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PubMed2006

Cortical motor areas are activated early in a characteristic sequence during post-movement processing.

During motor learning in goal-directed reactions, a specific movement has to be associated with feedback about the movement's success. Such feedback often follows when the movement is already over. We investigated the time-course of post-movement cortical motor processing by high-resolution analysis of lateralized post-movement potentials in forewarned and simple reaction time tasks. In both paradigms we could separate a post-movement component (motor postimperative negative variation-mPINV) peaking about 500 ms after the button press (confirmed by electromyogram and accelerometer). mPINV could not be sufficiently explained by motor cortex activity related to EMG output and/or by sensory feedback. mPINV was enhanced by long intertrial intervals and its lateralization changed with response movement side. Its scalp potential distribution resembled (pre-)motor cortex activity during preceding movement stages and differed from the frontal motor potential peak (proprioceptive and somatosensory reafferent feedback); suggesting post-movement activation of pre-/primary motor cortex. Dipole source analysis yielded a single radial source near premotor cortex which explained lateralized mPINV almost completely. mPINV was present in simple reaction time tasks, indicating that mPINV is an independent component and does not represent delayed resolution of pre-movement negativity. An equivalent of "classical" PINV (cPINV) occurred later over prefrontal and anterior temporal sites in simple and forewarned reaction time tasks. Our results suggest that high-resolution analysis of lateralized movement-related potentials allows to image post-movement motor cortex activity and might provide insights into basic mechanisms of motor learning: A characteristic sequence might involve motor cortex activation (mPINV) before "higher order associative areas" come into play (cPINV).

Adult↗
PubMed2006

Motor imagery of complex everyday movements. An fMRI study.

The present study aimed to investigate the functional neuroanatomical correlates of motor imagery (MI) of complex everyday movements (also called everyday tasks or functional tasks). 15 participants imagined two different types of everyday movements, movements confined to the upper extremities (UE; e.g., eating a meal) and movements involving the whole body (WB; e.g., swimming), during fMRI scanning. Results showed that both movement types activated the lateral and medial premotor cortices bilaterally, the left parietal cortex, and the right basal ganglia. Direct comparison of WB and UE movements further revealed a homuncular organization in the primary sensorimotor cortices (SMC), with UE movements represented in inferior parts of the SMC and WB movements in superior and medial parts. These results demonstrate that MI of everyday movements drives a cortical network comparable to the one described for more simple movements such as finger opposition. The findings further are in accordance with the suggestion that motor imagery-based mental practice is effective because it activates a comparable cortical network as overt training. Since most people are familiar with everyday movements and therefore a practice of the movement prior to scanning is not necessarily required, the current paradigm seems particularly appealing for clinical research and application focusing on patients with low or no residual motor abilities.

Adult↗
PubMed1999

The utilization of visual information in the control of rapid sequential aiming movements.

Two experiments were conducted to examine the role of vision in the execution of a movement sequence. Experiment 1 investigated whether individual components of a sequential movement are controlled together or separately. Participants executed a rapid aiming movement to two targets in sequence. A full vision condition was compared to a condition in which vision was eliminated while in contact with the first target. The size of the first target was constant, while the second target size was varied. Target size had an influence on movement time and peak velocity to the first target. Vision condition and target size did not affect the time spent on the first target. These results suggest that preparation of the second movement is completed before the first movement is terminated. Experiment 2 examined when this preparation occurred. A full vision condition was compared to a condition in which vision was occluded during the flight phase of the first movement. Movement initiation times were shorter when vision was continually available. Total movement time was reduced with vision in two-target condition, but not in a control one-target condition. The time spent on the first target was greater when vision was not available during the first movement component. The results indicate that vision prior to movement onset can be used to formulate a movement plan to both targets in the sequence [Fischman & Reeve (1992).

Adolescent↗
PubMed1998

Analysis of inter-fragmentary movement as a function of musculoskeletal loading conditions in sheep.

