Publications (90)47.82 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: The aim of the present work was to study the interaction between the ability to learn a new motor skill and the preference for the right or left forelimb on performing manipulatory movements in rats. The new skill was the Morris water test, in which the animals were initially trained to find a platform hidden beneath the water by swimming from the sector opposite the platform and then by swimming from sectors located to the left and right of the platform. Forelimb preference was identified in terms of the animal’s grasping food from a narrow horizontal tube, such that the rats were divided into left-handed and right-handed animals. Our findings showed that a change in the start position for the first episodes of swimming from the left or right sector significantly increased the platform-finding time in right-handed rats, as compared with left-handed.
- [Show abstract] [Hide abstract] ABSTRACT: The aim was to examine the relationship between the ability to learn new motor skills and preference to the right or left front paw when performing manipulation movements in rats. As a new skill used the Morris water maze, in which the animals are initially trained to detect platform hidden under water at the swim of the sector of the opposite platform, and then when sailing from sectors on the left or the right of the platform. Preference paw was determined by using the taking of animal food from a narrow horizontal tube and, accordingly, the rats were divided into left-handedness and right-handedness. We found that when changing the place of launch, that is the first voyage from the left or right of the sector, are right-handed, unlike left-handed, spent significantly more time to find the platform.
- [Show abstract] [Hide abstract] ABSTRACT: Early stage Parkinson's disease (PD) shares certain symptoms with essential tremor (ET), which makes it difficult to differentiate between the two. We analyzed cyclical body bends in order to find kinematic parameters that are capable of differentiating among PD, ET and normal control (NC) subjects. A linear discriminant analysis of the joint angles showed a reliable distinction between NC and the two groups of patients, while differentiating reasonably well between PD and ET. PD patients showed difficulty performing hip segment rotation around the vertical axis, whereas ET patients demonstrated enlarged torso sway in the frontal plane. These findings suggest that kinematic parameters of body movement in the standing position are sensitive enough to serve as subclinical marks in the early diagnosis of PD and ET.
- [Show abstract] [Hide abstract] ABSTRACT: Motor evoked potentials (MEPs) in the right first dorsal interosseous (FDI) muscle elicited by transcranial magnetic stimulation of left motor cortex were assessed in ten healthy subjects during maintenance of a fixed FDI contraction level. Subjects maintained an integrated EMG (IEMG) level with visual feedback and reproduced this level by memory afterwards in the following tasks: stationary FDI muscle contraction at the level of 40 ± 5 % of its maximum voluntary contraction (MVC; 40 % task), at the level of 20 ± 5 % MVC (20 % task), and also when 20 % MVC was preceded by either no contraction (0-20 task), by stronger muscle contraction (40-20 task) or by no contraction with a previous strong contraction (40-0-20 task). The results show that the IEMG level was within the prescribed limits when 20 and 40 % stationary tasks were executed with and without visual feedback. In 0-20, 40-20, and 40-0-20 tasks, 20 % IEMG level was precisely controlled in the presence of visual feedback, but without visual feedback the IEMG and force during 20 % IEMG maintenance were significantly higher in the 40-0-20 task than those in 0-20 and 40-20 tasks. That is, without visual feedback, there were significant variations in muscle activity due to different prehistory of contraction. In stationary tasks, MEP amplitudes in 40 % task were higher than in 20 % task. MEPs did not differ significantly during maintenance of the 20 % level in tasks with different prehistory of muscle contraction with and without visual feedback. Thus, in spite of variations in muscle background activity due to different prehistory of contraction MEPs did not vary significantly. This dissociation suggests that the voluntary maintenance of IEMG level is determined not only by cortical mechanisms, as reflected by corticospinal excitability, but also by lower levels of CNS, where afferent signals and influences from other brain structures and spinal cord are convergent.
