Frontal lobe contribution to voluntary movements in humans

We assessed the contribution of human prefrontal cortex to movement related potentials (MRPs) generated prior to voluntary movements. MRPs were recorded during self-paced movements of the right thumb (experimental condition I), the left thumb (experimental condition II) and both thumbs (experimental condition III) from patients with focal lesions centered in dorsolateral frontal association cortex (PFCx, n = 11) and in age matched controls (n = 11). Controls generated a slowly rising readiness potential (RP) beginning at about 1000 ms prior to movement. A negative shift (NS') began at about 450 ms and a motor potential (MP) appeared at about 100 ms prior to movement. Both the NS' and MP were maximal over scalp sites contralateral to movements. Unilateral PFCx lesions preferentially reduced the RP and NS' components of the MRP. This indicates that PFCx is involved in a neural network beginning at least 1000 ms prior to movement. The differential PFCx effects on the early (RP, NS') and late components (MP) suggest that these MRPs index different movement-related circuits.     

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.     

Recording of movement-related potentials from the human cortex

A patient with intractable epilepsy secondary to a brain tumor was evaluated with a chronically implanted array of 64 stainless-steel subdural electrodes covering the perirolandic area. Cortical potentials associated with voluntary, self-paced middle-finger extension were recorded simultaneously from subdural and scalp electrodes using a computer-assisted method for averaging movement-related potential (MRP) in relation to electromyographic (EMG) onset. A high-amplitude negative potential, Bereitschaftspotential/negative slope (BP/NS'), preceding the onset of the EMG activity by more than 1 sec was recorded in an extremely localized fashion exclusively from electrodes placed in the precentral hand motor area as well as in the more medial part of the somatosensory hand area. These results suggest that the hand motor and sensory areas have an essential participation in the generation of MRPs and, therefore, also in the preparation of voluntary finger movements.     

Cortical potentials preceding voluntary movement: evidence for three periods of preparation in man

We have recorded movement-related cortical potentials (MRCPs) to voluntary middle finger extension from 10 young and 10 old subjects free of neurological disease using the method of detecting EMG onset associated with each movement described by Barrett et al. (1985). The slow potential shifts preceding movement were measured by fitting a linear regression line to the wave forms to obtain a measure of their slope. Three separate potential shifts were identified. The first had a scalp distribution and onset latency similar to the Bereitschaftspotential (BP) first reported by Kornhuber and Deecke (1964, 1965). The potential shift immediately preceding movement corresponded with the NS' of Shibasaki et al. (1980). We identified, for the first time, a third shift intervening between BP and NS' and named it the intermediate shift (IS). The onset of BP occurred about 1.6 sec before EMG onset and was followed by IS which began about 875 msec before movement. The onset of NS' occurred 300 msec before EMG onset and terminated about 90 msec before this event. The slope of BP preceding right finger movement was steeper than that preceding left hand movement in all our right-handed subjects. The distribution of BP was symmetric about the midline. The IS potential shift had a slope which was steeper on the average preceding left finger movement than right. The distribution of IS was symmetric about the midline preceding left finger movement but had a contralateral tendency preceding right hand movement. NS' had a maximum slope at contralateral electrodes over the hand motor area and parietal areas. It was suggested that the BP potential shift originates in the supplementary motor area on the medial surface of the cerebral cortex. The differing distribution of the IS shift for the two hands suggests that this potential may be generated bilaterally preceding left finger movement but from the contralateral hemisphere only preceding movement of the right finger. The most likely origin of this potential was thought to be superior premotor cortex. NS' was considered to originate in primary motor cortex with possible contributions from other cortical areas associated with movement.     

