Brain-behavior relations in reading and dyslexia: implications of Chinese results.
Explore the source record for details and available documents.
Asian People↗
Biomedical subjects
Li Hai Tan
Publications and source records attributed to Li Hai Tan.
Cognitive processing in Chinese literate and illiterate subjects: an fMRI study.
Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) were used to map brain activation during language tasks. While previous studies have compared performance between alphabetic literate and illiterate subjects, there have been no such data in Chinese-speaking individuals. In this study, we used fMRI to examine the effects of education on neural activation associated with silent word recognition and silent picture-naming tasks in 24 healthy right-handed Chinese subjects (12 illiterates and 12 literates). There were 30 single Chinese characters in the silent word recognition task and 30 meaningful road-signs in the silent picture-naming task. When we compared literate and illiterate subjects, we observed education-related differences in activation patterns in the left inferior/middle frontal gyrus and both sides of the superior temporal gyrus for the silent word recognition task and in the bilateral inferior/middle frontal gyrus and left limbic cingulated gyrus for the silent picture-naming task. These results indicate that the patterns of neural activation associated with language tasks are strongly influenced by education. Education appears to have enhanced cognitive processing efficiency in language tasks.
Aged↗
Reading depends on writing, in Chinese.
Language development entails four fundamental and interactive abilities: listening, speaking, reading, and writing. Over the past four decades, a large body of evidence has indicated that reading acquisition is strongly associated with a child's listening skills, particularly the child's sensitivity to phonological structures of spoken language. Furthermore, it has been hypothesized that the close relationship between reading and listening is manifested universally across languages and that behavioral remediation using strategies addressing phonological awareness alleviates reading difficulties in dyslexics. The prevailing view of the central role of phonological awareness in reading development is largely based on studies using Western (alphabetic) languages, which are based on phonology. The Chinese language provides a unique medium for testing this notion, because logographic characters in Chinese are based on meaning rather than phonology. Here we show that the ability to read Chinese is strongly related to a child's writing skills and that the relationship between phonological awareness and Chinese reading is much weaker than that in reports regarding alphabetic languages. We propose that the role of logograph writing in reading development is mediated by two possibly interacting mechanisms. The first is orthographic awareness, which facilitates the development of coherent, effective links among visual symbols, phonology, and semantics; the second involves the establishment of motor programs that lead to the formation of long-term motor memories of Chinese characters. These findings yield a unique insight into how cognitive systems responsible for reading development and reading disability interact, and they challenge the prominent phonological awareness view.
Asian People↗
Differential activity in left inferior frontal gyrus for pseudowords and real words: an event-related fMRI study on auditory lexical decision.
After Newman and Twieg and others, we used a fast event-related functional magnetic resonance imaging (fMRI) design and contrasted the lexical processing of pseudowords and real words. Participants carried out an auditory lexical decision task on a list of randomly intermixed real and pseudo Chinese two-character (or two-syllable) words. The pseudowords were constructed by recombining constituent characters of the real words to control for sublexical code properties. Processing of pseudowords and real words activated a highly comparable network of brain regions, including bilateral inferior frontal gyrus, superior, middle temporal gyrus, calcarine and lingual gyrus, and left supramarginal gyrus. Mirroring a behavioral lexical effect, left inferior frontal gyrus (IFG) was significantly more activated for pseudowords than for real words. This result disconfirms a popular view that this area plays a role in grapheme-to-phoneme conversion, as such a conversion process was unnecessary in our task with auditory stimulus presentation. An alternative view was supported that attributes increased activity in left IFG for pseudowords to general processes in decision making, specifically in making positive versus negative responses. Activation in left supramarginal gyrus was of a much larger volume for real words than for pseudowords, suggesting a role of this region in the representation of phonological or semantic information for two-character Chinese words at the lexical level.
Acoustic Stimulation↗
Neuroanatomical correlates of phonological processing of Chinese characters and alphabetic words: a meta-analysis.