Chapter: Cerebellar Control of Posture[Show abstract] [Hide abstract] ABSTRACT: Cerebellar control of posture is mainly based on the connections of the cerebellum with brainstem reticular formation and vestibular system, which are the source of the medial descending system providing the control of the body, i.e., posture and balance. The story of studying the role of cerebellum in postural control started from the works of Rolando, Flourens, Magendie, and especially Luciani who pointed out the role of the cerebellum in control of postural tone and muscle force. He described the main results of cerebellar lesions: atonia, asthenia, astasia, and dysmetria. The studies were continued by Lewandowsky, Thomas, Babinski, Bekhterev, Sherrington and, in twentieth century, by Dow and Moruzzi, Ito, Diener, Dichgans, and others. Postural disturbances after cerebellar lesions are described both in animals and in patients. Particularly, MRI data were very efficient to provide correlations between lesions of a definite area of the cerebellum and disturbances of posture and locomotion. The fMRI studies of human locomotor centers revealed the activation including pacemakers for gait initiation and speed regulation in the interfastigial cerebellum and bilateral midbrain tegmentum (cerebellar and mesencephalic locomotor regions), their descending target regions in the pontine reticular formation, and the rhythm generators in the cerebellar vermis and paravermal cortex. A genetic approach is actively used for studying cerebellar control of posture. Specific genes expressed in cerebellum encoding glutamate receptors and other molecules were shown to affect postural control in mice. Plasticity in cerebellum (synaptogenesis, increasing dendritic trees) was described after complicated motor training. The role of cerebellum in learning was studied by Brindley, Marr, Albus, Thach, Ito, and others. The role of the cerebellum in the reorganization of posture and in learning new postural tasks in animals and humans has also been investigated. Though other brain systems such as the basal ganglia and the motor cortex-pyramidal system are specifically involved in this process as well, the cerebellum seems to be one of the main structures providing learning of voluntary control of posture. The cerebellar mechanisms of feedback learning could be a basis of this process. In particular, the motor cortex might be involved in feedback control whereas the cerebellum might play a role in feedforward control by acquiring inverse models in new postural tasks.
- [Show abstract] [Hide abstract] ABSTRACT: We studied voluntary control of integrated electromyogram (IEMG) in the range of 20 +/- 5% and 40 +/- 5% of the IEMG of m. abductor pollicis brevis during its maximum voluntary contraction with and without visual feedback. Healthy subjects performed IEMG control with visual feedback in 5 trials; IEMG control with visual feedback in 5 trials for 5 days, and the reproduction of memorized IEMG value without visual feedback after 5 trials of IEMG under the visual control. The accuracy of IEMG control was estimated by the following parameters: time of IEMG being out of the required 10% range (ERROR); IEMG variability (VARIABILITY), and the bias of IEMG mean level (BIAS) during 30-sec trials. The IEMG control in the range of 20 +/- 5% with visual feedback improved in all subjects over the course of 5 trials. Within 5-day training, ERROR and VARIABILITY reduced on the first day only; during the last 4 days there was no accuracy increase. ERROR increased more than twice when the 20% IEMG level was reproduced without vision. The IEMG control in the range of 40 +/- 5% improved neither during 5 trials, nor during 5 days of training with visual feedback. ERROR increased for about 1.5 times when the 40% IEMG level was reproduced without vision. It was concluded that the motor system, particularly the motor cortex, could control the given level of muscle activity using the visual feedback.
Article: [Regulation of motor behaviour][Show abstract] [Hide abstract] ABSTRACT: The review is devoted to analysis of the basic links of motor behavior control systems: sensorimotor cortex, cerebellum, a red nucleus and striatum. The organization and communications of these structures and their participation in learning and memory processes are described. The synaptic neurotransmitter and nonsynaptic neuromodulatory systems innervating these structures are also described. Hierarchical synaptic networks are formed by GABA and glutamatergic systems. The nonsynaptic dopaminergic system innervates both of these structures, but carries out a modulatory function. The mesocorticolimbic dopaminergic system induces an emotional and motivational state - processes of reinforcement, and participates in realization of purposeful behavior. The nigrostriatal dopaminergic system, through triggering an endocellular signal and the processes ofphosphorylation and dephosphorylation modulates activity ofGABA and glutamatergic receptors ofdorsal striatum spiny neurons and adapted thalamocortical networks.
