance of closely controlling and monitoring for shifts in attention and suggest the potential importance of cerebral laterality in mediating EDRs to stimuli presented in a nonatttended channel.     

语义距离半球效应的ERP研究

以通过视觉通路呈现的汉语双字词为实验材料,操纵启动词与目标词的语义距离。在词汇决定实验中记录ERP,发现：（1）除N300外,P240亦对语义距离敏感,它可能是一种与语义加工有关的新的ERP成分;（2）P240在头皮中央偏左的部位较早出现,但在头皮右侧波幅较大;（3）N300和P240都不存在语义距离的半球效应,该结果没有证实右脑更专擅远距离语义加工的假设,表明使用汉语与使用拼音文字的脑机制存在差异。     

Contextual modulation of N400 amplitude to lexically ambiguous words

Though much is known about the N400 component, an event-related EEG potential that is sensitive to semantic manipulations, it is unclear whether modulations of N400 amplitude reflect automatic processing, controlled processing, or both. We examined this issue using a semantic judgment task that manipulated local and global contextual cues. Word triplets (prime-noun-target, e.g., finance-bank-money) were sequentially presented on a computer screen (500 ms duration, 1000 ms stimulus onset asynchrony), in which the second word was a homograph. The first word (prime) created a neutral-, dominant-meaning- or subordinate-meaning-biased "global context," and the third word (target) created a dominant- or subordinate-biased "local context" that was either congruent or incongruent with the "global context" established by the first prime word. Participants were instructed to read all three words but to decide only whether the second and third words were semantically related. Event-related potentials (ERPs), specifically the N400, were recorded to the third terminal word. N400 amplitudes evoked by dominant meaning-related third words incongruent with the globally biased subordinate context (e.g., river-bridge-money) were significantly more negative than dominant endings in neutral contexts (e.g., taxi-bank-money), but not different from unrelated filler triplets. In addition, there was some indication that left hemisphere, temporal-parietal electrode sites were associated with greater N400 negativity for dominant targets in conflicting subordinate global contexts than homologous right hemisphere electrode sites, the latter of which showed significant activation to subordinate meanings in cooperating contexts. Thus, N400 amplitude was more affected by global than local context suggesting that controlled processes may take priority over automatic processes in modulating N400 amplitude, especially for left hemisphere electrode sites.     

Right Hemisphere Activation during Indirect Semantic Priming: Evidence from Event-Related Potentials

Healthy subjects performed a lexical decision task in a semantic priming paradigm while event-related potentials (ERPs) were recorded from 64 channels. Semantic distance between prime and target was varied by including directly, indirectly, and nonrelated word pairs. At centro-parietal electrodes an N400 to nonrelated pairs was elicited bilaterally which was sensitive only to direct, but not to indirect semantic priming. These N400 priming effects were mirrored by the RT data. At inferior fronto-temporal sites directly related words showed ERP priming effects over both hemispheres. However, indirectly related words only elicited ERP priming effects over the right hemisphere. These results support the hypothesis that the right hemisphere semantic system is involved in processing of remote semantic information.     

Event-related potential studies of cerebral specialization during reading: I. Studies of normal adults

A number of methodological features were incorporated in a paradigm designed to maximize the likelihood of finding reliable event-related potential (ERP) signs of functional specializations between and within the cerebral hemispheres. Every subject was more accurate in identifying words presented to the right than to the left visual field. The morphology of the ERPs elicited by these words varied considerably as a function of electrode position both within and between the hemispheres. Amplitude asymmetries of ERP components recorded from occipital regions of the two hemispheres varied systematically with the position of the word in the visual field. On the other hand, ERPs from more anterior (temporal and frontal) regions displayed large asymmetries which were in the same direction regardless of the visual field of word presentation. The most prominent such asymmetry was in the negativity in the region 300–500 msec (N410) which was larger in the left than the right hemisphere in every subject. These results demonstrate that in this paradigm which demands specialized language processing ERPs are sensitive to aspects of cerebral organization both within and between the two hemispheres.     

