O. G. Pavlova

Rehabilitation of Stroke Patients with a Bioengineered “Brain–Computer Interface with Exoskeleton” System

Objective. To study the potential for use of a bioengineered system consisting of an electroencephalograph, a personal computer running a program for the synchronous data transmission, recognition, and classification of electroencephalogram (EEG) signals, and formation of control commands in real time, combined with a hand exoskeleton (a bioengineered “brain–computer interface (BCI) with exoskeleton” system) for the motor rehabilitation of patients with poststroke upper limb paresis. Materials and methods. Brain–computer interfaces have potential for use in neurorehabilitation. A total of five patients with poststroke upper limb paresis received neurorehabilitation courses consisting of 8–10 sessions. All the patients had large foci of poststroke changes of cortical-subcortical locations as demonstrated by MRI scans. Results. Improvements in neurological status on the NIHSS were seen after courses of sessions, with significant increases in the volume and strength of movements in the paralyzed hand, improvements in the coordination of its movements, and minor decreases in the level of spasticity. There was an increase in daily activity on the Barthel index, mainly due to improvement in fi ne motor function. Levels of disability showed clear changes on the modified Rankin scale. Conclusions. Use of the “brain–computer interface (BCI) with exoskeleton” system in the rehabilitation of patients with poststroke paresis of the hand gave positive results, pointing to the need to continue these studies.

Recovery of the motor function of the arm with the aid of a hand exoskeleton controlled by a brain–computer interface in a patient with an extensive brain lesion

The dynamics of motor function recovery in a patient with an extensive brain lesion has been investigated during a course of neurorehabilitation assisted by a hand exoskeleton controlled by a brain–computer interface. Biomechanical analysis of the movements of the paretic arm recorded during the rehabilitation course was used for an unbiased assessment of motor function. Fifteen procedures involving hand exoskeleton control (one procedure per week) yielded the following results: (a) the velocity profile for targeted movements of the paretic hand became nearly bell-shaped; (b) the patient began to extend and abduct the hand, which was flexed and adducted at the beginning of the course; and (c) the patient started supinating the forearm, which was pronated at the beginning of the rehabilitation course. The first result is interpreted as improvement of the general level of control over the paretic hand, and the two other results are interpreted as a decrease in spasticity of the paretic hand.

The Counting Function and Its Representation in the Parietal Cortex in Humans and Animals

Current data provide evidence that the ability to assess numbers is present not only in adult humans, but also in animals and children of preverbal age. Studies of behavior in infants and animals have demonstrated that the perception of number, the discrimination of quantities, and elementary addition and subtraction appear during onto- and phylogenesis before the appearance of speech. Number perception in humans and animals has common features: the greater the difference between numbers, the easier they are to discriminate; for a given difference between numbers, increases in size lead to increased difficulty in discrimination. Clinical data on counting impairments in patients and functional tomography studies of number operations in healthy subjects have shown that the key structures involved in number perception in humans are located in the parietal cortex. As demonstrated by experiments on monkeys and dogs, recognition of number in these species is also associated with the parietal area of the cortex. The similarity of the morphofunctional bases of “counting behavior” in humans and animals suggests that counting can be regarded as a functional mechanism of adaptive behavior which formed during evolution.

Instrumentalization of Movements Evoked by Stimulation of the Motor Cortex by Food Reinforcement in Dogs

The possibility that hindlimb movements (elevations) evoked by stimulation of the corresponding contralateral area of the motor cortex could be instrumentalized by reinforcement with food was demonstrated, contradicting some previously published data. Operant movements (interstimulus voluntary high elevations of the hindlimb) were acquired as a result of consistent combinations: cortical stimulation – movement – food. Acquisition required more than 50–200 combinations. Delivery of food was accompanied by a click at exactly the moment at which the hindlimb reached the required height. The click became the food-related conditioned signal and served as a secondary operant reinforcement, which facilitated acquisition of the operant movement. These results support the view that the motor cortex can have an immediate role in forming “operant” temporary connections (motivation-movement) and that simple operant movements can be initiated via this arc.The possibility that hindlimb movements (elevations) evoked by stimulation of the corresponding contralateral area of the motor cortex could be instrumentalized by reinforcement with food was demonstrated, contradicting some previously published data. Operant movements (interstimulus voluntary high elevations of the hindlimb) were acquired as a result of consistent combinations: cortical stimulation – movement – food. Acquisition required more than 50–200 combinations. Delivery of food was accompanied by a click at exactly the moment at which the hindlimb reached the required height. The click became the food-related conditioned signal and served as a secondary operant reinforcement, which facilitated acquisition of the operant movement. These results support the view that the motor cortex can have an immediate role in forming “operant” temporary connections (motivation-movement) and that simple operant movements can be initiated via this arc.

