Hemispheric specialization for reading

Behavioral laterality tasks with linguistic stimuli were used to assess the differential processing efficiencies of the cerebral hemispheres in right- and left-handed adults. Findings from a lateralized lexical decision task with concrete nouns supported Zaidel's (1983) "direct access" model of hemispheric functioning. A dual task consisting of oral and silent reading indicated that the right hand was significantly more disrupted than the left during unimanual finger tapping; however, some bilateral interference was observed. Taken together the findings suggest that although the left hemisphere was relatively more efficient, the right hemisphere was dynamically involved in the reading process.     

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。     

Probing hemispheric processes in an on-line reading task

Coney (1998) used a priming procedure to obtain evidence that the left and right hemispheres contributed equally to lexical processing of concrete nouns in a continuous reading task. In that study, however, there was no direct validation of the involvement of the right hemisphere in the task, and the possibility of left hemisphere processing of left visual field target stimuli could not be ruled out. The present study was designed to obtain validating evidence by using abstract and concrete noun primes in a similar reading task on the assumption that if the right hemisphere was contributing to the task there would be demonstrable differences between the visual fields in processing targets primed by abstract nouns. The results supported this expectation. While concrete targets projected to each visual field were primed by concrete nouns, there was significant priming by abstract nouns only in respect of targets presented to the right visual field. It is argued that this finding supports the involvement of the right hemisphere in continuous reading and further delimits the scope of its contribution to this process. Somewhat unexpectedly, the results also revealed that absolute response times were faster to left visual field targets when they were preceded by abstract nouns, even when there was no semantic relationship between the two words. It was suggested that this effect derives from the inability of the right hemisphere to process abstract nouns in that the failure of abstract nouns to engage lexical processing mechanisms leaves the right hemisphere relatively unencumbered when required to process a subsequent target.     

Responses on a lateralized lexical decision task relate to both reading times and comprehension

Research over the last few years has shown that the dominance of the left hemisphere in language processing is less complete than previously thought [Beeman, M. (1993). Semantic processing in the right hemisphere may contribute to drawing inferences from discourse. Brain and Language, 44, 80–120; Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827–835; Weems, S. A., & Zaidel, E. (2004). The relationship between reading ability and lateralized lexical decision. Brain and Cognition, 55(3), 507–515]. Engaging the right brain in language processing is required for processing speaker/writer intention, particularly in those subtle interpretive processes that help in deciphering humor, irony, and emotional inference. In two experiments employing a divided field or lateralized lexical decision task (LLDT), accuracy and reaction times (RTs) were related to reading times and comprehension on sentence reading. Differences seen in RTs and error rates by visual fields were found to relate to performance. Smaller differences in performance between fields tended to be related to better performance on the LLDT in both experiments and, in Experiment 1, to reading measures. Readers who can exploit both hemispheres for language processing equally appear to be at an advantage in lexical access and possibly also in reading performance.     

Responses on a lateralized lexical decision task relate to both reading times and comprehension

Research over the last few years has shown that the dominance of the left hemisphere in language processing is less complete than previously thought [Beeman, M. (1993). Semantic processing in the right hemisphere may contribute to drawing inferences from discourse. Brain and Language, 44, 80–120; Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827–835; Weems, S. A., & Zaidel, E. (2004). The relationship between reading ability and lateralized lexical decision. Brain and Cognition, 55(3), 507–515]. Engaging the right brain in language processing is required for processing speaker/writer intention, particularly in those subtle interpretive processes that help in deciphering humor, irony, and emotional inference. In two experiments employing a divided field or lateralized lexical decision task (LLDT), accuracy and reaction times (RTs) were related to reading times and comprehension on sentence reading. Differences seen in RTs and error rates by visual fields were found to relate to performance. Smaller differences in performance between fields tended to be related to better performance on the LLDT in both experiments and, in Experiment 1, to reading measures. Readers who can exploit both hemispheres for language processing equally appear to be at an advantage in lexical access and possibly also in reading performance.     

