Publications from 2011
Developmental differences in phonological and orthographic processing of Chinese spoken words were examined in 9-year-olds, 11-year-olds and adults using functional magnetic resonance imaging (fMRI). Rhyming and spelling judgments were made to two-character words presented sequentially in the auditory modality. Developmental comparisons between adults and both groups of children combined showed that age-related changes in activation in visuo-orthographic regions depended on a task. There were developmental increases in the left inferior temporal gyrus and the right inferior occipital gyrus in the spelling task, suggesting more extensive visuo-orthographic processing in a task that required access to these representations. Conversely, there were developmental decreases in activation in the left fusiform gyrus and left middle occipital gyrus in the rhyming task, suggesting that the development of reading is marked by reduced involvement of orthography in a spoken language task that does not require access to these orthographic representations. Developmental decreases may arise from the existence of extensive homophony (auditory words that have multiple spellings) in Chinese. In addition, we found that 11-yearolds and adults showed similar activation in the left superior temporal gyrus across tasks, with both groups showing greater activation than 9-year-olds. This pattern suggests early development of perceptual representations of phonology. In contrast, 11-year-olds and 9-year-olds showed similar activation in the left inferior frontal gyrus across tasks, with both groups showing weaker activation than adults. This pattern suggests late development of controlled retrieval and selection of lexical representations. Altogether, this study suggests differential effects of character acquisition on development of components of the language network in Chinese as compared to previous reports on alphabetic languages.
We investigated whether brain activity was predictive of future reading skill, and if so, how this brain-behavior correlation informs developmental models of reading. A longitudinal study followed 26 normally developing children ranging in age from 9 – 15 years who were initially assessed for reading skill and performed a rhyming judgment task during functional magnetic resonance imaging (fMRI). Patterns of brain activation in this task predicted changes between initial and a follow-up assessment of nonword reading skill administered up to 6 years later. Brain activity in areas typically active during imaging studies of reading was found to predict future nonword reading ability, however the predictive ability of these areas depended on age. Increased activity relative to peers in neural circuits associated with phonological recoding (i.e. inferior frontal gyrus and basal ganglia) was predictive of greater gains in reading fluency in younger children, whereas increased activity relative to peers in orthographic processing circuits (i.e. fusiform gyrus) was predictive of smaller gains in fluency for older children. Interpreted within the context of a connectionist model of reading, these results suggest that younger children who are more sensitive to higher-order phonological word characteristics (e.g., co-articulations) may make greater reading proficiency gains, whereas older children who focus more on whole-word orthographic representations may make smaller proficiency gains.
Functional magnetic resonance imaging (fMRI) was used to examine the neural correlates of semantic judgments to Chinese words in a group of 10-15 year old Chinese children. Two semantic tasks were used: visual-visual versus visual-auditory presentation. The first word was visually presented (i.e. character) and the second word was either visually or auditorily presented, and the participant had to determine if these two words were related in meaning. Different from English, Chinese has many homophones in which each spoken word corresponds to many characters. The visual-auditory task, therefore, required greater engagement of cognitive control for the participants to select a semantically appropriate answer for the second homophonic word. Weaker association pairs produced greater activation in the mid-ventral region of left inferior frontal gyrus (BA 45) for both tasks. However, this effect was stronger for the visual-auditory task than for the visual-visual task and this difference was stronger for older compared to younger children. The findings suggest greater involvement of semantic selection mechanisms in the cross-modal task requiring the access of the appropriate meaning of homophonic spoken words, especially for older children.
In this paper, we propose a novel symmetrical EEG/fMRI fusion method which combines EEG and fMRI by means of a common generative model. We use a total variation (TV) prior to model the spatial distribution of the cortical current responses and hemodynamic response functions, and utilize spatially adaptive temporal priors to model their temporal shapes. The spatial adaptivity of the prior model allows for adaptation to the local characteristics of the estimated responses and leads to high estimation performance for the cortical current distribution and the hemodynamic response functions. We utilize a Bayesian formulation with a variational Bayesian framework and obtain a fully automatic fusion algorithm. Simulations with synthetic data and experiments with real data from a multimodal study on face perception demonstrate the performance of the proposed method.
Neural changes related to learning of the pronunciation of Chinese characters in English speakers were examined using functional magnetic resonance imaging (fMRI). We examined item specific learning effects for trained characters, and the generalization of phonetic knowledge to novel transfer characters that shared a phonetic radical (part of a character that gives a clue to the whole character’s pronunciation) with trained characters. Behavioral results showed that shared phonetic information improved performance for transfer characters. Neuroimaging results for trained characters over learning found increased activation in right lingual gyrus and greater activation enhancement in left inferior frontal gyrus (BA 44) was correlated with higher accuracy improvement. Moreover, greater activation for transfer characters in these two regions at the late stage of training was correlated with better knowledge of the phonetic radical in a delayed recall test. The current study suggests that right lingual gyrus and left inferior frontal gyrus are crucial for learning of Chinese characters and generalization of that knowledge to novel characters. Left inferior frontal gyrus is likely involved in phonological segmentation, whereas right lingual gyrus may subserve processing visual-orthographic information.
The present study examined developmental differences in event-related potentials between second graders and adults in arithmetic. Consistent with previous literature in adults, multiplication for both children and adults produced a greater left anterior negativity from 400 to 900 ms, whereas addition produced a greater right posterior negativity from 400 to 900 ms. Adults showed larger left anterior negativities in the time window suggesting that adults rely more than children on a verbal processing system for solving these problems. Children showed larger right posterior negativities in the time window suggesting that they rely more on quantitative manipulation for solving these problems.
