Biomedical subjects

Colin Humphries

Publications and source records attributed to Colin Humphries.

4 recordsLinked to original sources

PubMed2006

Syntactic and semantic modulation of neural activity during auditory sentence comprehension.

In previous functional neuroimaging studies, left anterior temporal and temporal-parietal areas responded more strongly to sentences than to randomly ordered lists of words. The smaller response for word lists could be explained by either (1) less activation of syntactic processes due to the absence of syntactic structure in the random word lists or (2) less activation of semantic processes resulting from failure to combine the content words into a global meaning. To test these two explanations, we conducted a functional magnetic resonance imaging study in which word order and combinatorial word meaning were independently manipulated during auditory comprehension. Subjects heard six different stimuli: normal sentences, semantically incongruent sentences in which content words were randomly replaced with other content words, pseudoword sentences, and versions of these three sentence types in which word order was randomized to remove syntactic structure. Effects of syntactic structure (greater activation to sentences than to word lists) were observed in the left anterior superior temporal sulcus and left angular gyrus. Semantic effects (greater activation to semantically congruent stimuli than either incongruent or pseudoword stimuli) were seen in widespread, bilateral temporal lobe areas and the angular gyrus. Of the two regions that responded to syntactic structure, the angular gyrus showed a greater response to semantic structure, suggesting that reduced activation for word lists in this area is related to a disruption in semantic processing. The anterior temporal lobe, on the other hand, was relatively insensitive to manipulations of semantic structure, suggesting that syntactic information plays a greater role in driving activation in this area.

Adult↗

PubMed2005

Response of anterior temporal cortex to syntactic and prosodic manipulations during sentence processing.

Previous research has implicated a portion of the anterior temporal cortex in sentence-level processing. This region activates more to sentences than to word-lists, sentences in an unfamiliar language, and environmental sound sequences. The current study sought to identify the relative contributions of syntactic and prosodic processing to anterior temporal activation. We presented auditory stimuli where the presence of prosodic and syntactic structure was independently manipulated during functional magnetic resonance imaging (fMRI). Three "structural" conditions included normal sentences, sentences with scrambled word order, and lists of content words. These three classes of stimuli were presented either with sentence prosody or with flat supra-lexical (list-like) prosody. Sentence stimuli activated a portion of the left anterior temporal cortex in the superior temporal sulcus (STS) and extending into the middle temporal gyrus, independent of prosody, and to a greater extent than any of the other conditions. An interaction between the structural conditions and prosodic conditions was seen in a more dorsal region of the anterior temporal lobe bilaterally along the superior temporal gyrus (STG). A post-hoc analysis revealed that this region responded either to syntactically structured stimuli or to nonstructured stimuli with sentence-like prosody. The results suggest a parcellation of anterior temporal cortex into 1) an STG region that is sensitive both to the presence of syntactic information and is modulated by prosodic manipulations (in nonsyntactic stimuli); and 2) a more inferior left STS/MTG region that is more selective for syntactic structure.

Acoustic Stimulation↗

PubMed2003

Word length modulates neural activity in auditory cortex during covert object naming.

Several lines of evidence show that posterior portions of left auditory cortex participate in aspects of speech production. A current hypothesis is that these regions play a specific role in processing phonological codes. We used event-related fMRI to test this hypothesis. Subjects covertly named objects that had names varying in length from one to four syllables. Behavioral data, both in previous work and in the present study, show an increase in naming reaction time as words get longer, reflecting the increase in phonological load. If left posterior auditory areas participate in phonological aspects of production, word length should modulate neural activity in this region. Object naming activated the left planum temporale in each subject, confirming previous findings of auditory cortex involvement in speech production. The timecourse of activation in this region showed a length effect, consistent with its hypothesized role in phonological processing. Similar effects were also observed in premotor cortex, but not in occipital-temporal cortex, which presumably supports visual processing of the pictures to be named.

Auditory Cortex↗

PubMed2003

Auditory-motor interaction revealed by fMRI: speech, music, and working memory in area Spt.

The concept of auditory-motor interaction pervades speech science research, yet the cortical systems supporting this interface have not been elucidated. Drawing on experimental designs used in recent work in sensory-motor integration in the cortical visual system, we used fMRI in an effort to identify human auditory regions with both sensory and motor response properties, analogous to single-unit responses in known visuomotor integration areas. The sensory phase of the task involved listening to speech (nonsense sentences) or music (novel piano melodies); the "motor" phase of the task involved covert rehearsal/humming of the auditory stimuli. A small set of areas in the superior temporal and temporal-parietal cortex responded both during the listening phase and the rehearsal/humming phase. A left lateralized region in the posterior Sylvian fissure at the parietal-temporal boundary, area Spt, showed particularly robust responses to both phases of the task. Frontal areas also showed combined auditory + rehearsal responsivity consistent with the claim that the posterior activations are part of a larger auditory-motor integration circuit. We hypothesize that this circuit plays an important role in speech development as part of the network that enables acoustic-phonetic input to guide the acquisition of language-specific articulatory-phonetic gestures; this circuit may play a role in analogous musical abilities. In the adult, this system continues to support aspects of speech production, and, we suggest, supports verbal working memory.

Acoustic Stimulation↗