Hemispheric processing of lexical information in Chinese character recognition and its relationship to reading performance

Hemispheric predominance has been well documented in the visual perception of alphabetic words. However, the hemispheric processing of lexical information in Chinese character recognition and its relationship to reading performance are far from clear. In the divided visual field paradigm, participants were required to judge the orthography, phonology, or semantics of Chinese characters, which were presented randomly in the left or right visual field. The results showed a right visual field/left hemispheric superiority in the phonological judgment task, but no hemispheric advantage in the orthographic or semantic task was found. In addition, reaction times in the right visual field for phonological and semantic tasks were significantly correlated with the reading test score. These results suggest that both hemispheres involved in the orthographic and semantic processing of Chinese characters, and that the left lateralized phonological processing is important for Chinese fluent reading.     

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.     

Plasticity for recovery, plasticity for development: cognitive outcome in twins discordant for mid-childhood ischemic stroke.

Cognitive and language profiles in a set of likely monozygotic 13-year-old twins raised together and discordant for an extensive left hemisphere stroke are described 6 years post-stroke. Recovery differed across four skill profiles, created based on a model of plasticity. Full recovery of lost skills and full or partial development of new skills typically involved either semantic memory or right hemisphere lateralized functions such as visual perception skills. Limited development of new skills and full or partial recovery of lost skills took place in either active verbal memory or oral language skills that are left hemisphere lateralized. Language skills concerned with real-time lexical retrieval, or the use and understanding of morphology and grammar, phonological processing skills, and auditory working memory were least likely to recover and continue to develop.     

The relationship between reading ability and lateralized lexical decision

Although lexical decision remains one of the most extensively studied cognitive tasks, very little is known about its relationship to broader linguistic performance such as reading ability. In a correlational study, several aspects of lateralized lexical decision performance were related to vocabulary and reading comprehension measures, as assessed using the Nelson-Denny Reading Test. This lateralized lexical decision task has been previously shown to demonstrate (1) independent contributions from both hemispheres, as well as (2) interhemispheric interactions during word recognition. Lexical decision performance showed strong relationships with both reading measures. Specifically, vocabulary performance correlated significantly with left visual field (LVF) word accuracy and LVF non-word latency, both measures of right hemisphere performance. There were also significant, though somewhat weaker, correlations between reading comprehension and RVF non-word latency. Lexicality priming, a measure of interhemispheric communication during lexical decision, was also correlated with reading comprehension. These results suggest that hemispheric interaction during word recognition is common, and that lexical processing contribution from the right hemisphere, something commonly taken as minor and inconsequential, can lead to significant performance benefits and to individual differences in reading.     

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.     

Are creativity and schizotypy products of a right hemisphere bias?

Prior research has shown associations between higher creativity (e.g., semantic association, verbal fluency), higher schizotypy (e.g., magical ideation), and relatively stronger right hemisphere laterality measures--when each of the three pairings has been studied individually. Our prior study related creativity and schizotypy to signal detection theory response criterion aspects of laterality. The present study attempted to integrate findings regarding these three constructs and to replicate the signal detection theory laterality results by providing measures of all three constructs in a within subjects design. Participants were 60 undergraduates who completed a test battery including two measures of creativity, three measures of schizotypy, a lateralized lexical decision task, and a dichotic listening task. Results are consistent with individual differences in creativity and schizotypy being partly related to a response criterion favoring right hemisphere, possibly nonconscious, processing. Dichotic listening results revealed a strong association of better right hemisphere (left ear) localization ability and creativity.     

音高模式加工的大脑偏侧化研究

作为一种超音段成分,音高在言语的理解和产生过程中承担着重要作用,这些作用主要包括:区别不同声调的词汇意义,区别陈述、疑问等不同的语调,标志话语的情绪色彩等。音段、语义和句法信息的加工具有左脑优势,但音高模式加工的单侧优势及其机制还存在很多争论,本文从音高模式加工的两个主要理论———功能假设和声音信号假设出发,对相关研究加以评述。     

The brain's hemispheres and controlled search of the lexicon: evidence from fixated words and pseudowords

Difference between the brain's hemispheres in efficiency of intentional search of the mental lexicon with phonological, orthographic, and semantic strategies was investigated. Letter strings for lexical decision were presented at fixation, with a lateralized distractor to the LVF or RVF. Word results revealed that both hemispheres were capable of using each of the three strategies, but the right hemisphere had better baseline processing of orthography and was better at processing semantics. Pseudoword results supported the right hemisphere advantage for orthography and showed a left hemisphere advantage for phonology and assessment of possible semantic relationships. Taken together, the data support the idea that the right hemisphere uses orthography to make efficient decisions about novelty of an item, while the left engages in grapheme-to-phoneme conversion to test hypotheses about unfamiliar items. The convergence of data with previous research reveals that the procedure, as well as analyses of pseudowords, inform laterality research.     

