Access to concrete word meanings in the cerebral hemispheres: facilitation and inhibition effects

In 2002 Shibahara and Lucero-Wagoner, using a priming paradigm, reported a larger facilitation for concrete noun pairs in the right than left hemisphere when the stimulus onset asynchrony was 250 msec. Their related prime-target pairs were similar not only in meaning but also perceptual attributes, such as shape. They had reported such perceptual information to be available only in the right hemisphere early in target processing. Thus, we predicted that, when the stimulus onset asynchrony is long, there would be no effect of perceptual information on target processing in the right hemisphere, resulting in no hemispheric differences in the amount of facilitation. We also predicted that target processing would be inhibited by prior presentation of unrelated primes only in the left hemisphere because inhibition seems to be produced by the attention system in the left hemisphere. The present experiment was designed to test these predictions, using the stimulus onset asynchrony of 550 msec. and the same prime-target pairs. Analysis showed no hemispheric differences in the amount of facilitation, and inhibition effects for unrelated pairs were produced in both hemispheres. It is suggested that the inhibition effects in each hemisphere might be produced by different mechanisms.     

汉语同形歧义词歧义消解的两半球差异

实验探讨汉语同形歧义词(homographs)歧义消解的过程及大脑两半球的差异。被试为华中科技大学96名大学生,实验采用词汇判断任务。句子语境呈现在被试的视野中央,探测词在SOA(stimulus onset asynchronism)为100毫秒或400毫秒时呈现在左视野或右视野。结果发现,(1)当SOA为100毫秒时,在左视野(右半球)上,与语境一致的同形歧义词的主要意义得到激活,与语境不一致的次要意义也有一定程度的激活。在右视野(左半球)上,只有与语境一致的同形歧义词的主要意义得到激活。(2)当SOA为400毫秒时,在左、右视野(两半球)上,与语境一致的同形歧义词的主要意义和次要意义都得到激活。结果表明,大脑左半球对汉语歧义词的歧义消解具有一定的优势,语境敏感模型可以较好地解释本实验的结果。     

The effect of associative strength on priming in the cerebral hemispheres

Recent studies have suggested that semantic memory is more diffusely organized in the right hemisphere of the brain and that words directed to this hemisphere are more likely to activate meanings distantly related to the input. It is argued that this model of language processes predicts that variations in the associative strength of word pairs should give rise to different patterns of priming in each hemisphere. Specifically, the right hemisphere should exhibit relatively more facilitation than the left in response to weaker associative relationships, whereas the left hemisphere should exhibit relatively more facilitation than the right in the context of stronger relationships. This study varied the strength of the semantic association between prime and target in a divided visual field priming procedure. The results were unequivocal in demonstrating similar associative strength functions in each hemisphere, under conditions that encouraged either automatic or controlled processing. Visual field differences in absolute RTs to words and in magnitude of facilitation effects support the claim that the data collected in this study are veridical with respect to priming processes in the hemispheres. It is suggested that current models of hemispheric language processes require further refinement.     

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.     

Cerebral hemispheric mechanisms in the retrieval of ambiguous word meanings

Targets related to ambiguous primes were projected to the left and right visual fields in a lexical priming experiment with stimulus onset asynchronies (SOA) of 35 and 750 msec. Right visual field results were similar to our earlier results with central projection (G. B. Simpson & C. Burgess, 1985, Journal of Experimental Psychology: Human Perception and Performance, 11, 28-39). Facilitation was found for the more frequent meaning at both SOAs and a decrease in facilitation for the less frequent meaning at the longer SOA. In contrast, left visual field results indicated a decay of facilitation for the more frequent meaning at the longer SOA, while activation for the subordinate meaning increased. Results suggest that, while automatic processing occurs in both hemispheres, only the left hemisphere engages in controlled processing of ambiguous word meanings. In addition, the present results support the idea that the right hemisphere has a special role in ambiguity resolution and that the right hemisphere lexicon possesses a richer endowment than earlier thought.     