It is well accepted that inter-fragmentary movement influences the fracture healing process. Small axial movement can stimulate callus formation whereas larger shear movement delays the healing process. It is, therefore, essential for optimal fracture healing to minimize shear and to control axial movement. Unfortunately, the complex gap movements are mostly unknown under the large variety of clinical as well as experimental conditions of fracture fixation. To further understand the complex interactions of musculoskeletal loading and inter-fragmentary movements in bones and to reduce the need for animal experiments, a three-dimensional (3D) musculoskeletal model of the left hind limb of a sheep was developed. From 3D ground reaction forces and inverse dynamics, resultant joint loading was determined over a gait cycle. Muscle and joint contact forces were derived from an optimization routine and internal loads in the tibia and metatarsus from beam theory. Finally, inter-fragmentary movements were calculated from the bony loading condition and experimentally determined stiffness matrices of monolateral AISF external fixator constructs. Both the joint contact forces at the hip and gap movement of a mid-shaft tibial fracture agree with in vivo data reported in the literature. The bones proved to be mainly axially loaded with slightly increasing shear forces toward their ends. The results suggest that inter-fragmentary movement of metatarsal fractures is fairly independent of the fracture location whereas the movement increases in proximal tibial fractures compared to those in the distal and diaphyseal tibia. Considerable shear movement was found for all locations and external fixator mountings. However, shear movement could be minimized with a cranio-lateral rather than a cranio-medial shift from the cranial fixator plane.

Animals↗
PubMed2005

The cerebellum in the cerebro-cerebellar network for the control of eye and hand movements--an fMRI study.

The coordination of optical information and manipulation of objects in space by eye and hand movements is controlled by a cerebro-cerebellar network. The differential influence of prefrontal, motor, or parietal areas in combination with cerebellar areas, especially within the posterior hemispheres, on the control of eye and hand movements is not very well defined. Using fMRI we investigated the functional representation of isolated or combined eye and hand movements within the cerebellum and the impact of differential cognitive preload on the activation patterns. Each task consisted of the performance of saccades or hand movements triggered by a cue presented on a screen in front of the scanner. Saccades were tested for visually guided saccades, triple step saccades, and for visuospatial memory. Sequential finger opposition movements were tested for predictive and nonpredictive movements. Combined and isolated eye-hand reaching movements were tested toward a target presented in 5 different horizontal positions. Visually guided saccades activated the cerebellar vermis lobuli VI-VII, triple step saccades, including visuospatial memorization, in addition the cerebellar hemispheres lobuli VII-VIII. Sequential finger movements and reaching movements activated a cerebellar network consisting of the lobuli IV-VI, the vermis, and the lobuli VII-VIII with broader areas and additional regions especially within the lobus VII for more complex movements. The combined in contrast to the isolated performance of eye and hand movements demonstrated specialized activation foci within the cerebellar vermis and posterior hemispheres. We could demonstrate a differential representation of eye and hand movements within the cerebellum. Additional "cognitive" preload within a given task leads to additional activation of the posterior cerebellar hemispheres, with a subspecialization corresponding to premotor and parietal area connections.

Cerebellum↗
PubMed2002

Does order and timing in performance of imagined and actual movements affect the motor imagery process? The duration of walking and writing task.

The purpose of the present study was to investigate the effects on the duration of imagined movements of changes in timing and order of performance of actual and imagined movement. Two groups of subjects had to actually execute and imagine a walking and a writing task. The first group first executed 10 trials of the actual movements (block A) and then imagined the same movements at different intervals: immediately after actual movements (block I-1) and after 25 min (I-2), 50 min (I-3) and 75 min (I-4) interval. The second group first imagined and then actually executed the tasks. The duration of actual and imagined movements, recorded by means of an electronic stopwatch operated by the subjects, was analysed. The duration of imagined movements was very similar to those of actual movements, for both tasks, regardless of either the interval elapsed from the actual movements (first group) or the order of performance (second group). However, the variability of imagined movement duration was significantly increased compared to variability of the actual movements, for both motor tasks and groups. The findings give evidence of similar cognitive processes underlying both imagination and actual performance of movement.

Adult↗
PubMed2003

Long-Evans and Sprague-Dawley rats have similar skilled reaching success and limb representations in motor cortex but different movements: some cautionary insights into the selection of rat strains for neurobiological motor research.

