Publications from 2006

Chou TL, Davis MH, Marslen-Wilson WD, Booth JR (2006). Phonological priming in visual word recognition for English words: An event related functional MRI study. Chinese Journal of Pscyhology, 4, 1-18. [pdf]

Functional magnetic resonance imaging (fMRI) was used to explore the nature of the mappings between orthography, phonology, and semantics in reading English words. Stimulus pairs were arranged in a priming paradigm with lexical decision to understand the neural correlates of phonological processes. Homophonic targets varied in the regularity of the mapping from spelling to sound (e.g., feet-feat, bare-bear). There were three main findings. First, the results revealed that the left middle temporal gyrus (BA 21) showed increased neural activity for phonologically primed irregular pairs consistent with increased semantic involvement in making lexical decisions when the mapping between orthography and phonology is made difficult. Second, the left supramarginal gyrus (BA 40) was associated with reduced neural activity for phonologically-identical pairs with regular spelling to sound correspondences, when the mapping between orthography and phonology is made easy. Third, the visual association cortex including the left fusiform gyrus (BA 37) showed more activation in the homophone pairs compared to the unrelated pairs and more activation for pseudoword targets compared to word targets, suggesting that this region may have been involved in a spelling check on lexical decisions. These three findings show how phonological priming effects on behaviour can result from a complex interaction of several processing phases involving both increases and decreases of activity.

Booth JR, Harasaki Y& Burman, DD (2006). Development of lexical and sentence level context effects for dominant and subordinate word meanings of homonyms. Journal of Psycholinguistic Research, 35, 531-554. [pdf]

Nine, ten and twelve year old children (N = 75) read aloud dominant, subordinate or ambiguous bias sentences (N = 120) that ended in a homonym (BALL). After the sentence (1000 ms), children read aloud targets that were related to the dominant (BAT) or subordinate (DANCE) meaning of the homonym or control targets. Participants were also divided into three reading skill groups based on an independent measure of single word oral reading accuracy. There were three main developmental and reading skill findings. First, 9-year-olds and low skill readers showed lexical level facilitation in accuracy. Second, 9- and 10-year-olds or low and moderate skill readers showed lexical level facilitation in reaction time. Third, 12-year-olds or high skill readers showed sentence level facilitation in reaction time with high skill readers additionally showing sentence level inhibition in reaction time. These results show that lexical level context effects decreased and that sentence level context effects increased with development and skill. These results are discussed in terms of connectionist models of visual word recognition that incorporate distributed attractor principles.

Cao F, Bitan T, Chou TL, Burman DD & Booth JR (2006). Deficient orthographic and phonological representations in developmental dyslexics revealed by brain activation patterns. Journal of Child Psychology and Psychiatry, 40, 1041-1050. [pdf]

The current study examined the neuro-cognitive network of visual word rhyming judgment in 14 children with dyslexia and 14 age-matched control children (8- to 14-year-olds) using functional magnetic resonance imaging (fMRI). In order to manipulate the difficulty of mapping orthography to phonology, we used conflicting and non-conflicting trials. The words in conflicting trials either had similar orthography but different phonology (e.g. pint-mint) or similar phonology but different orthography (e.g. jazz-has). The words in non-conflicting trials had similar orthography and phonology (e.g. gate-hate) or different orthography and phonology (e.g. press-list). There were no differences in brain activation between the controls and children with dyslexia in the easier non-conflicting trials. However, the children with dyslexia showed less activation than the controls in left inferior frontal gyrus (BA 45/44/47/9), left inferior parietal lobule (BA 40), left inferior temporal gyrus/fusiform gyrus (BA 20/37) and left middle temporal gyrus (BA 21) for the more difficult conflicting trials. For the direct comparison of conflicting minus non-conflicting trials, controls showed greater activation than children with dyslexia in left inferior frontal gyrus (BA 9/45/46) and medial frontal gyrus (BA 8). Children with dyslexia did not show greater activation than controls for any comparison. Reduced activation in these regions suggests that children with dyslexia have deficient orthographic representations in ventral temporal cortex as well as deficits in mapping between orthographic and phonological representations in inferior parietal cortex. The greater activation for the controls in inferior frontal gyrus could reflect more effective top-down modulation of posterior representations.