Lateralized repetition priming for familiar faces: Evidence for asymmetric interhemispheric cooperation

Repetition priming refers to facilitated recognition of stimuli that have been seen previously. Although a great deal of work has examined the properties of repetition priming for familiar faces, little has examined the neuroanatomical basis of the effect. Two experiments are presented in this paper that combine the repetition priming paradigm with a divided visual field methodology to examine lateralized recognition of familiar faces. In the first experiment participants were presented with prime faces unilaterally to each visual field and target faces foveally. A significant priming effect was found for prime faces presented to the right hemisphere, but not for prime faces presented to the left hemisphere. In Experiment 2, prime and target faces were presented unilaterally, either to the same visual field or to the opposite visual field (i.e., either within hemisphere or across hemispheres). A significant priming effect was found for the within right hemisphere condition, but not for the within left hemisphere condition, replicating the findings of the first experiment. Priming was also found in both of the across hemispheres conditions, suggesting that interhemispheric cooperation occurs to aid recognition. Taken in combination these experiments provide two main findings. First, an asymmetric repetition priming effect was found, possibly as a result of asymmetric levels of activation following recognition of a prime face, with greater priming occurring within the right hemisphere. Second, there is evidence for asymmetric interhemispheric cooperation with transfer of information from the right hemisphere to the left hemisphere to facilitate recognition.     

Lateralized repetition priming for familiar faces: Evidence for asymmetric interhemispheric cooperation

Repetition priming refers to facilitated recognition of stimuli that have been seen previously. Although a great deal of work has examined the properties of repetition priming for familiar faces, little has examined the neuroanatomical basis of the effect. Two experiments are presented in this paper that combine the repetition priming paradigm with a divided visual field methodology to examine lateralized recognition of familiar faces. In the first experiment participants were presented with prime faces unilaterally to each visual field and target faces foveally. A significant priming effect was found for prime faces presented to the right hemisphere, but not for prime faces presented to the left hemisphere. In Experiment 2, prime and target faces were presented unilaterally, either to the same visual field or to the opposite visual field (i.e., either within hemisphere or across hemispheres). A significant priming effect was found for the within right hemisphere condition, but not for the within left hemisphere condition, replicating the findings of the first experiment. Priming was also found in both of the across hemispheres conditions, suggesting that interhemispheric cooperation occurs to aid recognition. Taken in combination these experiments provide two main findings. First, an asymmetric repetition priming effect was found, possibly as a result of asymmetric levels of activation following recognition of a prime face, with greater priming occurring within the right hemisphere. Second, there is evidence for asymmetric interhemispheric cooperation with transfer of information from the right hemisphere to the left hemisphere to facilitate recognition.     

Hemispheric Differences in Context Sensitivity During Lexical Ambiguity Resolution

Three experiments were conducted to investigate the influence of contextual constraint on lexical ambiguity resolution in the cerebral hemispheres. A cross-modal priming variant of the divided visual field task was utilized in which subjects heard sentences containing homonyms and made lexical decisions to targets semantically related to dominant and subordinate meanings. Experiment 1 showed priming in both hemispheres of dominant meanings for homonyms embedded in neutral sentence contexts. Experiment 2 showed priming in both hemispheres of dominant and subordinate meanings for homonyms embedded in sentence contexts that biased a central semantic feature of the subordinate meaning. Experiment 3 showed priming of dominant meanings in the left hemisphere (LH), and priming of the subordinate meaning in the right hemisphere (RH) for homonyms embedded in sentences that biased a peripheral semantic feature of the subordinate meaning. These results are consistent with a context-sensitive model of language processing that incorporates differential sensitivity to semantic relationships in the cerebral hemispheres.     

Homotopic callosal inhibition in hemispheric priming: A test of cook’s topographical inhibitory model

This study set out to evaluate Cook’s (1986) topographical inhibitory model of language processing in the hemispheres. The model employs the neurophysiological mechanism of homotopic callosal inhibition to explain recent findings which suggest that the left hemisphere processes denotative meaning, while the right hemisphere specializes in connotative meaning. Specific predictions in relation to lateralized priming phenomena were derived from the model. The first experiment tested the prediction that word repetition and denotative priming would facilitate responses to right visual field targets, while connotative priming would favour the left visual field. None of these predictions were confirmed. A second experiment modified in a number of ways, provided a more extensive test of the predictions but produced essentially the same result. It was concluded that no evidence could be obtained to support the topographical inhibitory model. Instead, the results extend previous findings by suggesting that associative priming has more or less equivalent effects in each hemisphere, provided the interval between prime and target is sufficiently long.     

