Developmental and skill effects on the neural correlates of semantic processing to visually presented words

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments to visual words in a group of 9- to 15-year-old children. Subjects were asked to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral inferior frontal gyri (Brodmann area [BA] 47, 45) and left middle temporal gyrus (BA 21). Words with strong semantic association elicited significantly greater activation in bilateral inferior parietal lobules (BA 40), suggesting stronger integration of highly related semantic features. By contrast, words with weak semantic association elicited greater activation in left inferior frontal gyrus (BA 45) and middle temporal gyrus (BA 21), suggesting more difficult feature search and more extensive access to semantic representations. We also examined whether age and skill explained unique variance in the patterns of activation. Increasing age was correlated with greater activation in left middle temporal gyrus (BA 21) and inferior parietal lobule (BA 40), suggesting that older children have more elaborated semantic representations and more complete semantic integration processes, respectively. Decreasing age was correlated with activation in right superior temporal gyrus (BA 22) and decreasing accuracy was correlated with activation in right middle temporal gyrus (BA 21), suggesting the engagement of ancillary systems in the right hemisphere for younger and lower-skill children.     

Brain activation for lexical decision and reading aloud: two sides of the same coin?

This functional magnetic resonance imaging study compared the neuronal implementation of word and pseudoword processing during two commonly used word recognition tasks: lexical decision and reading aloud. In the lexical decision task, participants made a finger-press response to indicate whether a visually presented letter string is a word or a pseudoword (e.g., "paple"). In the reading-aloud task, participants read aloud visually presented words and pseudowords. The same sets of words and pseudowords were used for both tasks. This enabled us to look for the effects of task (lexical decision vs. reading aloud), lexicality (words vs. nonwords), and the interaction of lexicality with task. We found very similar patterns of activation for lexical decision and reading aloud in areas associated with word recognition and lexical retrieval (e.g., left fusiform gyrus, posterior temporal cortex, pars opercularis, and bilateral insulae), but task differences were observed bilaterally in sensorimotor areas. Lexical decision increased activation in areas associated with decision making and finger tapping (bilateral postcentral gyri, supplementary motor area, and right cerebellum), whereas reading aloud increased activation in areas associated with articulation and hearing the sound of the spoken response (bilateral precentral gyri, superior temporal gyri, and posterior cerebellum). The effect of lexicality (pseudoword vs. words) was also remarkably consistent across tasks. Nevertheless, increased activation for pseudowords relative to words was greater in the left precentral cortex for reading than lexical decision, and greater in the right inferior frontal cortex for lexical decision than reading. We attribute these effects to differences in the demands on speech production and decision-making processes, respectively.     

An fMRI study comparing brain activation between word generation and electrical stimulation of language-implicated acupoints

We compared the brain activation on functional magnetic resonance imaging (MRI) during word generation with the activation during electrical stimulation of two language-implicated acupoints in 17 healthy, Mandarin-speaking, Chinese male volunteers (age 19-26 years). All subjects were strongly right handed according to a handedness inventory. Using a standard functional MRI procedure and a word-generation paradigm, significant activation was seen in the left and right inferior frontal gyri (BA 44, 45) as well as the left superior temporal gyrus (BA 22, 42). Stronger activation with a larger volume was seen in the left hemisphere. Electrical stimulation of either one of the two language-implicated acupoints, SJ 8 (11 subjects) and Du 15 (6 subjects), without the word-generation paradigm in the same cohort, produced significant activation in the right inferior frontal gyrus (BA 44, 46) and in the left and right superior temporal gyri (BA 22, 42), respectively. Nevertheless, no activation was seen in the left inferior frontal gyrus. In addition, electrical stimulation of the adjacent non-acupoints did not produce any significant brain activation. Although our results support the notion of acupoint-brain activation, applying acupuncture at SJ 8 or Du 15 does not activate the typical language areas in the left inferior frontal cortex.     

