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PubMed2003

The relationship between anthropometric factors and body-balancing movements in postural balance.

OBJECTIVE: To evaluate the relationship between anthropometric characteristics and body-balancing movements when standing on 2 legs with eyes open and eyes closed. DESIGN: Cross-sectional. SETTING: A university physiatry laboratory. PARTICIPANTS: One hundred randomly selected subjects (50 men, 50 women; age range, 31-80y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Anthropomorphic: body height, weight, lower-extremity distances, foot lengths, and widest widths of the forefeet and heels. Body movements: 2-legged stance with eyes open and eyes closed, measured with the MacReflex Motion Capture System and calculated as maximal and total movements in 3 dimensions. The relation between the measured anthropometric characteristics and body-balancing movements was calculated by using regression analysis. RESULTS: In the eyes-open condition, maximal lateral knee movement was related to body height and foot length (R(2)=.065, P<.05). Both anteroposterior (AP) head movement (R(2)=.068, P<.05) and AP navel movement (R(2)=.083, P<.05) were related to heel width. AP knee movement was related to foot length and heel width (R(2)=.089, P<.05). Body mass index was related to AP ankle movement (R(2)=.074, P<.05) and to vertical ankle movement (R(2)=.063, P<.05). In the eyes-closed condition, body mass index was related to the vertical navel movement (R(2)=.059, P<.05) and body height to AP knee movement (R(2)=.041, P<.05). CONCLUSION: The levels of significance are not high but warrant attention. It seems that there was no single anthropometric factor that explained the variations in body-balancing movements during standing.

Adult↗
PubMed1997

Developmental sequence of human fetal body movements in the second half of pregnancy.

To describe fetal body movements precisely and to clarify their developmental sequence in the second half of pregnancy, fetal body movements were observed in 31 normal fetuses between 20 and 41 weeks of pregnancy by using multiple ultrasonic machines. All movements of the whole trunk were able to be classified into six fundamental movements: flexion, stretch, rolling, startle, stepping, and writhing. Startle was always observed as a single movement, but others were more frequently observed as a part of combination rather than as a single movements. The incidence of flexion and stretch peaked at 28-31 weeks, whereas the incidence of startle and stepping lowered at the period. The incidence of rolling and upper half trunk movements increased at 40-41 weeks. Limb movements were frequent and did not exhibit characteristic change in the incidence. In conclusion, we classified fetal body movements into several fundamental movements instead of using the expression of "general movements" by focusing principally on movements of the trunk. In particular, some of the fundamental movements seem to appear in characteristic ways as related to gestational age. In view of that fetal behaviors are closely related to the neural activity, the present findings may contribute to an understanding of the developmental process of the central nervous system.

Abdomen↗
PubMed2002

Arm movement control: differences between children with and without attention deficit hyperactivity disorder.

The purpose of this study was to examine performance differences in arm movement control (programmingvs. "on-line" control) between children with and without attention deficit hyperactivity disorder (ADHD). Twenty children (10 with ADHD and 10 without ADHD) from the ages of 8 to 13 years participated in the study. On the surface of a digitizer, each participant completed three types of aiming arm movements (10 trials for each) and 10 baseline trials (without accuracy requirement). Multivariate analyses of variance with repeated measures were used to analyze the variables of reaction time, movement time, normalized jerk, intersegment-interval (ISI), and movement timing. Children with ADHD appeared to use "on-line " monitoring during the arm movement and did not perform the entire movement sequence as afunctional unit. They executed the arm movements more slowly, had greater variability in movement timing, and demonstrated longer ISIs than their counterparts. Children with ADHD had multiple peaks in the velocity profiles. Children withoutADHD, however, appeared to program their entire arm movements and execute the sequence as a unit. Their velocity profiles were symmetrical with a single peak, and the movement segments were temporally coordinated. Thesefindings suggested that cognitive functions are important resources for controlling rapid aiming arm movements. Children with ADHD might rely more on visual feedback during the movements, which resulted in slower and more variant movement outcomes than children who did not have ADHD.

Adult↗
PubMed1999

Perception of self-generated movement following left parietal lesion.

