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1.  Cracking the Language Code: Neural Mechanisms Underlying Speech Parsing 
Word segmentation, detecting word boundaries in continuous speech, is a critical aspect of language learning. Previous research in infants and adults demonstrated that a stream of speech can be readily segmented based solely on the statistical and speech cues afforded by the input. Using functional magnetic resonance imaging (fMRI), the neural substrate of word segmentation was examined on-line as participants listened to three streams of concatenated syllables, containing either statistical regularities alone, statistical regularities and speech cues, or no cues. Despite the participants’ inability to explicitly detect differences between the speech streams, neural activity differed significantly across conditions, with left-lateralized signal increases in temporal cortices observed only when participants listened to streams containing statistical regularities, particularly the stream containing speech cues. In a second fMRI study, designed to verify that word segmentation had implicitly taken place, participants listened to trisyllabic combinations that occurred with different frequencies in the streams of speech they just heard (“words,” 45 times; “partwords,” 15 times; “nonwords,” once). Reliably greater activity in left inferior and middle frontal gyri was observed when comparing words with partwords and, to a lesser extent, when comparing partwords with nonwords. Activity in these regions, taken to index the implicit detection of word boundaries, was positively correlated with participants’ rapid auditory processing skills. These findings provide a neural signature of on-line word segmentation in the mature brain and an initial model with which to study developmental changes in the neural architecture involved in processing speech cues during language learning.
PMCID: PMC3713232  PMID: 16855090
fMRI; language; speech perception; word segmentation; statistical learning; auditory cortex; inferior frontal gyrus
2.  Neural basis of irony comprehension in children with autism: the role of prosody and context 
Brain : a journal of neurology  2006;129(0 4):932-943.
While individuals with autism spectrum disorders (ASD) are typically impaired in interpreting the communicative intent of others, little is known about the neural bases of higher-level pragmatic impairments. Here, we used functional MRI (fMRI) to examine the neural circuitry underlying deficits in understanding irony in high-functioning children with ASD. Participants listened to short scenarios and decided whether the speaker was sincere or ironic. Three types of scenarios were used in which we varied the information available to guide this decision. Scenarios included (i) both knowledge of the event outcome and strong prosodic cues (sincere or sarcastic intonation), (ii) prosodic cues only or (iii) knowledge of the event outcome only. Although children with ASD performed well above chance, they were less accurate than typically developing (TD) children at interpreting the communicative intent behind a potentially ironic remark, particularly with regard to taking advantage of available contextual information. In contrast to prior research showing hypoactivation of regions involved in understanding the mental states of others, children with ASD showed significantly greater activity than TD children in the right inferior frontal gyrus (IFG) as well as in bilateral temporal regions. Increased activity in the ASD group fell within the network recruited in the TD group and may reflect more effortful processing needed to interpret the intended meaning of an utterance. These results confirm that children with ASD have difficulty interpreting the communicative intent of others and suggest that these individuals can recruit regions activated as part of the normative neural circuitry when task demands require explicit attention to socially relevant cues.
PMCID: PMC3713234  PMID: 16481375
autism; brain development; fMRI; language pragmatics; social cognition
3.  Developmental changes in the neural basis of interpreting communicative intent 
Understanding the intended meaning of a remark beyond what is explicitly stated is an integral part of successful social interactions. Here, we examined the neural circuitry underlying the interpretation of communicative intent in children and adults using irony comprehension as a test case. Participants viewed cartoon drawings while listening to short scenarios ending with a potentially ironic remark and were asked to decide whether the speaker was being sincere or ironic. In both children and adults, instructions to attend to the cues provided by the speaker's facial expression or tone of voice modulated the activity in visual and language cortices, respectively. Overall, children engaged the medial prefrontal cortex and left inferior frontal gyrus more strongly than adults, whereas adults recruited the fusiform gyrus, extrastriate areas and the amygdala more strongly than children. Greater involvement of prefrontal regions in children may subserve the integration of multiple cues to reconcile the discrepancy between the literal and intended meaning of an ironic remark. This developmental shift from a reliance on frontal regions to posterior occipitotemporal regions may reflect the automatization of basic reasoning about mental states. This study is the first to examine developmental changes in the neural circuitry underlying natural language pragmatics.
PMCID: PMC2555444  PMID: 18985123
development; functional Magnetic Resonance Imaging (fMRI); irony; language; theory of mind

Results 1-3 (3)