Spontaneous recovery of precise movement and of the postural fixation of the extremities after excision of the somatosensory cortex in dogs

The extirpation of the foreleg area in the somatosensory cortex (SI) in dogs was performed in order to study the role of this area in motor control of the corresponding limb. Stable precise avoidance and escape reactions were established before the cortical lesion. Avoidance reactions disappeared during the first week after the surgery but then they were gradually restored without retraining. At the third weak there was a practically complete recovery of the precision of movements, the ability to fix the leg position and of the duration of successive phases of the reactions. The conclusion was drawn that the initial disturbances of avoidance reactions were most likely the result of diaschisis (shock). The initial disturbances of visually guided instrumental movements and escape reactions were much weaker than those of avoidance reactions (lifting of the foreleg in response to conditioned signal).     

Activity of pre-entral neurones in conscious monkeys: effects of deafferentation and cerebellar ablation.

After limb deafferentation, there was no gross alteration in the initiation and performance of a sound-triggered ballistic movement. The pattern of neuronal discharge in the arm area of the motor cortex was not significantly modified. In the absence of cerebellum, the reaction time of motor cortex cells was about 150 msec longer than the reaction time observed in normal and deafferented animals. This was associated with an equal retardation in the onset of ENG changes in the limb muscles. This observation is compatible with the idea that the motor cortex is normally situated downstream to the cerebellum in the initiation of some movements. However, the motor cortex is necessary for the initiation and execution of simple sound-triggered movements since its removal results in a permanent inability to perform the task. Finally, in the absence of peripheral feedback, the pattern of motor output to the agonistic and antagonistic muscles was initiated normally and thus appeared to be preprogrammed centrally. The importance of the motor cortex as a "reflex center" in the control of slower movements is obviously not challenged by these observations since the motor task that we have used depends very little or not at all on sensory feedback (Stark, 1968). What these results indicate, however, is that the execution of some voluntary fast ballistic movements can be entirely preprogrammed independently of peripheral and cerebellar influences, and that the program, which is mainly concerned with generating velocity signals, appears to require the integrity of the motor cortex for its execution.     

The role of the motor cortex in rearrangement of the innate movement coordination in the dog

In chronical experiments in dogs the pattern of shoulder muscle recruitment was examined during the forelimb flexion by which the animal lifted and held a cup of food during eating. At the early stage of the instrumental reaction learning the forelimb lifting was performed with the anticipatory deviation of the head in up direction, when the head bent down to the foodwell the lifted forelimb lowered. Simultaneous holding of the flexed forelimb and lowered head providing food reinforcement was achieved only by learning. It was found that the forelimb lifting in the innate coordination in untrained dogs was performed with activation of m. deltoideus and m. teres major, whereas m. teres minor was active whilst the dog was standing but the muscle activity was abolished before the limb lifting. In the course of learning m. teres minor activity was changed into opposite one. In the learned coordination the limb lifting was accompanied by the activation of all three shoulder flexors. The lesion of the motor cortex in the area of the "working" forelimb, but not in other areas led to disturbance of the learned coordination and the novel pattern of the shoulder muscle activity. The data obtained led to the following conclusion: the rearrangement of the innate coordination is connected with the formation of the novel way of the forelimb lifting which pattern of muscle recruitment is provided by the motor cortex.     

Disruption of acquired head and paw movement coordination after unilateral lesioning of the motor cortex in dogs (a kinematic analysis)

Dogs were trained to remove a cup with meat to the head bent down to the feeder and hold the limb flexed during eating. At the early stage of learning, the stable innate head-forelimb coordination characteristic for untrained animals was manifest. The forelimb flexion was accompanied by anticipatory lifting of the bent head, and the following bending of the head led to an extension of the flexed forelimb. The opposite coordination, i.e., the lifting and holding of the forelimb when the head is bent down, was achieved only by training. The lesion of the motor cortex contralateral to the working forelimb in the trained dogs led to a prolonged disturbance of the simultaneous holding of the flexed forelimb and the head bent down. The lesion of the motor cortex did not affect the individual movements but disturbed their coordination. In the operated dogs the innate relationships between the head and forelimb movement recovered. The results support the previous finding that the lesion of the motor cortex led to recovery of the innate coordination transformed in the process of learning.     