We used the activation likelihood estimation (ALE) method to quantitatively synthesize data from 19 published brain mapping studies of phonological processing in reading, six with Chinese and 13 with alphabetic languages. It demonstrated high concordance of cortical activity across multiple studies in each written language system as well as significant differences of activation likelihood between languages. Four neural systems for the phonological processing of Chinese characters included: (1) a left dorsal lateral frontal system at Brodmann area (BA) 9; (2) the dorsal aspect of left inferior parietal system; (3) a bilateral ventral-occipitotemporal system including portions of fusiform gyrus and middle occipital gyrus; and (4) a left ventral prefrontal system covering the superior aspect of inferior frontal gyrus. For phonological processing of written alphabetic words, cortical areas identified here are consistent with the three neural systems proposed previously in the literature: (1) a ventral prefrontal system involving superior portions of left inferior frontal gyrus; (2) a left dorsal temporoparietal system including mid-superior temporal gyri and the ventral aspect of inferior parietal cortex (supramarginal region); and (3) a left ventral occipitotemporal system. Contributions of each of these systems to phonological processing in reading were discussed, and a covariant learning hypothesis is offered to account for the findings that left middle frontal gyrus is responsible for addressed phonology in Chinese whereas left temporoparietal regions mediate assembled phonology in alphabetic languages. Language form, cognitive process, and learning strategy drive the development of functional neuroanatomy.
Brain↗
The lexical constituency model: some implications of research on Chinese for general theories of reading.
The authors examine the implications of research on Chinese for theories of reading and propose the lexical constituency model as a general framework for word reading across writing systems. Word identities are defined by 3 interlinked constituents (orthographic, phonological, and semantic). The implemented model simulates the time course of graphic, phonological, and semantic priming effects, including immediate graphic facilitation followed by graphic inhibition with simultaneous phonological facilitation, a pattern unique to the Chinese writing system. Pseudocharacter primes produced only facilitation, supporting the model's assumption that lexical thresholds determine phonological and semantic, but not graphic, effects. More generally, both universal reading processes and writing system constraints exist. Although phonology is universal, its activation process depends on how the writing system structures graphic units.
Humans↗
Spatial congruence in working memory: an ERP study.
The Simon effect refers to the finding that reaction times are faster when stimulus and response locations are congruent than when they are not, even stimulus locations are task irrelevant. Zhang and Johnson reported a Simon-like spatial congruence effect in working memory. This study examined the neural mechanisms of this memory-based spatial congruence effect by recording event-related potentials to probe stimuli. Behavioral results showed a clear congruence effect. The P300 amplitudes were larger in the congruent condition than in the incongruent condition. The results suggest that the memory-based congruence effect and the classical Simon effect were mediated by similar neural mechanisms and support theories assigning response selection an essential role in spatial congruence effects.
Adolescent↗
Biological abnormality of impaired reading is constrained by culture.
Developmental dyslexia is characterized by a severe reading problem in people who have normal intelligence and schooling. Impaired reading of alphabetic scripts is associated with dysfunction of left temporoparietal brain regions. These regions perform phonemic analysis and conversion of written symbols to phonological units of speech (grapheme-to-phoneme conversion); two central cognitive processes that mediate reading acquisition. Furthermore, it has been assumed that, in contrast to cultural diversities, dyslexia in different languages has a universal biological origin. Here we show using functional magnetic resonance imaging with reading-impaired Chinese children and associated controls, that functional disruption of the left middle frontal gyrus is associated with impaired reading of the Chinese language (a logographic rather than alphabetic writing system). Reading impairment in Chinese is manifested by two deficits: one relating to the conversion of graphic form (orthography) to syllable, and the other concerning orthography-to-semantics mapping. Both of these processes are critically mediated by the left middle frontal gyrus, which functions as a centre for fluent Chinese reading that coordinates and integrates various information about written characters in verbal and spatial working memory. This finding provides an insight into the fundamental pathophysiology of dyslexia by suggesting that rather than having a universal origin, the biological abnormality of impaired reading is dependent on culture.
Asian People↗
Comparison of TCA and ICA techniques in fMRI data processing.
PURPOSE: To make a quantitative comparison of temporal cluster analysis (TCA) and independent component analysis (ICA) techniques in detecting brain activation by using simulated data and in vivo event-related functional MRI (fMRI) experiments. MATERIALS AND METHODS: A single-slice MRI image was replicated 150 times to simulate an fMRI time series. An event-related brain activation pattern with five different levels of intensity and Gaussian noise was superimposed on these images. Maximum contrast-to-noise ratio (CNR) of the signal change ranged from 1.0 to 2.0 by 0.25 increments. In vivo visual stimulation fMRI experiments were performed on a 1.9 T magnet. Six human volunteers participated in this study. All imaging data were analyzed using both TCA and ICA methods. RESULTS: Both simulated and in vivo data have shown that no statistically significant difference exists in the activation areas detected by both ICA and TCA techniques when CNR of fMRI signal is larger than 1.75. CONCLUSION: TCA and ICA techniques are comparable in generating functional brain maps in event-related fMRI experiments. Although ICA has richer features in exploring the spatial and temporal information of the functional images, the TCA method has advantages in its computational efficiency, repeatability, and readiness to average data from group subjects
Brain Mapping↗
Correlation between temporal response of fMRI and fast reaction time in a language task.