- [Show abstract] [Hide abstract] ABSTRACT: We have undertaken for the first time in this country a study of the effect of motor training under conditions of virtual reality (VR) based on the use of the PlayStation II apparatus with the input of video images via a color digital video camera and the Eye Toy Play-3 computer animation program (Sony) for the medical rehabilitation of 47 patients aged from 21 to 76 years who presented with post-stroke arm/hand paresis. The mean duration of this pathology was roughly 8 months. Each training session lasted 20-30 minutes; a total of 5 times per week were carried out during 10 days. The effect was evaluated either clinically (based on the motor assessment scale, MAS) or biomechanically with the help of the Mini Birds electromagnetic system (Ascension Technology Corporation, USA). It was shown that the application of the virtual reality technology is especially efficacious in the patients with stroke localization in the right hemisphere. It decreased the severity of paresis not only in the proximal segments of the limb but also in its distal parts (wrist). This effect can be attributed to neuroplasticity. Moreover, the training increased the accuracy of hitting the target, decreased the curvature of the trajectory of motion, and reduced the time needed to fully accomplish the task. (in Russian): Применение технологии виртуальной реальности при восстановлении движений в паретичной руке у больных, перенесших инсульт. Впервые в России проведено изучение эффекта двигательного обучения в условиях технологии виртуальной реальности (ВР). С этой целью использовали аппаратуру PlayStation II с видеовводом изображения через цветную цифровую видеокамеру и анимационную компьютерную программу Eye Toy Play-3 (фирма "Sony") для реабилитации 47 пациентов с постинсультным парезом руки в возрасте от 21 года до 76 лет, со средней давностью заболевания около 8 мес. Тренировка проводилась по 20—30 мин 5 раз в неделю, курс состоял из 10 процедур. Эффект обучения оценивался клинически (по шкале Motor Assessment Scale — MAS) и биомеханически с помощью электромагнитной системы Mini Birds ("Ascension Technology Corporation", США). Показано, что использование технологии ВР особенно эффективно у больных с локализацией очага в правом полушарии, оно способствует уменьшению степени пареза не только в проксимальных отделах руки, на тренировку которых в основном направлены игровые задания, но также и в кисти, что можно объяснить с позиции нейропластичности мозга. Кроме того, повышается точность попадания в цель, уменьшается кривизна траектории движения и снижается время, затраченное на выполнение двигательного задания в целом.
- [Show abstract] [Hide abstract] ABSTRACT: В первой части работы исследовали ход обучения произвольному управлению центром давлений (ЦД) у больных постинсультными гемипарезами (поражение кортико-спинальной системы), болезнью Паркинсона (поражение нигро-стриарной системы) и мозжечковыми атаксиями. Стоя на стабилографе, больные играли в две компьютерные игры, ≪Мячики≫ (М) и ≪Кубики≫ (К), в которых они должны были совмещать ЦД (курсор) с мишенью и перемещать мишень в нужное положение. В игре М мишень появлялась в неожиданных положениях, и больной обучался общей стратегии управления ЦД. В игре К больной обучался известной точной траектории перемещения ЦД. У больных обе игры были нарушены по сравнению с нормой, В течение 10 дней обучения выполнение обеих игр улучшалось по-разному в разных группах больных. Общая стратегия управления ЦД (принятие решения о направлении движения) была больше нарушена при поражении нигро-стриарной системы, а контроль точности траектории ЦД – при поражении кортико-спинальной системы. Хуже всего обеим играм обучались больные с мозжечковыми поражениями. Предполагается, что мозжечок определяет программу изменения позы, а моторная кора – контроль по обратной связи. Вторая часть работы связана с исследованием роли моторной коры в обучении бимануальной координации позы и движения (стабилизация предплечья при его разгрузке) у здорового человека. Испытуемые удерживали предплечьем правой (позной) руки груз, который фиксировался с помощью электромагнита. Разгрузка позной руки испытуемого инициировалась подъемом такого же груза левой рукой. В контрольных сериях подъем груза не приводил к разгрузке позной руки. Изменение возбудимости моторной коры исследовали методом транскраниальной магнитной стимуляции (ТМС). При повторных пробах разгрузки наблюдались прогрессивное уменьшение амплитуды движения предплечья разгружаемой руки и усиление упреждающего торможения ЭМГ бицепса разгружаемого плеча (обучение). Нормированная величина мышечного ответа на ТМС (ответ/фон) в конце обучения достоверно увеличилась. Результаты говорят о роли моторной коры в торможении мешающих синергий и координаций в процессе обучения.