Three apraxic patients with lesions in the left parietal cortex were required to execute finger movements with either hand, while the visual feedback they received about the movement was manipulated systematically. We used a device which allowed us to present on a video monitor either the patient's hand or the examiner's hand simultaneously performing an identical or a different movement. In each trial, patients were required to decide whether the hand shown on the screen was their own or not. Hand movements produced in response to verbal command included simple (single-finger extension) and complex gestures (multi-finger extension). Ownership judgements were analysed and compared with those produced by six normal controls and two non-apraxic neurological patients. Apraxic patients and controls accurately recognized their own hand on the screen (own movement condition) and correctly identified the viewed hand as the examiner's when it performed a movement different from their own movement (incongruent movement condition). However, when the viewed hand was the examiner's hand executing their own movement (congruent movement condition), apraxic patients were significantly more impaired than controls. When the results were analysed as a function of gesture type, the number of correct responses was significantly lower for apraxic patients with respect to controls only for complex gestures. Interestingly, when patients executed the finger gestures inaccurately, they still failed to recognize the examiner's hand as alien, and claimed that the correct movement presented on the screen was their own. These results confirm that parietal lesions alter the representational aspects of gestures, and suggest a failure in evaluating and comparing internal and external feedback about movement. We conclude that the parietal cortex plays an important role in generating and maintaining a kinaesthetic model of ongoing movements.

Aged↗
PubMed2004

Involvement of human thalamus in the preparation of self-paced movement.

Cortical areas participating in the preparation of voluntary movements have been studied extensively. There is emerging evidence that subcortical structures, particularly the basal ganglia, also contribute to movement preparation. The thalamus is connected to both the basal ganglia and the cerebellar pathways, but its role in movement preparation has not been studied extensively in humans. We studied seven patients who underwent deep brain stimulation (DBS) electrode implantation in the thalamus for treatment of tremor (six patients) and myoclonus-dystonia (one patient). We recorded from the DBS contacts and scalp simultaneously, while patients performed self-paced wrist extension movements. Post-surgical MRI was used for precise localization of the DBS contacts in six patients. Back-averaging of the scalp recordings showed a slow negative movement-related potential (MRP) in all patients (onset 1846 +/- 189 ms prior to electromyography onset), whereas DBS electrode recordings showed pre-movement MRP in five out of seven patients. The thalamic MRP preceded both contralateral and ipsilateral wrist movements. There was no significant difference between the onset time of thalamic MRP (-2116 +/- 607 ms) and cortical MRP. Neither the scalp nor the thalamus showed pre-movement potentials with passive wrist extensions in two patients. In four patients with postoperative MRI who had thalamic MRP, the maximum amplitude or phase reversal occurred at contacts located in the ventral lateral nucleus. Frequency analysis was performed in the five patients with thalamic MRP. The medial frontocentral scalp contacts and the thalamic contacts with maximum MRP amplitude showed two discrete frequency bands in the alpha (mean peak 9 Hz) and beta (mean peak 17 Hz) range. Both frequency bands showed pre-movement event-related desynchronization (ERD). In the grand average, alpha and beta ERD in the scalp and beta ERD in the thalamus began 2.5-2.8 s prior to the onset of movement. However, the thalamic alpha ERD began considerably later, at 1.2 s before EMG onset. The beta band showed cortico-thalamic coherence from the beginning of the baseline period until approximately 0.5 s before the onset of movement. There was no cortico-thalamic coherence in the alpha band. Our findings suggest that the cerebellar thalamus is involved early in the process of movement preparation. Different cortico-subcortical circuits may mediate alpha and beta oscillations. During movement preparation, the motor thalamus and the supplementary motor area predominantly interact in the beta band.

Adult↗
PubMed1997

In vitro measurement of orthodontic tooth movement in rats given beta-aminopropionitrile or hydrocortisone using a time-lapse videotape recorder.

In vitro tooth movement of rat molars in response to an orthodontic force was recorded using a time-lapse videotape recorder and analysed by a computer system. Rats received daily s.c. injections of beta-aminopropionitrile (BAPN, 300 mg/kg/day) or hydrocortisone (10 mg/kg/day) for a period of 7 days. After drug administration, the animals were killed and the mandibles dissected. The jaw was then held under a stereomicroscope with a haemostatic clamp and an elastic band was inserted between the first and second molars. The movements of reference points on the occlusal surfaces of the first and second molars were recorded for 20 hours using a time-lapse videotape recorder. Mesiolingual movement of the first molar and distobuccal movement of the second molar were observed. During the experimental period, the greatest amount of total tooth movement in the first and second molars was seen in the group pretreated with BAPN, less movement was observed in the control group, and the group pretreated with hydrocortisone exhibited the least amount of movement. The highest rates of tooth movement were observed during the initial hour in each of the groups, and decreased thereafter. The initial rates of movement were also greatest in the BAPN group, less in the control group, and least in the hydrocortisone group. These results indicate that treatment with BAPN accelerated experimental tooth movements in vitro and hydrocortisone treatment inhibited the movements, suggesting that, although a part of the tooth movement measured in this experiment was due to deformation of the alveolar bone, the mechanical properties of the periodontal ligament play an important role in the regulation of orthodontic tooth movement.