Correlation between behavioral parameters and fMRI responses can provide an advanced understanding of the neuronal processes. A lexical decision task was employed to examine the correlation between the reaction time (RT) and the temporal parameters in event-related BOLD responses. Word frequency was manipulated in the experiment. RTs for high-frequency, low-frequency and pseudowords were measured during fMRI (417 +/- 9 ms, 631 +/- 22 ms and 658 +/- 15 ms, respectively). For high-frequency words, RTs were significantly shorter than that for low-frequency and pseudowords (p < 0.0005). In the left inferior frontal region, the FWHM of the fMRI responses was significantly correlated with RT (p < 0.001), which may correspond to areas with sustained activation during the whole processing.
Adult↗
Neural representations of nouns and verbs in Chinese: an fMRI study.
The neural representation of nouns and verbs has been a focus of many recent neuroimaging and neuropsychological studies. These studies have in general found that in English and other Indo-European languages, verbs are represented in the frontal region (e.g., the left prefrontal cortex) while nouns in the posterior regions (the temporal-occipital regions). There is accumulating evidence, however, that the picture may have been overly simplified. In the present study, we examine the representations of nouns and verbs in Chinese, a language that has unique properties in its grammar and particularly in the structure of nouns and verbs. In an fMRI experiment, subjects viewed a list of disyllabic nouns, verbs, and class-ambiguous words and performed a lexical decision on the target. Results from the experiment indicate that nouns and verbs in Chinese activate a wide range of overlapping brain areas in distributed networks, in both the left and the right hemispheres. The results provide support for the prediction regarding the impact of linguistic typology and language-specific influences on the neural representation of grammatical categories. They are consistent with recent proposals that specific linguistic experience shapes neural systems of reading and speaking and that the language-specific properties of the Chinese grammar affect the representation, processing, and acquisition in this language.
Adult↗
CBF changes during brain activation: fMRI vs. PET.
The changes in regional cerebral blood flow (rCBF) associated with the changes in neuronal activity are routinely measured both by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) techniques. However, direct comparison has not been performed to determine similarities and differences of PET and fMRI techniques in determining the rCBF response to brain activation. In the present study, a quantitative comparison of the functional rCBF maps obtained by PET and fMRI are made by performing an activation study in a single group of subjects under precisely controlled conditions and using identical visual stimuli. Twelve healthy volunteers participated in the activation study using the visual checkerboard stimulation with flip frequency at 8 Hz. By selecting the conjunctive pixels which activated on both PET and fMRI maps, the change in rCBF measured by fMRI was 36.95 +/- 2.54%, whereas the value measured by PET was 38.79 +/- 2.63%. Our results have demonstrated that there is no statistically significant difference (P = 0.22) in the measurements of rCBF change between MRI and PET methods.
Algorithms↗
Neural systems for word meaning modulated by semantic ambiguity.
One important issue in neuroimaging research on language is how the brain processes and represents lexical semantics. Past studies with various paradigms reveal that the left inferior prefrontal and mid-superior temporal regions play a crucial role in semantic processing. Those studies, however, typically utilize words having a precise and dominant meaning as stimuli and have not manipulated lexico-semantic ambiguity, a key feature of human language, as an experimental variable. Here, we used a word generation paradigm to examine whether neuroanatomical networks for meaning are modulated by lexical ambiguity. We found that, compared with semantically precise words, semantically ambiguous words were mediated by strong brain activations in the left dorsal-lateral frontal areas, the anterior cingulate, and the right inferior parietal lobe. Semantically precise words, instead, were associated with the left inferior prefrontal and mid-superior temporal sites. These findings indicate that semantic analysis of written words is a dynamic process involving coordination of widely distributed neural subsystems, which are weighted by semantic ambiguity.
Adult↗
Is left inferior frontal gyrus a general mechanism for selection?
