Movement related slow potentials. II. A contrast between finger and foot movements in left-handed subjects

Finger and foot movement related potentials (MRPs) were recorded over the frontal, central and parietal areas of both hemispheres in 20 left-handed subjects. A unilateral flexion of the index finger and a plantar flexion of the foot were studied on either side. MRPs were larger preceding foot movements than preceding finger movements, their onset being earlier also. Prior to a finger flexion amplitudes were larger over the hemisphere contralateral to the movement than over the ipsilateral hemisphere. Preceding a foot movement, however, amplitudes were larger over the ipsilateral hemisphere. These results indicate differently localized sources of the MRPs in the two kinds of movement, in accordance with data obtained in right-handed subjects. No indication of a hemisphere effect, possibly related to motor dominance, was found in left-handers. This is in contrast to a slight hemisphere effect found with foot movements in right-handed subjects in the former study.     

Movement-related potentials accompanying unilateral and bilateral finger movements with different inertial loads.

The present study was aimed at investigating the effect of inertial loading on movement-related potentials (MRPs) recorded from the scalps of normal subjects while performing finger movements. Two experiments were performed. Experiment 1. MRPs preceding and accompanying the execution of voluntary, unilateral finger movements were investigated in 8 subjects under the 3 experimental conditions of: no inertial load, small inertial load (250 g), and large inertial load (400 g). A significant effect of the inertial load on Bereitschaftspotential (BP) amplitude was observed for the 100 msec period preceding movement onset (BP -100 to 0) at precentral electrode sites and following movement onset (N0 to 100) at both precentral and parietal electrode sites. Pairwise comparisons revealed that significant effects were due to differences between the loading and non-loading conditions and not for different amounts of loading. No significant differences were observed for BP onset or early BP amplitudes, indicating that scalp negativity immediately prior to, and during, movement onset is primarily influenced by conditions of inertial loading. Experiment 2. This experiment examined the effect of inertial loading on MRPs for bilateral, simultaneous voluntary finger movements in 10 subjects under conditions of: no inertial load, inertial load applied separately to the left and right fingers, and with identical inertial loads applied to both fingers. No significant effect of inertial load on MRP amplitude was observed. These results are contrasted with those of experiment 1 which show significant effects of inertial loading for unilateral movements and are interpreted in terms of the hypothesis that bilateral movement organization involves 'higher' aspects of motor control than those reflecting adjustment to conditions of inertial loading.     

Movement-related potentials and control of associated movements

Previous studies have shown a relationship of the readiness potential (RP) preceding a motor act to motor control, as indexed by eye movement (EM). Greater EM and, therefore, less motor control was associated with increased positivity in preresponse RP components. It was hypothesized that these positive components may reflect processes involved in the inhibition of extraneous or associated movement during the performance of a motor act, especially in younger subjects with less motor development. We developed a finger lift task for detecting irrelevant associated movements (AM) from the responding hand and the nonresponding contralateral hand. During each target finger lift, small movements of the other nontarget fingers from the target hand and the contralateral hand were considered movements that should have been inhibited. Trials for each subject were divided into two bins: associated movement (AM) trials which had movement of target plus nontarget fingers, and trials with only target finger movement detected (NAM). Difference waveforms indicated a positive-going shift on trials with discrete target finger movements (NAM). Age and RP positivity at ipsilateral and posterior regions were significantly correlated. We suggest that, on trials on which associated movements are successfully inhibited, the negativity of the RP is confounded by an overlapping slow positivity. The positivity may be related to the effort needed to inhibit associated movements in order to perform a sharper and more discrete response. This relationship is a function of motor control and, indirectly, of age.     

Movement-related cortical potentials in aged subjects]

Cortical potentials related to freely-executed voluntary wrist flexion (MRPs) were studied in 35 subjects aged 23-80 years. The characteristics of the MPRs in aged subjects were determined in comparison data from 14 young subjects aged 23-40 years. The analysis concerned 3 components of the MRPs: the slow negative shifts (NS1 and NS2) before the movement onset and the motor potential (MP). In the aged subject, the latencies measured at Cz show a significant lengthening of the NS1 and of the duration of NS2 (NS' of Shibasaki et al, 1980). The mean amplitude of the NS1 peak at Cz is decreased, and those of N1 (the negative peak before the movement) and MP are not significantly different from those of the young subjects. The NS2 component in the aged subject (between NS1 and N1) is thus increased. In contrast to the young subjects, who present a predominance of N1 and MP amplitudes of the contralateral motor cortex over the ipsilateral cortex, the aged subjects lose lateralization of these components. Recording of MRPs with subdural electrodes (Neshige et al, 1988) shows taht NS1 results from the activity of the supplementary motor area and from the ipsi-contralateral primary motor cortex. The increase in NS2 might be interpreted as an expression of activity coming from other structures to compensate for the reduction in NS1 in the aged subject and to maintain the level of the motor potential MP.     

