Tai-Li Chou

Specialization of phonological and semantic processing in Chinese word reading

The purpose of this study was to examine the neurocognitive network for processing visual word forms in native Chinese speakers using functional magnetic resonance imaging (fMRI). In order to compare the processing of phonological and semantic representations, we developed parallel rhyming and meaning association judgment tasks that required explicit access and manipulation of these representations. Subjects showed activation in left inferior/middle frontal gyri, bilateral medial frontal gyri, bilateral middle occipital/fusiform gyri, and bilateral cerebella for both the rhyming and meaning tasks. A direct comparison of the tasks revealed that the rhyming task showed more activation in the posterior dorsal region of the inferior/middle frontal gyrus (BA 9/44) and in the inferior parietal lobule (BA 40). The meaning task showed more activation in the anterior ventral region of the inferior/middle frontal gyrus (BA 47) and in the superior/middle temporal gyrus (BA 22,21). These findings are consistent with previous studies in English that suggest specialization of inferior frontal regions for the access and manipulation of phonological vs. semantic representations, but also suggest that this specialization extends to the middle frontal gyrus for Chinese. These findings are also consistent with the suggestion that the left middle temporal gyrus is involved in representing semantic information and the left inferior parietal lobule is involved in mapping between orthographic and phonological representations.

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. Hum. Brain Mapping 2006.

Developmental changes in the neural correlates of semantic processing.

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments in the auditory modality in a group of 9- to 15-year-old children. Subjects were required to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral superior temporal gyri (BA 22) for recognizing spoken words as well as activations in bilateral inferior frontal gyri (BAs 47, 45) and left middle temporal gyrus (BA 21) for semantic processing. The neural substrates of semantic association and age differences were also investigated. Words with strong semantic association elicited significantly greater activation in the left inferior parietal lobule (BA 40), whereas words with weak semantic association elicited activation in left inferior frontal gyrus (BAs 47/45). Correlations with age were observed in the left middle temporal gyrus (BA 21) and the right inferior frontal gyrus (BA 47). The pattern of results for semantic association implies that the left inferior parietal lobule effectively integrates highly related semantic features and the left inferior frontal gyrus becomes more active for words that require a greater search for semantic associations. The developmental results suggest that older children recruit the right inferior frontal gyrus as they conduct a broader semantic search and the left middle temporal gyrus to provide more efficient access to semantic representations.

The Interaction Between Orthographic and Phonological Information in Children: An fMRI Study

We examined the neural representations of orthographic and phonological processing in children, while manipulating the consistency between orthographic and phonological information. Participants, aged 9–15, were scanned while performing rhyming and spelling judgments on pairs of visually presented words. The orthographic and phonological similarity between words in the pair was independently manipulated, resulting in four conditions. In the nonconflicting conditions, both orthography and phonology of the words were either (1) similar (lime‐dime) or (2) different (staff‐gain); in conflicting conditions, words had (3) similar phonology and different orthography (jazz‐has) or (4) different phonology and similar orthography (pint‐mint). The comparison between tasks resulted in greater activation for the rhyming task in bilateral inferior frontal gyri (BA 45/47), and greater activation for the spelling task in bilateral inferior/superior parietal lobules (BA 40/7), suggesting greater involvement of phonological and semantic processing in the rhyming task, and nonlinguistic spatial processing in the spelling task. Conflicting conditions were more difficult in both tasks and resulted in greater activation in the above regions. The results suggest that when children encounter inconsistency between orthographic and phonological information they show greater engagement of both orthographic and phonological processing. Hum Brain Mapp 2006.

Segregating the comprehension and elaboration processing of verbal jokes: An fMRI study

The comprehension-elaboration theory of humor claims that the elicitation of humor can be segregated into two stages, comprehension and elaboration. Comprehension includes detection and resolution of incongruity, and elaboration involves inducement of the experience of amusement. Previous imaging research has sought to identify the neural substrates of humor processing by comparing funny and unfunny conditions. However, such studies have not been able to segregate the comprehension and elaboration stages. The present study was designed to differentiate the respective brain areas corresponding to comprehension and elaboration with an additional condition, garden path sentences. The results suggest that the bilateral inferior frontal gyri and left superior frontal gyrus may be associated with humor comprehension, whereas the cortical region in left ventromedial prefrontal cortex and the subcortical regions in bilateral amygdalae and bilateral parahippocampal gyri may be responsible for the feeling of amusement during the elaboration process.

The role of inferior frontal gyrus and inferior parietal lobule in semantic processing of Chinese characters

Functional magnetic resonance imaging was used to explore the neural correlates of semantic judgments to Chinese characters. Adult participants were asked to indicate if character pairs were related in meaning that were arranged in a continuous variable according to association strength. This parametric manipulation allowed for a more precise determination of the role of the left inferior parietal lobule in processing meaning, which has not been reported in previous Chinese studies. Consistent with previous findings in English, participants showed activation in left inferior frontal gyrus (BA 47, 45) and left posterior middle temporal gyrus (BA 21). Characters with stronger semantic association elicited greater activation in left inferior parietal lobule (BA 39), suggesting stronger integration of highly related semantic features. By contrast, characters with weaker semantic association elicited greater activation in both an anterior ventral region (BA 47) and a mid-ventral region of left inferior frontal gyrus (BA 45), suggesting a controlled retrieval process and a selection process. Our findings of association strength are discussed in a proposed neuro-anatomical model of semantic processing.