Specificity of nuclear elements of the motor region of the cortex in organizing a precise motor response

After elaboration and consolidation of precise instrumental avoidance reflexes in dogs (lifting of a fore-leg to a 4-centimeters wide "safety zone"), a part of motor cortex in the area of moving leg was ablated. After the operation the search for "safety zone" i. e. the precision of estimating the position of the leg was irreversibly impaired, but the animal was still able to hold its extremity at the same level for a long period of time. Artifically elaborated motor coordination--antagonistic to the innate one--also showed irreversible impairment. However, in case of an extremely "drilled" reaction (5.000 pairings) the elaborated coordination persisted. Minimal amplitude of correction movements increased too (i. e. subtlety of movements decreased), but during retraining this parameter of the movement became compensated. The data obtained suggest that the specificity of central cellular elements of the cortical motor area consists in estimation of extremity position which is necessary for finding a given point in space.     

Responses of motor cortex neurons of the cat to auditory stimulation and their role in the instrumental food reflex

The responses of motor cortex neurons in the cat to the presentation of a single auditory click and a series of 10 clicks presented with 1,000/sec frequency were studied under conditions of chronic experiments before and after the development of an instrumental food reflex. After reflex development a single presentation of a positive conditioned stimulus (single click) markedly influenced for 7 sec the appearance of instrumental movements. At the same time, the immediate responses of motor cortex neurons to presentation of the conditioned auditory stimulus had no impact on the appearance in the motor cortex of discharges leading to the realization of instrumental movements. Consequently, motor cortex neurons do not require activation from afferent sensory inputs for the generation of such discharges. The immediate neuronal responses to conditioned stimulation did not inhibit the realization of the instrumental reflex. It is proposed that they are associated with the realization of motor function in the unconditioned defensive response evoked by the presentation of an auditory stimulus. The presence or absence of responses to auditory conditioned stimulation was dependent upon the signal meaning of the stimulus, its physical parameters, and the degree of excitability of the animal.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 539–550, July–August, 1985.     

Serial recording of sensory,corticomotor, and brainstem-derived motor evoked potentials in the rat

A method is presented for serial recording of corticomotor evoked potentials (CMEPs), brainstem-derived motor evoked potentials (BMEPs), and somatosensory evoked potentials (SEPs) via permanently implanted cranial screws. One screw was positioned posterior to lambda (posterior screw), and two screws were positioned over the cortical hind limb areas (cortical screws). SEPs were elicited by stimulation of the hind paw and recorded from the contralateral cortex. BMEPs were stimulated via the posterior screw and recorded from both hind limbs, whereas CMEPs were elicited by repeated bipolar stimulation of the cortex and recorded from the contralateral hind limb. BMEPs and CMEPs differed in several points and can be considered as completely separate motor evoked potentials. While BMEPs consisted of a prominent negative peak with short latency (5–7.5 ms), CMEPs were represented by polyphasic signals with long latencies (17–22 ms). The cortical origin of the CMEPs was confirmed by transecting the corticospinal tracts, which abolished the CMEPs but spared the BMEPs. SEPs consisted of three consecutive peaks with mean latencies of the initial peak ranging between 15 and 17 ms. Dorsal column transection also abolished SEPs. In healthy rats, all three signals were recorded for six consecutive weeks. Signal parameters did not change significantly within this observation period. Rats tolerated the screws and the repeated measurements very well and no negative affect on animal behavior was noted. Thus, this method allows serial recording of SEPs, CMEPs, and BMEPs in chronic rat models.     

Serial recording of sensory, corticomotor, and brainstem-derived motor evoked potentials in the rat

A method is presented for serial recording of corticomotor evoked potentials (CMEPs), brainstem-derived motor evoked potentials (BMEPs), and somatosensory evoked potentials (SEPs) via permanently implanted cranial screws. One screw was positioned posterior to lambda (posterior screw), and two screws were positioned over the cortical hind limb areas (cortical screws). SEPs were elicited by stimulation of the hind paw and recorded from the contralateral cortex. BMEPs were stimulated via the posterior screw and recorded from both hind limbs, whereas CMEPs were elicited by repeated bipolar stimulation of the cortex and recorded from the contralateral hind limb. BMEPs and CMEPs differed in several points and can be considered as completely separate motor evoked potentials. While BMEPs consisted of a prominent negative peak with short latency (5-7.5 ms), CMEPs were represented by polyphasic signals with long latencies (17-22 ms). The cortical origin of the CMEPs was confirmed by transecting the corticospinal tracts, which abolished the CMEPs but spared the BMEPs. SEPs consisted of three consecutive peaks with mean latencies of the initial peak ranging between 15 and 17 ms. Dorsal column transection also abolished SEPs. In healthy rats, all three signals were recorded for six consecutive weeks. Signal parameters did not change significantly within this observation period. Rats tolerated the screws and the repeated measurements very well and no negative affect on animal behavior was noted. Thus, this method allows serial recording of SEPs, CMEPs, and BMEPs in chronic rat models.     