Exploring the contribution of the cerebral hemispheres to language comprehension deficits in adults with developmental language disorder

A divided visual field, priming paradigm was used to observe how adults who have a history of developmental language disorder (DLD) access lexically ambiguous words. The results show that sustained semantic access to subordinate word meanings (such as BANK-RIVER), which is seen in control subjects, is disrupted in the right cerebral hemisphere for this special population of readers. In the left hemisphere, only the most dominant meaning of the ambiguous word shows sustained priming in both controls and DLD participants. Therefore, for the DLD readers the subordinate meanings of words are not primed in either hemisphere and, thus, may not be available during online processing and integration of discourse. This right hemisphere lexical access deficit might contribute to the language comprehension difficulties exhibited by adult readers with a history of DLD.     

Understanding metaphoric sentences in the two cerebral hemispheres

Previous studies indicate that the right hemisphere (RH) has a unique role in maintaining activation of metaphoric single word meanings. The present study investigated hemispheric asymmetries in comprehending metaphoric word meanings within a sentence context. Participants were presented with incomplete priming sentences followed by (literally) true, false, or metaphoric lateralized target words and were asked to decide whether each sentence is literally true or false. Results showed that responses to metaphoric sentences were slower and less accurate than to false sentences when target words were presented to the right visual field (RVF)-LH as well as to the left visual field (LVF)-RH. This suggests that the understanding of lexical metaphors within a sentence context involves LH as well as RH processing mechanisms and that the role of each hemisphere in processing nonliteral language is flexible and may depend on the linguistic task at hand.     

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.     

Processing the emotions in words: The complementary contributions of the left and right hemispheres

A dual-process model is suggested for the processing of words with emotional meaning in the cerebral hemispheres. While the right hemisphere and valence hypotheses have long been used to explain the results of research on emotional stimulus processing, including nonverbal and verbal stimuli, data on emotional word processing are mostly inconsistent with both hypotheses. Three complementary lines of research data from behavioral, electrophysiological, and neuroimaging studies seem to suggest that both hemispheres have access to the meanings of emotional words, although their time course of activation may be different. The left hemisphere activates these words automatically early in processing, whereas the right hemisphere gains access to emotional words slowly when attention is recruited by the meaning of these words in a controlled manner. This processing dichotomy probably corroborates the complementary roles the two hemispheres play in data processing.     

Hemispheric asymmetry in a perceptual priming task: evidence from patients with unilateral brain damage.

The present study examined the relationship between unilateral brain damage and the effect of nonverbal perceptual priming using a picture-fragment completion task. Subjects consisted of 11 left brain-damaged patients, 8 right brain-damaged patients, and 10 healthy normal controls. The mean score of normal controls was significantly higher than those of left and right brain-damaged patients. Although there were significant effects of priming in all the groups, a significant difference in amplitude of priming effects was found only between right brain-damaged patients and normal controls. The correlation between amount of fragmentation at which there was identification and priming effect was not significant. We conclude that the right hemisphere is more involved in perceptual priming of form than is the left hemisphere, and form-dependent processing in the perceptual priming task has an asymmetrical distribution in the right and left hemispheres.     

Cerebral hemispheric mechanisms linking ambiguous word meaning retrieval and creativity

The deferral of ambiguity resolution has been thought to be an important component of creativity. The time course of priming of dominant and subordinate meanings of ambiguous words was investigated using a divided visual field priming paradigm with subjects that varied on a measure of creativity. The Wallach-Kogan similarities subtest was used to group 72 subjects into three levels of verbal creativity to compare their performance on the ambiguity resolution task (Burgess & Simpson, 1988a). Results suggest that both the left and right hemispheres contribute to the maintenance of multiple word meanings in highly creative subjects, while less creative subjects show sustained subordinate priming only in the right hemisphere or no sustained subordinate priming. These results support an interactive, collaborative theory of verbal creativity (Bogen & Bogen, 1969) and suggest that there are important individual differences that expand on the basic time course model of hemispheric processing (Burgess & Simpson, 1988a).     

