Biomedical subjects

Roger Woods

Publications and source records attributed to Roger Woods.

4 recordsLinked to original sources

PubMed2004

Mood disturbances and regional cerebral metabolic abnormalities in recently abstinent methamphetamine abusers.

BACKGROUND: Mood disturbances in methamphetamine (MA) abusers likely influence drug use, but the neurobiological bases for these problems are poorly understood. OBJECTIVE: To assess regional brain function and its possible relationships with negative affect in newly abstinent MA abusers. DESIGN: Two groups were compared by measures of mood and cerebral glucose metabolism ([18F]fluorodeoxyglucose positron emission tomography) during performance of a vigilance task. SETTING: Participants were recruited from the general community to a research center. PARTICIPANTS: Seventeen abstaining (4-7 days) MA abusers (6 women) were compared with 18 control subjects (8 women). MAIN OUTCOME MEASURES: Self-reports of depressive symptoms and anxiety were measured, as were global and relative glucose metabolism in the orbitofrontal, cingulate, lateral prefrontal, and insular cortices and the amygdala, striatum, and cerebellum. RESULTS: Abusers of MA provided higher self-ratings of depression and anxiety than control subjects and differed significantly in relative regional glucose metabolism: lower in the anterior cingulate and insula and higher in the lateral orbitofrontal area, middle and posterior cingulate, amygdala, ventral striatum, and cerebellum. In MA abusers, self-reports of depressive symptoms covaried positively with relative glucose metabolism in limbic regions (eg, perigenual anterior cingulate gyrus and amygdala) and ratings of state and trait anxiety covaried negatively with relative activity in the anterior cingulate cortex and left insula. Trait anxiety also covaried negatively with relative activity in the orbitofrontal cortex and positively with amygdala activity. CONCLUSIONS: Abusers of MA have abnormalities in brain regions implicated in mood disorders. Relationships between relative glucose metabolism in limbic and paralimbic regions and self-reports of depression and anxiety in MA abusers suggest that these regions are involved in affective dysregulation and may be an important target of intervention for MA dependence.

Adult↗

PubMed2004

Quantitative comparison of four brain extraction algorithms.

In a companion paper (Rehm et al., 2004), we introduced Minneapolis Consensus Strip (McStrip), a hybrid algorithm for brain/non-brain segmentation. In this paper, we compare the performance of McStrip and three brain extraction algorithms (BEAs) in widespread use within the neuroimaging community--Statistical Parametric Mapping v.2 (SPM2), Brain Extraction Tool (BET), and Brain Surface Extractor (BSE)--to the "gold standard" of manually stripped T1-weighted MRI brain volumes. Our comparison was based on quantitative boundary and volume metrics, reproducibility across repeat scans of a single subject, and assessments of performance consistency across datasets acquired on different scanners at different institutions. McStrip, a hybrid method incorporating warping to a template, intensity thresholding, and edge detection, consistently outperformed SPM2, BET, and BSE, all of which rely on a single algorithmic strategy.

Algorithms↗

PubMed2004

Putting our heads together: a consensus approach to brain/non-brain segmentation in T1-weighted MR volumes.

We describe an approach to brain extraction from T1-weighted MR volumes that uses a hierarchy of masks created by different models to form a consensus mask. The algorithm (McStrip) incorporates atlas-based extraction via nonlinear warping, intensity-threshold masking with connectivity constraints, and edge-based masking with morphological operations. Volume and boundary metrics were computed to evaluate the reproducibility and accuracy of McStrip against manual brain extraction on 38 scans from normal and ataxic subjects. McStrip masks were reproducible across six repeat scans of a normal subject and were significantly more accurate than the masks produced by any of the individual algorithmic components.

Algorithms↗

PubMed2004

Ankle dorsiflexion as an fMRI paradigm to assay motor control for walking during rehabilitation.

The ability to walk independently with the velocity and endurance that permit home and community activities is a highly regarded goal for neurological rehabilitation after stroke. This pilot study explored a functional magnetic resonance imaging (fMRI) activation paradigm for its ability to reflect phases of motor learning over the course of locomotor rehabilitation-mediated functional gains. Ankle dorsiflexion is an important kinematic aspect of the swing and initial stance phase of the gait cycle. The motor control of dorsiflexion depends in part on descending input from primary motor cortex. Thus, an fMRI activation paradigm using voluntary ankle dorsiflexion has face validity for the serial study of walking-related interventions. Healthy control subjects consistently engaged contralateral primary sensorimotor cortex (S1M1), supplementary motor area (SMA), premotor (PM) and cingulate motor (CMA) cortices, and ipsilateral cerebellum. Four adults with chronic hemiparetic stroke evolved practice-induced representational plasticity associated with gains in speed, endurance, motor control, and kinematics for walking. For example, an initial increase in activation within the thoracolumbar muscle representation of S1M1 in these subjects was followed by more focused activity toward the foot representation with additional pulses of training. Contralateral CMA and the secondary sensory area also reflected change with practice and gains. We demonstrate that the supraspinal sensorimotor network for the neural control of walking can be assessed indirectly by ankle dorsiflexion. The ankle paradigm may serve as an ongoing physiological assay of the optimal type, duration, and intensity of rehabilitative gait training.

Adult↗