Cortical circuits for silent speechreading in deaf and hearing people

This fMRI study explored the functional neural organisation of seen speech in congenitally deaf native signers and hearing non-signers. Both groups showed extensive activation in perisylvian regions for speechreading words compared to viewing the model at rest. In contrast to earlier findings, activation in left middle and posterior portions of superior temporal cortex, including regions within the lateral sulcus and the superior and middle temporal gyri, was greater for deaf than hearing participants. This activation pattern survived covarying for speechreading skill, which was better in deaf than hearing participants. Furthermore, correlational analysis showed that regions of activation related to speechreading skill varied with the hearing status of the observers. Deaf participants showed a positive correlation between speechreading skill and activation in the middle/posterior superior temporal cortex. In hearing participants, however, more posterior and inferior temporal activation (including fusiform and lingual gyri) was positively correlated with speechreading skill. Together, these findings indicate that activation in the left superior temporal regions for silent speechreading can be modulated by both hearing status and speechreading skill.     

Abnormal functional activation during a simple word repetition task: A PET study of adult dyslexics

Eight dyslexic subjects, impaired on a range of tasks requiring phonological processing, were matched for age and general ability with six control subjects. Participants were scanned using positron emission tomography (PET) during three conditions: repeating real words, repeating pseudowords, and rest. In both groups, speech repetition relative to rest elicited widespread bilateral activation in areas associated with auditory processing of speech; there were no significant differences between words and pseudowords. However, irrespective of word type, the dyslexic group showed less activation than the control group in the right superior temporal and right post-central gyri and also in the left cerebellum. Notably, the right anterior superior temporal cortex (Brodmann's area 22 [BA 22]) was less activated in each of the eight dyslexic subjects, compared to each of the six control subjects. This deficit appears to be specific to auditory repetition as it was not detected in a previous study of reading which used the same sets of stimuli (Brunswick, N., McCrory, E., Price, C., Frith, C.D., & Frith, U. [1999]. Explicit and implicit processing of words and pseudowords by adult developmental dyslexics: A search for Wernicke's Wortschatz? Brain, 122, 1901-1917). This implies that the observed neural manifestation of developmental dyslexia is task-specific (i.e., functional rather than structural). Other studies of normal subjects indicate that attending to the phonetic structure of speech leads to a decrease in right-hemisphere processing. Lower right hemisphere activation in the dyslexic group may therefore indicate less processing of non-phonetic aspects of speech, allowing greater salience to be accorded to phonological aspects of attended speech.     

The signer and the sign: Cortical correlates of person identity and language processing from point-light displays

In this study, the first to explore the cortical correlates of signed language (SL) processing under point-light display conditions, the observer identified either a signer or a lexical sign from a display in which different signers were seen producing a number of different individual signs. Many of the regions activated by point-light under these conditions replicated those previously reported for full-image displays, including regions within the inferior temporal cortex that are specialised for face and body-part identification, although such body parts were invisible in the display. Right frontal regions were also recruited – a pattern not usually seen in full-image SL processing. This activation may reflect the recruitment of information about person identity from the reduced display. A direct comparison of identify-signer and identify-sign conditions showed these tasks relied to a different extent on the posterior inferior regions. Signer identification elicited greater activation than sign identification in (bilateral) inferior temporal gyri (BA 37/19), fusiform gyri (BA 37), middle and posterior portions of the middle temporal gyri (BAs 37 and 19), and superior temporal gyri (BA 22 and 42). Right inferior frontal cortex was a further focus of differential activation (signer > sign).These findings suggest that the neural systems supporting point-light displays for the processing of SL rely on a cortical network including areas of the inferior temporal cortex specialized for face and body identification. While this might be predicted from other studies of whole body point-light actions (Vaina, Solomon, Chowdhury, Sinha, & Belliveau, 2001) it is not predicted from the perspective of spoken language processing, where voice characteristics and speech content recruit distinct cortical regions (Stevens, 2004) in addition to a common network. In this respect, our findings contrast with studies of voice/speech recognition (Von Kriegstein, Kleinschmidt, Sterzer, & Giraud, 2005). Inferior temporal regions associated with the visual recognition of a person appear to be required during SL processing, for both carrier and content information.     

