Ipsilateral Motor Cortex Activation Research Articles

Ipsilateral motor cortex activation on functional magnetic resonance imaging during unilateral hand movements is related to interhemispheric interactions

Distal, unilateral hand movements can be associated with activation of both sensorimotor cortices on functional MRI. The neurophysiological significance of the ipsilateral activation remains unclear. We examined 10 healthy right-handed subjects with and without activation of the ipsilateral sensorimotor area during unilateral index-finger movements, to examine ipsilateral, uncrossed-descending pathways and interhemispheric interaction between bilateral motor areas, using transcranial magnetic stimulation (TMS). No subject showed ipsilateral activation during right hand movement. Five subjects showed ipsilateral sensorimotor cortical activation during left hand movement (IpsiLM1). In these subjects, paired-pulse TMS revealed a significant interhemispheric inhibition of the left motor cortex by the right hemisphere that was not present in the 5 subjects without IpsiLM1. Neither ipsilateral MEPs nor ipsilateral silent periods were evoked by TMS in any subjects. Our observation suggests that IpsiLM1 is not associated with the presence of ipsilateral uncrossed-descending projections. Instead, IpsiLM1 may reveal an enhanced interhemispheric inhibition from the right hemisphere upon the left to suppress superfluous, excessive activation.

Investigation of the normal proximal somatomotor system using magnetoencephalography

The role of the ipsilateral cortex in proximal muscle control in normal human subjects is still under debate. One clinical finding, rapid recovery of proximal muscle relative to distal muscle use following stroke, has led to the suggestion that the ipsilateral as well as the contralateral motor cortex may be involved in normal proximal muscle control. The primary goal of this project was to identify contralateral and ipsilateral motor cortex activation associated with proximal muscle movement in normal subjects using magnetoencephalography (MEG). We developed protocols for a self-paced bicep motor task and a deltoid, electrical-stimulation somatosensory task. The MEG data were analyzed using automated multi-dipole spatiotemporal modeling techniques to localize the sources and characterize the associated timing of these sources. Reliable contralateral primary motor and somatosensory sources localized to areas consistent with the homunculus. Ipsilateral M1 activation was only found in 2/12 hemispheres. Robust contralateral motor cortex activation and sparse ipsilateral motor cortex activation suggest that the ipsilateral motor cortex is not involved in normal proximal muscle control. The results suggest that proximal and distal muscle control is similar in normal subjects in the sense that proximal muscle control is primarily governed by the contralateral motor cortex.

最新の脳卒中画像診断 ｆＭＲＩと光トポグラフィーによる脳卒中後の機能画像診断

The mechanism of poststroke motor functional recovery remains to be elucidated. We used functional MRI (fMRI) and near-infrared spectroscopic topography (NIRS) to evaluate the compensatory motor activation of cortical regions during a hand movement task in patients who recovered from poststroke hemiparesis. 1) We evaluated 9 patients with various types of stroke with mild-moderate hemiparesis using fMRI within 1 month of stroke onset and after 2-3 months. At the first examination, the activation of the contralateral hemisphere (primary sensorimotor cortex and supplementary motor area) was markedly reduced during the paretic hand movement. At the second examination, the contralateral activation had recovered in 8 of 9 patients. It addition, activation of ipsilateral motor cortex was seen during the paretic hand movement in 4 of 9 patients. 2) We evaluated 6 patients with massive cerebral infarction in the territory of middle cerebral artery without severe residual hemiparesis using both fMRI and NIRS. Both techniques showed that the activation of ipsilateral primary motor cortex was activated during the paretic hand movement in addition to activation of extended motor areas of the contralateral hemisphere. These observations suggest that motor cortical reorganization, including the ipsilateral hemisphere, contributes to the recovery from poststroke hemiparesis.