- [Show abstract] [Hide abstract] ABSTRACT: Patients with the initial stage of Parkinson disease (PD) and matched controls performed repetitive bendings and turnings in standing position. Tasks included trunk movements in each of the anatomical planes: sagittal, frontal and axial. Electromagnetic system Flock of Birds was used for movement registration. Sensors were fixed at different segments of subject's body. Joint angles in the ankle, hip and torso as well as coordinates of the center of pressure served as output parameters. The amplitudes of joint angles were found to be lower in PD patients. Performance of the axial rotation revealed most pronounced differences. Thus, the amplitudes of joint angles of trunk movements in different anatomical planes reliably discriminate between PD patients and healthy subjects.
- [Show abstract] [Hide abstract] ABSTRACT: Using the transcranial magnetic stimulation (TMS) of motor cortex we examined changes in the motor evoked potential (MEP) during natural bimanual unloading, during lifting of an equivalent weight by the contralateral arm while the ipsilateral forearm was held stationary (CONTRA) and during practice of unnatural unloading. During natural unloading, MEP amplitude decreased proportionally to the muscle activity. In CONTRA task MEP amplitude decreased, but the muscle activity was not changed. It suggests that the motor cortex activity related to the "postural" arm was inhibited by the contralateral motor cortex related to the "lifting" arm. This inhibition was diminished during the unloading task. When learning the unnatural unloading, the muscle activity decreased significantly with insignificant changes of MEP amplitude. Active role of the motor cortex during learning of the new task might be related to the reduction of the contralateral inhibition. This suggestion is supported by the observation that MEP amplitude decreased stronger than muscle activity in the first learning session similar to that in CONTRA task. MEP amplitude and background activity of the muscle proportionally decreased in the last learning trial. The results show that motor cortex activity in natural and unnatural unloading task might be related to the reduction of the interhemispheric inhibition.
- [Show abstract] [Hide abstract] ABSTRACT: There are a number of studies concerning difference of postural control following left or right hemisphere lesions. Few studies, however, compare the role of the right and left hemisphere in learning new postural tasks. This study aimed to address this question. Twenty patients with hemiparesis after ischemic stroke in the middle cerebral artery territory (11 with a right and 9 with a left hemispheric lesion) were investigated. All subjects were trained using two different tasks during ten training sessions. In both tasks, the subjects stood on a force platform and were taught to change the position of the center of pressure (COP) presented as a cursor on a monitor screen in front of the patient. The subjects were instructed to align the COP with the target and then move the target by shifting the COP in the indicated direction. In the "Balls" task, the position of the target (a ball) varied randomly, so the subject had to learn a general strategy of voluntary COP control. In "Bricks", the subject always had to move the target in a single direction (downward) from the top to the bottom of the screen, so that a precise postural coordination had to be learned. The number of correctly performed trials for a session was scored. The task performance and its rate were analyzed and compared with respect to the lesion lateralization between two patient groups. The voluntary control of the COP position and learning course were initially impaired in all groups of patients in both tasks. In "Balls", there were no differences between the two groups of patients. In contrast, in "Bricks", there was a greater initial deficit in patients with right hemisphere lesions, while the rate of postural learning and the final performance level did not differ between the groups. With a lower initial deficit and similar rate of learning, the maximal level of the task performance was reached earlier (on the 5th day of training) in patients with left hemisphere lesions. This group stopped improving its performance during follow-up training. The results suggest that the motor structures of the right hemisphere are more involved in the precise control of COP trajectory, but not in learning. There is no difference between hemispheres in the initial performance and learning of the general strategy of voluntary COP control. Possibly, the control of specific COP trajectory needs more sensory feedback that is associated with greater involvement of the right hemisphere. This might be a reason for the greater initial impairment of this task after lesions in the right hemisphere.
