Biomedical subjects

S Duke Han

Publications and source records attributed to S Duke Han.

6 recordsLinked to original sources

PubMed2026

Social support and cognitive function in postmenopausal women.

OBJECTIVE: An active social lifestyle may protect against cognitive decline in older adults, but few studies have examined specific social support dimensions in relation to specific cognitive domains. This study examines associations between social support dimensions and cognitive function in older women. METHODS: The Early versus Late Intervention Trial with Estradiol (ELITE) was a randomized, double-blinded, placebo-controlled trial of oral 17β-estradiol versus placebo in postmenopausal women, designed primarily to evaluate the timing hypothesis on atherosclerosis progression and cognitive decline; the present analysis is a secondary, hypothesis-generating examination of the psychosocial substudy data (2009-2012). A total of 448 women completed psychosocial assessments every 6 months. Cognitive function was assessed at baseline, 2.5, and 5 years using composite scores for executive function, verbal memory, visual memory, and global cognition derived from 14 standardized tests. Perceived social support was assessed using the Medical Outcomes Study-Social Support Survey (MOS-SSS; 0-100 scale). Paired cognitive-psychosocial assessments were analyzed using linear mixed-effects models adjusted for age, marital status, blood pressure medication, BMI, education, income, race, and randomized treatment (hormone therapy or placebo). RESULTS: A total of 298 women (mean age 60.3 y) provided 322 paired visits. Positive associations were observed between instrumental social support and visual memory (β(SE)=0.0044(0.0022), 95% CI: -0.00002 to 0.0088, P=0.051) and between positive social interaction and global cognition (β(SE)=0.0092(0.0046), 95% CI: 0.0001-0.0182, P=0.047). In age-stratified analyses, the positive social interaction-global cognition association was significant among women <65 years (P=0.042) but not women ≥65 years (P=0.34). No association survived false discovery rate (FDR) correction for multiple comparisons. CONCLUSIONS: In this sample of healthy middle- to older-aged women, no association between specific dimensions of social support and cognitive domains was statistically significant after correction for multiple comparisons. These hypothesis-generating findings suggest any association is modest at best and warrant confirmation in studies designed specifically for this question.

Cognitive function↗

PubMed2007

Functional neuroimaging of word priming in males with chronic schizophrenia.

Word-priming studies have suggested that the associative disturbance of schizophrenia may reflect aberrant spread of activation through the lexicon of the brain. To explore this, we examined lexical activation using a semantic word-priming paradigm coupled with functional magnetic resonance imaging (fMRI). We also wanted to determine whether brain activation to this paradigm correlated with relevant clinical symptom measures. In addition to completing clinical symptom measures, twelve chronic patients and twelve demographically matched control subjects completed a lexical-decision semantic-priming paradigm developed as an event-related BOLD fMRI task. This paradigm consisted of words that differed in connectivity. Words with many connections between shared semantic associates are considered high in connectivity and produce the largest behavioral semantic priming effects in control subjects, while words with few connections between shared semantic associates are considered low in connectivity and produce a relatively smaller amount of semantic priming. In fMRI, a respective step-wise increase in activation from high connectivity to low connectivity to unrelated word pairs was expected for normal subjects. Controls showed the expected pattern of activation to word connectivity; however, patients showed a less robust pattern of activation to word connectivity. Furthermore, this aberrant response correlated with measures of Auditory Hallucinations, Distractive Speech, Illogicality, and Incoherence. The patients did not display left frontal and temporal activation as a function of the degree of word connectivity as seen in healthy controls. This may reflect a disease-related disturbance in functional connectivity of lexical activation, which in turn may be associated with clinical symptomatology.

Adult↗

PubMed2006

Verbal paired-associate learning by APOE genotype in non-demented older adults: fMRI evidence of a right hemispheric compensatory response.

