Orthographic neighborhood effects in the right but not in the left cerebral hemisphere

Two lexical decision experiments investigated orthographic neighborhood effects in the hemispheres. In the first experiment, lexical decision was affected by orthographic neighborhood size when stimuli were presented to the right hemisphere (RH) but not to the left hemisphere (LH). In a four-field masked-prime lexical decision task (Experiment 2), a larger shared orthographic neighborhood between prime and target facilitated lexical decision in the RH but not in the LH. The patterns of activation invoked in the two cerebral hemispheres by a written word and its orthographic neighbors may be qualitatively different.     

Brain lateralization of complex movement: Neuropsychological evidence from unilateral stroke

Complex movement (CM) refers to the representation of a goal-oriented action and is classified as either transitive (use of tools) or intransitive (communication gestures). Both types of CM have three specific components: temporal, spatial, and content, which are subdivided into specific error types (SET). Since there is debate regarding the contribution of each brain hemisphere for the types of CM, our objective was to describe the brain lateralization of components and SET of transitive and intransitive CM. We studied 14 patients with a left hemisphere stroke (LH), 12 patients with a right hemisphere stroke (RH), and 16 control subjects. The Florida Apraxia Screening Test-Revised (FAST-R, Rothi et al., 1988) was used for the assessment of CM. Both clinical groups showed a worse performance than the control group on the total FAST-R and transitive movement scores (p < 0.001). Failures in Spatial and Temporal components were found in both clinical groups, but only LH patients showed significantly more Content errors (p < 0.01) than the control group. Also, only the LH group showed a higher number of errors for intransitive movements score (p = 0.017), due to lower scores in the content component, compared to the control group (p = 0.04). Transitive and intransitive CMs differ in their neurocognitive representation; transitive CM shows a bilateral distribution of its components when compared to intransitive CM, which shows a preferential left hemisphere representation. This could result from higher neurocognitive demands for movements that require use of tools, compared with more automatic communication gestures.     

Hemispheric asymmetries in meaning selection: Evidence from the disambiguation of homophonic vs. heterophonic homographs

Research investigating hemispheric asymmetries in meaning selection using homophonic homographs (e.g., bank), suggests that the left hemisphere (LH) quickly selects contextually relevant meanings, whereas the right hemisphere (RH) maintains a broader spectrum of meanings including those that are contextually irrelevant (e.g., Faust & Chiarello, 1998). The present study investigated cerebral asymmetries in maintaining the multiple meanings of two types of Hebrew homographs: homophonic homographs and heterophonic homographs (e.g., tear). Participants read homographs preceded by a biasing, or a non-biasing sentential context, and performed a lexical decision task on targets presented laterally, 1000 ms after the onset of the sentence-final ambiguous prime. Targets were related to either the dominant or the subordinate meaning of the preceding homograph, or unrelated to it. When targets were presented in the LVF/RH, dominant and subordinate meanings, of both types of homographs, were retained only when they were supported by context. In a non-biasing context, only dominant meanings of homophonic homographs were retained. Alternatively, when targets were presented in the RVF/LH, priming effects for homophonic homographs were only evident when meanings were supported by both context and frequency (i.e., when context favored the dominant meaning). In contrast, heterophonic homographs resulted in activation of dominant meanings, in all contexts, and activation of subordinate meanings, only in subordinate-biasing contexts. The results challenge the view that a broader spectrum of meanings is maintained in the right than in the left hemisphere and suggest that hemispheric differences in the time course of meaning selection (or decay) may be modulated by phonology.     

Using morphology when spelling in a shallow orthographic system: The case of Spanish

Deep orthographies usually represent morphology and phonology simultaneously; both resources are necessary for spelling. In shallow orthographies, such as Spanish, phonology would be enough to spell most words. However, morphological knowledge may also take part in spelling. This study examined how Spanish children in 1st (N = 148), 2nd (N = 155) and 3rd grade (N = 155) use morphological information to spell plural nouns and verbs. A word dictation task was designed. The task included high and low frequency plural nouns ending in “s” (morphological “-s” condition) and verbs in the 2nd person ending in “s” (morphological “-s” condition). A lexical condition including words with a final “s” which was not morphologically motivated was used as a control condition (lexical “-s” condition). The results show that, although Spanish spelling is influenced by phonology, morphological information is also used. These results are discussed in relation to current models of word spelling.     