Evidence for cortical encoding specificity in episodic memory: memory-induced re-activation of picture processing areas

Functional magnetic resonance imaging (fMRI) was used to examine whether neural pathways used to encode pictures into memory were re-activated during retrieval of those memories. At encoding, subjects semantically classified common objects presented as pictures or words. At retrieval, subjects performed yes/no recognition memory judgments on words that had been encoded as pictures or as words. The retrieval test probed memory for the encoded item, but not memory for the modality of the encoded item (picture/word). Results revealed that a subset of the brain regions involved specifically in encoding of pictures were also engaged during recognition memory for the encoded pictures. Specifically, encoding of pictures relative to words engaged bilateral extrastriate visual cortex, namely fusiform, lingual, middle occipital, and inferior temporal gyri (Broadman area (BA) 18/19/37). Recognition memory judgments about words that were encoded as pictures relative to those that were encoded as words activated fusiform and inferior temporal gyri primarily in the left hemisphere. Thus, cortical areas originally involved in perception of a visual experience become part of the long-term memory trace for that experience. These findings suggest a neural basis for encoding specificity and transfer appropriate processing in human memory.     

Inner ear hearing loss modulates ipsilateral temporal lobe activation by monaural speech stimuli

We examined cortical activation by speech in patients with moderate inner ear hearing loss using PET to investigate the response of the language network to insufficient speech input. We made two word lists, well-perceived words and poorly-perceived words, and measured rCBF during monaural presentation of these words. Well-perceived words activated bilateral temporal lobes, bilateral inferior frontal gyri (IFG) and left angular gyrus (AG) regardless of the ear stimulated, Poorly-perceived words activated contralateral temporal lobe and bilateral IFG, while little or no activation was observed in the ipsilateral temporal lobe and left AG. Insufficient activation of the temporal lobe ipsilateral to the ear stimulated might correlated with less accurate word comprehension in patients with inner ear hearing loss.     

Effect of retrieval effort and switching demand on fMRI activation during semantic word generation in schizophrenia

Verbal fluency deficits in schizophrenia are difficult to interpret because the tasks are multi-factorial and groups differ in total words generated. We manipulated retrieval and switching demands by requiring alternation between over-learned sequences in which retrieval is relatively automatic (OS) and semantic categories requiring increased retrieval effort (SC). Controlled processing was also manipulated by including switching and non-switching conditions, and formal thought disorder (FTD) was assessed with the communication disorders index (CDI). The OS/SC semantic fluency paradigm was administered during fMRI to 13 patients with schizophrenia and 14 matched controls. Images were acquired on a 3 Tesla Siemens scanner using compressed image acquisition to allow for cued overt word production. Subjects alternated between OS, SC, OS-switch, SC-switch, and baseline blocks. Images were pre-processed in SPM-2, and a two-stage random effects analysis tested within and between group contrasts. There were no group performance differences. fMRI analysis did not reveal any group differences during the OS non-switching condition. Both groups produced expected activation in bilateral prefrontal and inferior parietal regions. However, during the SC condition patients had greater activation than controls in left prefrontal, right anterior cingulate, right superior temporal, bilateral thalamus, and left parietal regions. There was also evidence of patient over-activation in prefrontal, superior temporal, superior parietal, and visual association areas when a switching component was added. FTD was negatively correlated with BOLD response in the right anterior cingulate, cuneus and superior frontal gyrus during increased retrieval demand, and positively correlated with fMRI activation in the left lingual gyrus, right fusiform gyrus and left superior parietal lobule during increased switching demand. These results indicate that patients are able to successfully perform effortful semantic fluency tasks during non-speeded conditions. When retrieval is relatively automatic there does not appear to be an effect of schizophrenia on fMRI response. However, when retrieval and controlled processing demands increase, patients have greater activation than controls despite unimpaired task performance. This inefficient BOLD response may explain why patients are slower and less accurate on standard self-paced fluency tasks.     

Activation of right fronto-temporal cortex characterizes the 'living' category in semantic processing.

It is a vital ability for humans to distinguish between living and non-living objects. Whether the semantic features of these two classes of objects are represented in distinct brain areas, is unknown. In our study, words belonging to the categories 'living' and 'non-living' were presented visually to twelve right-handed volunteers, while brain activation was measured with event-related fMRI. Subjects had to judge whether the item belonged to one of these categories. Common areas of activation (P<0.05, corrected) during processing of both categories include the inferior occipital gyri bilaterally (BA 17/18), left inferior frontal gyrus (BA 44/45) and left inferior parietal lobe (BA 40). During processing of 'living' minus 'non-living' items, signal changes (P<0.05, corrected) were present in the the right inferior frontal (BA 47), middle temporal (BA 21) and fusiform gyrus (BA 19). Our results are in line with findings from patients with a deficit in semantic processing of living things, who specifically suffer from right hemispheric lesions.     