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 potentials during development: a replication and extension of relationships to age, motor control, mental status and IQ

Three age groups of normals (children, preadolescents, and adults) and a group of mentally retarded adults performed a noncued button press task from which averaged movement-related potentials (MRPs) were derived. MRP wave shapes replicated our previously reported modal waveform types, except for the preadolescents, who showed no modal MRP. The normal groups showed a developmental shift in the prevalence of waveforms with the retarded differing from normal adults. The modal child waveform had a large amplitude positive-negative-positive form; the retarded had a uniphasic positive form; while normal adults showed the usual negative form. Major MRP types among children could not be attributed to differences in sampling or number of the trials averaged, or to trial-to-trial MRP variability. Background EEG activity did not differ in different modal MRP types. Modal child MRPs showed an initial peak positivity at Fz, and a late peak at Cz. The retarded had a sustaining central positivity developed by midepoch. MRP positivity and negativity were related to age, inhibition of extraneous eye movement (EM), and IQ. In children, greater cognitive proficiency is associated with adult-like MRP. The results suggest that positivity, in part, reflects a subject's efforts at inhibiting movement extraneous to the instructed task.     

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.     

Cortical topography of premotor and motor potentials preceding self-paced, voluntary movement of dominant and non-dominant hands.

The cortical potentials preceding movement, negative slope (NS'), premovement positivity (PMP), and the initial slope of motor potential (MP), were studied in detail with a 29-channel averaged EEG mapping technique in normal subjects. Self-paced, voluntary movements of the right and left index fingers were performed up to 150 times, and topographic color maps were created from the averaged wave forms. The maps revealed NS' of the dominant hand on the vertex and NS' of the non-dominant hand on the contralateral centroparietal area. PMP appeared on the ipsilateral precentral area, and the initial slope of MP appeared on a small, distinct contralateral precentral area, presumably the hand motor area. The amplitudes of the potentials did not show significant differences between dominant and non-dominant hands. PMP and the initial slope of MP appeared significantly earlier preceding non-dominant hand movement as compared with dominant movement. The findings indicate some difference in cortical activity relating to dominant and non-dominant hand movement.     

Changes in movement-related cortical potentials in Parkinson's patients before and after treatment with levodopa

Cortical potentials associated with voluntary, self-paced wrist flexion (MRPs) were recorded from 3 scalp locations (Cz and psi contralateral hand motor area) in patients with Parkinson's disease (9 de novo patients and 30 L-Dopa treated patients). The analysis concerned 3 components of the MRPs: the 2 slow negative shifts (NS1 and N1) before the movement onset and the motor potential (MP). The NSI amplitude was measured at Cz, the peak negativity N1 and MP from contralateral hand motor area location. The potential distribution was also studied. The amplitude of the MRPs components was the same as in the normals. But in de novo patients, the potential distribution of the NS1 component was different; a Cz preponderance of the NS1 amplitude was not found. In patients treated with L-Dopa, there is a negative correlation between the changes in amplitude and the changes in clinical rating for NS1, N1 and MP components. The decrease in the MRPs components was significant from stage III and IV of the Hoehn and Yahr scales. After L-Dopa therapy, the NS1 component from de novo patients was increased in amplitude. The amplitude of the MRPs components from patients with L-Dopa induced clinical fluctuations was reduced during "off" period in comparison to "on" period. The findings suggest that the NS1 potential and the N1 and MP components share 2 distinct systems for the control of voluntary movement. Their mechanism in Parkinson's disease is discussed.     

Movement-Related Potentials Associated with Motor Timing Errors as Determined by Internally Cued Movement Onset

ObjectiveAccurate motor timing is critical for efficient motor control of behaviors; however, the effect of motor timing abilities on movement-related neural activities has rarely been investigated. The current study aimed to examine the electrophysiological correlates of motor timing errors. MethodsTwenty-two healthy volunteers performed motor timing tasks while their electroencephalographic and electromyographic (EMG) activities were simultaneously recorded. The average of intervals between consecutive EMG onsets was calculated separately for each subject. Motor timing error was calculated as an absolute discrepancy value between the subjects’ produced and given time interval. A movement-related potential (MRP) analysis was conducted using readings from Cz electrode. ResultsMotor timing errors and MRPs were significantly correlated. Our principal finding was that only Bereitschaftpotential (BP) and motor potential (MP), not movement monitoring potential, were significantly attenuated in individuals with motor timing errors. Motor timing error had a significant effect on the amplitude of the late BP and MP. ConclusionThe findings provide electrophysiological evidence that motor timing errors correlate with the neural processes involved in the generation of self-initiated voluntary movement. Alterations in MRPs reflect central motor control processes and may be indicative of motor timing deficits.     

