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- Lindberg, Påvel, et al.
(författare)
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Wallerian degeneration of the corticofugal tracts in chronic stroke : A pilot study relating diffusion tensor imaging, transcranial magnetic stimulation, and hand function
- 2007
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Ingår i: Neurorehabilitation and Neural Repair. - : SAGE Publications. - 1545-9683 .- 1552-6844. ; 21:6, s. 551-560
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Tidskriftsartikel (refereegranskat)abstract
- Objective. This study tested the hypothesis that degeneration of the corticofugal tracts (CFTs) is related to poor functional outcome in the upper limb after stroke. Methods. The authors used diffusion tensor imaging to determine the degree of white matter integrity of the CFT (FAAH/UH) in chronic stroke patients and controls. The functional integrity of the corticospinal pathway was examined using transcranial magnetic stimulation. Recruitment curves and silent period duration were measured. The relationship between FA AH/UH and functional outcome of the upper limb was also assessed using a battery of upper limb function tests. Results. In patients, FA AH/UH correlated positively with the slope of recruitment curves (RC AH/UH) and grip strength. FAAH/UH also correlated negatively with the silent period duration (SPAH/UH). According to the FA AH/UH, patients were also classified into groups with minimal or extensive Wallerian degeneration (WD). Patients with more extensive WD had poorer grip strength, dexterity, and range of movement. Conclusions. The authors' results suggest that structural and functional integrity of the CFT is essential to maintain function of the upper limb after stroke.
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| 6. |
- Ehrsson, HH, et al.
(författare)
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Holding an object: neural activity associated with fingertip force adjustments to external perturbations
- 2007
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 97:2, s. 1342-1352
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Tidskriftsartikel (refereegranskat)abstract
- When you hold an object, a sudden unexpected perturbation can threaten the stability of your grasp. In such situations grasp stability is maintained by fast reflexive-like grip-force responses triggered by the somatosensory feedback. Here we use functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms involved in the grip-force responses associated with unexpected increases (loading) and decreases (unloading) in the load force. Healthy right-handed subjects held an instrumented object (of mass 200 g) between the tips of right index finger and thumb. At some time during an interval of 8 to 45 s the weight of the object was suddenly increased or decreased by 90 g. We analyzed the transient increases in the fMRI signal that corresponded precisely in time to these grip-force responses. Activity in the left primary motor cortex was associated with the loading response, but not with unloading, suggesting that sensorimotor processing in this area mediates the sensory-triggered reflexive increase in grip force during loading. Both the loading and the unloading events activated the cingulate motor area and the medial cerebellum. We suggest that these regions could participate in the updating of the sensorimotor representations of the fingertip forces. Finally, the supplementary somatosensory area located on the medial wall of the parietal lobe showed an increase in activity only during unloading, indicating that this area is involved in the sensorimotor processing generating the unloading response. Taken together, our findings suggest different central mechanisms for the grip-force responses during loading and unloading.
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| 7. |
- Forssberg, Eric, et al.
(författare)
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Recovery of metals from shredded television scrap
- 2008
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Ingår i: Proceedings of XXIV International Mineral Processing Congress. - Beijing : American Science Press Inc.. - 9787900249548 ; , s. 3461-3468
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Konferensbidrag (refereegranskat)
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