A Functional Magnetic Resonance Imaging Study of Pathophysiological Changes Responsible for Mirror Movements in Parkinson’s Disease

Mirror movements correspond to involuntary movements observed in the limb contralateral to the one performing voluntary movement. They can be observed in Parkinson’s disease (PD) but their pathophysiology remains unclear. The present study aims at identifying their neural correlates in PD using functional magnetic resonance imaging. Ten control subjects and 14-off drug patients with asymmetrical right-sided PD were included (8 with left-sided mirror movements during right-hand movements, and 6 without mirror movements). Between-group comparisons of BOLD signal were performed during right-hand movements and at rest (p<0.005 uncorrected). The comparison between PD patients with and without mirror movements showed that mirror movements were associated with an overactivation of the insula, precuneus/posterior cingulate cortex bilaterally and of the left inferior frontal cortex and with a deactivation of the right dorsolateral prefrontal cortex, medial prefrontal cortex, and pre-supplementary motor area and occipital cortex. These data suggest that mirror movements in Parkinson’s disease are promoted by: 1- a deactivation of the non-mirroring inhibitory network (dorsolateral prefrontal cortex, pre-supplementary motor area); 2- an overactivation of prokinetic areas (notably the insula). The concomitant overactivation of a proactive inhibitory network (including the posterior cingulate cortex and precuneus) could reflect a compensatory inhibition of mirror movements.     

Natural coordination of the head and limb movements and its transformation by learning in dogs

Kinematic analysis of the head and the forelimb movements in dogs has been done during elaboration the instrumental tonic forelimb flexion when the head was bent down to foodwell. It was found, that in naive dogs the forelimb flexion was accompanied by anticipatory lifting of the head, the head lowering evoked extension of the flexed forelimb. Therefore simultaneous holding of the lifted limb and the lowered head was impossible and could be achieved only by learning. Studying of the dynamics of transformation of the innate (natural) head-forelimb coordination during learning has shown that innate relationship between phasic head-forelimb movements, which was lost at the early stage could spontaneously restore for a short time in trained dogs. It was found between low-amplitude head-forelimb oscillations which did not disturb the learnt tonic forelimb flexion, when the head was bent down. The innate coordination is supposed to be an inborn and in the given conditions the only possible way of the forelimb lifting, in which the anticipatory lifting of the head might facilitate the limb flexion. That's why lowering of the head provoked extension of the flexed limb. Contrary to the known hypothesis [4] that the mechanism of elaboration of the novel coordination is connected with suppression of the interfering innate coordination, it is proposed to consider the elaborated coordination as the novel way of the forelimb lifting in the forced posture of the lowered head. The novel flexion of the forelimb, as supposed, became possible by changing its innate organization (muscular pattern).     

Effect of damage to the parietal associative cortex on the function of acquired motor coordination in dogs

The effect of ablation of the parietal associative cortex on the performance of a complex food instrumental reaction was studied in dogs. The reaction consisted in two movements of the forelimb which were of similar pattern, but differed by their coordination. The first one was the lifting and holding of the paw at a required level for a required time, with the head in natural position (lifted), and the second one was the same movement of the paw with the head bent down for feeding, i.e. a new coordination, for the natural coordination consists in lowering of the forelimb associated with lowering of the head. During two sessions after the lesion, both reactions became irregular (so that the dogs performed only one of two movements or none). In the course of four months, the precision of the first movement was reduced, the amplitude of lifting the paw and duration of holding it were diminished. The new coordination persisted after ablation of the parietal associative cortex, though the holding (fixation) of the paw was less perfect. As was shown before by one of the present authors (M. E. Ioffe), lesion of the sensorimotor cortex resulted in profound disturbance of acquired coordination.     

Study of different kinds of locomotor movements in rats

The kinematics and electromyographic activity of the hind limb muscles of intact rats fixed in a special frame were investigated during locomotor movements of different kinds. A change in the external conditions determining the degree of limb loading (the presence or absence of support, and so on) was shown to lead to changes in the pattern and (or) amplitude of the movements. Six types of locomotion were distinguished, and in accordance with the kinematics of the hind limb movements these can be divided into two types: swimming and stepping. The analysis showed marked variability of the parameters (frequency, duration of the swing phase and of the support phase) of the different locomotor movements.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 183–189, March–April, 1985.     