Movement-related cortical potentials associated with voluntary relaxation of foot muscles.

OBJECTIVE: In our previous study of movement-related cortical potential (MRCP) in association with the voluntary relaxation of the hand muscle, Bereitschaftspotential (BP) was maximal at the vertex and symmetrically distributed, and Negative Slope (NS') was maximal over the contralateral central region. In order to clarify the generator sources of MRCP with voluntary muscle relaxation, we recorded MRCP in association with voluntary relaxation of the foot. METHODS: MRCP in association with plantar flexion of the foot caused by voluntary relaxation of the tibialis anterior muscle was recorded in 10 normal subjects. RESULTS: The BP started at about 1.7 s before the onset of the muscle relaxation, followed by NS' starting at about 650 ms before it. Both were maximal at the vertex and symmetrically distributed. There was no additional EEG activity in the lateral frontal areas, which are presumably located over the primary negative motor areas (PNMA). CONCLUSIONS: It is concluded that the voluntary muscle relaxation, similarly to the voluntary muscle contraction, involves the cortical preparatory activity at least in the primary motor area (M1) and probably the supplementary motor areas (SMAs). There is no evidence to suggest that the PNMA is also active prior to the voluntary muscle relaxation.     

Sources of movement-related cortical potentials derived from foot, finger, and mouth movements.

Movement-related cortical potentials (MRCPs) register brain electrical activity before and during movement execution. In an attempt to delineate the components of MRCPs that reflect common sources to various movements and that are movement-specific, simple self-paced voluntary foot, finger, and mouth movements were studied. MRCPs were recorded in eight healthy volunteers with 30 electrodes placed on the scalp. Data were analyzed using Brain Electric Source Analysis software, and multiple equivalent dipole models were developed to separate spatial and temporal aspects of brain activity related to the execution of voluntary movements. Independent models were separately developed for the grand average data and for the individual subjects' data for each movement type. MRCPs derived from foot movements were accounted for using a 5-dipole model, finger movements using an 8-dipole model, and mouth movements with a 7-dipole model, yielding the grand average residual variances of 3%, 2%, and 6%, respectively. Based on individual models, intersubject variability of dipole locations was less than 10 mm (+/- SD). Overlaying the mean dipole coordinates onto the stereotaxic atlas provided proof that the sensorimotor cortical areas, supplementary motor area, and also cerebellum and thalamus were active in all three movements. Locations of the dipoles in the contralateral sensorimotor area clearly implied well-known medial to lateral somatotopic organization of foot, finger, and mouth movements. Temporal separation of the activity spread over different brain areas was demonstrated by evolution in the moments of dipole source potentials. The authors' models support the view of simultaneous activation of the primary motor cortex and supplementary motor area at the time of movement execution. Multiple equivalent dipole models developed in this study implied the activity originating in corresponding brain areas as previously detected by positron emission tomography or functional magnetic resonance imaging. However, MRCPs provided additional information regarding the temporal evolution of the brain activity related to the execution of voluntary movements. Thus, the concurrent use of MRCPs and other imaging techniques may provide complementary information not easily obtained by the other imaging techniques themselves.     

Movement-related slow potentials during motor imagery and motor suppression in humans

Electro-encephalograms (EEGs) associated with motor imagery and motor suppression were recorded from motor-related frontal regions in humans. A negative potential was observed both during motor imagery and during NO-GO responses, as well as in movement trials. The negative potentials observed in the motor imagery trials had a similar pattern to those observed in the movement trials, although the potentials were different from those during NO-GO responses. The peak amplitude of the negative potential recorded at FCz was significantly larger than those recorded at F3, F4, C3, and C4 in the imagery task. The peak amplitude of the negative component in movement trials was larger than that in the imagery trials of all recording positions. By contrast, during the GO/NO-GO task, the peak amplitude during NO-GO responses was larger than that during the GO responses at every position. It appears, therefore, that motor imagery and motor suppression are associated with their own specific internal processes which are reflected by specific EEG patterns in motor-related frontal areas.     