Cognitive consequences of asymmetrical visual distraction

The authors explored whether manipulating the location of distraction in the participants' visual field influences the degree of competition between visual and other cognitive processes. If a cognitive task is lateralized to a particular hemisphere, visual distraction directed toward that same hemisphere should impair performance on that task more than should visual distraction directed toward the other hemisphere. Consistent with this hypothesis, the authors found in Experiments 1 and 2 that participants better recalled words of high imageability in a verbal memory task when the examiner was in the participant's left visual field (right hemisphere) than when the examiner was in the participant's right visual field (left hemisphere). In Experiment 3, the authors found that this effect reversed for performance on a right-hemisphere spatial task.     

Reading disability and hemispheric interaction on a lexical decision task

The assumptions tested were that the relative contribution of each hemisphere to reading alters with experience and that experience increases suppression of the simultaneous use of identical strategies by the non-dominant hemisphere. Males that were reading disabled and phonologically impaired, reading disabled and phonologically normal, or with no reading disability were presented familiar words, orthographically correct pseudowords, and orthographically incorrect non-words for lexical decision. Accuracy and response times in all groups showed a shift from no asymmetry in processing non-words to a stable left hemisphere advantage and clear suppression of the right hemisphere in processing words. In the pseudoword condition, accuracy scores were higher when both hemispheres were free to engage, especially in those with a reading disability and responses slowed in the phonologically impaired group but not the phonologically normal groups when the right hemisphere was disengaged. As familiar words typically invoke lexical processing by both hemispheres while pseudowords invoke lexical processing by the right and non-lexical processing by the left hemisphere, and as non-lexical processing is weak in the phonologically impaired, the results support the assumptions that were tested.     

Visual field differences in verbal tasks: Effects of task familiarity and sex of subject

Four experiments using normal subjects investigated differences in magnitude of the right visual field (RVF) superiority as a function of word material (frequency and concreteness/imageability status), nonword letter strings (some of which were homophonic with nonpresented real words), and type of task (overt naming or lexical decision with discriminatory manual responses) as well as sex of the subject and the subject's familiarity with the material. Both latency and error measures showed that RVF superiority was more consistent when overt naming was required and with male subjects. For female subjects engaged in lexical decisions, a left visual field (LVF) superiority was often apparent, especially in the first half of an experimental sequence; when actually naming the items aloud, they showed field asymmetries similar to males. Except from an analysis of errors, there was little evidence to support differential right hemisphere mediation of high frequency concrete/imageable materials. It is suggested that in females, right hemisphere space normally reserved for visuospatial processing may have been invaded by secondary speech mechanisms. These mechanisms appear to operate at an essentially lexical level and may act in a supportive or auxiliary capacity for difficult or unfamiliar material; they seem to be equally concerned with both phonological and graphological processing and may account for the well-known female superiority in verbal tasks and inferiority in visuospatial tasks. Other findings are discussed such as the degree of consistency of the field differences, both for the same subjects and for the same stimulus materials under different task requirements and experimental conditions.     