Many rat strains are used for neurobiological studies of nervous system function and behavior. The most widely used strain for studies of the neural basis of movement is the out bred, pigmented Long-Evans strain, while the most widely used strains for the study of movement impairments in neurological disease are out bred albino rats, including Sprague-Dawley rats. Although previous research has indicated that there are strain differences in skilled movements displayed by different rat strains, there has been no explicit comparison of the Long-Evans and Sprague-Dawley strains. This was the purpose of the present study. The rats were video recorded as they learned to reach for single food pellets and the video records were subjected to frame-by-frame analysis. Component movements of reaching were scored using a system derived from Eshkol-Wachman Movement Notation (EWMN). The quality of movements was described using Laban Movement Analysis (LMA). Forelimb representations in motor cortex were defined electrophysiologically. Acquisition scores and success in reaching did not differ between the two strains, nor did the topographical representation of the forelimb in motor cortex. Long-Evans and Sprague-Dawley rats did differ in the movements used for reaching and on the quality of their movements. The movements of Sprague-Dawley rats resembled the movements of Long-Evans rats with motor system injury. That rat strains can show both quantitative and qualitative differences in movement is useful for the understanding of the genetic, neural, and behavioral organization of the motor system. The results are also relevant to the question of appropriateness of particular rat strains for studies of neurological diseases and the effects of albinism on motor behavior, and suggest that some of the most widely used rat strains for neurological investigations may be less than appropriate.

Animals↗
PubMed1999

Cortical potentials during imagined movements in individuals with chronic spinal cord injuries.

A closed-loop model of motor control predicts that central deafferentation should disrupt cortical motor processes when imagining movements of paralyzed limbs. To test this prediction, event-related potentials (ERP) were recorded from the supplementary motor area and the primary sensorimotor area in individuals with paraplegia or quadriplegia as well as able-bodied controls during executed/attempted and imagined movements of the hand and foot. The cross-correlation of ERPs generated during hand movement and imagery was slightly negative for controls, moderate and positive for paraplegics, and high and positive for quadriplegics. The cross-correlation between foot movement and imagery was moderate for controls, moderate to high for paraplegic and high for quadriplegic groups. For hand tasks, ERPs were uncorrelated between controls and quadriplegics; for the foot tasks, the correlations were low between controls and both paraplegics and quadriplegics. Amplitudes and latencies of the ERP were also compared between movement and imagery and between the three injury groups. A biphasic waveform appears prior to and during movements in controls that is absent during imagery and when attempting/imagining movements of paralyzed limbs. Two hypotheses are proposed to explain the differences in cortical processing between movement and imagery and between injury groups. First, cortical motor processes are altered by the absence of kinesthetic feedback during attempted movement of a deafferented limb as well as during imagery. Second, inhibitory processes, present during imagined movements of an intact limb, may be weakened by a spinal cord injury (SCI) so that movement and imagery processes appear isomorphic. While the absence of kinesthetic feedback from deafferented limbs likely contributes to some variability in motor processing, the influence of an SCI on movement inhibition requires further testing.

Adult↗
PubMed1997

Involvement of pallidal and nigral GABA mechanisms in the generation of tremulous jaw movements in rats.

Four experiments were conducted to investigate the role of pallidal and nigral GABA in the generation of tremulous jaw movements in rats. In these experiments, tremulous jaw movements were induced by i.p. injections of the anticholinesterase tacrine (5.0 mg/kg). Previous work has shown that the tremulous jaw movements induced by cholinomimetics and dopamine depletion are dependent upon striatal mechanisms. Thus, the present study investigated potential striatal output pathways that could be involved in the generation of these movements. Because there are GABAergic projections from neostriatum to entopeduncular nucleus (medial globus pallidus) and substantia nigra pars reticulata, the GABA agonist muscimol was injected directly into these structures to study the effects of GABA stimulation on tacrine-induced jaw movements. Injections of muscimol into the entopeduncular nucleus (25-100 ng) failed to have any significant effects on tacrine-induced vacuous jaw movements. However, injections of muscimol (12.5-50 ng) into the substantia nigra pars reticulata blocked the jaw movements induced by tacrine. In the third experiment, it was again demonstrated that 25.0 ng of muscimol injected directly into the substantia nigra pars reticulata blocked the jaw movements induced by tacrine; in addition, it was shown that injections of this dose 2.0 mm dorsal to the substantia nigra pars reticulata failed to affect tacrine-induced tremulous jaw movements. It was shown in the fourth experiment that injections of muscimol into a more medial portion of the substantia nigra pars reticulata also reduced tacrine-induced tremulous jaw movements. These results indicate that stimulation of GABA(A) receptors in substantia nigra pars reticulata can block tacrine-induced tremulous jaw movements. This finding is consistent with the notion that striatonigral GABA projections are involved in the generation of tremulous jaw movements. It is also possible that striatonigral GABA mechanisms are involved in human clinical phenomena such as parkinsonian tremor.