- [Show abstract] [Hide abstract] ABSTRACT: Several studies on mice have demonstrated a correlation between the concentrations of dopamine and its metabolites in the nucleus accumbens and asymmetry in forelimb preference. Dopamine concentrations were greater in the nucleus accumbens ipsilateral in relation to the preferred paw. Limb preference was demonstrated in rats during performance of a response consisting of withdrawing food from a horizontal tube. Brain tissue dopamine concentrations were estimated by high-performance liquid chromatography with electrochemical detection. The results showed that in "left-handed" rats, the dopamine concentration in the left nucleus accumbens was significantly greater than that in "right-handed" rats. In right-handed rats, the dopamine concentration in the right nucleus accumbens was greater than that in the left. The results obtained here are significantly consistent with data obtained in mice and support the suggestion that the dopamine level in rats is greater in the nucleus accumbens ipsilateral to the preferred limb.
- [Show abstract] [Hide abstract] ABSTRACT: Anticipatory postural adjustment (APA) during bimanual action is observed when participants hold an object in one hand and then lift that object with the other hand. The decrease in activity of a forearm flexor muscle prior to an active forearm unloading acts to stabilize the forearm position. Recent studies have investigated the influence of the corticospinal system on muscle activity during APA through transcranial magnetic stimulation. It was shown that at different times during APA, the amplitude of motor-evoked potentials in the forearm flexors decreased in conjunction with the decrease of muscle activity. If the unloading is triggered via an electromagnet by lifting an equal weight by the other arm, the anticipatory postural adjustment is learned through the repetition of unloading (three series of 20 trials). Using the transcranial magnetic stimulation, we examined changes in the motor-evoked potential in the forearm flexors before and after APA learning. Motor-evoked potential amplitude did not significantly change as forearm flexor activity decreased. The motor-evoked potential/background electromyogram ratio, however, increased in the final learning session in comparison to the initial learning session and stationary loading. The present results corroborate a hypothesis on the fundamental role of the motor cortex in the suppression of synergies that interfere with the execution of the new coordination in the process of motor learning.
- [Show abstract] [Hide abstract] ABSTRACT: The concentration of dophamine and its derivates is known to correlate with the degree of handedness in manipulative movements in rodents. In this work we studied a possibility to changing handedness in rats by injection of a dopamine agonist into the nucleus accumbens. Retrieving food from a horizontal tube was used to determine the limb preference (10 food retrievals by the preferred limb). Then apomorphine was injected into the n. accumbens ipsilateral to the preferred limb in the course of 7 days. The same volume of buffer solution was injected into the contralateral n. accumbens. Just after the last injection the limb preference was tested. It was shown that the chronic injection of the non-specific agonist of dophamine receptors significantly changed the limb preference.
- [Show abstract] [Hide abstract] ABSTRACT: The role of the motor cortex in forming a learned coordination (stabilization of the forearm on unloading) was studied in humans. Subjects maintained a 1-kg weight with the right (postural) forearm, the weight being attached via an electromagnet. Unloading of the postural arm was initiated by the subjects by lifting a similar load with the left arm. In control experiments, lifting of the load did not lead to unloading of the postural arm. Changes in motor cortex excitability were studied by transcranial magnetic stimulation applied to the representation area of the right biceps muscle in the motor cortex at the beginning and end of the experiments. Repeated unloading tests showed progressive decreases in the amplitude of the movement of the unloaded forearm, which were accompanied by increases in the anticipatory inhibition of the electromyogram of the biceps muscle of the unloaded arm (learning). Muscle responses to transcranial magnetic stimulation during the learning process showed no significant changes. Analysis of normalized muscle responses to transcranial magnetic stimulation (response/baseline) showed that these increased at the end of training and reached a significantly higher level than seen at the beginning of training. These results lead to the conclusion that the motor cortex plays a fundamental role in inhibiting synergies and coordinations which would interfere with the formation of the new coordination during motor learning.