The contribution of the right cerebral hemisphere to the recovery from aphasia: a single longitudinal case study

We examined the role of the right cerebral hemisphere in the recovery from aphasia of HJ, a 50-year-old right-handed and unilingual man who suffered from severe aphasia caused by an extensive left hemisphere (LH) lesion. He was followed-up over 10 months at 4-month intervals, with a lateralized lexical decision task (LDT), an attentional task, and a language battery. Testing started when HJ was 2 months poststroke. In the LDT, words were presented to central vision or lateralized to the left or right visual hemifield. At each test period, we examined the effect of the degree of imageability (high vs. low), and the grammatical class (noun vs. verb) of the targets on HJ's response times and error rates, with left visual field, right visual field, and central vision presentations. The results of the experiment showed that the pattern obtained with the LDT could not be accounted for by fluctuations in attention. There was an interaction of grammatical class with degree of imageability with left visual field displays only. The right hemisphere (RH) was faster with high-imageability words than with low-imageability words, regardless of their grammatical class. There was also an overall RH advantage on response times at 2 and 6 months after onset. This RH predominance coincided with a major recovery of language comprehension and the observation of semantic paralexias, while no major change in language expression was observed at that point. Ten months after onset, the pattern of lateralization changed, and response times for the LDT with either presentation site were equivalent. This LH improvement coincided with some recovery of language expression at the single-word level. The results of this study suggest that, in cases of severe aphasia caused by extensive LH lesions, the RH may play an important role in the recovery process. Furthermore, these results show that the contribution of the two cerebral hemispheres to recovery may vary overtime and affect specific aspects of language.     

Multitask investigation of individual differences in hemispheric asymmetry

Right-handed subjects (N = 120) participated in four different laterality tasks designed to measure aspects of cerebral hemisphere asymmetry: identification of dichotically presented consonant-vowel syllables (CVs), examination of the effects of concurrent repetition of CVs and concurrent anagram solution on finger-tapping by the right and left hands, lateralized identification of CVs presented tachistoscopically to the left and right visual fields, and left/right biases on a free-vision face task involving judgments of emotion. Ear differences in the dichotic listening task were related to the pattern of lateralized interference in the dual-task finger-tapping paradigm. There were no other significant relations between pairs of tasks, but when the present results are considered in the light of other recent experiments, there appears to be a relation between lateral bias on the free-vision face task and visual field differences in tachistoscopic identification. The pattern of results has implications for hypothesized individual differences among right-handers in cerebral dominance for verbal processes, input pathway dominance, and asymmetric arousal of the two cerebral hemispheres.     

Effects of visual complexity and sublexical information in the occipitotemporal cortex in the reading of Chinese phonograms: a single-trial analysis with MEG

We employ a linear mixed-effects model to estimate the effects of visual form and the linguistic properties of Chinese characters on M100 and M170 MEG responses from single-trial data of Chinese and English speakers in a Chinese lexical decision task. Cortically constrained minimum-norm estimation is used to compute the activation of M100 and M170 responses in functionally defined regions of interest. Both Chinese and English participants’ M100 responses tend to increase in response to characters with a high numbers of strokes. English participants’ M170 responses show a posterior distribution and only reflect the effect of the visual complexity of characters. On the other hand, the Chinese participants’ left hemisphere M170 is increased when reading characters with high number of strokes, and their right hemisphere M170 is increased when reading characters with small combinability of semantic radicals. Our results suggest that expertise with words and the decomposition of word forms underlies processing in the left and right occipitotemporal regions in the reading of Chinese characters by Chinese speakers.     

Hemispheric processing of inferences: The effects of textual constraint and working memory capacity

In this study, we investigated hemispheric differences in the generation of bridging and predictive inferences. Participants read texts that provided either strong or weak causal constraints for a particular bridging (Experiment 1) or predictive (Experiment 2) inference and performed a lexical decision task to inference-related targets presented to the left or the right hemisphere. Facilitation for strongly constrained bridging and predictive inferences was found in both hemispheres. In contrast, facilitation for weakly constrained inferences was stronger in the right than in the left hemisphere for both bridging and predictive inferences, although for the latter there was some facilitation in the left hemisphere as well. We also considered whether these effects differ as a function of the working memory capacity of the reader. High working memory capacity readers showed greater facilitation for strongly constrained inferences than for weakly constrained inferences in both hemispheres, whereas low working memory capacity readers showed this same pattern in the left hemisphere but showed equal facilitation for strongly and weakly constrained inferences in the right hemisphere. These results suggest that hemispheric processing, textual constraint, and working memory capacity interact to affect how readers generate causal inferences.