Is transfer of acquired coordination of head and forepaw movements possible in dogs

Dogs were trained to tonic elevation of the forepaw and to use a lever to lift and maintain in position a food-containing cup during eating, this being accompanied by inclination of the head towards the feeder. In the conditions used here, the pretraining situation was that dogs would elevate the paw with an anticipatory upward movement of the lowered head; when the head tilted to the feeder, the paw flexed. The effect of special training, in which the initial coordination of the head and paw movements were remodeled, was that the animals maintained the paw elevated with the head in the lowered position. Dogs trained to perform the operant response with one paw did not transfer the acquired reaction when the “working” paw was changed. After the first training, the initial coordination was changed only between movements of the head and the “working” limb, but not between head movements and the non-trained paw. Remodeling of the initial movement coordination of the head with the second paw also occurred only as a result of the learning process.Dogs were trained to tonic elevation of the forepaw and to use a lever to lift and maintain in position a food-containing cup during eating, this being accompanied by inclination of the head towards the feeder. In the conditions used here, the pretraining situation was that dogs would elevate the paw with an anticipatory upward movement of the lowered head; when the head tilted to the feeder, the paw flexed. The effect of special training, in which the initial coordination of the head and paw movements were remodeled, was that the animals maintained the paw elevated with the head in the lowered position. Dogs trained to perform the operant response with one paw did not transfer the acquired reaction when the “working” paw was changed. After the first training, the initial coordination was changed only between movements of the head and the “working” limb, but not between head movements and the non-trained paw. Remodeling of the initial movement coordination of the head with the second paw also occurred only as a result of the learning process.

Method for Qualitative and Quantitative Assessment of Proprioceptive Perception of Single-joint Arm Movements

The phenomenon of reproduction of the series of passive single-joint movements in the tested arm by the contralateral arm just in the course of passive movements with no visual control was studied in 35 healthy subjects and 13 post-stroke patients in order to develop a new method for objective assessment of sense of the arm motion for the detection of proprioceptive deficit and for monitoring of the changes in proprioception during rehabilitation. We examined the reproduction of flexion–extension at the elbow and wrist joints, abduction–adduction at the wrist joint and the forearm pronation–supination in both right and left arms in healthy subjects and in the affected arm in post-stroke patients. Displacements of the angles in the tested joint and a homonymous joint of the other arm were acquired by means of video recording system, goniometers, or 9-DoF inertional-magnetometric sensors. Qualitative and quantitative indicators were evaluated to assess the similarity of the passive and active movements. It has been found that the healthy subjects are able to actively reproduce the repeated passive movements at different joints of either the left or right tested arm almost simultaneously and with quite accurate reproduction of an amplitude and shape of movement. At the same time, most of post-stroke patients reproduce movements either with qualitative errors demonstrating incorrect location or wrong estimation of direction or number of repeated test movements, or with significant reduction of accuracy (increased latency or shape distortion). We proposed a method for the assessment of movement proprioception at individual joints. The procedure is easy and convenient for both physicians and patients. It does not require special heavy equipment and can easily be performed under different conditions in a wide range of patients.

