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Biomedical subjects

Gad Alon

Publications and source records attributed to Gad Alon.

6 recordsLinked to original sources
PubMed2005

Reliability estimation of grouped functional imaging data using penalized maximum likelihood.

We analyzed grouped fMRI data and developed a reliability analysis for such data using the method of penalized maximum likelihood (ML). Specifically, this technique was applied to a somatosensory paradigm that used a mechanical probe to provide noxious stimuli to the foot, and a paradigm consisting of four levels of graded peripheral neuromuscular electrical stimulation (NMES). In each case, reliability maps of activation were generated. Receiver operating characteristic (ROC) curves were constructed in the case of the graded NMES paradigm for each level of stimulation, which revealed an increase in the specificity of activation with increasing stimulation levels. In addition, penalized ML was used to determine whether the grouped reliability maps obtained from one stimulus level were significantly different from those obtained at other levels. The results show a significant difference (P < 0.01) in the reliability of activation from one stimulation level to the next. These results are in agreement with those obtained using generalized linear modeling (GLM). While the reliability maps generated are not directly comparable, they are qualitatively similar to those obtained by controlling the expected false discovery rate (FDR). The proposed methodology can be used to objectively compare activation maps between groups, as well as to perform reliability assessments. Furthermore, this method potentially can be used to assess the longitudinal effect of treatment therapies within a group.

Analysis of Variance↗
PubMed2003

Functional MRI determination of a dose-response relationship to lower extremity neuromuscular electrical stimulation in healthy subjects.

Although empirical evidence supports the use of neuromuscular electrical stimulation (NMES) to treat physical impairments associated with stroke, the mechanisms underlying the efficacy of this modality are poorly understood. Recent studies have employed functional imaging to investigations of brain responses to median nerve stimulation. These studies suggest a dose-response relationship may exist between selected stimulation parameters and hemodynamic responses in sensorimotor regions. However, substantial gaps exist in this literature. The present study was designed to address these deficiencies. Ten healthy subjects participated. In phase one, four stimulus intensity levels were established: (1). sensory threshold [Th], (2). (MM-Th)x0.333+Th [low-intermediate level, LI], (3). (MM-Th)x0.666+Th [high-intermediate level, HI], and (4). maximal motor (MM). In phase two, subjects were scanned using a spiral-echoplanar imaging technique at each stimulus level. Image sets were analyzed to determine hemodynamic responses at the highest Pearson correlation level ( r) ascertained for each of five areas of interest (AOI): (1). primary sensory, (2). primary motor, (3). cingulate gyrus, (4). thalamus, and (5). cerebellum. ANOVA demonstrated significant main effects for BOLD signal amplitude ( p<0.05) changes in all AOI. Similarly, ANOVA showed significant differences in the volume of activation ( p<0.05) with increasing stimulus intensity in four AOI. Secondary analyses of pooled data showed increasing probabilities of activation at higher stimulus intensities within each AOI. Collectively, these data indicate a dose-response relationship exists between lower extremity NMES and brain activation in specific neural regions. The current results, while limited in their generalizability, are foundational for future studies of interventions using NMES.

Adult↗
PubMed2003

Persons with C5 or C6 tetraplegia achieve selected functional gains using a neuroprosthesis.

OBJECTIVE: To test the efficacy and safety of the NESS Handmaster neuroprosthesis with subjects with C5 or C6 tetraplegia. DESIGN: Interventional, nonrandomized case series. SETTING: Subjects' residence and university research laboratory. PARTICIPANTS: Men, 3 to 17 years after C5 (n=5) and C6 (n=2) spinal cord injury (SCI). INTERVENTION: Subjects practiced with the neuroprosthesis daily to regain grasp, hold, and release ability and to restore selected functions of 1 of the 2 paralyzed hands. Subjects were observed 2 to 3 times weekly for 3 weeks. MAIN OUTCOME MEASURES: Three activities of daily living (ADL) tasks: (1) pick up a telephone, (2) eat food with a fork, and (3) perform 1 individually selected ADL task and 2 grasp, hold, and release tasks (lift a videocassette, lift a 150-g weight). Secondary outcomes were grip strength, electrically induced finger motion, and Fugl-Meyer spherical grasp. Nonparametric data were analyzed with the Wilcoxon signed-rank test, and parametric data (grip strength and finger motion) were analyzed by analysis of variance. All tests were considered significant at P equal to.01. RESULTS: At study completion, all 7 subjects were 100% successful at using the Handmaster in the studied ADL and grasp, hold, and release tasks. Significant improvements occurred in grip strength (from.57+/-.98N at baseline to 16.5+/-4.4N), finger linear motion (from 0.0cm at baseline to 8.4+/-3.2cm), and Fugl-Meyer scores. No safety issues were encountered. Six of 7 subjects rated their overall performance as "excellent." CONCLUSIONS: The Handmaster is a safe, noninvasive neuroprosthesis that improves hand function of selected subjects with C5 or C6 SCI.

Activities of Daily Living↗
PubMed2003

A home-based, self-administered stimulation program to improve selected hand functions of chronic stroke.

OBJECTIVES: To test if a combined stimulation-training program can improve selected hand functions and impairments of chronic stroke survivors. DESIGN: Pretest-Posttest, multi-site 5-week training program. Stroke survivors (N = 77) with chronic upper limb paresis completed a home-based stimulation program combining activation of the wrist-fingers flexors and extensors with functional grasp, hold and release training. Subjects trained 2-3 times each day, 7 days a week. Outcome measures included: the Jebsen-Taylor simulated feeding (S-feed); light object lift (J-T light); heavy object lift (J-T heavy); Box and Blocks test (B+B); Nine-Hole Peg (9-HP); Ashworth scale (Spasticity); Visual analog scale-VAS (Pain). Paired t-tests (alpha < 0.01) were performed on each study outcome. RESULTS: Simulated feeding time decreased from 39.1 +/- 30.9 sec to 25.5 +/- 23.3 sec (34.8% improvement). The task time of the J-T light decreased by 13.3 sec and the J-T heavy by 11.5 sec (44.9% and 40.9% improvement respectively). The number of blocks moved increased from 19.4 +/- 11.6 to 24.5 +/- 12.5 (26.3% improvement) and the time to complete the 9-HP decreased from 178.8 +/- 170.8 to 105.0 +/- 117.1 sec (58.7% improvement). Mean reduction of spasticity was 0.87 and 0.78 points at the elbow and wrist respectively. Patients with persistent pain (N = 33) reported mean reduction from 3.5 +/- 2.5 to 1.9 +/- 1.8. CONCLUSIONS: Five weeks of daily home training with a task-specific stimulation program improved selected hand functions and upper limb impairments associated with chronic post-stroke paresis.

Activities of Daily Living↗