Hemispheric differences in the time-course of semantic priming processes: evidence from event-related potentials (ERPs)

To investigate hemispheric differences in the timing of word priming, the modulation of event-related potentials by semantic word relationships was examined in each cerebral hemisphere. Primes and targets, either categorically (silk-wool) or associatively (needle-sewing) related, were presented to the left or right visual field in a go/no-go lexical decision task. The results revealed significant reaction-time and physiological differences in both visual fields only for associatively related word pairs, but an electrophysiological difference also tended to reach significance for categorically related words when presented in the left visual field. ERP waveforms showed a different time-course of associative priming effects according to the field of presentation. In the right visual field/left hemisphere, both N400 and Late Positive Component (LPC/P600) were modulated by semantic relatedness, while only a late effect was present in the left visual field/ right hemisphere.     

Semantic additivity and semantic inhibition: dissociable processes in the cerebral hemispheres?

We report the results of two visual half-field semantic priming experiments using a high proportion of related trials to examine hemisphere asymmetries for semantic processes beyond those attributable to automatic meaning activation. Contrary to previous investigations, we obtained inhibition for unrelated trials in both visual fields. However, priming was additive (being greater for words related via category membership and association than for either single dimension) only when words were presented to the RVF/left hemisphere. A third experiment, using centrally presented stimuli, implied that semantic additivity should be attributed to post-access meaning comparisons and inhibition to the generation of semantic expectancies. These results suggest (1) that inhibition and additivity are potentially dissociable "controlled" semantic processes and (2) that the left hemisphere predominates for meaning integration across successively presented words. The availability of finely tuned meaning integration processes in the left hemisphere may contribute to its superiority in language processing, despite right hemisphere competence for some semantic operations.     

关于条件推理的ERP研究

以抽象的条件命题作为实验材料,测定13名大学生在完成MP、AC、DA、MT推理（推测判断任务）和基线任务（记忆判断任务）时的事件相关电位（ERP）,初步探讨不同推理类型的脑内时程动态变化。这是使用ERP技术来研究条件推理脑机制的初步尝试。结果发现,五种任务所诱发的ERP早成分均不存在显著差异,在头皮前部的左外侧额区和左颞区,MP与DA推理与基线任务相比,均诱发一个更明显的晚期正成分（450-1100ms）,在右外侧额区则诱发一个更明显的晚期负成分（450~1100ms）;与之相反,MT与AC推理与基线任务相比,在左侧诱发一个更明显的晚期负成分（450~1100ms）,在右侧诱发一个更明显的晚期正成分（450~1100ms）,这一结果可能是由于左右脑在推理中的认知功能以及四种推理类型之间存在的差异所致,同时也表明推测过程主要激活了左右侧的前额部、颞叶等区域,基本支持Goel等人的双加工理论     

Event-related potential studies of cerebral specialization during reading : II. Studies of congenitally deaf adults

A number of methodological features were incorporated in a paradigm designed to maximize the likelihood of finding reliable event-related potential (ERP) signs of functional specializations between and within the cerebral hemispheres. Every subject was more accurate in identifying words presented to the right than to the left visual field. The morphology of the ERPs elicited by these words varied considerably as a function of electrode position both within and between the hemispheres. Amplitude asymmetries of ERP components recorded from occipital regions of the two hemispheres varied systematically with the position of the word in the visual field. On the other hand, ERPs from more anterior (temporal and frontal) regions displayed large asymmetries which were in the same direction regardless of the visual field of word presentation. The most prominent such asymmetry was in the negativity in the region 300–500 msec (N410) which was larger in the left than the right hemisphere in every subject. These results demonstrate that in this paradigm which demands specialized language processing ERPs are sensitive to aspects of cerebral organization both within and between the two hemispheres.     

Dissociation of event-related potentials indexing arousal and semantic cohesion during emotional word encoding

Event-related potential (ERP) studies have shown that emotional stimuli elicit greater amplitude late positive-polarity potentials (LPPs) than neutral stimuli. This effect has been attributed to arousal, but emotional stimuli are also more semantically coherent than uncategorized neutral stimuli. ERPs were recorded during encoding of positive, negative, uncategorized neutral, and categorized neutral words. Differences in LPP amplitude elicited by emotional versus uncategorized neutral stimuli were evident from 450 to 1000 ms. From 450 to 700 ms, LPP effects at midline and right hemisphere frontal electrodes indexed arousal, whereas LPP effects at left hemisphere centro-parietal electrodes indexed semantic cohesion. This dissociation helps specify the processes underlying emotional stimulus encoding, and suggests the need to control for semantic cohesion in emotional information processing studies.     