Alveolar Process↗
PubMed2000

Role of laryngeal movement and effect of aging on swallowing pressure in the pharynx and upper esophageal sphincter.

OBJECTIVES: Describe contribution of laryngeal movement to pressure changes at the upper esophageal sphincter (UES) and the effect of aging on the swallowing function. STUDY DESIGN: Manofluorography on 56 nondysphagic adults divided into three age groups: the 21- to 31-year-old group (n = 32), the 61- to 74-year-old group (n = 12) and the 75- to 89-year-old group (n = 12). Analyses of the bolus transit time, the amplitudes and durations of pharyngeal pressures, the timing of a pressure fall at the UES and the laryngeal movements. METHODS: Intraluminal strain-gauge sensors recorded pressure changes in the oropharynx, hypopharynx and the UES. Motion pictures of the videotapes were fed into a personal computer, and movements of the hyoid bone were measured in both the horizontal and vertical directions as an indication of laryngeal movement. RESULTS: In 26- and 70-year-old men with calcification of the thyroid cartilage, it was determined that the larynx and hyoid bone moved in consonance until the end of the rapid hyoid movements in both the superior and anterior directions. In the 21- to 31-year-old group, the magnitude of the pressure fall at the UES was maximal before or almost at the same time as the bolus arrival, in preparation for smooth passage of the bolus from the pharynx to the esophagus. The rapid superior movements of the hyoid bone started significantly early as compared with its anterior movements (P = .0001). The rapid anterior movements of the hyoid bone started simultaneously with the pressure fall at the UES. In the elderly, all segmental transit times were significantly increased. The timing of the pressure fall at the UES was significantly delayed and the UES pressure reached its minimum value after arrival of the bolus at the UES. The minimum pressure at the UES increased to a significantly positive value. The rapid anterior movements of the hyoid were significantly delayed, suggesting that this delay causes the delay in the pressure fall at the UES. CONCLUSIONS: The rapid superior and anterior movements of the hyoid bone are considered to start at the same time as those of the larynx. In the young group, it is suggested that superior laryngeal movement protects the lower airway prior to the anterior laryngeal movement, causing the pressure fall at the UES to enable the passage of a bolus into the UES. In the elderly, smooth passage of the bolus from the pharynx to the esophagus is hindered and the system that prevents aspiration is rendered inefficient by changes in the swallowing pressures and laryngeal movements with aging.

Adult↗
PubMed1979

The incidence of different types of fetal movements during pregnancy.

In high risk pregnancies with severe fetal distress, a reduction of fetal movements may take place before fetal death occurs. This decrease is accompanied by a weakening of the fetal movements. One hundred and twenty pregnant women (310 recordings) between 20 and 41 weeks gestation recorded fetal movements and classified them into weak, strong, and rolling. The movements noted by the woman were correlated to those recorded by a fetal movements recorder. The rate of weak movements gradually decreased until the 36 to 37th week, while the strong and rolling movements increased. From the 36 to 37th week till term weak movements increased again with a decline in strong and rolling movements. Before fetal death, or in severe fetal distress with decreased total movements, the relative rate of weak movements increased. Reduction in daily total movements without a change in the distribution of the type of movement may not indicate fetal distress.

Adult↗
PubMed1984

The central control of fetal breathing and skeletal muscle movements.