Movement-related cortical potentials preceding repetitive and random-choice hand movements in parkinson's disease

The movement-related cortical electroencephalographic potential was recorded from scalp electrodes in 8 patients with idiopathic Parkinson's disease studied at least 12 hours after withdrawal of their normal drug therapy, and compared with the results from a group of 8 age-matched control subjects. Two types of self-paced voluntary arm movements were examined: repetitive forward movement of a joystick, and random-choice movements of the same joystick in which subjects had to choose freely the direction in which they were to move the stick (forward, backward, left, or right). In normal subjects, the movement-related cortical potential was larger prior to random-choice movements, whereas in the patients, the amplitude was the same in both tasks. The implication is that processes involved in self-selection of movement are abnormal in Parkinson's disease. This may contribute to the difficulty that patients have in initiating voluntary movement in the absence of any external cues.     

Cerebral potentials preceding unilateral and simultaneous bilateral finger movements.

Cerebral potentials preceding voluntary bilateral simultaneous finger movements were investigated in 19 right-handed young adult subjects, and were compared with unilateral right-sided finger m n the same experiment. With bilateral movements, the Bereitschaftspotential (BP) was not symmetrical or larger over the dominant hemisphere, but surprisingly, it was larger over the minor hemisphere. The BP averaged -3.66 microV (S.D. 1.96) over the left precentral region and -4.82 microV (S.D. 3.73) over the right precentral region in this condition. The difference was significant at 2P less than 0.01. This difference was pronounced in precentral leads but very small and almost missing in parietal leads. The pre-motion positivity (PMP) was well developed and even larger with bilateral than with unilateral (right-sides) movements. At the vertex it averaged +1.33 microV (S.D.4.16) with bilateral movements and only +0.15 microV (S.D. 1.42) with right-sided unilateral movements (2P less than 0.05). With bilateral movements the PMP could be observed in any record, but with unilateral movements it was missing at the left precentral lead, in accordance with previous publications (Deecke et al. 1969, 1976). The motor potential (MP), measured in a bipolar record from left and right precentral leads, was larger with unilateral (-1.25 microV, S.D. 1.33) than with bilateral movements (-0.36 microV, S.D. 0.92). Onset time differences of the BP preceding unilateral and bilateral movements were very small. However, there was a tendency towards earlier onset with unilateral than with bilateral movements (1031 msec, S.D. 358, as compared with 951 msec, S.D. 305). The averaged EMG revealed differences in movement onset. Muscular contraction tended to be earlier in the right than in the left m. flexor indicis in our right-handed subjects, on the average by 16 msec (S.D. 15). With unilateral right-sided movements, the left m. flexor indicis was not silent but showed an abortive mirror activity in the EMG, without visible movement. This activity occurred on the average 50 msec (S.D. 39) later on the non-moving side.     

Movement-related cortical potentials in myotonic dystrophy.

OBJECTIVE: To investigate a possible deficit of the voluntary movement mechanism within the central nervous system (CNS) in patients with myotonic dystrophy (MyD). METHODS: Movement-related cortical potentials preceding voluntary extension of the right middle and index fingers were studied in 9 patients with MyD and compared with those in 11 age-matched healthy subjects and 9 age-matched patients with other neuromuscular disorders (NMDs). RESULTS: The amplitudes of Bereitschaftspotential was smaller in MyD patients than in age-matched controls and age-matched patients with other NMDs although there was no statistically significant difference. The amplitude of negative slope was significantly smaller in MyD patients than in age-matched controls and age-matched patients with other NMDs. Clinical findings such as age, disease duration, degree of motor impairment and cognitive function had no effect on the individual electrophysiological parameters. CONCLUSIONS: The present results suggest that subclinical abnormalities exist in CNS function associated with motor preparation and execution, which is independent of muscle weakness.     

Cortical potentials following voluntary and passive finger movements

In order to clarify the time relationship and functional significance of post-motion components of the movement-related cortical potential, averaged cortical potentials associated with voluntary and passive movements were compared mainly with respect to their scalp topography. Fourteen channels of scalp EEG, together with EOG and EMG, were simultaneously recorded in 7 healthy adult subjects while the subject was either repeating a self-paced brisk extension of a middle finger or while the experimenter was extending the middle finger by pulling up a string attached to the finger. Potentials associated with the movement were averaged opisthochronically in relation to a trigger actuated by the finger interrupting a beam of light. Seven peaks were identified in the passive movement-evoked potential. A sharp negative peak occurred over the contralateral precentral region 16 msec after the photometer trigger (N15). Another negative component (N70) formed a composite of double-peaked negativity with N15 and was seen over the frontal region with a contralateral predominance. A positive peak (P65) was recorded over the contralateral parietal region with a similar latency to N70. This N70/P65 complex has some marked similarities in terms of wave form and spatial relationship with the N + 50/P + 90 complex recorded with voluntary movement of the same finger. It is postulated that these components may be the projected potential fields from a dipole source within the central sulcus and may represent a kinesthetic feedback from the muscle afferents.     