Previous studies of episodic memory report a greater extent of blood-oxygenation-level-dependent (BOLD) response in non-demented older adults with the apolipoprotein E epsilon-4 (APOE epsilon4) allele than in those without the allele. We conducted a functional MRI study to investigate whether APOE genotype is related to brain response to verbal paired-associate encoding and consolidation, particularly in the right hemisphere, among non-demented older adults. Structurally segmented volumes and BOLD response were measured in 13 non-epsilon4 and 12 epsilon4 subjects. The epsilon4 group displayed greater activation than the non-epsilon4 group in multiple right hemisphere regions for previously encoded word pairs relative to fixation. Activation within manually outlined hippocampal regions of interest also displayed genotype-specific dissociations consistent with whole brain analyses. Furthermore, this differential BOLD response occurred in the presence of equivalent behavioral and neuropsychological performances as well as comparable hippocampal and overall structural segmentation volumes between groups. Results implicate a widely distributed and interconnected network of right hemisphere brain regions that may be involved in compensating for APOE epsilon4-related deficiencies associated with verbal episodic memory encoding and consolidation.

Aged↗

PubMed2006

Connectivity among semantic associates: an fMRI study of semantic priming.

Semantic priming refers to a reduction in the reaction time to identify or make a judgment about a stimulus that has been immediately preceded by a semantically related word or picture and is thought to result from a partial overlap in the semantic associates of the two words. A semantic priming lexical decision task using spoken words was presented in event-related fMRI and behavioral paradigms. Word pairs varied in terms of semantic relatedness and the connectivity between associates. Thirteen right-handed subjects underwent fMRI imaging and 10 additional subjects were tested in a behavioral version of the semantic priming task. It was hypothesized priming would be greatest, reaction time fastest, and cortical activation reduced the most for related word pairs of high connectivity, followed by related word pairs of low connectivity, and then by unrelated word pairs. Behavioral and fMRI results confirmed these predictions. fMRI activity located primarily in bilateral posterior superior and middle temporal regions showed modulation by connectivity and relatedness. The results suggest that these regions are involved in semantic processing.

Adult↗

PubMed2006

fMRI of lexical-semantic priming in a chronic schizophrenia patient.

A neuropsychological hallmark of schizophrenia is a breakdown in semantic association networks that often impacts language and formal thought. Although computational models simulating this breakdown exist, studies have yet to investigate this phenomena using functional MRI (fMRI) coupled with an auditory lexical-decision semantic priming paradigm. Thus, this serves to functionally map brain activation to word pairs that differed with respect to a concept called "connectivity" in a patient with schizophrenia and a demographically matched control adult. Analyses revealed a striking difference with respect to the expected stepwise modulation of activation, with the control participant showing significantly greater areas of modulation than the participant with schizophrenia in regions classically implicated in language. Although the results are tentative because of the nature of this investigation (single-case study), they further support the characterization of schizophrenia as a breakdown in lexical-semantic association networks and represent one of the first fMRI studies of semantic priming in schizophrenia informed by a computer model.

Brain↗

PubMed2003

Associative memory in chronic schizophrenia: a computational model.

We developed a computer model to simulate associative memory recall of patients with chronic schizophrenia. Model inputs consisted of words derived from normative data that differed in terms of connectivity and network size, with the former quantitatively represented by parametric weights and the latter by the specific number of word associates that formed a particular network. Previous behavioral studies of normal subjects indicated better recall for words of high connectivity-small network (HCSN), followed by low connectivity-small network (LCSN), high connectivity-large network (HCLN), and low connectivity-large network (LCLN). This pattern of recall differed from that observed in behavioral studies of schizophrenic patients, which showed better recall for high connectivity words, regardless of network size. Holding constant network size while manipulating connection weights effectively simulated this schizophrenic pattern of recall. That is, manipulation of parametric weights coupled with a slight increase in noise significantly and reliably elicited the response pattern of abnormal connectivity demonstrated in the prior behavioral study of patients with chronic schizophrenia. An increase in noise was a necessary, but insufficient step in modeling the response pattern of abnormal connectivity. These findings provide support for the use of computational models to investigate dynamics of associative word recall in patients with chronic schizophrenia.

Chronic Disease↗