Biomedical subjects

W Caroline West

Publications and source records attributed to W Caroline West.

5 recordsLinked to original sources

PubMed2006

Determinants of bold signal correlates of processing object-extracted relative clauses.

Event-related functional magnetic resonance imaging (fMRI) was used to investigate the determinants of blood oxygenation level-dependent (BOLD) signal correlates of processing relative clauses. Matched pairs of sentences that differed in their processing demands were compared. One member of the pair consisted of a syntactically simpler object-subject (OS) sentence, containing a subject-relativized clause attached to the object noun phrase. The second member of the pair consisted of a syntactically more complex subject-object (SO) sentence, containing an object-relativized clause attached to the subject noun phrase. Participants made plausibility judgments about the sentences in whole sentence visual presentation. Voxel-wise statistical activation maps showed increased BOLD signal in multiple cortical regions for complex compared to simple syntactic structures. This pattern was found for plausible sentences only and, within the set of plausible sentences, for SO sentences in which the head noun of the relative clause was animate and the subject noun of the relative clause was inanimate. These results require a re-interpretation of previous results with the same materials using positron emission tomography.

Adolescent↗

PubMed2005

The neural organization of semantic memory: Electrophysiological activity suggests feature-based segregation.

Despite decades of research, it remains controversial whether semantic knowledge is anatomically segregated in the human brain. To address this question, we recorded event-related potentials (ERPs) while participants viewed pictures of animals and tools. Within the 200-600-ms epoch after stimulus presentation, animals (relative to tools) elicited an increased anterior negativity that, based on previous ERP studies, we interpret as associated with semantic processing of visual object attributes. In contrast, tools (relative to animals) evoked an enhanced posterior left-lateralized negativity that, according to prior research, might reflect accessing knowledge of characteristic motion and/or more general functional properties of objects. These results support the hypothesis of the neuroanatomical knowledge organization at the level of object features: the observed neurophysiological activity was modulated by the features that were most salient for object recognition. The high temporal resolution of ERPs allowed us to demonstrate that differences in processing animals and tools occurred specifically within the time-window encompassing semantic analysis.

Adolescent↗

PubMed2004

Question/statement judgments: an fMRI study of intonation processing.

We examined changes in fMRI BOLD signal associated with question/statement judgments in an event-related paradigm to investigate the neural basis of processing one aspect of intonation. Subjects made judgments about digitized recordings of three types of utterances: questions with rising intonation (RQ; e.g., "She was talking to her father?"), statements with a falling intonation (FS; e.g., "She was talking to her father."), and questions with a falling intonation and a word order change (FQ; e.g., "Was she talking to her father?"). Functional echo planar imaging (EPI) scans were collected from 11 normal subjects. There was increased BOLD activity in bilateral inferior frontal and temporal regions for RQ over either FQ or FS stimuli. The study provides data relevant to the location of regions responsive to intonationally marked illocutionary differences between questions and statements.

Acoustic Stimulation↗

PubMed2003

Regionally localized thinning of the cerebral cortex in schizophrenia.

BACKGROUND: Schizophrenia is characterized by small reductions in cortical gray matter volume, particularly in the temporal and prefrontal cortices. The question of whether cortical thickness is reduced in schizophrenia has not been addressed using magnetic resonance imaging (MRI) techniques. Our objectives were to test the hypothesis that cortical thinning in patients with schizophrenia (relative to control subjects) is greater in temporal and prefrontal regions of interest (ROIs) than in control ROIs (superior parietal, calcarine, postcentral, central, and precentral cortices), and to obtain an unbiased estimate of the distribution of cortical thinning in patients (relative to controls) by constructing mean and statistical cortical thickness difference maps. METHODS: Participants included 33 right-handed outpatients receiving medication and meeting DSM-IV criteria for schizophrenia and 32 healthy volunteers, matched on age and parental socioeconomic status. After high-resolution MRI scans, models of the gray-white and pial surfaces were generated for each individual's cortex, and the distance between these 2 surfaces was used to compute cortical thickness. A surface-based averaging technique that aligned the main cortical folds across individuals allowed between-group comparisons of thickness within ROIs, and at multiple, uniformly sampled loci across the cortical ribbon. RESULTS: Relative to controls, patients showed greater cortical thinning in temporal-prefrontal ROIs than in control ROIs, as revealed by a significant (P<.009) interaction between group and region type. Cortical thickness difference maps revealed significant (at P<.05, corrected) thinning within the orbitofrontal cortices bilaterally; the inferior frontal, inferior temporal, and occipitotemporal cortices on the left; and within the medial temporal and medial frontal cortices on the right. Superior parietal and primary somatosensory and motor cortices were relatively spared, even at subthreshold significance levels. CONCLUSIONS: Patients with chronic schizophrenia showed widespread cortical thinning that particularly affected the prefrontal and temporal cortices. This thinning might reflect underlying neuropathological abnormalities in cortical structure.

Adult↗

PubMed2002

Event-related potentials during discourse-level semantic integration of complex pictures.

This study examined event-related potentials (ERPs) elicited in response to semantic processing of non-verbal stories. ERPs were recorded from 29 scalp electrodes on 16 participants while they viewed series of complex gray-scale pictures, each of which relayed a simple story. The final picture of each story was either congruous or incongruous with the preceding context. Participants made delayed meaningfulness judgments for each story. Averaged ERPs time-locked to the onset of the final picture were more negative for incongruous than congruous pictures. Two distinct components were sensitive to congruency. The first component peaked at approximately 325 ms (N300) and was distributed over central and frontal sites. The second component peaked at approximately 500 ms and also had a centro-frontal maximum but was more widespread than the earlier component (anterior N400). The distinct scalp topographies of these two negativities provide strong evidence that the N300 and N400 are separate and distinguishable components. Furthermore, the presence of the N300 in this exclusively pictorial task suggests that the N300 is specific to the semantic processing of non-verbal stimuli and is not due to linguistic mediation. This study also revealed that the N400 can be modulated by discourse-level coherence manipulations with pictures. Finally, the different patterns of ERP effects observed during the semantic processing of verbal and non-verbal information suggest that non-identical neuronal sources, and thus non-identical representational systems, are accessed by these different types of materials. These findings strongly support at least partial modularity of semantic representations and processing mechanisms in the human brain.

Adult↗