Event-related potentials during word-reading and figure-matching in left-handed and right-handed males and females

In two experiments, event-related potentials at left and right occipital, parietal, and temporal sites were studied in 16 left-handers (8 male, 8 female) and 16 right-handers (8 male, 8 female). Subjects displayed extreme handedness, had a normal writing hand position, reported no left-handed relatives, and reported no perinatal traumata. In Experiment 1, centrally presented words had to be read, and nonverbal stimuli had to be matched. Condition-dependent asymmetries were found for P340 and SW components. Word-reading elicited a N500 component, whereas figure-matching did not. In Experiment 2, words presented to either the left or right visual field had to be read. It was found that N160 measures were larger, and P240, P400, and SW measures were smaller to words presented in the contralateral visual field compared to words in the ipsilateral field. Sex affected these pathway effects. In both experiments, hand preference did not significantly influence the ERP results.     

Effects of visual-field and matching instruction on event-related potentials and reaction time

Vertical letter pairs were presented randomly in the left and right visual hemifields in a physical identity match and name identity match condition. The reaction times showed a right visual field superiority for name matches, and a left visual field superiority for physical matches. Event-related potentials to letter pairs showed a sequence of three waves: a negative wave (N2, around 270 msec), a positive wave (P3, around 500 msec), and a broad positive slow wave (SW, around 600-700 msec), respectively. P3 and SW amplitudes were consistently larger at the left hemisphere than at the right hemisphere, regardless of the field of stimulation. At both hemispheres, N2 waves were always larger to stimuli presented in the visual field contralateral to a hemisphere than stimuli presented in the visual field ipsilateral to a hemisphere. The positive waves (P3, SW) showed the opposite pattern: smaller amplitudes to stimuli that were presented contralaterally than stimuli that were presented ipsilaterally to a given hemisphere. These results were attributed to a shift in sustained negativity on the directly stimulated hemisphere, relative to the indirectly stimulated hemisphere, reflecting either sensory at attentional processes in the posterior cerebral hemispheres.     

An fMRI investigation of the neural correlates underlying the processing of novel metaphoric expressions

The neural networks associated with processing related pairs of words forming literal, novel, and conventional metaphorical expressions and unrelated pairs of words were studied in a group of 15 normal adults using fMRI. Subjects read the four types of linguistic expressions and decided which relation exists between the two words (metaphoric, literal, or unrelated). According to the Graded Salience Hypothesis (GSH, ), which predicts a selective RH involvement in the processing of novel, nonsalient meanings, it is primarily the degree of meaning salience of a linguistic expression rather than literality or nonliterality, which modulates the degree of left hemisphere (LH) and right hemisphere (RH) processing of metaphors. In the present study, novel metaphorical expressions represented the nonsalient interpretations, whereas conventional metaphors and literal expressions represented the salient interpretations. A direct comparison of the novel metaphors vs. the conventional metaphors revealed significantly stronger activity in right posterior superior temporal sulcus, right inferior frontal gyrus, and left middle frontal gyrus. These results support the GSH and suggest a special role for the RH in processing novel metaphors. Furthermore, the right PSTS may be selectively involved in verbal creativity.     

Semantic and associative priming in the cerebral hemispheres: some words do, some words don't ... sometimes, some places

This study investigated spreading activation for words presented to the left and right hemispheres using an automatic semantic priming paradigm. Three types of semantic relations were used: similar-only (Deer-Pony), associated-only (Bee-Honey), and similar + associated (Doctor-Nurse). Priming of lexical decisions was symmetrical over visual fields for all semantic relations when prime words were centrally presented. However, when primes and targets were lateralized to the same visual field, similar-only priming was greater in the LVF than in the RVF, no priming was obtained for associated-only words, and priming was equivalent over visual fields for similar + associated words. Similar results were found using a naming task. These findings suggest that it is important to lateralize both prime and target information to assess hemisphere-specific spreading activation processes. Further, while spreading activation occurs in either hemisphere for the most highly related words (those related by category membership and association), our findings suggest that automatic access to semantic category relatedness occurs primarily in the right cerebral hemisphere. These results imply a unique role for the right hemisphere in the processing of word meanings. We relate our results to our previous proposal (Burgess & Simpson, 1988a; Chiarello, 1988c) that there is rapid selection of one meaning and suppression of other candidates in the left hemisphere, while activation spreads more diffusely in the right hemisphere. We also outline a new proposal that activation spreads in a different manner for associated words than for words related by semantic similarity.     