Learning by doing? The effect of gestures on implicit retrieval of newly acquired words

Meaningful gestures enhance speech comprehensibility. However, their role during novel-word acquisition remains elusive. Here we investigate how meaningful versus meaningless gestures impact on novel-word learning and contrast these conditions to a purely verbal training. After training, neuronal processing of the novel words was assessed by blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD-fMRI), disclosing that networks affording retrieval differ depending on the training condition. Over 3 days participants learned pseudowords for common objects (e.g., /klira/ -cap). For training they repeated the novel word while performing (i) an iconic, (ii) a grooming or (iii) no gesture. For the two conditions involving gestures, these were either actively repeated or passively observed during training. Behaviorally no substantial differences between the five different training conditions were found while fMRI disclosed differential networks affording implicit retrieval of the learned pseudowords depending on the training procedure. Most notably training with actively performed iconic gestures yielded larger activation in a semantic network comprising left inferior frontal (BA47) and inferior temporal gyri. Additionally hippocampal activation was stronger for all trained compared to unknown pseudowords of identical structure. The behavioral results challenge the generality of an ‘enactment-effect’ for single word learning. Imaging results, however, suggest that actively performed meaningful gestures lead to a deeper semantic encoding of novel words. The findings are discussed regarding their implications for theoretical accounts and for empirical approaches of gesture-based strategies in language (re)learning.     

Speech planning and execution in children who stutter: Preliminary findings from a fNIRS investigation

Few studies have investigated the neural mechanisms underlying speech production in children who stutter (CWS), despite the critical importance of understanding these mechanisms closer to the time of stuttering onset. The relative contributions of speech planning and execution in CWS therefore are also unknown. Using functional near-infrared spectroscopy, the current study investigated neural mechanisms of planning and execution in a small sample of 9–12 year-old CWS and controls (N = 12) by implementing two tasks that manipulated speech planning and execution loads. Planning was associated with atypical activation in bilateral inferior frontal gyrus and right supramarginal gyrus. Execution was associated with atypical activation in bilateral precentral gyrus and inferior frontal gyrus, as well as right supramarginal gyrus and superior temporal gyrus. The CWS exhibited some activation patterns that were similar to the adults who stutter (AWS) as reported in our previous study: atypical planning in frontal areas including left inferior frontal gyrus and atypical execution in fronto-temporo-parietal regions including left precentral gyrus, and right inferior frontal, superior temporal, and supramarginal gyri. However, differences also emerged. Whereas CWS and AWS both appear to exhibit atypical activation in right inferior and supramarginal gyri during execution, only CWS appear to exhibit this same pattern during planning. In addition, the CWS appear to exhibit atypical activation in left inferior frontal and right precentral gyri related to execution, whereas AWS do not. These preliminary results are discussed in the context of possible impairments in sensorimotor integration and inhibitory control for CWS.     

Reading fluent speech from talking faces: typical brain networks and individual differences

Listeners are able to extract important linguistic information by viewing the talker's face-a process known as 'speechreading.' Previous studies of speechreading present small closed sets of simple words and their results indicate that visual speech processing engages a wide network of brain regions in the temporal, frontal, and parietal lobes that are likely to underlie multiple stages of the receptive language system. The present study further explored this network in a large group of subjects by presenting naturally spoken sentences which tap the richer complexities of visual speech processing. Four different baselines (blank screen, static face, nonlinguistic facial gurning, and auditory speech) enabled us to determine the hierarchy of neural processing involved in speechreading and to test the claim that visual input reliably accesses sound-based representations in the auditory cortex. In contrast to passively viewing a blank screen, the static-face condition evoked activation bilaterally across the border of the fusiform gyrus and cerebellum, and in the medial superior frontal gyrus and left precentral gyrus (p < .05, whole brain corrected). With the static face as baseline, the gurning face evoked bilateral activation in the motion-sensitive region of the occipital cortex, whereas visual speech additionally engaged the middle temporal gyrus, inferior and middle frontal gyri, and the inferior parietal lobe, particularly in the left hemisphere. These latter regions are implicated in lexical stages of spoken language processing. Although auditory speech generated extensive bilateral activation across both superior and middle temporal gyri, the group-averaged pattern of speechreading activation failed to include any auditory regions along the superior temporal gyrus, suggesting that f luent visual speech does not always involve sound-based coding of the visual input. An important finding from the individual subject analyses was that activation in the superior temporal gyrus did reach significance (p < .001, small-volume corrected) for a subset of the group. Moreover, the extent of the left-sided superior temporal gyrus activity was strongly correlated with speechreading performance. Skilled speechreading was also associated with activations and deactivations in other brain regions, suggesting that individual differences ref lect the efficiency of a circuit linking sensory, perceptual, memory, cognitive, and linguistic processes rather than the operation of a single component process.     