- [Show abstract] [Hide abstract] ABSTRACT: A number of published studies reported a correlation between the paw preference in mice and asymmetry of tissue concentrations of dopamine (DA) and DA metabolites measured in the nucleus accumbens (NAcb) the DA concentration being higher in the nucleus ipsylateral to a preferred paw. This study aimed to investigate whether such asymmetry existed in rats. The paw preference was defined by reaching into a small horizontal tube for a food pellet. Tissue concentration of DA was measured by high-performance liquid chromatography with electrochemical detection. It was shown that the DA concentration in the left NAcb was significantly higher in "left-handed" rats than in "right-handed" animals. Within the group of "right-handers", the DA concentration was significantly higher in the right NAcb than in the left NAcb. The results confirm in part the experimental data obtained in mice and support the hypothesis that the paw preference is paralleled by elevated tissue DA in the ipsylateral NAcb of rodents.
- [Show abstract] [Hide abstract] ABSTRACT: For a long time, the cerebellum has been known to be a structure related to posture and equilibrium control. According to the anatomic structure of inputs and internal structure of the cerebellum, its role in learning was theoretically reasoned and experimentally proved. The hypothesis of an inverse internal model based on feedback-error learning mechanism combines feedforward control by the cerebellum and feedback control by the cerebral motor cortex. The cerebellar cortex is suggested to acquire internal models of the body and objects in the external world. During learning of a new tool the motor cortex receives feedback from the realized movement while the cerebellum produces only feedforward command. To realize a desired movement without feedback of the realized movement, the cerebellum needs to form an inverse model of the hand/arm system. This suggestion was supported by FMRi data. The role of cerebellum in learning new postural tasks mainly concerns reorganization of natural synergies. A learned postural pattern in dogs has been shown to be disturbed after lesions of the cerebral motor cortex or cerebellar nuclei. In humans, learning voluntary control of center of pressure position is greatly disturbed after cerebellar lesions. However, motor cortex and basal ganglia are also involved in the feedback learning postural tasks.
- [Show abstract] [Hide abstract] ABSTRACT: Снижение устойчивости вертикальной позы является одной из основных проблем, сопровождающих двигательные нарушения различной этиологии в клинике нервных болезней. Посту- ральная нестабильность снижает качество походки и скорость передвижения, нередко приводит к падениям больных, что усиливает их функциональную зависимость. Поэтому выявление на¬ рушений устойчивости вертикальной позы и их восстановление являются важными задачами физической реабилитации невроло¬ гических больных.
- [Show abstract] [Hide abstract] ABSTRACT: The aim of the present work was to study the effects of training on the restoration of a lateralized motor skill (a food-procuring forelimb movement) in Wistar rats (n = 83) after lesioning of the caudate nucleus in conditions of infrequent testing and intensive retraining. On the basis of the training results, the rats were divided into those preferring the right (right-handers) or left (left-handers) limb. Testing was followed by lesioning of the head of the caudate nucleus on the side contralateral to the preferred paw. Animals with identical initial preferences were then divided into two groups: an infrequently tested group in which recovery of the skill was tested once weekly for five months, and an intensive retraining group, in which experiments were performed 3-4 times weekly, again for five months. After surgery, animals had to perform the food-procuring skill only with the "impaired" paw. Differences in the recovery of the skill were seen in animals with different limb preferences both in conditions of spontaneous recovery and in those recovering with training. Overall, animals with lesions of the left caudate nucleus (right-handers) showed better recovery than animals with lesions of the right caudate nucleus (left-handers) in both spontaneous recovery and in recovery with training. These findings suggest that the central neural mechanisms of recovery of a lateralized motor skill after unilateral lesioning of the caudate nucleus are different after lesions to the right and left hemispheres.
Instituto de Salud Carlos IIIMadrid, Madrid, Spain
Russian Academy of Sciences
Moskva, Moscow, Russia
- Institute of Problems of Information Transmission