Encoding of motor skill in the corticomuscular system of musicians

How motor skills are stored in the nervous system represents a fundamental question in neuroscience. Although musical motor skills are associated with a variety of adaptations [1-3], it remains unclear how these changes are linked to the known superior motor performance of expert musicians. Here we establish a direct and specific relationship between the functional organization of the corticomuscular system and skilled musical performance. Principal component analysis was used to identify joint correlation patterns in finger movements evoked by transcranial magnetic stimulation over the primary motor cortex while subjects were at rest. Linear combinations of a selected subset of these patterns were used to reconstruct active instrumental playing or grasping movements. Reconstruction quality of instrumental playing was superior in skilled musicians compared to musically untrained subjects, displayed taxonomic specificity for the trained movement repertoire, and correlated with the cumulated long-term training exposure, but not with the recent past training history. In violinists, the reconstruction quality of grasping movements correlated negatively with the long-term training history of violin playing. Our results indicate that experience-dependent motor skills are specifically encoded in the functional organization of the primary motor cortex and its efferent system and are consistent with a model of skill coding by a modular neuronal architecture [4].     

The mechanisms of motor learning]

In the paper the general principles of the motor learning are analyzed. A thesis is argued that instrumental conditioning is the basis of the motor learning, but the mechanisms of insight and the apparatus of anticipation of the action result also play an important role. At comparison of some theories of learning a hypothesis is suggested about the possibility of synthetic approach. Two stages can be distinguished in the process of the motor learning: formation of semantic and coordination programs. Formation and realization of learned movements opposite to the initial coordinations are constantly controlled by the motor cortex, which realizes the learned inhibition of the interfering coordinations.     

Assessing the function of motor cortex: single-neuron models of how neural response is modulated by limb biomechanics

Do neurons in primary motor cortex encode the generative details of motor behavior, such as individual muscle activities, or do they encode high-level movement attributes? Resolving this question has proven difficult, in large part because of the sizeable uncertainty inherent in estimating or measuring the joint torques and muscle forces that underlie movements made by biological limbs. We circumvented this difficulty by considering single-neuron responses in an isometric task, where joint torques and muscle forces can be straightforwardly computed from limb geometry. The response for each neuron was modeled as a linear function of a "preferred" joint torque vector, and this model was fit to individual neural responses across variations in limb posture. The resulting goodness of fit suggests that neurons in motor cortex do encode the kinetics of motor behavior and that the neural response properties of "preferred direction" and "gain" are dual components of a unitary response vector.     

Neuronal responses in area 7 of the cat cortex during defensive conditioning

Responses of neurons in area 7 of the parietal association cortex during and after formation of a defensive conditioned reflex to sound were recorded in waking cats. Changes in spike responses of the neurons as a result of the onset of conditioned reflex limb movements were observed in 68% of neurons. Spike responses of neurons formed as a result of learning appeared only if conditioned-reflex limb movements appeared, and they were not observed if, for some reason or other, movements were absent after presentation of the positive conditioned stimulus or on extinction of the reflex. Responses of 46% neurons to conditioned stimulation preceded the conditioned-reflex motor responses by 50–450 msec. The remaining responding neurons were recruited into the response after the beginning of movement. Characteristic spike responses of neurons to the conditioned stimulus appeared 500–900 msec before the beginning of movement and, in the case of appearance of special, "prolonged" motor responses of limb withdrawal, evoked by subsequent reinforcing stimulation.     

Muscle afferent modulation by stimulation of motor and supplementary motor cortex in cats

Local stimulation in the zone of motor representation of the cat hind limb in the postcruciate cortex (area 4) modulates afferent activity of flexor spindles of the foot. An initial pause, connected with contraction of extrafusal fibers, is observed in this activity. After the muscle has returned to its original length, a sharp rise of discharge frequency develops followed by a return to its initial level. Similar phases, but less marked, are observed in secondary afferents. Stimulation of contralateral and ipsilateral regions of the medial precruciate cortex (area 6) causes selective, intensive, and prolonged facilitation of discharge of type Ia units followed by an after-effect, without involving extrafusal muscle fibers. Since influences of the premotor supplementary cortex on lumbar gamma motoneurons are relatively independent of influences coupled with activation of the alpha system on muscle afferents from the motor cortex, a specific role of area 6 in the regulation of segmental excitability of the gamma system can be postulated.     

