Biomedical subjects

Stephen M Sawrie

Publications and source records attributed to Stephen M Sawrie.

5 recordsLinked to original sources

PubMed2006

Reliability of language mapping with magnetic source imaging in epilepsy surgery candidates.

The external validity of a noninvasive language mapping protocol with magnetoencephalography (MEG) has been established through direct comparisons with invasive functional mapping techniques. This study examines the test-retest and interrater reliability of this protocol under realistic testing conditions in 21 epilepsy surgery candidates. Brain activation maps were obtained in the context of an auditory word recognition task and represented by temporally contiguous dipolar activity sources. Both the duration and strength of the associated magnetic flux were used as measures of the magnitude of regional brain activity. Hemispheric asymmetry indices based on these measures showed good interrater reliability and intraparticipant reproducibility. Similar findings were obtained with respect to the location of the geometric center of receptive language-specific cortex (Wernicke's) area in the dominant hemisphere. The results further support the adequacy of this MEG-based brain mapping protocol as a noninvasive tool for receptive language localization in epilepsy surgery candidates.

Adolescent↗

PubMed2005

Dynamic brain activation patterns for face recognition: a magnetoencephalography study.

The present study used magnetoencephalography (MEG) to investigate the spatiotemporal profile of neurophysiological activity associated with recognition of recently encountered human faces in seventeen healthy right-handed adults. Activity sources modeled as instantaneous equivalent current dipoles were found in ventral occipito-temporal regions during the early stages of stimulus processing and in lateral temporal cortices during later stages. Hemispheric asymmetries in regional activity were restricted to ventral occipitotemporal areas. The magnitude of magnetic flux originating in these regions was greater in the right hemisphere during the first 350 ms post-stimulus onset. In addition, the duration of neurophysiological activity was greater in the right hemisphere after 600 ms post-stimulus onset. The results indicate right hemisphere predominance in the degree of engagement of neurophysiological processes involved in both the pre- and post-recognition phases of face processing.

Adolescent↗

PubMed2002

In vivo hippocampal metabolic dysfunction in human temporal lobe epilepsy.

BACKGROUND: The nature of functional metabolic disturbances in mesial temporal lobe epilepsy remains unclear. OBJECTIVES: To compare in vivo measures of hippocampal metabolic abnormalities in mesial temporal lobe epilepsy, as acquired with fludeoxyglucose F 18 positron emission tomography and proton magnetic resonance spectroscopic imaging, and to determine the relationship between N-acetylaspartate (NAA) disturbances and well-established derangements of glucose metabolism. DESIGN: Measures of hippocampal glucose metabolism from fludeoxyglucose F 18 positron emission tomography were normalized to whole brain counts to provide a glucose uptake metabolic index. Proton magnetic resonance spectroscopic imaging was performed at 4.1 T, and measures of creatinine/NAA ratio were made from mostly hippocampal-only voxels. Direct comparisons and correlation analysis of measures were performed. SETTING: Presurgical evaluations for treatment of intractable epilepsy. PATIENTS: Twenty-nine patients between July 1994 and June 1996 who were candidates for anterior-medial temporal lobectomy at the epilepsy centers of the University of Alabama at Birmingham and Vanderbilt University schools of medicine were studied. RESULTS: The mean ipsilateral hippocampal glucose metabolic index (0.85) was normal, while the contralateral metabolic index (0.95) was nearly significant for an abnormally elevated measure. The mean ipsilateral hippocampal creatinine/NAA (1.26) was abnormally elevated; the mean contralateral creatinine/NAA (0.88) was normal. Hippocampal glucose and creatinine/NAA measures did not correlate; asymmetry measures also did not correlate. CONCLUSIONS: Hippocampal metabolic disturbances in mesial temporal lobe epilepsy as measured by fludeoxyglucose F 18 positron emission tomography vs proton magnetic resonance spectroscopic imaging reflect different mechanisms of biochemical dysfunction. This lack of correlation is hypothesized to reflect a differential effect of varying degrees of disturbed cellular energy metabolism on mechanisms of glucose use and biosynthesis of NAA.

Adolescent↗

PubMed2002

Analysis of cognitive change: a commentary on Keith et al. (2002).

There have been significant advances in the study of cognitive change in recent years, evolving from traditional group-level parametric methods to new techniques such as the reliable change index (RCI) and the standardized regression-based (SRB) change score. In the very interesting study of cognitive change following cardiopulmonary bypass, Keith et al. (2002) opted for a more traditional group-level analysis of change (the mixed factor analysis of variance). They cited several limitations of the individual-level analytic techniques such as the RCI. In this commentary, the author attempts to address these specific concerns as well as some of the more general difficulties presented by the analysis of cognitive change. Advantages and disadvantages of the RCI and SRB methods are discussed.

Cognition Disorders↗

PubMed2002

Narcissism and depression: MMPI-2 evidence for the continuum hypothesis in clinical samples.

According to one hypothesis, self-report measures of narcissism help describe a psychological continuum related to self-esteem. Most of the previous support for this idea appeared in studies of undergraduates responding to the Narcissistic Personality Inventory (NPI; Raskin & Hall, 1981) along with other self-report instruments. In this project, results consistent with the continuum hypothesis were obtained when Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) narcissism scales were correlated with depression in adults receiving treatment for alcoholism. Essentially identical outcomes emerged in a second sample of state psychiatric hospital patients. A third study upheld the hypothesis when narcissism scales were correlated with clinical assessments rather than self-reports of depression. None of these findings were easily explained in terms of alternative interpretations of self-reported narcissism, and these data demonstrate that empirical support for the continuum hypothesis was not limited to the NPI, undergraduates, or self-report measures.

Adult↗