Animals↗
PubMed1989

[Evolution of gross body movements during sleep in healthy infants aged from 1 to 4 months].

To assess the evolution of body motility according to sleep states and age in young children, we performed day-sleep polygraphic recordings in 45 normal and full-term newborn infants, grouped according to age: 5 to 7 weeks, 9 to 11 weeks, 13 to 15 weeks of age. Generalized gross body movements were only studied. Our results showed that generalized movements varied according to sleep states and also according to age. The number of movements, in each age-group was significantly higher in active (AS) and indeterminate (IS) sleep than in quiet sleep (QS). This work also found that the distribution of the number of movements differed between sleep states. In AS, movements were equally distributed whereas in quiet sleep 40% of movements occurred during the last three minutes of a stage. Our results also showed that the mean number of movements per sleep hour, the mean duration of body movements and the percentage of time spent with movements significantly decreased with age. The distribution of the number of movements as a function of duration, showed that most of them lasted from 5 to 10 sec in each age-group of infants, whatever the sleep state; however, the number of the longest movements, lasting more than 10 sec, significantly decreased with age in IS and AS. These results were difficult to compare with those already published in the literature because of the different techniques for recording body movements; so it seemed impossible to use normal values established by other authors.

Humans↗
PubMed2003

Measuring movement irregularity in the upper motor neurone syndrome using normalised average rectified jerk.

Movement irregularity is a feature of the upper motor neurone (UMN) syndrome which is difficult to measure. Average rectified jerk (ARJ) has been proposed as a measure of this movement irregularity, but ARJ depends upon the duration of movement. Since movements may be slower in UMN patients, duration dependence compromises ARJ as a measure of irregularity. A normalisation technique is proposed that generates a measure of movement irregularity which is independent of movement duration: normalised average rectified jerk (NARJ). This paper presents a validation of NARJ in the UMN syndrome. Nine control subjects, nine left hemiparetic stroke patients and nine right hemiparetic stroke patients were studied. Test movements comprised elbow extension/flexion in the horizontal plane; these were recorded with an electro-goniometer and accelerometer. The effectiveness of the normalisation technique has been demonstrated using trajectories of various durations; some of these were artificially generated from participants' trajectories, in order to preserve the movement profile. The variability of NARJ and ARJ have been compared in a sample of control subjects. NARJ has been criterion validated by correlation with expert subjective rating of irregularity in a heterogeneous set of trajectories. Construct validity has been tested by discrimination between movements of control subjects, left hemiparetic stroke patients and right hemiparetic stroke patients. When comparing trajectories of identical profile but two-fold difference in movement duration, NARJ differed only 2.6% whereas ARJ differed 706%. NARJ was less reproducible in healthy participants than ARJ: median non-parametric coefficients of variation for repeated movements were 55% and 41%, respectively. Spearman rank correlation coefficient for NARJ and expert rating was 0.92 (p<0.01). NARJ measurements on right hemiparetic patients differ significantly from those made on the control group (p<0.02); corresponding ARJ measurements do not attain statistical significance. NARJ is a valid measure of movement irregularity in the UMN syndrome.

Adult↗
PubMed2000

Simultaneous movements of upper and lower limbs are coordinated by motor representations that are shared by both limbs: a PET study.