Overt sentence production in event-related fMRI

The use of syntactic structures on a sentence level is a unique human ability. Functional imaging studies have usually investigated syntax comprehension. However, language production may be performed by different neuronal resources. We have investigated syntax generation on a sentence level with functional magnetic resonance imaging (fMRI). BOLD contrast was measured while subjects articulated utterances aloud. In the active condition 'sentence generation' (SG), subjects had to produce subject verb object (SVO) sentences (e.g. "The child throws the ball") according to syntactically incomplete stimuli (e.g. "throw ball child") presented visually. In the control condition 'word reading' (WR), subjects had to read identical stimuli without completing the syntactic structure, while in a second control condition 'sentence reading' (SR), subjects had to read complete sentences. The semantic meaning of all expressions was obvious despite the syntactically incomplete structure in conditions SG and WR. In both contrasts, SG minus WR and SG minus SR, activation was mainly present in the left inferior frontal (BA 44/45) and medial frontal (BA 6) gyri, the superior parietal lobule (BA 7) and the right insula (BA 13). A region of interest analysis revealed significantly stronger left-dominant activation in BA 45 compared to BA 44. Our data illustrates the crucial involvement of the left BA 45 in syntactic encoding and is in line with more recent imaging and brain lesion data on syntax processing on a sentence level, emphasizing the involvement of a distributed left and right hemispheric network in syntax generation.     

Modulation of activity in temporal cortex during generation of inner speech

Monitoring one's thoughts (in the verbal modality) is thought to be critically dependent on the interaction between areas that generate and perceive inner speech in the frontal and temporal cortex, respectively. We used functional magnetic resonance imaging (fMRI) to examine the relationship between activity in these areas while the rate of inner speech generation was varied experimentally. The faster rate was associated with activation in the left inferior frontal gyrus, the right pre- and postcentral gyri and both superior temporal gyri. Thus, temporal cortical activation was associated with increasing the rate of covert articulation, in the absence of external auditory input, suggesting that there is effective fronto-temporal connectivity. Furthermore, this may provide support for the existence of feed forward models, which suggest that activity in regions responsible for verbal perception is modulated by activity in areas that generate inner speech.     

A comparison of five fMRI protocols for mapping speech comprehension systems

Aims: Many fMRI protocols for localizing speech comprehension have been described, but there has been little quantitative comparison of these methods. We compared five such protocols in terms of areas activated, extent of activation, and lateralization. Methods: fMRI BOLD signals were measured in 26 healthy adults during passive listening and active tasks using words and tones. Contrasts were designed to identify speech perception and semantic processing systems. Activation extent and lateralization were quantified by counting activated voxels in each hemisphere for each participant. Results: Passive listening to words produced bilateral superior temporal activation. After controlling for prelinguistic auditory processing, only a small area in the left superior temporal sulcus responded selectively to speech. Active tasks engaged an extensive, bilateral attention, and executive processing network. Optimal results (consistent activation and strongly lateralized pattern) were obtained by contrasting an active semantic decision task with a tone decision task. There was striking similarity between the network of brain regions activated by the semantic task and the network of brain regions that showed task‐induced deactivation, suggesting that semantic processing occurs during the resting state. Conclusions: fMRI protocols for mapping speech comprehension systems differ dramatically in pattern, extent, and lateralization of activation. Brain regions involved in semantic processing were identified only when an active, nonlinguistic task was used as a baseline, supporting the notion that semantic processing occurs whenever attentional resources are not controlled. Identification of these lexical‐semantic regions is particularly important for predicting language outcome in patients undergoing temporal lobe surgery.     