Hemispheric asymmetries in meaning selection: Evidence from the disambiguation of homophonic vs. heterophonic homographs

Research investigating hemispheric asymmetries in meaning selection using homophonic homographs (e.g., bank), suggests that the left hemisphere (LH) quickly selects contextually relevant meanings, whereas the right hemisphere (RH) maintains a broader spectrum of meanings including those that are contextually irrelevant (e.g., Faust & Chiarello, 1998). The present study investigated cerebral asymmetries in maintaining the multiple meanings of two types of Hebrew homographs: homophonic homographs and heterophonic homographs (e.g., tear). Participants read homographs preceded by a biasing, or a non-biasing sentential context, and performed a lexical decision task on targets presented laterally, 1000 ms after the onset of the sentence-final ambiguous prime. Targets were related to either the dominant or the subordinate meaning of the preceding homograph, or unrelated to it. When targets were presented in the LVF/RH, dominant and subordinate meanings, of both types of homographs, were retained only when they were supported by context. In a non-biasing context, only dominant meanings of homophonic homographs were retained. Alternatively, when targets were presented in the RVF/LH, priming effects for homophonic homographs were only evident when meanings were supported by both context and frequency (i.e., when context favored the dominant meaning). In contrast, heterophonic homographs resulted in activation of dominant meanings, in all contexts, and activation of subordinate meanings, only in subordinate-biasing contexts. The results challenge the view that a broader spectrum of meanings is maintained in the right than in the left hemisphere and suggest that hemispheric differences in the time course of meaning selection (or decay) may be modulated by phonology.     

Semantic asymmetries are modulated by phonological asymmetries: Evidence from the disambiguation of homophonic versus heterophonic homographs

The present study investigated cerebral asymmetries in accessing multiple meanings of two types of homographs: homophonic homographs (e.g., bank) and heterophonic homographs (e.g., tear). Participants read homographs preceded by either a biasing or a non-biasing sentential context and performed a lexical decision on lateralized targets presented 150 ms after onset of the sentence-final ambiguous prime. Targets were either related to the dominant or the subordinate meaning of the preceding homograph or were unrelated to it. In the case of homophonic homographs – our results converge with previous findings: both activation and selection processes are faster in the LH than in the RH. Importantly, however, in the case of heterophonic homographs – opposite asymmetries were found. These results suggest that semantic asymmetries are modulated by phonology. They are discussed in the context of a model of functional architecture of reading in the two hemispheres in which orthography, phonology and semantics are fully interconnected in the LH, whereas in the RH, orthography and phonology are not directly connected, such that phonological processes are mediated by semantics.     

Early language development after peri-natal stroke

Early unilateral brain damage has different implications for language development than does similar damage in adults, given the plasticity of the developing brain. The goal of this study was to examine early markers of language and gesture at 12 and 24 months in children who had peri-natal right hemisphere (RH) or left hemisphere (LH) stroke (n = 71), compared with typically developing controls (n = 126). Parents completed the MacArthur-Bates Communicative Development Inventory (CDI): Words & Gestures (12 month data point), or the CDI: Words & Sentences (24 month data point). Statistical analyses were performed on percentile scores using analysis of variance techniques. At 12 months, there were no differences among groups for Words Understood, Phrases Understood or Words Produced. At 24 months, both lesion groups scored significantly lower than controls on Word Production, Irregular Words, and Mean Length of Sentences, but lesion groups did not differ from each other. In a longitudinal subset of participants, expressive vocabulary failed to progress as expected from 12 to 24 months in the stroke group, with no differences based on lesion side. Gesture and word production were dissociated in the left hemisphere subjects. Findings suggest that early language development after peri-natal stroke takes a different course from that of typical language development, perhaps reflecting brain reorganization secondary to plasticity in the developing brain.     

The Modulation of Visual and Task Characteristics of a Writing System on Hemispheric Lateralization in Visual Word Recognition—A Computational Exploration

Through computational modeling, here we examine whether visual and task characteristics of writing systems alone can account for lateralization differences in visual word recognition between different languages without assuming influence from left hemisphere (LH) lateralized language processes. We apply a hemispheric processing model of face recognition to visual word recognition; the model implements a theory of hemispheric asymmetry in perception that posits low spatial frequency biases in the right hemisphere and high spatial frequency (HSF) biases in the LH. We show two factors that can influence lateralization: (a) Visual similarity among words: The more similar the words in the lexicon look visually, the more HSF/LH processing is required to distinguish them, and (b) Requirement to decompose words into graphemes for grapheme‐phoneme mapping: Alphabetic reading (involving grapheme‐phoneme conversion) requires more HSF/LH processing than logographic reading (no grapheme‐phoneme mapping). These factors may explain the difference in lateralization between English and Chinese orthographic processing.     

Effects of classroom organization on letter-word reading in first grade

Teacher organization is a crucial part of classroom functioning; however, its relation to student achievement has not been investigated as extensively as that of instruction. In this study, organization is defined as the amount of time teachers spend explaining the purpose and procedures of learning activities and daily routines. Data from first-grade classrooms (N = 44) observed three times during the school year (fall, winter, and spring) are analyzed, along with students' (N = 108) literacy skills at fall and spring. Hierarchical Linear Modeling reveals that, controlling for students' fall word reading and vocabulary skills, as well as amount of language arts instruction they receive, both amount and change in amount over time in classroom organization significantly predicts spring word reading skills. Specifically, children in classrooms observed in higher amounts of classroom time in organization at the beginning of the school year, followed by sharp decreases over the school year, demonstrated stronger letter and word reading skills by spring, and this was a main effect (p < .05). Practical and research implications are discussed.     

