Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 4

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The purpose of this study was to investigate the differences in the brain organization of motor control in left- and right¬handers and to study whether early left-to-right handwriting switch changes the cortical representation of finger movements in the left and right hemispheres. Echo-planar MR imaging was performed in 52 subjects: consistent right-handers (RH), consistent left-handers (LH), and subjects who had been forced at an early age to switch their left-hand preferences toward the right side. The scanning was performed during simple (flexion/extension of the index finger) and complex (successive finger-thumb opposition) tasks. Subjects performed the tasks using both the preferred and non-preferred hand. In right¬handers, there was a general predominance of left-hemisphere activation relative to right hemisphere activation. In left¬handers this pattern was reversed. The switched subjects showed no such volumetric asymmetry. Increasing levels of complexity of motor activity resulted in an increase in the volume of consistently activated areas and the involvement of the ipsilateral in addition to contralateral activations. In both right- and left-handers, movements of the preferred hand activated mainly the contralateral hemisphere, whereas movements of the non-preferred hand resulted in a more balanced pattern of activation in the two hemispheres, indicating greater involvement of the ipsilateral activations. Overall, this study shows that in both left- and right-handed subjects, the preferred hand is controlled mainly by the hemisphere contralateral to that hand, whereas the non-preferred hand is controlled by both hemispheres. The switched individuals share features of both left¬handers and right-handers regarding their motor control architectures.
Recent development of neuroimaging techniques has opened new possibilities for the study of the relation between handedness and the brain functional architecture. Here we report fMRI measurements of dominant and non-dominant hand movement representation in 12 right-handed subjects using block design. We measured possible asymmetry in the total volume of activated neural tissue in the two hemispheres during simple and complex finger movements performed either with the right hand or with the left hand. Simple movements consisted in contraction/extension of the index finger and complex movements in successive finger-thumb opposition from little finger to index finger. A general predominance of left-hemisphere activation relative to right hemisphere activation was found. Increasing the complexity of the motor activity resulted in an enlargement of the volume of consistently activated areas and greater involvement of ipsilateral areas, especially in the left hemisphere. Movements of the dominant hand elicited large contralateral activation (larger than movements of the non-dominant hand) and relatively smaller ipsilateral activation. Movements of the non-dominant hand resulted in a more balanced pattern of activation in the two hemispheres, due to relatively greater ipsilateral activation. This suggests that the dominant (right) hand is controlled mainly by the contralateral (left) hemisphere, whereas the nondominant hand is controlled by both left and right hemispheres. This effect is especially apparent during execution of complex movements. The expansion of brain areas involved in motor control in the hemisphere contralateral to the dominant hand may provide neural substrate for higher efficiency and a greater motor skill repertoire of the preferred hand.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.