The purpose of this study was to examine the cerebral control of simultaneous movements of the upper and lower limbs. We examined two hypotheses on how the brain coordinates movement: (i) by the involvement of motor representations shared by both limbs; or (ii) by the engagement of specific neural populations. We used positron emission tomography to measure the relative cerebral blood flow in healthy subjects performing isolated cyclic flexion-extension movements of the wrist and ankle (i.e. movements of wrist or ankle alone), and simultaneous movements of the wrist and ankle (a rest condition was also included). The simultaneous movements were performed in the same directions (iso-directional) and in opposite directions (antidirectional). There was no difference in the brain activity between these two patterns of coordination. In several motor-related areas (e.g. the contralateral ventral premotor area, the dorsal premotor area, the supplementary motor area, the parietal operculum and the posterior parietal cortex), the representation of the isolated wrist movement overlapped with the representation of the isolated ankle movement. Importantly, the simultaneous movements activated the same set of motor-related regions that were active during the isolated movements. In the contralateral ventral premotor cortex, dorsal premotor cortex and parietal operculum, there was less activity during the simultaneous movements than for the sum of the activity for the two isolated movements (interaction analysis). Indeed, in the ventral premotor cortex and parietal operculum, the activity was practically identical regardless whether only the wrist, only the ankle, or both the wrist and the ankle were moved. Taken together, these findings suggest that interlimb coordination is mediated by motor representations shared by both limbs, rather than being mediated by specific additional neural populations.

Adult↗
PubMed2001

Transcranial magnetic stimulation over the cerebellum delays predictive head movements in the coordination of gaze.

We investigated coordinated saccadic eye and head movements following predictive horizontal visual targets at +/- 30 degrees by applying transcranial magnetic stimulation (TMS) over the cerebellum before the start of the gaze movement in 10 young subjects. We found three effects of TMS on eye-head movements: 1. Saccadic latency effect. When stimulation took place shortly before movements commenced (75-25 ms before), significantly shorter latencies were found between predictive target presentation and initiation of saccades. Eye latencies were significantly decreased by 45 ms on average, but head latencies were not. 2. Gaze amplitude effect. Without TMS, for the 60 degrees target amplitudes, head movements usually preceded eye movements, as expected (predictive gaze type 3). With TMS 5-75 ms before the gaze movement, the number of eye movements preceding head movements by 20-50 ms was significantly increased (p < 0.001) and the delay between eye and head movements was reversed (p < 0.001), i.e. we found eye-predictive gaze type 1. 3. Saccadic peak velocity effect. For TMS 5-25 s before the start of head movement, mean peak velocity of synkinetic eye saccades increased by 20-30% up to 600 degrees/s, compared to 350-400 degrees/s without TMS. We conclude that transient functional cerebellar deficits exerted by means of TMS can change the central synkinesis of eye-head coordination, including the preprogramming of the saccadic pulse and step of a coordinated gaze movement.

Adult↗
PubMed2002

The role of cutaneous feedback for anticipatory grip force adjustments during object movements and externally imposed variation of the direction of gravity.

Grip force adjustments to changes of object loading induced by external changes of the direction of gravity during discrete arm movements with a grasped object were analyzed during normal and anesthetized finger sensibility. Two subjects were seated upright in a rotatable chair and rotated backwards into a horizontal position during discrete movements with a hand-held instrumented object. The movement direction varied from vertical to horizontal inducing corresponding changes in the direction of gravity, but the orientation of the movement in relation to the body remained unaffected. During discrete vertical movements a maximum of load force occurs early in upward and late in downward movements; during horizontal movements two load force peaks result from both acceleratory and deceleratory phases of the movement. During performance with normal finger sensibility grip force was modulated in parallel with fluctuations of load force during vertical and horizontal movements. The grip force profile adopted to the varying load force profile during the transition from the vertical to the horizontal position. The maximum grip force occurred at the same time of maximum load force irrespective of the movement plane. During both subjects' first experience of digital anesthesia the object slipped from the grasp during rotation to the horizontal plane. During the following trials with anesthetized fingers subjects substantially increased their grip forces, resulting in elevated force ratios between maximum grip and load force. However, grip force was still modulated with the movement-induced load fluctuations and maximum grip force coincided with maximum load force during vertical and horizontal movements. This implies that the elevated force ratio between maximum grip and load force does not alter the feedforward system of grip force control. Cutaneous afferent information from the grasping digits seems to be important for the economic scaling of the grip force magnitude according to the actual loading conditions and for reactive grip force adjustments in response to load perturbations. However, it plays a subordinate role for the precise anticipatory temporal coupling between grip and load forces during voluntary object manipulation.