Bereitschaftspotential in tardive dyskinesia

The bereitschaftspotential or motor readiness potential is a slow negative electroencephalographic wave occurring 150-1500 ms prior to the onset of a voluntary movement. It was measured in 33 subjects: 11 normal controls, 11 medicated schizophrenics with no tardive dyskinesia or evidence of drug-induced parkinsonism, and 11 patients with tardive dyskinesia. The bereitschaftspotential amplitude was more than two times larger in patients with tardive dyskinesia than in normal controls or schizophrenic patients without tardive dyskinesia. The increased amplitude correlated with the degree of severity of the tardive dyskinesia as measured on the Abnormal Involuntary Movement Scale (AIMS). The finding of the increased bereitschaftspotential amplitude in tardive dyskinesia, taken together with earlier findings of low amplitude in Parkinson's disease, suggests that this potential may reflect the level of dopaminergic activity in the basal ganglia.     

Different neuroendocrine profiles of remitted and nonremitted schizophrenic patients

BACKGROUND: Thyrotropin-releasing hormone (TRH) test and Dexamethasone Suppression Test (DST) are two neuroendocrine tests that have been extensively used in an attempt to predict treatment response and outcome in schizophrenia. The objectives of this study were to investigate (1) the relationship between TRH test and DST and various psychiatric symptoms and (2) the potential value of these tests in prediction of short-term outcome in schizophrenic patients. METHODS: TRH test and DST were administered to 58 patients with schizophrenia. All patients were evaluated with a battery of rating scales before neuroendocrine test procedures and at regular intervals for 1 year. Patients were divided into two groups as remitted (RP; n = 30) and nonremitted patients (NRP; n = 28). Baseline results of these two groups were compared with each other and 30 healthy controls. RESULTS: Basal levels of total T3 (T3T) and free T3 (T3F) were higher in RP group than controls. Basal prolactin (PRL) level was higher in RP group, but not in NRP, compared to controls. Basal growth hormone (GH) and thyroid-stimulating hormone (TSH) levels of NRP were significantly higher than those of RP. DST nonsuppression was observed at a significantly higher rate in RP than NRP and control group. Blunted TSH response rate in RP group was higher significantly compared to other two groups. CONCLUSIONS: The data implicate that higher basal TSH and GH levels may be associated with a poorer treatment response, whereas higher total and free T3 levels, a blunted TSH response to TRH and nonsuppression on the DST may indicate a better response in schizophrenics.     

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.     

The initiation of voluntary movements by the supplementary motor area

The hypothesis is formulated that in all voluntary movements the initial neuronal event is in the supplementary motor areas (SMA) of both cerebral hemispheres. Experimental support is provided by three lines of evidence. 1. In voluntary movements many neurones of the SMA are activated probably up to 200 ms before the pyramidal tract discharge. 2. Investigations of regional cerebral blood flow by the radioactive Xenon technique reveal that there is neuronal activity in the SMA of both sides during a continual series of voluntary movements, and that this even occurs when the movement is thought of, but not executed. 3. With voluntary movement there is initiation of a slow negative potential (the readiness potential, RP) at up to 0.8 s before the movement. The RP is maximum over the vertex, i.e. above the SMA, and is large there even in bilateral Parkinsonism when it is negligible over the motor cortex. An account is given of the SMA, particularly its connectivities to the basal ganglia and the cerebellum that are active in the preprogramming of a movement. The concept of motor programs is described and related to the action of the SMA. It is proposed that each mental intention acts on the SMA in a specific manner and that the SMA has an 'inventory' and the 'addresses' of stored subroutines of all learnt motor programs. Thus by its neuronal connectivities the SMA is able to bring about the desired movement. There is a discussion of the manner in which the mental act of intention calls forth neural actions in the SMA that eventually lead to the intended movement. Explanation is given on the basis of the dualist-interactionist hypothesis of mind-brain liaison. The challenge is to the physicalists to account for the observed phenomena in voluntary movement.     