Converging lines of research in neuroimaging recognize selection as one of the critical functions of prefrontal cortex (e.g., see Annu. Rev. Neurosci. 24, 2001 167). We examined a central thesis of a selection hypothesis (Neuropsychologia 41, 2003 280) that the left inferior frontal gyrus (LIFG) serves as a general mechanism for selecting among competing representations (Annu. Rev. Neurosci. 18, 1995 193). Participants were presented with two sets of letters to remember and then cued to select one set from the two as the target set for subsequent recognition. LIFG showed significantly more activation when the cue elicited a strong need for selection, relative to when it did not, suggesting that the involvement of this area in selection is generalizable beyond semantic retrieval tasks as originally found. This result provides supporting evidence for the selection hypothesis.
Adult↗
More workload on the central executive of working memory, less attention capture by novel visual distractors: evidence from an fMRI study.
The present study examined the interaction of the central executive in working memory with visual attention. Native Chinese participants were given two versions of a number subtraction task, one of low demand and one of high demand, and were asked to ignore a simultaneously presented peripheral distractor. The distractor could be Chinese or Korean characters, familiar or novel to participants, respectively. Compared with the low-demand subtraction task, brain regions commonly associated with central executive functions, including left middle prefrontal cortex, anterior cingulate cortex, and precentral gyrus/sulcus, were significantly activated in the high-demand task. Critically, there was a significant interaction between distractor type and task demand. Novel distractors captured attention and elicited automatic visual analysis, shown by primary visual cortex activation, only when the subtraction task was of low demand but not when it was of high demand. The results provide confirmatory evidence that the extent to which higher level cognitive resources, specifically, the central executive component of working memory, are absorbed by a cognitive task has an impact upon automatic processing that occurs in response to distracting items.
Adult↗
Neural systems of second language reading are shaped by native language.
Reading in a second language (L2) is a complex task that entails an interaction between L2 and the native language (L1). To study the underlying mechanisms, we used functional magnetic resonance imaging (fMRI) to visualize Chinese-English bilinguals' brain activity in phonological processing of logographic Chinese and alphabetic English, two written languages with a sharp contrast in phonology and orthography. In Experiment 1, we found that phonological processing of Chinese characters recruits a neural system involving left middle frontal and posterior parietal gyri, cortical regions that are known to contribute to spatial information representation, spatial working memory, and coordination of cognitive resources as a central executive system. We assume that the peak activation of this system is relevant to the unique feature of Chinese that a logographic character has a square configuration that maps onto a monosyllabic unit of speech. Equally important, when our bilingual subjects performed a phonological task on English words, this neural system was most active, whereas brain areas mediating English monolinguals' fine-grained phonemic analysis, as demonstrated by Experiment 2, were only weakly activated. This suggests that our bilingual subjects were applying their L1 system to L2 reading and that the lack of letter-to-sound conversion rules in Chinese led Chinese readers to being less capable of processing English by recourse to an analytic reading system on which English monolinguals rely. Our brain imaging findings lend strongest support to the idea that language experience tunes the cortex.
Adult↗
Distinct brain regions associated with syllable and phoneme.
The syllable and the phoneme are two important units in the phonological structure of speech sounds. In the brain mapping literature, it remains unsolved as to whether there are separate brain regions mediating the processing of syllables and phonemes. Using functional magnetic resonance imaging (fMRI), we investigated the neural substrate of these phonological units with Chinese subjects. Results revealed that the left middle frontal cortex contributes to syllabic processing, whereas the left inferior prefrontal gyri contributes to phonemic processing. This pattern of findings offers compelling evidence for distinct cortical areas relevant to the representation of syllables and phonemes.
Adult↗
Modulation of neural connectivity during tongue movement and reading.
In a functional magnetic resonance imaging (fMRI) study, a novel connectivity analysis method termed within-condition interregional covariance analysis (WICA) was introduced for investigation into brain modulation during tongue movement and reading Chinese pinyins and logographic characters. We found that performing a horizontal tongue movement task generated a specific brain module with hierarchical orders of neural computation. Such functional modularity was further examined during both overt and silent Chinese reading tasks. Our results showed that overt pinyin reading was associated with the following distributed regions involved in tongue movement: the primary motor cortex (M1), the supplementary motor area (SMA), Broca's area, and Wernicke's area. Furthermore, we have used the WICA and demonstrated task-dependent covariance patterns that are strongly associated with the M1 mouth/tongue region, in which the Broca-Wernicke pathway is implicated in a meaning access procedure based on assembled phonology, while the SMA-Broca pathway is implicated in a meaning access procedure based on addressed phonology. Our functional connectivity analysis of the neural pathway involved in language processing may provide a basis for future studies of the dynamic neural network associated with language learning and reading in both developmental and disease conditions.
Adult↗