Breathing movements in the sheep fetus have been observed from a gestational age of about 40 days. From 95 to 115 days fetal breathing movements are almost continuous, interrupted by apnoea rarely exceeding 2 min. From 115 days until term (about 147 days) breathing and movements of the trunk and limbs are episodic. Breathing normally occurs only during rapid-eye-movement sleep as identified by low-voltage cortical electrical activity. Active movements of the neck muscles occur predominantly in high-voltage electrocortical activity. Hypercapnia or acid cerebrospinal fluid perfusion cause an increase in the regularity and depth of breathing when present, and recruit intercostal and laryngeal abductor activity. Isocapnic hypoxia, however, in contrast to the hyperventilation seen postnatally, causes arrest of fetal breathing movements. This effect is due to a central inhibition. Section of the brain stem, from the caudal hypothalamus rostrally, causes dissociation of fetal breathing movements and electrocortical activity into independent rhythms. Section of the brain stem caudally, in the upper pons or at the inferior colliculus, also causes a dissociation of electrocortical activity from breathing movements, which become almost continuous. Isocapnic hypoxia causes an increase in the rate and depth of breathing movements. It is concluded that the arrest of breathing in intact fetal lambs is not due to a direct effect on the respiratory centre in the medulla. The lumbar polysynaptic flexor reflex response becomes episodic after 115 days gestation but, in contrast to fetal breathing movements, is enhanced during high-voltage electrocortical activity. Isocapnic hypoxia arrests movements of the fetal limbs and trunk and inhibits the lumbar flexor reflex. This inhibition of the reflex is prevented by section of the spinal cord at T12, but persists after section of the brain stem in the upper pons. It is attributed to an action on the medulla, independent of the systemic arterial chemoreceptors. Small doses of pentobarbitone (5 mg/kg) cause arrest of fetal breathing movements by a suprapontine mechanism, abolished by brain stem transection, and inhibition of the lumbar flexor reflex by an action on the spinal cord, persisting after transection at T12. Inhibitors of prostaglandin synthetase (indomethacin, meclofenamate or aspirin) induce continuous fetal breathing movements, while prostaglandin E2 arrests fetal breathing. The site of action is on the medulla, as shown by section of the brain stem and of afferents from the systemic arterial chemoreceptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

Movement illusions evoked by ensemble cutaneous input from the dorsum of the human hand.

1. In this study we tested the hypothesis that ensemble activity in human cutaneous sensory afferents evoked by the stretching of skin over and around the finger joints contributes to the conscious perception of movement of the fingers. 2. In nineteen normal adults, ensembles of cutaneous afferents were activated either by electrical stimulation, delivered through an array of electrodes on the dorsum of the hand and fingers, or by mechanical stretching of the skin over and around the joints. The stretching was applied through an array of threads stuck to the skin, in such a way as to avoid or minimize moving the underlying joints and to avoid applying pressure to underlying tendons and ligaments. Perceived movements were mimicked by voluntary movements of the fingers of the contralateral hand. 3. By way of comparison, kinaesthetic illusions were also evoked by activation of muscle receptors by vibration. 4. Illusions of movement were elicited with each type of stimulus. Electrical stimulation of skin afferents caused clear illusory movements in six out of seventeen subjects (35%), and borderline movement illusions in three out of the same seventeen subjects (total 9/17, 53%). Various other localized skin sensations were also reported. Skin stretch evoked movement illusions in eleven out of nineteen of subjects (58%). In all subjects who received both cutaneous stimuli, twelve out of seventeen (71%) reported some movement sensations with one or other of the stimulation techniques. Vibration tended to be the most reliable stimulus modality, eliciting illusory movements in fourteen out of sixteen subjects (88%). 5. Although the skin stretching technique did cause minute movements of nearby joints in several cases, these were monitored and shown in separate control experiments to be below perceptual threshold, and so the movement illusions could be safely attributed to the cutaneous afferent input evoked by skin stretch. 6. The results support the hypothesis that input from skin stretched during finger movement contributes to the conscious perception of the movement. Vibration-evoked muscle afferent input tended to be more reliable than the skin input in producing kinaesthetic illusions, though comparisons of the relative efficacy of the three techniques must be made with caution.

Adolescent↗
PubMed2004

The sense of movement elicited by transcranial magnetic stimulation in humans is due to sensory feedback.