Biofeedback of slow cortical potentials. I

An experiment was performed to investigate the self-regulation of slow cortical potentials (SCP) found in a previous study (Elbert et al. 1979). Seventeen subjects received continuous visual feedback of their actual cortical shift perceptible as a rocket moving across a TV-screen during intervals of 6 sec; subjects had to direct the rocket into one of two goals representing more or less cortical negativity, depending on the pitch of two signal tones. Within two identical experimental sessions feedback trials alternated with test trials without feedback. Highly significant differences of SCP between the two required polarities were demonstrated. The most pronounced differences were observed during test trials without feedback of the second session in which a positive shift below baseline level occurred when positivity (or less negativity) was required.     

Topography of scalp-recorded motor potentials in human finger movements

Four distinct negative events were identified in the averaged, scalp-recorded EEGs of normal subjects before and after the onset of self-paced, voluntary finger movements; reaction-time movements and passive movements were also studied. These events are the peak of the negative slope (NS'), the initial slope of motor potential (isMP), the parietal peak of motor potential (ppMP), and the frontal peak of motor potential (fpMP). For self-paced movements, NS' and isMP occurred before the onset of electromyographic (EMG) activity, and ppMP and fpMP occurred after the onset of EMG activity. NS' had a wide distribution, covering the parietal region with slight contralateral predominance. The isMP mapped focally over the contralateral hand motor area on the scalp. The location of ppMP was similar to that of isMP. The fpMP was localized anterior and medial to motor cortex with a contralateral preponderance and possible location over the supplementary motor area. The isMP and fpMP also were identified in the recordings of reaction-time movements, but only the fpMP persisted in the recordings of passive movements. The isMP appears to reflect activation of the cortical cells in the hand area of motor cortex for the execution of voluntary movement, and the fpMP appears to reflect proprioceptive feedback from the periphery.     

Movement-related cortical potentials in patients with Machado-Joseph disease.

ObjectiveMovement-related cortical potentials (MRCP; nomenclature of MRCP components according to Shibasaki and Hallett (Shibasaki H, Hallett M. What is the Bereitschaftspotential? Clin Neurophysiol 2006;117:2341–56) were studied in patients with Machado–Joseph disease (MJD) to elucidate the pathophysiology of voluntary movement.MethodsWe studied nine genetically proven MJD patients and eight age-matched healthy subjects. Multi-channel electroencephalogram (EEG) recordings were obtained during self-paced fast extensions of the wrist. EEG epochs were time-locked to electromyography (EMG) onset or offset of the voluntary EMG burst and averaged.ResultsIn the MJD patients, the early Bereitschaftspotential (early BP, −1500 to −500 ms) was not affected but the late BP was reduced over the central midline area and contralaterally to the movement side. The amplitude of the fpMP, a post-movement MRCP component, was also reduced. In addition, the offset cortical potential in the first 500 ms after EMG offset (Moff + 500) was attenuated bilaterally over a wide cortical area.ConclusionsFindings suggest that cortical activations associated with the initiation and termination of a voluntary movement are impaired in MJD patients.SignificanceAbnormalities of pre- and post-movement MRCP components provide researchers with pathophysiological insight into voluntary motor dysfunction in MJD.     

Asymmetries in classically conditioned head movements and cingulate cortex slow potentials in cats.

Presuming that conditioned head movements in the cat indicate a preference for a specific direction, asymmetries were also expected to be found in bilaterally recorded cingulate cortex slow potentials to a symmetrical tone stimulus during discriminative conditioning. Conditioned stimuli (CS, 1000 and 2500 Hz tones) were delivered through two miniature loudspeakers fitted to the head in front of both ears. The unconditioned stimulus (US) was an electrical stimulation of either the left or right lateral hypothalamus yielding, in addition to its rewarding effects, an unconditioned head turning response (UR) either to the left, right, forwards or upwards. Discrimination learning appeared as more extended and more rapid headturns and greater negativity in the cingulate cortex to the CS+ than to the CS-. The preferred conditioned behavioral response (CR) was a headturn to the left in 11 of 12 cats accompanying increased negativity in evoked slow potentials in the right cingulate cortex during the 128-324 ms period after the CS onset. No differences in the movements and in the cingulate potentials were found between the left versus right US stimulations. The results showed that regardless of the direction of the original unconditioned head movement, the direction of the CR was at the end of the training period to the left in 11 out of the 12 cats. Larger evoked slow potentials observed in the right cingulate cortex which were not present in the baseline measurements suggest a population bias between the hemispheres.     