Hemisphere dynamics in lexical access: automatic and controlled priming

Hemisphere differences in lexical processing may be due to asymmetry in the organization of lexical information, in procedures used to access the lexicon, or both. Six lateralized lexical decision experiments employed various types of priming to distinguish among these possibilities. In three controlled (high probability) priming experiments, prime words could be used as lexical access clues. Larger priming was obtained for orthographically similar stimuli (BEAK-BEAR) when presented to the left visual field (LVF). Controlled priming based on phonological relatedness (JUICE-MOOSE) was equally effective in either visual field (VF). Semantic similarity (INCH-YARD) produced larger priming for right visual field (RVF) stimuli. These results suggest that the hemispheres may utilize different information to achieve lexical access. Spread of activation through the lexicon was measured in complementary automatic (low probability) priming experiments. Priming was restricted to LVF stimuli for orthographically similar words, while priming for phonologically related stimuli was only obtained in the RVF. Automatic semantic priming was present bilaterally, but was larger in the LVF. These results imply hemisphere differences in lexical organization, with orthographic and semantic relationships available to the right hemisphere, and phonological and semantic relations available to the left hemisphere. Support was obtained for hemisphere asymmetries in both lexical organization and directed lexical processing.     

Repetition priming within and between the two cerebral hemispheres

Two experiments explored repetition priming benefits in the left and right cerebral hemispheres. In both experiments, a lateralized lexical decision task was employed using repeated target stimuli. In the first experiment, all targets were repeated in the same visual field, and in the second experiment the visual field of presentation was switched following repetition. Both experiments demonstrated hemispheric specialization for the task (a RVF advantage for word identification) and hemispheric interaction for word processing (lexicality priming from contralateral distracters). In the first experiment, words were identified more quickly and accurately following repetition, with repetition facilitating faster but fewer correct responses for non-words. Complex interactions between visual field of first and second presentation in the second experiment indicate asymmetric interhemispheric repetition priming effects. These results provide a broad picture of hemispheric asymmetries in word processing and of complex interaction between the hemispheres during word recognition.     

Differential cerebral involvement in the cognitive functioning of bilinguals

The cognitive processing strategies of two groups of French-English bilinguals were studied by means of an auditory Stroop test designed to evaluate cerebral hemispheric involvement. An “early bilingual” group were bilingual before the age of 5, and a “late bilingual” group were bilingual after the age of 10. Stimuli were words uttered in pitches that were related to word meanings either congruently (as in the word “high” uttered in a high pitch) or incongruently (the word “haute” uttered in a low pitch). In one condition, subjects were to differentiate low from high pitches, disregarding meaning, while in a second condition, they were to disregard pitch and respond to word meanings. Measures of field independence were also taken. Results of data analyses suggest that male early bilinguals—the most field independent subgroup—process meaning efficiently in both cerebral hemispheres, but process pitch better in the right hemisphere. However, male late bilinguals and female bilinguals, both early and late, process meaning more rapidly in the right cerebral hemisphere and pitch equally rapidly in both hemispheres. The findings are interpreted as reflecting hemisphere-based strategy and sex differences in information-processing by the two bilingual groups.     

Mediated priming in the cerebral hemispheres

The present experiment investigates hemispheric differences in mediated priming. Theories of lexical representation have argued for an asymmetrical coding between the right and left hemispheres ([Beeman, 1998]), claiming that the right hemisphere is more diffusely represented compared to the left hemisphere. Thus, the right hemisphere activates a larger semantic field compared to the left hemisphere. Mediated (two-step) priming is an ideal task to examine this representational claim, because of the distant nature of the prime-target pairs. Results showed no difference in the magnitude of priming (both mediated and direct) between the right and left hemispheres. These results suggest that the lexical representation of the two hemispheres is equivalent, not asymmetrical as Beeman suggests.