Features of targeted arm movement after unilateral excisions that included the supplementary motor area in humans.

The strategies used to make rapid targeted flexion movements at the elbow were assessed for the right and left arms of ten neurologically normal subjects and seven patients who had unilateral cortical resections that included all or part of one supplementary motor area (SMA). Visual targets were displaced either a constant distance (fixed step task) or a variable distance (variable step task). The reaction time (RT) for SMA patients as a group did not differ significantly from normal, although for some patients, RT exceeded the normal range bilaterally. Total movement time (TMT) was longer than normal for the SMA group, and again, increased TMTs tended to occur bilaterally. Both groups of subjects used a combination of duration and velocity scaling to adjust movement amplitude. In normal subjects, however, velocity scaling predominated, whereas in SMA patients, duration scaling was increased bilaterally. Our data indicate that the initiation of rapid elbow movement to a target presented visually is not consistently delayed after lesions that include part of the SMA, but the movement speed and strategy used to adjust movement amplitude may be changed bilaterally.

Lack of detectable radiation hypersensitivity in lymphoblastoid cells from multiple pedigrees of familial Alzheimer disease.

Recent reports suggest that cultivated nonneuronal cells from individuals with Alzheimer disease (AD) and other specific hereditary neurodegenerative disorders show hypersensitivity to DNA-damaging agents such as x-rays and radiomimetic chemicals. The hypothesis proposed is that a number of chronic neurologic degenerations, including AD, may be the result of accumulation of damaged DNA, resulting from a defect in DNA repair. We investigated this hypothesis by evaluating cells from individuals from pedigrees of familial Alzheimer disease (FAD) for hypersensitivity to x-irradiation. Sensitivity was assayed by viability measured by trypan blue dye exclusion and micronucleus formation. We tested B-lymphoblastoid cell lines from nine patients and nine unaffected family members from pedigrees with FAD, three unrelated controls, three ataxia telangiectasia (AT) patients, and three Down syndrome individuals. The AT cell lines showed the expected reduced viability and increased micronucleus formation after x-ray treatment. The FAD and control lines showed marked heterogeneity with both assays. There was no significant differences between the FAD patients and controls. The wide variability in the response of cell lines from controls and patients indicates the need for more sensitive assays for detection of radiation sensitivity in cells from various neurologic disorders.