Motor cortex representation of the upper-limb in individuals born without a hand

The body schema is an action-related representation of the body that arises from activity in a network of multiple brain areas. While it was initially thought that the body schema developed with experience, the existence of phantom limbs in individuals born without a limb (amelics) led to the suggestion that it was innate. The problem with this idea, however, is that the vast majority of amelics do not report the presence of a phantom limb. Transcranial magnetic stimulation (TMS) applied over the primary motor cortex (M1) of traumatic amputees can evoke movement sensations in the phantom, suggesting that traumatic amputation does not delete movement representations of the missing hand. Given this, we asked whether the absence of a phantom limb in the majority of amelics means that the motor cortex does not contain a cortical representation of the missing limb, or whether it is present but has been deactivated by the lack of sensorimotor experience. In four upper-limb amelic subjects we directly stimulated the arm/hand region of M1 to see 1) whether we could evoke phantom sensations, and 2) whether muscle representations in the two cortices were organised asymmetrically. TMS applied over the motor cortex contralateral to the missing limb evoked contractions in stump muscles but did not evoke phantom movement sensations. The location and extent of muscle maps varied between hemispheres but did not reveal any systematic asymmetries. In contrast, forearm muscle thresholds were always higher for the missing limb side. We suggest that phantom movement sensations reported by some upper limb amelics are mostly driven by vision and not by the persistence of motor commands to the missing limb within the sensorimotor cortex. We propose that prewired movement representations of a limb need the experience of movement to be expressed within the primary motor cortex.     

Evoked potential correlates of early conditioning in the rat ontogeny.

In rats aged 2-8 weeks cortical EP to CS (20 flash - tone combinations, 0,9/sec, reinforced since the 10th application by electric shocks to the hind leg) were studied within different kinds of behavioral responses during avoidance learning and extinguishing. In contrast to our results in freely moving rats no developmental trend was found in this kind of avoidance (lifting of the hind leg). Average EP within reinforced trials (with escape or no reactions) differed in isolated application of CS from those when both CS and US were acting together. In younger animals the EP to CS combined with US were characterized by an evident late negative wave which shifted later (5-6 weeks toward the early negative complex. The EP changes in the auditory cortex were more pronounced, whereas visual EP with CS-US combination were rather decreased. In the youngest animals (2 weeks) the auditory EP within trials with avoidance were characterized by a distinct short latency deflection of the first positive wave, whereas in EP to extinguished CS the second deflection of the first positive wave prevailed. Also in these phenomena, the typical changes were clearly revealed in the auditory cortex. At later developmental stages (starting the 3rd, more prominently the 4th and 5th week) the wave following primary positive - negative complex was shifted toward the negativity if the animal responded by an avoidance; on the contrary an ample positive, often a double-peak wave arose if the response was extinguished. The stimulus and reaction dependence in the cortical EP showed the role of not yet fully mature cerebral cortex in avoidance learning. Both, fast as well as with some delay running processes participated in the observed phenomena during the ontogenetical development.     

Sensorimotor Learning of Acupuncture Needle Manipulation Using Visual Feedback

Objective

Humans can acquire a wide variety of motor skills using sensory feedback pertaining to discrepancies between intended and actual movements. Acupuncture needle manipulation involves sophisticated hand movements and represents a fundamental skill for acupuncturists. We investigated whether untrained students could improve their motor performance during acupuncture needle manipulation using visual feedback (VF).

Methods

Twenty-one untrained medical students were included, randomly divided into concurrent (n = 10) and post-trial (n = 11) VF groups. Both groups were trained in simple lift/thrusting techniques during session 1, and in complicated lift/thrusting techniques in session 2 (eight training trials per session). We compared the motion patterns and error magnitudes of pre- and post-training tests.

Results

During motion pattern analysis, both the concurrent and post-trial VF groups exhibited greater improvements in motion patterns during the complicated lifting/thrusting session. In the magnitude error analysis, both groups also exhibited reduced error magnitudes during the simple lifting/thrusting session. For the training period, the concurrent VF group exhibited reduced error magnitudes across all training trials, whereas the post-trial VF group was characterized by greater error magnitudes during initial trials, which gradually reduced during later trials.

Conclusions

Our findings suggest that novices can improve the sophisticated hand movements required for acupuncture needle manipulation using sensorimotor learning with VF. Use of two types of VF can be beneficial for untrained students in terms of learning how to manipulate acupuncture needles, using either automatic or cognitive processes.