Acceleration↗
PubMed1980

Brain control of conjugate horizontal and vertical eye movements: a survey of the structural and functional correlates.

(1) It appears that all oculomotor pathways originating within the cerebrum and mediating stimulations and lesions, project from the two sides of the brain through the diencephalon to the brain-stem. (2) The pathways subserving horizontal movements decussate at the level of the oculomotor and trochlear nuclei, across the midsagittal plane. The direction of vector action within the brain above the 'electroanatomical' oculomotor decussation is predominately contraversive; below this levelit is ipsiversive. (3) The pontine reticular formation, the abducens and oculomotor nuclei and the median longitudinal fasciculus play an important role in the physiology of ipsilateral conjugate gaze. A 1 mm lesion within the paramedian pontine reticular formation causes paralysis of ipsilateral conjugate gaze, while a 1 mm lesion within the median longitudinal fasciculus causes impairment of contralateral (disconjugate) gaze with paralysis of adduction of the ipsilateral eye and nystagmus in the contralateral or abducting eye. (4) True binocular vertical movements occur only when both sides of the brain are activated either directly or through bilateral sensory (visual or vestibular) inputs. Vertical and oblique monocular movements can be elicited on unilateral stimulation at the level of the oculmotor nucleus. (5) Paralysis of vertical gaze is caused by bilateral lesions. Bilateral (1 to 2 mm) lesions within the region of the rostral interstitial nucleus of the median longitudinal fasciculus result in isolated paralysis of downward gaze. More caudally, bilateral (1 mm) lesions within the pretectum or midsection of the posterior commissure result in paralysis of upward gaze. (6) In different regions of the brain a theoretical transverse plane can be drawn between pathways which transmit impulses for vertical eye movements. Those which transmit impulses for binocular downward movement are situated dorsal to this plane, while those that trasmit impulses for upward movement are located ventrally to this plane. This topographical relationship can be demonstrated in the occipital lobe and to some extent in the frontal lobes. A hypothetical transverse plane separating the down and up eye movement can also be drawn at the mesodiencephalic junction. At the level of the oculmotor nucleus stimulations at the most rostral pole result in monocular downward movements, while the most caudal pole stimulations produce monocular upward movements. There is no evidence that the pathways which mediate binocular upward and binocular downward movement project across a hypothetical transverse plane. (7) Our knowledge of the synaptic connections between the cerebrum, diencephalon and the brain-stem nuclei, especially the paramedian pontine reticular formation, involved in binocular movements remains incomplete. Moreover, the anatomical location of the decussation of the right and left cerebral pathways which transmit conjugate eye movements are still unknown...

Abducens Nerve↗
PubMed1990

Movement variability and bradykinesia in Parkinson's disease.

When making discrete aiming movements, patients with Parkinson's disease show greater inherent variability in the endpoints of their movements than do normal subjects. Endpoint variability can be reduced, by moving more slowly, by utilizing visual guidance, and by making small amplitude movements. The greater variability of patients is not a universal finding, but depends on the conditions of movement. For small movements the performance of patients equates to that of controls. For larger movements the results indicate that if sufficient time is available, patients can use visual guidance (if available) to reduce the variability of their movements to the level of normals. Patients can generate fast and/or large amplitude arm movements if required, but they are erratic if made in the dark or over a short duration. Their difficulty lies not so much in the magnitude of muscle force available to them, but rather in an inability to produce it consistently for any given movement attempted. Bradykinesia may in part result from this inherent variability in that parkinsonian patients, in order to maintain accuracy within acceptable limits, are forced to increase the duration of their movements to a level where they can make use of visual guidance. In any event, theoretical explanations for the movement disorder in Parkinson's disease advanced in the literature need to take some account of this increased variability of movement.

