Biomedical subjects

Stephen T Moelter

Publications and source records attributed to Stephen T Moelter.

6 recordsLinked to original sources

PubMed2005

Organization of semantic category exemplars in schizophrenia.

Semantic memory was investigated in 27 individuals with schizophrenia and 30 healthy controls using an animal similarity judgment and organization test with reduced retrieval demands. Participants arranged 12 common animal names according to similarity on a computer screen and provided verbal descriptions of organizational strategies. Distance between each animal pair was compared to the number of shared semantic attributes between the pairs (e.g., size, diet, habitat). The three primary organizational strategies included single animals not related to other exemplars, isolated clusters of animals that shared a single strategic relationship (e.g., pets), and overlapping clusters that combined more than one strategic relationship (e.g., cats and mammals). A strong negative correlation was observed between distance ratings and number of shared semantic attributes, confirming that semantic features related to visual distances in both groups. Animal pairs that shared few semantic attributes were placed in closer proximity in the schizophrenia group, whereas the groups placed animal pairs sharing more features equidistantly. Analyses of clustering strategies revealed a double dissociation, with patients relying on isolated, non-overlapping clusters and controls producing more overlapping semantic clusters. Results suggest that performance differences on semantic tasks with limited retrieval demands in schizophrenia relate to difficulties utilizing higher-order categorization strategies.

Adult↗

PubMed2005

Levels-of-processing effect on frontotemporal function in schizophrenia during word encoding and recognition.

OBJECTIVE: Patients with schizophrenia improve episodic memory accuracy when given organizational strategies through levels-of-processing paradigms. This study tested if improvement is accompanied by normalized frontotemporal function. METHOD: Event-related blood-oxygen-level-dependent functional magnetic resonance imaging (fMRI) was used to measure activation during shallow (perceptual) and deep (semantic) word encoding and recognition in 14 patients with schizophrenia and 14 healthy comparison subjects. RESULTS: Despite slower and less accurate overall word classification, the patients showed normal levels-of-processing effects, with faster and more accurate recognition of deeply processed words. These effects were accompanied by left ventrolateral prefrontal activation during encoding in both groups, although the thalamus, hippocampus, and lingual gyrus were overactivated in the patients. During word recognition, the patients showed overactivation in the left frontal pole and had a less robust right prefrontal response. CONCLUSIONS: Evidence of normal levels-of-processing effects and left prefrontal activation suggests that patients with schizophrenia can form and maintain semantic representations when they are provided with organizational cues and can improve their word encoding and retrieval. Areas of overactivation suggest residual inefficiencies. Nevertheless, the effect of teaching organizational strategies on episodic memory and brain function is a worthwhile topic for future interventional studies.

Adult↗

PubMed2003

Levels-of-processing effect on word recognition in schizophrenia.

BACKGROUND: Individuals with schizophrenia have difficulty organizing words semantically to facilitate encoding. This is commonly attributed to organizational rather than semantic processing limitations. By requiring participants to classify and encode words on either a shallow (e.g., uppercase/lowercase) or deep level (e.g., concrete/abstract), the levels-of-processing paradigm eliminates the need to generate organizational strategies. METHODS: This paradigm was administered to 30 patients with schizophrenia and 30 healthy comparison subjects to test whether providing a strategy would improve patient performance. RESULTS: Word classification during shallow and deep encoding was slower and less accurate in patients. Patients also responded slowly during recognition testing and maintained a more conservative response bias following deep encoding; however, both groups showed a robust levels-of-processing effect on recognition accuracy, with unimpaired patient performance following both shallow and deep encoding. CONCLUSIONS: This normal levels-of-processing effect in the patient sample suggests that semantic processing is sufficiently intact for patients to benefit from organizational cues. Memory remediation efforts may therefore be most successful if they focus on teaching patients to form organizational strategies during initial encoding.

Adult↗

PubMed2002

Motor vehicle collision factors influence severity and type of TBI.

PRIMARY OBJECTIVE: To analyse the relationship between motor vehicle collision factors and TBI. RESEARCH DESIGN: Retrospective design analysed the difference between the types of brain injuries sustained in distinct collision configurations. METHODS AND PROCEDURES: Medical charts and police accident reports were reviewed for individuals sustaining TBI in 168 motor vehicle collisions between 1985-1998. MAIN OUTCOMES AND RESULTS: Lateral collisions and collisions involving contact with a fixed object were associated with the most severe brain injuries. Analysis of safety restraints revealed that seatbelts not only reduce the probability of injury, but they also mediate the severity of brain injury when it is sustained. CONCLUSIONS: Future research should focus the prevention of injury by better defining the minimum physical thresholds at which brain injury might be sustained and the mechanisms by which these thresholds are achieved during natural collisions.

Accident Prevention↗

PubMed2002

Retrospective assessment of rehabilitation outcome after traumatic brain injury: development and utility of the functional independence level.

OBJECTIVE: To develop a measure suitable for retrospective analysis of qualitative brain injury outcome data, the Functional Independence Level (FIL), and document its reliability, validity, and utility. DESIGN: Retrospective analysis of existing records, with inclusion based on availability of records, and quantitative or qualitative documentation of functional status at a minimum of 1.5 years after injury. SETTING: Statewide acute and postacute rehabilitation facilities, as part of a State Head Injury Program. PARTICIPANTS: A total of 338 individuals, with documented moderate to severe traumatic brain injury; primarily males ages 16 to 45. MAIN OUTCOME MEASURES: Disability Rating Scale (DRS) at discharge from primary rehabilitation, Living Situation and Functional Independence Level coded from information in postacute rehabilitation reports, at an average of approximately 6 years after injury. RESULTS: Inter-rater reliability coefficients for FIL ratings extracted from rehabilitation records, and between retrospective and in vivo assessments were highly significant. DRS scores at discharge from primary rehabilitation predicted a significant amount of variance in FIL scores at an average of 5 years after injury, and DRS scores remained a stable and significant predictor of FIL scores as the time period between discharge from rehabilitation and outcome ratings increased to 10 years after injury. FIL ratings were significantly lower for individuals living in residential facilities than those living with their families, as compared to living alone. CONCLUSIONS: The FIL is a reliable and useful tool for retrospective and prospective assessments of rehabilitation outcome. Gains made during primary rehabilitation by people with severe traumatic brain injury are generally maintained at long-term follow up. Retrospective ratings using the DRS and FIL can help guide postacute rehabilitation planning within state or regional head injury programs.

Activities of Daily Living↗

PubMed2002

Memory-delineated subtypes of schizophrenia: relationship to clinical, neuroanatomical, and neurophysiological measures.

Memory performance was examined in patients with schizophrenia to determine whether subgroups conforming to cortical and subcortical dementias could be identified and, if so, whether subgroups differed on clinical, neuroanatomical, and neurophysiological measures. A cluster analysis of California Verbal Learning Test performance classified patients into 3 subgroups. Two groups exhibited memory deficits consistent with the cortical-subcortical distinction, whereas 1 group was unimpaired. Cortical patients tended to be male, and they had earlier illness onset, reduced temporal lobe gray matter, and hypometabolism. Subcortical patients had ventricular enlargement and more negative symptoms. Unimpaired patients had fewer negative symptoms and dorsal medial prefrontal hypermetabolism. The authors conclude that categorizing patients on the basis of memory deficits may yield neurobiologically meaningful disease subtypes.

Adult↗