Encoding operation and transcoding as the major loci of the frequency effect

The present study used a lexical naming task as well as a regular naming task and a lexical decision task for locating the frequency effects in lexical decision and naming. The naming of Chinese characters in the lexical naming task (pseudocharacters also presented as in the lexical decision task) involves decision processes, while they are absent in the regular naming task. Since naming a Chinese character necessarily involves lexical access, a decision component of the frequency effect in lexical decision can be isolated. This procedure will not work for alphabetic orthographies, because sublexical processes underestimate the frequency effect in the regular naming task. As a consequence, not only can a prelexical component of the frequency effect in lexical decision be estimated, but a postlexical component of the frequency effect in naming can be estimated.

Item-specific and generalization effects on brain activation when learning Chinese characters

Neural changes related to learning of the meaning of Chinese characters in English speakers were examined using functional magnetic resonance imaging (fMRI). We examined item specific learning effects for trained characters, but also the generalization of semantic knowledge to novel transfer characters that shared a semantic radical (part of a character that gives a clue to word meaning, e.g. water for lake) with trained characters. Behavioral results show that acquired semantic knowledge improves performance for both trained and transfer characters. Neuroimaging results show that the left fusiform gyrus plays a central role in the visual processing of orthographic information in characters. The left superior parietal cortex seems to play a crucial role in learning the visual-spatial aspects of the characters because it shows learning related decreases for trained characters, is correlated with behavioral improvement from early to late in learning for the trained characters, and is correlated with better long-term retention for the transfer characters. The inferior frontal gyrus seems to be associated with the efficiency of retrieving and manipulating semantic representations because there are learning related decreases for trained characters and this decrease is correlated with greater behavioral improvement from early to late in learning.

Neural correlates of inhibitory control and visual processing in youths with attention deficit hyperactivity disorder: a counting Stroop functional MRI study

BACKGROUND Despite evidence of inhibitory control and visual processing impairment in attention deficit hyperactivity disorder (ADHD), knowledge about its corresponding alterations in the brain is still evolving. The current study used counting Stroop functional MRI and the Cambridge Neuropsychological Test Automated Battery (CANTAB) to investigate if brain activation of inhibitory control and visual processing would differ in youths with ADHD relative to neurotypical youths. METHOD We assessed 25 youths with ADHD [mean age 10.9 (s.d.=2.2) years] and 23 age-, gender- and IQ-matched neurotypical youths [mean age 11.2 (s.d.=2.9) years]. The participants were assessed by using the Wechsler Intelligence Scale for Children, third edition, and two tests from the CANTAB: rapid visual information processing (RVP) and pattern recognition memory (PRM) outside the scanner. RESULTS Youths with ADHD showed more activation than neurotypical youths in the right inferior frontal gyrus [Brodmann area (BA) 45] and anterior cingulate cortex, which were correlated with poorer performance on the RVP test in the CANTAB. In contrast, youths with ADHD showed less activation than neurotypical youths in the left superior parietal lobule (BA 5/7), which was correlated with the percentage of correct responses on the PRM test in the CANTAB. CONCLUSIONS Our findings suggest that youths with ADHD might need more inhibitory control to suppress interference between number and meaning and may involve less visual processing to process the numbers in the counting Stroop task than neurotypical youths.

Differential therapeutic effects of 12-week treatment of atomoxetine and methylphenidate on drug-naïve children with attention deficit/hyperactivity disorder: A counting Stroop functional MRI study

Methylphenidate and atomoxetine are effective in treating attention-deficit/hyperactivity disorder (ADHD) with underlying distinct pharmacological mechanisms. To relate neural mechanisms to clinical response, we conducted a comparative trial to differentiate the changes in brain activation of drug-naïve children with ADHD when performing neuropsychological tasks after 12 weeks of pharmacotherapy. We randomized 50 drug-naïve children with ADHD, aged 7-17, to treatment with methylphenidate (n=25) or atomoxetine (n=25). These children were scanned twice with functional magnetic resonance imaging (fMRI) during the counting Stroop task before and after treatment. Focused attention and impulsivity were assessed twice by using the Conners Continuous Performance Test (CCPT). The final sample for fMRI analysis comprised 20 in the methylphenidate group and 22 in the atomoxetine group. Atomoxetine decreased activations in the dorsal anterior cingulate cortex and dorsolateral prefrontal cortex, which correlated with improvement in focused attention assessed by the CCPT. In contrast, methylphenidate increased activations in the inferior frontal gyrus, which correlated with the decreasing severity of impulsivity assessed by the CCPT. The current findings suggest that differential therapeutic effects on neuronal changes induced by 12-week treatment atomoxetine and methylphenidate may contribute to behavioral improvement.