Biomedical subjects

Willis Chen

Publications and source records attributed to Willis Chen.

4 recordsLinked to original sources

PubMed2005

Large-scale neural network for sentence processing.

Our model of sentence comprehension includes at least grammatical processes important for structure-building, and executive resources such as working memory that support these grammatical processes. We hypothesized that a core network of brain regions supports grammatical processes, and that additional brain regions are activated depending on the working memory demands associated with processing a particular grammatical feature. We used functional magnetic resonance imaging (fMRI) to test this hypothesis by comparing cortical activation patterns during coherence judgments of sentences with three different syntactic features. We found activation of the ventral portion of left inferior frontal cortex during judgments of violations of each grammatical feature. Increased recruitment of the dorsal portion of left inferior frontal cortex was seen during judgments of violations of specific grammatical features that appear to involve a more prominent working memory component. Left posterolateral temporal cortex and anterior cingulate were also implicated in judging some of the grammatical features. Our observations are consistent with a large-scale neural network for sentence processing that includes a core set of regions for detecting and repairing several different kinds of grammatical features, and additional regions that appear to participate depending on the working memory demands associated with processing a particular grammatical feature.

Adolescent↗

PubMed2003

Neural basis for sentence comprehension deficits in frontotemporal dementia.

Many patients with frontotemporal dementia (FTD) have impaired sentence comprehension. However, the pattern of comprehension difficulty appears to vary depending on the clinical subgroup. The purpose of this study was to elucidate the neural basis for these deficits in FTD. We studied patients with two different presentations: Three patients with Progressive Non-Fluent Ahasia (PNFA), and five non-aphasic patients with a dysexecutive and social impairment (EXEC). The FTD patient subgroups were compared to a cohort of 11 healthy seniors with intact sentence comprehension. We monitored regional cerebral activity with blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) while subjects read sentences featuring both a grammatically complex object-relative center-embedded clause and a long linkage between the head noun phrase (NP) and the gap where the NP is interpreted in the center-embedded clause. Subjects decided whether the agent of the action is a male or a female. Healthy seniors activated both ventral portions of inferior frontal cortex (vIFC) and dorsal portions of IFC (dIFC) in the left hemisphere, often associated with grammatical and working memory components of these sentences, respectively. PNFA patients differed from healthy controls since they have reduced activation of left vIFC, while EXEC patients have less recruitment of left dIFC. We conclude that FTD subgroups have distinct patterns of sentence comprehension difficulty in part because of selective interruptions of a large-scale neural network for sentence processing.

Aged↗

PubMed2002

Sentence processing strategies in healthy seniors with poor comprehension: an fMRI study.

We used fMRI to examine patterns of brain recruitment in 22 healthy seniors, half of whom had selective comprehension difficulty for grammatically complex sentences. We found significantly reduced recruitment of left posterolateral temporal [Brodmann area (BA) 22/21] and left inferior frontal (BA 44/6) cortex in poor comprehenders compared to the healthy seniors with good sentence comprehension, cortical regions previously associated with language comprehension and verbal working memory, respectively. The poor comprehenders demonstrated increased activation of left prefrontal (BA 9/46), right dorsal inferior frontal (BA 44/6), and left posterior cingulate (BA 31/23) cortices for the grammatically simpler sentences that they understood. We hypothesize that these brain regions support an alternate, nongrammatical strategy for processing complex configurations of symbolic information. Moreover, these observations emphasize the crucial role of the left perisylvian network for grammatically guided sentence processing in subjects with good comprehension.

Aged↗

PubMed2002

Age-related changes in working memory during sentence comprehension: an fMRI study.

Sentence comprehension declines with age, but the neural basis for this change is unclear. We monitored regional brain activity in 13 younger subjects and 11 healthy seniors matched for sentence comprehension accuracy while they answered a simple probe about written sentences. The sentences varied in their grammatical features (subject-relative vs object-relative subordinate clause) and their verbal working memory (WM) demands (short vs long antecedent noun-gap linkage). We found that young and senior subjects both recruit a core written sentence processing network, including left posterolateral temporal and bilateral occipital cortex for all sentences, and ventral portions of left inferior frontal cortex for object-relative sentences with a long noun-gap linkage. Differences in activation patterns for seniors compared to younger subjects were due largely to changes in brain regions associated with a verbal WM network. While seniors had less left parietal recruitment than younger subjects, left premotor cortex, and dorsal portions of left inferior frontal cortex showed greater activation in seniors compared to younger subjects. Younger subjects recruited right posterolateral temporal cortex for sentences with a long noun-gap linkage. Seniors additionally recruited right parietal cortex for this sentence-specific form of WM. Our findings are consistent with the hypothesis that the neural basis for sentence comprehension includes dissociable but interactive large-scale neural networks supporting core written sentence processes and related cognitive resources involved in WM. Seniors with good comprehension appear to up-regulate portions of the neural substrate for WM during sentence processing to achieve comprehension accuracy that equals young subjects.

Adult↗