Biomedical subjects

Leonid Kopylev

Publications and source records attributed to Leonid Kopylev.

4 recordsLinked to original sources

PubMed2004

Enhancing encoding of a motor memory in the primary motor cortex by cortical stimulation.

Motor training results in encoding of motor memories, a form of use-dependent plasticity. Here we tested the hypothesis that transcranial magnetic stimulation (TMS) synchronously applied to a motor cortex engaged in a motor training task could enhance this plastic process. Healthy volunteers were studied in four sessions: training consisting of performance of directionally specific voluntary thumb movements (Train alone), training with TMS delivered during the execution of the training movement in a strictly temporal relationship to the motor cortex contralateral (Train+TMS synchronous(contra)) and ipsilateral (Train+TMS synchronous(ipsi)) to the training hand, and training with TMS delivered asynchronous to the training movement to the motor cortex contralateral to the training hand (Train+TMS asynchronous(contra)). Train alone, Train+TMS synchronous(contra), and Train+TMS asynchronous(contra) but not Train+TMS synchronous(ipsi) elicited a clear motor memory. The longevity of the encoded memory was significantly enhanced by Train+TMS synchronous(contra) when compared with Train alone and Train+TMS asynchronous(contra). Therefore use-dependent encoding of a motor memory can be enhanced by synchronous Hebbian stimulation of the motor cortex that drives the training task and reduced by stimulation of the homologous ipsilateral motor cortex, a result relevant for studies of cognitive and physical rehabilitation.

Adult↗

PubMed2004

Intraoperative infrared imaging of brain tumors.

OBJECT: Although clinical imaging defines the anatomical relationship between a brain tumor and the surrounding brain and neurological deficits indicate the neurophysiological consequences of the tumor, the effect of a brain tumor on vascular physiology is less clear. METHODS: An infrared camera was used to measure the temperature of the cortical surface before, during, and after removal of a mass in 34 patients (primary brain tumor in 21 patients, brain metastases in 10 and falx meningioma, cavernous angioma, and radiation necrosis-astrocytosis in one patient each). To establish the magnitude of the effect on blood flow induced by the tumor, the images were compared with those from a group of six patients who underwent temporal lobectomy for epilepsy. In four cases a cerebral artery was temporarily occluded during the course of the surgery and infrared emissions from the cortex before and after occlusion were compared to establish the relationship of local temperature to regional blood flow. Discrete temperature gradients were associated with surgically verified lesions in all cases. Depending on the type of tumor, the cortex overlying the tumor was either colder or warmer than the surrounding cortex. Spatial reorganization of thermal gradients was observed after tumor resection. Temperature gradients of the cortex in patients with tumors exceeded those measured in the cortex of patients who underwent epilepsy surgery. CONCLUSIONS: Brain tumors induce changes in cerebral blood flow (CBF) in the cortex, which can be made visible by performing infrared imaging during cranial surgery. A reduction in CBF beyond the tumor margin improves after removal of the lesion.

Adenocarcinoma↗

PubMed2003

Age-dependent changes in the ability to encode a novel elementary motor memory.

In healthy individuals, motor training elicits cortical plasticity that encodes the kinematic details of the practiced movements and is thought to underlie recovery of function after stroke. The influence of age on this form of plasticity is incompletely understood. We studied 55 healthy subjects and identified a substantial decrease in training-dependent plasticity as a function of age in the absence of differences in training kinematics. These results suggest that the ability of the healthy aging motor cortex to reorganize in response to training decreases with age.

Adolescent↗

PubMed2002

Modulation of use-dependent plasticity by d-amphetamine.

Use-dependent plasticity, thought to contribute to functional recovery after brain injury, is elicited by motor training. The purpose of this study was to determine if administration of d-amphetamine facilitates the effects of motor training on use-dependent plasticity. Healthy human volunteers underwent a training period of voluntary thumb movements under the effects of placebo or d-amphetamine in different sessions in a randomized double-blind, counterbalanced design. Previous work in a drug-naive condition showed that such training causes changes in the direction of thumb movements evoked by transcranial magnetic stimulation and in transcranial magnetic stimulation-evoked electromyographic responses. The endpoint measure of the study was the magnitude of training-induced changes in transcranial magnetic stimulation-evoked kinematic and electromyographic responses in the d-amphetamine and in the placebo conditions. Motor training resulted in increased magnitude, faster development and longer lasting duration of use-dependent plasticity under d-amphetamine compared to the placebo session. These results document a facilitatory effect of d-amphetamine on use-dependent plasticity, a possible mechanism mediating the beneficial effect of this drug on functional recovery after cortical lesions.

Adult↗