Hemispheric asymmetry of ipsilateral motor cortex activation during unimanual motor tasks: further evidence for motor dominance

Objectives: To test to which extent the increase in ipsilateral motor cortex excitability during unimanual motor tasks shows hemispheric asymmetry. Methods: Six right-handed healthy subjects performed one of several motor tasks of different complexity (including rest) with one hand (task hand) while the other hand (non-task hand) was relaxed. Focal transcranial magnetic stimulation was applied to the motor cortex ipsilateral to the task hand and the amplitude of the motor evoked potential (MEP) in the non-task hand was measured. In one session, the task hand was the right hand, in the other session it was the left hand. The effects of motor task and side of the task hand were analyzed. Spinal motoneuron excitability was assessed using F-wave measurements. Results: Motor tasks, in particular complex finger sequences, resulted in an increase in MEP amplitude in the non-task hand. This increase was significantly less when the right hand rather than the left hand was the task hand. This difference was seen only in muscles homologous to primary task muscles. The asymmetry could not be explained by changes in F-wave amplitudes. Conclusions: Hemispheric asymmetry of ipsilateral motor cortex activation either supports the idea that, in right handers, the left motor cortex is more active in ipsilateral hand movements, or alternatively, that the left motor cortex exerts more effective inhibitory control over the right motor cortex than vice versa. We suggest that hemispheric asymmetry of ipsilateral motor cortex activation is one property of motor dominance of the left motor cortex.

An fMRI study of the lateralization of motor cortex activation in acallosal patients.

Transcranial magnetic stimulation (TMS) studies have suggested that callosal afferents may mediate inhibition of the ipsilateral motor cortex (IMC) during unilateral hand movements. To test this concept, we used fMRI to determine whether acallosal patients have increased IMC activation with either complex or simple unilateral finger movements. Neither the localization of motor cortical regions activated, the volumes of activation, or the relative hemispheric lateralization of activations were different between the patients and normal controls. The potential callosal inhibitory pathway identified by TMS therefore does not appear to contribute to the interhemispheric suppression of physiologically relevant activations in the motor cortex as measured by fMRI.

Activation of right ipsilateral motor cortex in patients with arteriovenous malformations in the left paracentral region

Activation of right ipsilateral motor cortex in patients with arteriovenous malformations in the left paracentral region

Normal activation of the supplementary motor area in patients with Parkinson's disease undergoing long-term treatment with levodopa.

Regional cerebral blood flow (rCBF) changes in cortical motor areas were measured during a movement of the dominant right hand in 15 patients with Parkinson's disease deprived of their usual levodopa treatment, in 11 patients with Parkinson's disease undergoing long-term treatment with levodopa, and in 15 normal volunteers. The supplementary motor areas were significantly activated in the normal subjects and in the patients receiving levodopa but not in the patients deprived of levodopa. The contralateral primary sensory motor area was significantly activated in all three groups. The ipsilateral primary sensory motor cortex was not activated in the normal subjects and the non-treated patients but was in the patients treated with levodopa. It is concluded that the supplementary motor area hypoactivation which is observed in akinetic non-treated patients with Parkinson's disease is not present in patients undergoing long-term treatment with levodopa. This result suggests that (a) levodopa improves the functional activity of supplementary motor areas in Parkinson's disease and (b) there is no pharmacological tolerance to this effect. The ipsilateral primary motor cortex activation observed in the patients treated with levodopa could be related to levodopa-induced abnormal involuntary movements.

Functional cooperativity of human cortical motor areas during self-paced simple finger movements. A high-resolution MRI study.

Magnetic resonance imaging of changes in cerebral blood oxygenation (CBO) delineated areas of neural activation during self-paced unilateral middle finger tapping in five normal volunteers. Four contiguous imaging sections parallel to the bicommissural plane covered the hand area of the primary sensori-motor cortex bilaterally. All measurements were performed at 2.0 T using rapid gradient-echo sequences (TR/TE = 63/30 ms) with high spatial resolution (0.8 x 1.6 x 4 mm) and both strong (40 degrees flip angle) and weak (10 degrees) radiofrequency excitation pulses. This allows differentiation of flow and CBO contributions to the observed signal alterations. Functional cooperativity was analysed by a pixel-by-pixel correlation of signal intensity time courses with the stimulus protocol. Areas of activation included the contralateral primary motor cortex, the homologue part of the primary sensory cortex, the supplementary motor area (SMA) and the lateral premotor areas in all volunteers. Task-related activation of ipsilateral primary motor cortex above a threshold correlation coefficient of 0.5 was seen in two out of five volunteers (at 40 degrees) and one out of five (at 10 degrees) when performing the right-hand task. The present MRI findings readily demonstrate in single subjects that the SMA is involved in self-paced finger tapping. Only sparse activation in the ipsilateral primary motor cortex is consistent with the motor paradigm used.