Impaired movement-related potentials in acute frontal traumatic brain injury.

OBJECTIVE: Focal brain lesions due to traumatic brain injury (TBI) do not only lead to functional deficits in the lesion area, but also disturb the structurally intact neuronal network connected to the lesion site. Therefore we hypothesized dysfunctions of the cortical motor network after frontal TBI. The movement related potential (MRP) is an EEG component related to voluntary movement consisting of the Bereitschaftspotential (BP), the negative slope (NS), and the motor potential (MP). The aim of our study was to demonstrate alterations in the movement related cortical network in the acute stage after TBI by comparing our patients' MRPs to those of a healthy control group. METHODS: EEGs of 22 patients with magnetic resonance imaging defined contusions of the prefrontal cortex were recorded within 8 weeks after TBI. We further recruited a healthy control group. The paradigm consisted of self-paced abductions of the right index finger. RESULTS: Compared to healthy controls, the BP in the patient group was significantly reduced and its onset delayed. Moreover, an enhanced contribution of the postrolandic hemisphere ipsilateral to the movement and a reduced contribution of the left frontal cortex, ipsilateral to the lesion in the majority of the patients, were observed during motor execution (MP). CONCLUSIONS: Anatomical connections between the prefrontal cortex and the supplementary motor area (SMA) are known to exist. We suggest that prefrontal lesions lead to reduced neuronal input into the SMA. This deficit in the preparatory motor network may cause the reduced BPs in our patients. Moreover, an increased need for attentional resources might explain the enhanced motor potentials during movement execution. In conclusion, we demonstrated altered MRPs in the acute stage after frontal TBI, which are a consequence of disturbed neuronal networks involved in the preparation and execution of voluntary movements.     

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

Movement-related potentials ( MRPs ) preceding a finger flexion and a plantar flexion of the foot on either side were compared over the frontal, central and parietal areas of both hemispheres. MRP amplitudes were larger preceding foot than preceding finger movements. In the first case their onset was earlier and their presence in the frontal area was more marked. Prior to a finger flexion amplitudes over the hemisphere contralateral to the movement side were larger than those recorded over the ipsilateral hemisphere. On the contrary, prior to a plantar flexion of the foot, amplitudes were larger over the hemisphere ipsilateral to the movement. These findings point to differently localized sources of the MRPs in the two cases. In other experiments larger amplitudes preceding foot movements were found near the midline. It is suggested that the ipsilateral preponderance prior to foot movements is caused by a contralateral source in the depth near the longitudinal fissure. The dipoles are presumably directed obliquely to the median plane. The ipsilateral preponderance is present both prior to and following the plantar flexion. This suggests comparable directions of the dipoles in the motor and somatosensory areas.     

Cardiovascular phase relationships to the cortical event-related potential of schizophrenic, depressed, and normal subjects.

Cardiovascular phase, especially diastole, influences attention and the event-related potential (ERP) of the right hemisphere of the brain. Depression and schizophrenia are characterized by attentional deficits, unique lateralization of brain function, and deviant phase relationships of biological oscillators. In the present study, the ERP was recorded during stimulation triggered by diastole and systole in control (n = 16), depressed (n = 16), and schizophrenic (n = 9) subjects. Fifty tones were presented and subjects were instructed to count them silently. Previous findings were supported of delayed latencies and increased amplitude in depressed patients and decreased amplitudes and delayed latencies in schizophrenics. An exaggerated effect of diastole on the ERP in the right hemisphere was observed in depressed patients, however, no cardiovascular effect on the ERP was apparent in schizophrenic patients. Results suggested that heart/brain networks are tightly coupled in normal controls, perhaps "overdriven" in depressed patients, and uncoupled in schizophrenics.     