The Role of the Motor Cortex in the Control of Axial and Proximal Muscles in Learning

The involvement of the motor cortex in controlling the muscles of the shoulder and scapula during formation of a new motor coordination of the head and forelimb was studied in dogs. Dogs were trained to flex the forelimb to operate a lever to raise a bowl containing food and hold it up during feeding with the head tilted towards the feeder. At the early stage of training, raising of the limb occurred with anticipatory upwards displacement of the head and, on lowering the head to the feeder, lowering of the elevated limb; this is the natural coordination of head and limb movements. The new coordination needed to obtain food – maintaining the elevated limb in a posture with the head lowered – could be achieved only as a result of learning and was critically dependent on the integrity of the motor cortex. In the natural coordination, limb elevation consistently involved the main shoulder flexors, i.e., the deltoid and teres major muscles, and inconsistently involved teres minor, infraspinatus, supraspinatus, and trapezius. In this latter group, muscles often operated in antiphase to the main shoulder flexors, i.e., were active on standing and stopped being active before limb elevation. Learned limb elevation in the posture with the lowered head involved all the muscles listed, some rearranging their initial activity to the opposite. Lesioning of the greater part of the forelimb representation in the motor cortex in trained dogs led to recovery of the natural coordination of head and limb movements and the initial muscular pattern during limb elevation. Thus, it was only with involvement of the motor cortex that the initial pattern of the activity of the phylogenetically ancient axial and proximal musculature underwent rearrangement and started to operate in a new way.

Role of the motor cortex in the rearrangement of a natural movement coordination in dogs

Chronic experiments on dogs were performed to study the activity of the shoulder muscles involved in elevating the forelimb used by the animal to lift a food-containing cup and keep it elevated during eating. At the early stage of acquisition of this operant reaction, limb-lifting occurred with an anticipatory upward head movement; lowering of the head to the feeder was associated with lowering of the lifted limb. The new coordination required for food to be obtained, i.e., maintaining the elevated limb in a posture with the head lowered, could only be achieved as a result of learning. In untrained dogs with the natural coordination, elevation of the limb occurred with activation of the deltoid and teres major muscles, teres minor being active on standing but ceasing its activity before limb elevation. During training the activity of the teres minor muscle changed to the opposite pattern. Limb elevation in the learned coordination was accompanied by activation of all three shoulder flexors. Lesioning of the motor cortex in the projection area of the “working” limb, but not in other areas, led to impairments of the acquired coordination and a new pattern of shoulder muscle activity. These data led to the conclusion that rearrangement of the initial coordination was linked with the formation of a new means of elevating the limb in which the muscle pattern was supported by the motor cortex.

Role of the Parietal Associative Area of the Cortex for "Counting" Behavior in Dogs

Experiments were performed on six dogs to study the effects of simultaneous and separate ablation of fields 5 and 7 of the parietal cortex on “counting” behavior. Dogs were trained to discriminate series of five sound clicks presented with variable interstimulus intervals from similar series consisting of three clicks. A food-related operant response (elevation of the right forepaw to place it on the feeder) was used to develop asymmetrical differentiation; the positive signal was a series of five clicks with variable interstimulus intervals and the negative (unreinforced) stimulus was a series of three clicks. Simultaneous bilateral ablation of fields 5 and 7 of the parietal cortex, like bilateral ablation only of field 5, produced profound impairment of differentiation lasting 2–3 months. Isolated bilateral ablation of field 7 produced no impairment of differentiation. These data led to the conclusion that field 5 of the parietal cortex is important for discriminating the numbers of sequential signals.

The roles of various projection areas of the motor cortex in the reorganization of the natural coordination of head and forelimb movements in dogs.

A food-related operant reaction was developed in dogs, in which animals had to maintain tonic elevation of the forelimb to hold a bowl while eating with the head tilted towards the feeder. The acquisition of this reaction involved rearrangement of the natural coordination of head and limb movements which appeared at an early stage of training of the dogs. Forelimb elevation was initially accompanied by anticipatory raising of the head, while lowering of the head led to lowering of the elevated limb. Limb elevation could only be maintained in the posture in which the head was raised. The new coordination required for obtaining food, contrary to the innate coordination and consisting of tonic elevation of the limb with the head lowered, could only be achieved as a result of training. Previous studies have established that lesioning of the primary motor cortex (MI) in the hemisphere contralateral to the working limb leads to stable impairment of the learned coordination, with regression to the initial coordination. The present report describes studies of the effects of local lesions of various projection areas of MI on performance of the learned coordination. Dogs which had acquired the learned operant reaction requiring the new head/limb coordination showed impairment only after lesioning of the representation area of the working limb in the MI; lesioning of the representation area of the head had no such effect.