汉语单字词音、义加工的脑激活模式

目的：研究汉字音、义加工的脑机制。方法：采用汉字单字词为实验材料，通过功能磁共振成像扫描执行语音和语义两种认知任务的脑区。结果：语音任务激活的脑区有，左侧顶叶下部和颞上回(BA 40／39／22，BA：Brodmann Area，即布鲁德曼分区，下同)，左侧枕中回(BA18／19)，右侧枕下回(BA18／19)，以及左中央前回(BA6)。语义任务激活的脑区有，左侧顶叶下部(BA40／39)和左侧颞上回(BA22)，左侧额下回(BA10／47)，右侧额中回和额上回(BA10／11)，以及左侧额中回(BA11)。语义任务减去语音任务激活的脑区有，左侧额下回(BA47)，左侧海马(BA36)和右侧海马旁回(BA36)。语音任务减去语义任务没有发现任何脑区的显著激活。结论：在语义任务中与语音有关的脑区得到激活；而在语音任务中与语义有关的脑区没有激活。     

Localizing the distributed language network responsible for the N400 measured by MEG during auditory sentence processing

We studied auditory sentence comprehension using magnetoencephalography while subjects listened to sentences whose correctness they had to judge subsequently. The localization and the time course of brain electrical activity during processing of correct and semantically incorrect sentences were estimated by computing a brain surface current density within a cortical layer for both conditions. Finally, a region of interest (ROI) analysis was conducted to determine the time course of specific locations. A magnetic N400 was present in six spatially different ROIs. Semantic anomalies caused an exclusive involvement of the ventral portion of the left inferior frontal gyrus (BA 47) and left pars triangularis (BA 45). The anterior parts of the superior (BA 22) and inferior (BA 20/21) temporal gyri bilaterally were activated by both conditions. The activation for the correct condition, however, peaked earlier in both left temporal regions (approximately 32 ms). In general, activation due to semantic violations was more pronounced, started later, and lasted longer as compared to correct sentences. The findings reveal a clear left-hemispheric dominance during language processing indicated firstly by the mere number of activated regions (four in the left vs. two in the right hemisphere) and secondly by the observed specificity of the left inferior frontal ROIs to semantic violations. The temporal advantage observed for the correct condition in the left temporal regions is supporting the notion that the established context eases the processing of the final word. Semantically incorrect words that do not fit into the context result in longer integration times.     

Neural correlates of metaphor processing

Metaphoric language is used to express meaning that is otherwise difficult to conceptualize elegantly. Beyond semantic analysis, understanding the figurative meaning of a metaphor requires mental linkage of different category domains normally not related to each other. We investigated processing of metaphoric sentences using event-related functional magnetic resonance imaging (fMRI). Stimuli consisted of 60 novel short German sentence pairs with either metaphoric or literal meaning. The pairs differed only in their last one to three words and were matched for syntax structure, word frequency, connotation and tense. Fifteen healthy subjects (six female, nine male, 19-51 years) read these sentences silently and judged by pressing one of two buttons whether they had a positive or negative connotation. Reading metaphors in contrast to literal sentences revealed signal changes in the left lateral inferior frontal (BA 45/47), inferior temporal (BA 20) and posterior middle/inferior temporal (BA 37) gyri. The activation in the left inferior frontal gyrus may reflect semantic inferencing processes during the understanding of a metaphor. This is in line with the results from other functional imaging studies showing an involvement of the left inferior frontal gyrus in integrating word and sentence meanings. Previous results of a right hemispheric involvement in metaphor processing might reflect understanding of complex sentences.     

Brain activation in the processing of Chinese characters and words: a functional MRI study

Functional magnetic resonance imaging was used to identify the neural correlates of Chinese character and word reading. The Chinese stimuli were presented visually, one at a time. Subjects covertly generated a word that was semantically related to each stimulus. Three sorts of Chinese items were used: single characters having precise meanings, single characters having vague meanings, and two-character Chinese words. The results indicated that reading Chinese is characterized by extensive activity of the neural systems, with strong left lateralization of frontal (BAs 9 and 47) and temporal (BA 37) cortices and right lateralization of visual systems (BAs 17-19), parietal lobe (BA 3), and cerebellum. The location of peak activation in the left frontal regions coincided nearly completely both for vague- and precise-meaning characters as well as for two-character words, without dissociation in laterality patterns. In addition, left frontal activations were modulated by the ease of semantic retrieval. The present results constitute a challenge to the deeply ingrained belief that activations in reading single characters are right lateralized, whereas activations in reading two-character words are left lateralized.