It has been claimed that transcranial magnetic stimulation (TMS) of the human motor cortex can produce a sense of movement of the contralateral hand, even when the hand is paralysed. The sense of movement was equated with a 'corollary discharge', a nulling mechanism originally posited for maintaining constancy of the visual field during eye movements. Our experiments were designed to test whether the sensation that accompanies TMS-evoked finger movements is generated centrally or whether it arises as a result of sensory feedback. Matched twitches of the left and right fingers were elicited either by bilateral electrical stimulation of forearm extensor muscles, or by a combination of TMS of left motor cortex (eliciting twitches of the right forefinger), and electrical stimulation of the left forearm muscles (eliciting twitches of the left forefinger). The time interval between stimuli activating left and right twitches was varied randomly (range +/- 90 ms) from trial to trial. Subjects reported whether they sensed that the left or the right movement occurred first, or if they could detect no difference. The left and right movements evoked by bilateral electrical stimulation of muscles were sensed as near simultaneous when there was zero delay between them. When TMS was applied in conjunction with unilateral muscle stimulation, the TMS-evoked movement was felt, on average, 20 ms after the movement evoked by muscle stimulation. Similar results were obtained when the skin under the cathodal electrodes was anaesthetized. Since the TMS-evoked movements were felt later rather than earlier than the electrically evoked movements, the results do not support the idea that the sensation of movement was elicited centrally by TMS. Rather, they favour sensory feedback as the source of the sense of movement. The earlier perception of electrically evoked versus TMS-evoked movements was probably due to earlier sensory responses in the periphery rather than a suppression of the excitability of somatosensory cortex.

Adult↗
PubMed2000

Dissociation of anosognosia and phantom movement during the Wada test.

OBJECTIVE: Patients who misperceive that they are moving their paralysed arm (phantom movements) may not recognise its weakness. Therefore, the relation between phantom limb movements and anosognosia for hemiplegia during selective right hemispheric anaesthesia (the Wada test) was examined. METHODS: Nine patients with intractable epilepsy underwent the Wada test. During the right hemispheric injection, after the onset of hemiparesis, anosognosia was assessed by asking patients if they were weak. The patient's vision was limited such that they could not see the position of their limbs. Phantom movements were tested for by asking patients to attempt to lift their left upper limb, and to demonstrate their left limb's position by placing their right limb in the same position as their left. Proprioception was tested by lifting the patient's paretic upper limb and having patients demonstrate this position by lifting their right limb to the same position. RESULTS: Three patients experienced left phantom limb movements, and five were anosognosic for their hemiplegia. However, phantom movement occurred in only one patient with anosognosia. The other two patients with phantom movement were without anosognosia. The patient with phantom movement and anosognosia had impaired proprioception. The two patients with phantom movement but without anosognosia had intact proprioception. CONCLUSIONS: Phantom movement in the presence of a proprioceptive deficit could contribute to anosognosia. However, anosognosia and phantom movement are dissociable; therefore phantom movement cannot alone account for anosognosia. Because phantom movement occurred with and without proprioceptive deficits, proprioceptive loss is not a prerequisite for phantom movement.

Adult↗
PubMed2004

Ipsilateral motor cortex activity during unimanual hand movements relates to task complexity.

Functional imaging studies have revealed recruitment of ipsilateral motor areas during the production of sequential unimanual finger movements. This phenomenon is more prominent in the left hemisphere during left-hand movements than in the right hemisphere during right-hand movements. Here we investigate whether this lateralization pattern is related specifically to the sequential structure of the unimanual action or generalizes to other complex movements. Using event-related fMRI, we measured activation changes in the motor cortex during three types of unimanual movements: repetitions of a sequence of movements with multiple fingers, repetitive "chords" composed of three simultaneous key presses, and simple repetitive tapping movements with a single finger. During sequence and chord movements, strong ipsilateral activation was observed and was especially pronounced in the left hemisphere during left-hand movements. This pattern was evident for both right-handed and, to a lesser degree, left-handed individuals. Ipsilateral activation was less pronounced in the tapping condition. The site of ipsilateral activation was shifted laterally, ventrally, and anteriorly with respect to that observed during contralateral movements and the time course of activation implied a role in the execution rather than planning of the movement. A control experiment revealed that strong ipsilateral activity in left motor cortex is specific to complex movements and does not depend on the number of required muscles. These findings indicate a prominent role of left hemisphere in the execution of complex movements independent of the sequential nature of the task.

Analysis of Variance↗
PubMed1980

Simple-spike activity of cerebellar Purkinje cells related to visually guided wrist tracking movement in the monkey.