Aged↗
PubMed1998

A review of differences between basal ganglia and cerebellar control of movements as revealed by functional imaging studies.

The role of the basal ganglia and cerebellum in the control of movements is unclear. We summarize results from three groups of PET studies of regional CBF. The results show a double dissociation between (i) selection of movements, which induces differential effects in the basal ganglia but not the cerebellum, and (ii) sensory information processing, which involves the cerebellum but not the basal ganglia. The first set of studies concerned motor learning of a sequence of finger movements; there was a shift of activation in the anterior-posterior direction of the basal ganglia which paralleled changes in the motor areas of the frontal cortex. During new learning, the dorsolateral prefrontal cortex and striatum (caudate nucleus and anterior putamen) were activated. When subjects had to select movements, the premotor cortex and mid-putamen were activated. With automatic (overlearned) movements, the sensorimotor cortex and posterior putamen were activated. When subjects paid attention to overlearned actions, activation shifted back to the dorsolateral prefrontal cortex and striatum. The cerebellum was not activated when subjects made new decisions, attended to their actions or selected movements. These results demonstrate components of basal ganglia-(thalamo)-cortical loops in humans. According to earlier studies in animals we propose that the basal ganglia may be concerned with selecting movements or the selection of appropriate muscles to perform a movement selected by cortical areas (e.g. premotor cortex). Secondly, a visuomotor co-ordination task was examined. In the absence of visual control over arm movements, subjects were required to use a computer mouse to either generate new lines or to re-trace lines on a computer screen. The neocerebellum (hemispheres of the posterior lobe, cerebellar nuclei and cerebellar vermis), not the basal ganglia, was more engaged when lines were re-traced (compared with new line generation). Animal experiments have shown that error detection (deviation from given lines) and correction occurs during line re-tracing but not line generation. Our data suggest that the neocerebellum (not the basal ganglia) is involved in monitoring and optimizing movements using sensory (proprioceptive) feedback. Thirdly, the relative contribution of sensory information processing to the signal during active/passive execution of a motor task (flexion and extension of the elbow) was examined; it was found that 80-90% of the neocerebellar signal could be attributed to sensory information processing. The basal ganglia were not involved in sensory information processing. They may be concerned with movement/ muscle selection (efferent motor component); the neocerebellum may be concerned with monitoring the outcome (afferent sensory component) and optimizing movements using sensory (feedback) information.

Basal Ganglia↗
PubMed2000

Multimodal EEG analysis in man suggests impairment-specific changes in movement-related electric brain activity after stroke.

Movement-related slow cortical potentials and event-related desynchronization of alpha (alpha-ERD) and beta (beta-ERD) activity after self-paced voluntary triangular finger movements were studied in 13 ischaemic supratentorial stroke patients and 10 age-matched control subjects during movement preparation and actual performance. The stroke patients suffered from central arm paresis (n = 8), somatosensory deficits (n = 3) or ideomotor apraxia (n = 2). The multimodal EEG analysis suggested impairment-specific changes in the movement-related electrical activity of the brain. The readiness potential of paretic subjects was centred more anteriorly and laterally; during movement, they showed increased beta-ERD at left lateral frontal recording sites. Patients with somatosensory deficits showed reduced alpha-ERD and beta-ERD during both movement preparation and actual performance. Patients with ideomotor apraxia showed more lateralized frontal movement-related slow cortical potentials during both movement preparation and performance, and reduced left parietal beta-ERD during movement preparation. We conclude that (i) disturbed motor efference is associated with an increased need for excitatory drive of pyramidal cells in motor and premotor areas or an attempt to drive movements through projections from these areas to brainstem motor systems during movement preparation; (ii) an undisturbed somatosensory afference might contribute to the release of relevant cortical areas from their 'idling' state when movements are prepared and performed; and (iii) apraxic patients have a relative lack of activity of the mesial frontal motor system and the left parietal cortex, which is believed to be part of a network subserving ideomotor praxis.

Adult↗