Chemistry, physiology and neuropsychology of schizophrenia: towards an earlier diagnosis of schizophrenia I

Data supporting the glutamate hypothesis of schizophrenia are presented. The glutamate hypothesis is linked to the dopamine hypothesis by the fact that dopamine synapses inhibit the release of glutamate in the striate and mesolimbic system. The glutamate hypothesis of schizophrenia may open a way to find better drugs for treatment. The concept of schizophrenia I is described. It consists of "negative symptoms" such as disconcentration or reduction of energy. Schizophrenia I precedes and follows schizophrenia II with "positive symptoms," e.g. hallucinations and delusions. Schizophrenia I so far cannot be diagnosed as schizophrenia unless schizophrenia II appears. Chemical, physiological or neuropsychological methods for the diagnosis of schizophrenia I would render an earlier treatment of schizophrenia possible and thus make social and occupational rehabilitation more efficient. An objective diagnosis of schizophrenia I may also elucidate the mode of genetic transmission of schizophrenia. Several neuropsychological methods distinguish schizophrenic patients as a group from normals. Some of them are based on a specific disturbance of long term concentration. The EEG also distinguishes schizophrenics from normals when analyzed during voluntary movement. For schizophrenics it takes more effort to initiate a voluntary movement, and there are several features of the EEG correlated to this. Moreover, the longer motor reaction time of schizophrenics is paralleled by a longer duration of the Bereitschaftspotential in schizophrenia. Furthermore, there is a difference in the theta rhythm between schizophrenic patients and normals in a task which requires concentration. Some of the children of schizophrenic parents show a disturbance of concentration in both reaction time tasks and the d 2 test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of slow brain potentials related to motor preparation and stimulus anticipation in a time estimation task

Subjects had to press a button at regular intervals of 20 sec. Two seconds after each button press a stimulus was presented indicating the length of the past interval. EEG was analysed from 2500 msec preceding the button press until the presentation of the stimulus. Preceding the button press a readiness potential (RP) was recorded with amplitudes that were larger over the hemisphere contralateral to the movement side. Preceding the stimulus negative waves were recorded which were larger over the right hemisphere, irrespective of the movement side. In a warned reaction time experiment, the CNV late wave represents both motor preparation and stimulus anticipation. In the present study motor preparation and stimulus anticipation are no longer confounded factors. Thus, it is shown that stimulus anticipation is indeed reflected by negative activity, as is motor preparation. The potential distribution of the RP, however, is different from the stimulus-preceding negativity (SPN), a pointing to a different electrophysiological source. The potential distribution of the SPN has been investigated and a right hemisphere preponderance of the SPN has been found.     

Spectral analysis of EEG during self-paced movements: differences between untreated schizophrenics and normal controls.

Thirteen untreated schizophrenic patients, among them nine who had never been treated, were compared with a corresponding number of matched normal controls with regard to changes of the spectral composition of the electroencephalogram (EEG) accompanying voluntary movements. Triggered by self-paced movements of the right fingers (fast fist closure), the spectral composition of three epochs was analyzed: (1) rest (2,5-1,5 sec before movement), (2) movement preparation (last sec before movement onset), and (3) movement execution (1st sec following movement onset). For frequencies above 6 Hz, marked differences between schizophrenics and controls were evident, in particular over the parietal electrodes. Whereas patients exhibited a clear decrease of power density during movement as compared to rest, controls showed only a small decrease (left and mid parietal) or virtually none (only right parietal). Consequently there were significant differences over the right parietal area (P4) between patients and controls in the theta, alpha- and beta-bands with regard to the mean power density and center frequencies of these bands. Also at parietal positions, schizophrenics lacked the enhancement of theta-power during the preparatory epoch that was characteristic for normal controls at all parietal positions. The results are discussed with regard to the well-known disturbances of voluntary motor behavior in schizophrenia.