Motor stability in visuomotor control of repetitive hand movements and its differential cerebral control in right-handed subjects.

The stability of asymmetric motor control was studied in right-handed subjects. Hand skill was assessed by a peg moving task in ten trials. The mean peg moving time (PMT) and its standard deviation (SD) were calculated for each hand. Standard deviation was taken as an index of the stability of visuomotor control. The mean rate of a repetitive movement (mean PMT) did not always show an association with its stability (SDs). This depended upon familial sinistrality, sex, and cerebral lateralization such as eye and foot preferences of the subjects. The left-right differences in movement stabilities also showed different contributions of the right and left brains of the subjects depending upon these factors. It was suggested that these factors should be taken into consideration in studies concerning the hemispheric control of especially corrective components of skilled movements of hands.     

Movement-related cortical potentials before jaw excursions in oromandibular dystonia.

Oromandibular dystonia is a neurological disorder characterized by involuntary contraction of masticatory and/or tongue muscles. Cortical negative shifts preceding voluntary movements called "movement-related cortical potentials" (MRCPs) reflect a central motor control process. Reduced amplitude of MRCPs has been reported in other types of dystonia. To elucidate whether the abnormality is observed also in oromandibular dystonia, we compared MRCPs associated with mandibular movements in 6 patients with this condition and in 8 normal subjects. Electroencephalograms (EEGs) were recorded from 11 electrodes, and electromyograms (EMGs) were recorded from the masseter muscle and the suprahyoid muscles. The subjects were asked to repeat mouth opening, closing, and left and right lateral mandibular excursions. MRCPs were obtained by averaging the EEG using the EMG onset as the trigger signal. In the patient group, MRCP amplitudes over central and parietal areas for mouth opening and lateral movements were significantly reduced compared to normal subjects. In normal controls, the MRCPs at mouth opening and closing were symmetrically distributed, whereas those at lateral movements showed predominance over the hemisphere ipsilateral to the direction of the movement. This laterality was lost in the patient group. These results suggest impaired cortical preparatory process for jaw movements in oromandibular dystonia.     

Analysis of slow cortical potentials preceding self-paced hand movements in the monkey.

Cortical potentials related to the self-paced “voluntary” hand movement were recorded in unanesthetized, freely moving monkeys with the electrodes implanted chronically on the surface and in the depth of the cortex, and analyzed with the method of electronic averaging. Prior to the movement, surface negative — deep positive slow potential changes appeared in the motor and premotor cortices contralateral to the moving hand. The potential changes started about 1 s before the hand movement and increased gradually to about 100 ms before the movement. The contours of the potential changes preceding the movement were remarkably constant in daily recording for several weeks. Based on the laminar field potential analyses of cortical evoked potentials made in previous acute experiments, the slow potential was interpreted to be due to the currents of slowly increasing EPSPs that were generated in superficial parts of the cortical pyramidal neurons via certain thalamocortical projections. The EPSPs would activate the neurons in the motor and premotor cortices and contribute to the initiation of voluntary movement.     

Movement-related potentials in high-functioning autism and Asperger's disorder

Autism and Asperger's disorder (AD) are neurodevelopmental conditions that affect cognitive and social-communicative function. Using a movement-related potential (MRP) paradigm, we investigated the clinical and neurobiological issue of 'disorder separateness' versus 'disorder variance' in autism and AD. This paradigm has been used to assess basal ganglia/supplementary motor functioning in Parkinson's disease. Three groups (high functioning autism [HFA]: 16 males, 1 female; mean age 12y 5mo [SD 4y 4mo]; AD: 11 males, 2 females; mean age 13y 5mo [SD 3y 8mo]; comparison group: 13 males, 8 females; mean age 13y 10mo [SD 3y 11mo]) completed a cued motor task during electroencephalogram recording of MRPs. The HFA group showed reduced peak amplitude at Cz, indicating less activity over the supplementary motor area during movement preparation. Although an overall significant between-group effect was found for early slope and peak amplitude, sub-analysis revealed that the group with AD did not differ significantly from either group. However, it is suggested that autism and AD may be dissociated on the basis of brain-behaviour correlations of IQ with specific neurobiological measures. The overlap between MRP traces for autism and Parkinson's disease suggests that the neurobiological wiring of motor functioning in autism may bypass the supplementary motor area/primary motor cortex pathway.