Right Hemisphere Semantic Performance and Competence in a Case of Partial Interhemispheric Disconnection

Various forms of right hemisphere (RH)-spontaneous or provoked-performance changes were observed in a partial split-brain patient. Variations in hemispheric activation levels and their interhemispheric balance were retained as the most plausible mechanisms for accounting for these facts. This article presents our attempts to obtain higher RH lexical semantic performance than that observed in a preliminary study where RH performance was at chance level: two forms of the dual-task paradigm were used in order to improve the expression of an assumed RH potential for lexical semantics. Experiment 1 was aimed at activating the RH with a visuo-spatial task as a prior activity before each semantic decision trial. Experiment 2 was intended to overload LH processing systems with a concurrent verbal memory task and induce RH release from LH inhibition. As expected, better RH lexical semantic performance was obtained in these two conditions. Using pictures as stimuli, the aim of Experiment 3 was to observe the spontaneous temporal course of RH implementation in a semantic decision task devoid of written words. These results are discussed along with the issues of performance/competence and the dynamics of neurocognitive function.     

Sulcal morphology and volume of Broca's area linked to handedness and sex

We investigated the effect of handedness and sex on: (i) sulcal contours defining PO and PTR and (ii) volume estimates of PO and PTR subfields in 40 left- and 42 right-handers. Results show an effect of handedness on discontinuity of the inferior frontal sulcus (IFS: P < 0.01). Discontinuity of IFS was observed in: 43% left- and 62% right hemispheres in right-handers and in 65% left- and 48% right-hemispheres in left-handers. PO volume asymmetry was rightward in left-handed males (P = 0.007) and females (P = 0.02), showed a leftward trend in right-handed males (P = 0.06), and was non-asymmetrical in right-handed females (P = 0.96, i.e. left- and right-hemisphere PO volumes did not differ significantly). PO volume asymmetry in males differed significantly between handedness groups (P = 0.001). Findings indicate a high degree of variability in the sulcal contours of PO and PTR and volume asymmetry of PO: the factors sex and handedness can explain some of this variability.     

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.     

汉语名词、动词和动名兼类词语义加工的偏侧化现象——来自ERP的研究

将ERP技术和半视野技术相结合,采用词汇判断任务,对汉语名词、动词和动名兼类词在左脑和右脑中的加工机制进行了考察。实验结果显示,名词和动词的N400仅在左视野/右脑存在差异,名词和动词的N400在左视野/右脑和右视野/左脑中都比偏（动）和偏（名）更负。不同词类的LPC在右视野/左脑中没有显著差异;偏（名）和偏（动）的LPC在左视野/右脑中比名词和动词更正。实验结果表明,在没有语境条件下,汉语名词和动词的差异主要在具体性上,动名兼类词体现出不同于名词、动词的加工机制。     

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.     

Effect of neurofeedback on hemispheric word recognition

We applied SMR/θ neurofeedback (NF) training at central sites of 20 Israeli children aged 10–12 years, half boys and half girls. Half of the subjects received C3 training and the other half C4 training, consisting of 20 half-hour sessions. We assessed the effects of training on lateralized lexical decision in Hebrew. The lateralized lexical decision test reveals an independent contribution of each hemisphere to word recognition (Barnea, Mooshagian, & Zaidel, 2003). Training increased accuracy and sensitivity. It increased left hemisphere (LH) specialization under some conditions but it did not affect interhemispheric transfer. Training did affect psycholinguistic processing in the two hemispheres, differentially at C3 and C4. Training also increased hemispheric independence. There were surprising sex differences in the effects of training. In boys, C4 training improved LH accuracy, whereas in girls C3 training improved LH accuracy. The results suggest that the lateralized NF protocol activates asymmetric hemispheric control circuits which modify distant hemispheric networks and are organized differently in boys and girls.     

Facilitative orthographic neighborhood effects: the SERIOL model account

A large orthographic neighborhood (N) facilitates lexical decision for central and left visual field/right hemisphere (LVF/RH) presentation, but not for right visual field/left hemisphere (RVF/LH) presentation. Based on the SERIOL model of letter-position encoding, this asymmetric N effect is explained by differential activation patterns at the orthographic level. This analysis implies that it should be possible to negate the LVF/RH N effect and create an RVF/LH N effect by manipulating contrast levels in specific ways. In Experiment 1, these predictions were confirmed. In Experiment 2, we eliminated the N effect for both LVF/RH and central presentation. These results indicate that the letter level is the primary locus of the N effect under lexical decision, and that the hemispheric specificity of the N effect does not reflect differential processing at the lexical level.     

The role of the right hemisphere in speech act comprehension

In this research the role of the RH in the comprehension of speech acts (or illocutionary force) was examined. Two split-screen experiments were conducted in which participants made lexical decisions for lateralized targets after reading a brief conversation remark. On one-half of the trials the target word named the speech act performed with the preceding conversation remark; on the remaining trials the target did not name the speech act that the remark performed. In both experiments, lexical decisions were facilitated for targets representing the speech act performed with the prior utterance, but only when the target was presented to the left visual field (and hence initially processed by the RH) and not when presented to the right visual field. This effect occurred at both short (Experiment 1: 250 ms) and long (Experiment 2: 1000 ms) delays. The results demonstrate the critical role played by the RH in conversation processing.     

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.     

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.