Bitan T, Burman DD, Lu D, Cone NE, Gitelman DR, Mesulam MM & Booth JR (2006). Weaker top-down modulation from inferior frontal gyrus in children. Neuroimage, 33, 991-998. [pdf]

Previous studies have shown that developmental changes in the structure and function of prefrontal regions can continue throughout childhood and adolescence. Our recent results suggested a role for the left inferior frontal cortex in modulating task-dependent shifts in effective connectivity when adults focus on orthographic versus phonological aspects of presented words. Specifically, the top-down influence of the inferior frontal cortex determined whether incoming word-form information from the fusiform gyrus would have a greater impact on the parietal areas involved in orthographic processing or temporal areas involved in phonological processing (Bitan, et al., 2005). In the current study, we find that children displayed an identical pattern of task-dependent functional activations within this network. In comparison to adults, however, children had significantly weaker top-down modulatory influences emanating from the inferior frontal area. Adult language processing may thus involve greater top-down cognitive control compared to children, resulting in less interference from task-irrelevant information.

Chou TL, Booth JR, Bitan T, Burman DD, Bigio JD, Cone NE, Lu D & Cao, F (2006). Developmental and skill effects on the neural correlates of semantic processing to visually presented words. Human Brain Mapping, 27, 915-924. [pdf]

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 (BAs 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.

Blumenfeld, HK, Booth JR, Burman DD (2006). Differential prefrontal-temporal neural correlates of semantic processing in children. Brain and Language, 99, 226-235. [pdf]

This study used functional magnetic resonance imaging (fMRI) to examine brain-behavior correlations in a group of 16 children (9- to 12-year-olds). Activation was measured during a semantic judgment task presented in either the visual or auditory modality that required the individual to determine whether a final word was related in meaning to one of two previous words (e.g. found – tank – lost). The main finding was that higher performers (i.e. accuracy) were associated with more activation in posterior representational systems including the inferior and middle temporal gyri, whereas lower performers were associated with more activation in anterior regions including the inferior and middle frontal gyri. This pattern of results was interpreted as reflecting an elaborated semantic representational system in temporal areas for the high accuracy performers that allowed them to efficiently and accurately make meaning based judgments. The low accuracy performers may have an inaccurate or weakly interconnected semantic system that results in greater use of frontal areas in a feature selection process.

Booth JR, Lu D, Burman DD, Chou TL, Jin Z, Peng DL, Zhang L, Ding GS, Deng Y, Liu L (2006). Specialization of phonological and semantic processing in Chinese word reading. Cognitive Brain Research, 1071, 197-207. [pdf]

The purpose of this study was to examine the neuro-cognitive 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 versus 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.

Chou TL, Booth JR, Burman DD, Bitan T, Bigio JD, Lu D & Cone NE (2006). Developmental changes in the neural correlates of semantic processing. Neuroimage, 29, 1141-1149. [pdf]

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments in the auditory modality in a group of 9-15 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.

Plaut DC & Booth JR (2006). More modeling but still no stages: Reply to Borowsky and Besner (2006). Psychological Review, 113, 196-200. [pdf]

Plaut and Booth (2000, Psychological Review, 107, 786-823) developed a distributed connectionist model of written word comprehension, and evaluated it against empirical findings on individual and developmental differences in semantic priming in visual lexical decision. Borowsky and Besner (2006, Psychological Review) raised a number of challenges for this model. First, the model was not shown capable of accurately distinguishing words from orthographically matched non-words. Second, its use of a semantic measure for performing lexical decision appears to be inconsistent with evidence of normal lexical decision in brain-damaged patients with semantic impairments. Third, the explanation offered for additive and interactive effects in the model appear to be incompatible with certain aspects of existing empirical findings on the joint effects of frequency, priming context and stimulus quality. In this reply, we demonstrate with additional modeling that none of these issues is problematic for the model.