1. Three rhesus monkeys were trained to perform a rapid (greater than 100 degrees/s) and a slow (less than 100 degrees/s) wrist movement guided by a visual cue. While the monkey performed wrist flexion or extension from a neutral position, Purkinje cell (P-cell) discharges were recorded from intermediate and lateral parts of lobules IV--VI of the cerebellum. 2. By the visually guided movement, we could control the direction of the wrist movement; the holding position at three different angles of the wrist joint: neutral, about 30 degrees flexed, and extended; and the velocity in four ranges: a) 10--30, b) 30--100, c) 100--300, and d) 300-650 degrees/s. 3. From 92 P-cells that significantly increased or decreased the discharge rate of simple spikes with task performance, we selected 45 P-cells ("response-locked" cells) as related to the wrist movement by statistical analyses of temporal correlation of P-cell activities to wrist movement. The direction of the frequency modulation (increase or decrease) was in a nonreciprocal fashion with oppositely directed wrist movements (flexion or extension) in 90% of the response-locked P-cells. The maintained frequencies at three holding positions did not significantly differ. 4. Nineteen P-cells changed their spike frequencies temporally locked to both rapid and slow wrist movements. By the discharge pattern in relation to the rapid and slow movements, these cells were classified into two groups. Discharge pattern in group I P-cells (n = 5) conformed very well to that of velocity, and a linear correlation between the instantaneous increase of the discharge rate and velocity was observed in analyses of individual trials. Group II cells showed increase (n = 9) or decrease (n = 5) of firing rate (20--50 spikes/s) larger than group I cells (less than 10 spikes/s) as long as the wrist was moving, even with very slow velocity (less than 30 degrees/s. The correlations between the increase of the discharge rate and the velocity in individual trials were less clear in group II than in group I cells. 5. The present study suggests the importance of the cerebellar cortex in controlling the slow limb movement as well as the rapid movement. The selected P-cells in this study also suggested that the velocity or some dynamic aspect related to the velocity of limb movement is the major information among the dissociated motion parameters coded by the simple-spike frequencies of the P-cells in the cerebellar hemisphere. Whether the latter suggestion represents an essential characteristic of all limb movement-related P-cells or reflects only a feature of a special subgroup among the movement-related cells should be clarified in future experiments.

Action Potentials↗
PubMed1989

Monkey primary motor and premotor cortex: single-cell activity related to prior information about direction and extent of an intended movement.

1. This study was devoted to the neuronal processes underlying the construction of the motor program. Two monkeys were trained in a choice reaction time task to perform precise wrist flexion and extension movements of small and large extent. During a trial, the first visual signal, the preparatory signal (PS), informed the animal completely, partially, or not at all about direction and/or extent of the forthcoming movement. After a constant waiting period, a second visual signal, the response signal (RS), was illuminated calling for execution of the requested movement. 2. Reaction time (RT) and movement time (MT) measurements during the training as well as the recording sessions revealed that providing prior information about movement parameters strongly affected RT, but only slightly affected MT. Reaction time decreased in relation to the amount (number of movement parameters precued) and the type of prior information. Providing information about movement direction shortened RT much more than providing information about movement extent. Behavioral data support a parametric conception of motor programming, i.e., that the programming of the different movement parameters results from assembling separate processes of different duration. These results are compatible with the model in which programming processes are serially and hierachically ordered, movement direction being processed before movement extent. 3. Single-cell recording techniques were used to study neuronal activity of the primary motor (MI) and the premotor (PM) cortex, contralateral to the active arm. The activity of 155 neurons of MI and 158 neurons of PM was recorded during performance of the task. Of these 313 neurons, only 14 neurons did not change their activity during execution of the task. Two hundred and seven neurons whose activity changes were related to movement direction and/or movement extent have been selected for the further study. They were classified into three main groups: 1) execution-related neurons (49 in MI, 27 in PM), 2) preparation- and execution-related neurons (48 in MI, 54 in PM), and 3) preparation-related neurons (8 in MI, 21 in PM). 4. Directionally selective, execution-related neurons were found to be more frequently located within MI (81/105, 77.1%) than within PM (55/102, 53.9%), whereas directionally selective, preparation-related neurons appeared to be more frequently located within PM (47/102, 46.1%) than within MI (24/105, 22.9%).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Impairments of reaching movements in patients without proprioception. I. Spatial errors.