Lateralized hemisphere activity in relation to personality and degree course

Personality dimensions of Psychoticism (P), Extraversion (E) and Neuroticism (N) were related to multiple measures of lateralized hemispheric processing in order to test the predictions of right hemisphere overactivation in E, right hemisphere underactivation in N, and left hemisphere under- activation/overactivation in P. It was also predicted that architecture students would be characterized by right hemisphere activation and language students by left hemisphere activation. Lateral eye movements, verbal and nonverbal dichotic listening tasks, and Block Design and Digit Span subtests of the WAIS were assessed in 43 undergraduates, together with personality and degree course. High P scores were characterized by fewer rightward eye movements and hence reduced left hemisphere activation, while high N scores were characterized by poorer Block Design and superior Digit Span performance. These results which indicate a relationship between Psychoticism and left hemisphere underactivation are in conflict with the finding of Raine and Manders (1988) (Br. J. Clin. Pschol. In press) overactivation in those with high schizoid personality scores, a discrepancy which may be resolved by the notion that P reflects a different form of psychosis-proneness to other schizoid scales.     

汉字视听再认的ERP效应与记忆提取脑机制

测定了正常青年人汉字再认的事件相关电位(ERP)。观察到对听觉汉字的认知产生“持续中央负成分”,而视觉汉字的认知出现“晚期正成分”,提示汉字的视听认知具有不同的脑机制。汉字视听认知皆出现了新旧效应,即旧词皆引起ERP晚期成分的正走向变化,但视听新旧效应的起始时间与头皮分布不同,听觉效应为右半球优势,视觉效应则出现在左侧顶叶、左侧颞叶后部与右侧枕叶。以上实验结果提示,“优势半球”概念已难以概括半球间的多维动态关系,需要修正。     

Picture-name priming in the cerebral hemispheres: evidence for phonological access in the right hemisphere

This study investigated right hemisphere involvement in access to phonology, using a picture-naming priming paradigm where pictures and names of common objects printed in Japanese Kana were presented in succession to the same visual field or different visual fields with a stimulus onset asynchrony of 250 msec. A naming task was used for this purpose. The result showed that, when primes and targets were presented to the same visual field, facilitation for related pairs was observed in each hemisphere, with overall naming latencies being slower in the right hemisphere than in the left hemisphere. This result indicates that the prior access to phonology for a picture in the right hemisphere facilitates phonological activation of a word that names the picture in this hemisphere, suggesting that the right hemisphere is involved in access to phonology. On the other hand, when primes and targets were presented to different visual fields, there was no facilitation for related pairs with inhibition for unrelated pairs, irrespective of prime and target visual fields. It is suggested that this inhibition-dominant pattern of priming may occur due to homotopic inhibition processes proposed by N. D. Cook.     

Behavioral performances in participants with phonological dyslexia and different patterns on the N170 component

Adults with phonological dyslexia and controls performed a lexical decision task while ERPs were recorded in the occipitotemporal pathway. Based on N170 durations, two subgroups were formed: dysl1 showing longer N170 durations and dysl2 showing normal N170 durations. While the dysl1 subgroup had poorer accuracy for infrequent words and pseudo-words, the dysl2 group responded more slowly than controls to pseudo-words. N170 amplitudes were larger in the left hemisphere for controls irrespective of items. In the dysl1 subgroup, N170 amplitudes were larger in the left hemisphere than the right for words but not for pseudo-words, a sign of hemispheric compensation, while in the dysl2 subgroup signs of bilateralization were observed. Moreover, in the dysl1 subgroup, P100 amplitudes were smaller than controls. These results indicate different behavioral profiles of dyslexics with different patterns of P100 and N170 components. The ERP changes may be due to different behavioral strategies employed by each subgroup, logographic in dysl2 and phonological in dysl1.