1. This paper introduces a series of studies in which we analyze the impairments in a planar reaching task in human patients with severe proprioceptive deficits resulting from large-fiber sensory neuropathy. We studied three patients, all of whom showed absence of discriminative tactile sensation, position sense, and stretch reflexes in the upper extremities. Muscle strength was normal. We compared the reaching movements of the patients with those of normal control subjects. The purpose of this first paper was no characterize the spatial errors in these patients that result primarily from impairments in the planning and execution of movement rather than in feedback control. This was done by using a task in which visual feedback of errors during movement was prevented. 2. Subjects were instructed to move their hand from given starting positions of different targets on a horizontal digitizing tablet. Hand position and targets were displayed on a computer screen. Subjects could not see their hand, and the screen display of hand position was blanked at the signal to move. Thus visual feedback during movement could not be used to achieve accuracy. Movement paths were displayed as knowledge of results after each trial. 3. Compared with controls, the patients made large spatial errors in both movement direction and extent. Directional errors were evident from movement onset, suggesting that they resulted from improper planning. In addition, patients' hand paths showed large curves and secondary movements after initial stops. 4. The overall control strategy used by patients appeared the same as that used by controls. Hand trajectories were approximately bell shaped, and movement extent was controlled by scaling a trajectory waveform in amplitude and time. However, both control subjects and patients showed systematic errors in movement extent that depended on the direction of hand movement. In control subjects, these systematic dependencies of extent on direction were small, but in patients they produced large and prominent errors. Analysis of the hand trajectories revealed that errors were associated with differences in velocity and acceleration for movements in different directions. In an earlier study, we showed that in subjects with normal sensation that the dependence of acceleration and velocity on direction results from a failure to take the inertial properties of the limb into account in programming the initial trajectory. In control subjects, these differences in initial acceleration are partially compensated by direction-dependent variations in movement time.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

Directional variation of spatial and temporal characteristics of limb movements made by monkeys in a two-dimensional work space.

1. The directional variation of kinematic and electromyographic (EMG) characteristics of two-joint arm movements made to targets in a two-dimensional work space was studied in monkeys trained to make targeted arm movements under different behavioral conditions. 2. In each animal, kinematic measures of movement (movement amplitude, movement time, peak velocity, and trajectory curvature) and endpoint spatial position within the target zone varied as a function of the direction of the target from the starting position. Movements made toward the body into the ipsilateral hemispace generally had the smallest amplitude, lowest peak velocity, and longest movement time. 3. Although the directional variation in peak velocity could partially be accounted for by predicted anisotropies in the inertial load imposed by the arm, deviations from these predictions suggest that movement amplitude is controlled more rigorously by the CNS. Adjustments in movement time may be used to compensate for inertial anisotropies. 4. The spatial characteristics of movements (amplitude, trajectory curvature, or endpoint error) were influenced little by the visibility of the target during movement, the advanced knowledge of target location, or the presence or absence of an external trigger cue. However, temporal characteristics (movement time, peak velocity, and for some animals, reaction time) varied more as sensory cues were changed. 5. The time of initial EMG activity in muscles acting around the shoulder varied systematically as a function of target direction. A cosine model accounted for a large fraction of the variability in initial onset time, as determined in a trial-by-trial analysis. The amplitude of the EMG activity was more narrowly tuned, however. Muscles acting at the elbow showed less activity and more variable directional tuning. 6. We conclude that directional variations in the kinematic characteristics of movement, and thus, the dynamic force requirements of the task, must be taken into consideration as contributors to the apparent directional coding described for neuronal populations in different portions of the CNS.

Animals↗
PubMed2000

Cortical potentials associated with voluntary mandibular movements.

Movement-related cortical potentials (MRCPs) are negative potentials over the scalp, which gradually increase prior to voluntary movements, and might be applied to elucidate the cortical efferent function of the mandibular movements. We compared the MRCPs accompanying various mandibular movements to study the motor control mechanism underlying these movements. Electroencephalograms (EEGs) were recorded from 11 electrodes placed over the scalp (F3, Fz, F4, T3, C3, Cz, C4, T4, P3, Pz, and P4), according to the International 10-20 System, and electromyograms (EMGs) were obtained from surface electrodes over the masseter muscle and the anterior belly of the digastric muscle. Ten healthy subjects were requested to make brisk and self-paced mandibular movements in 4 different directions (mouth-opening and -closing, and left and right lateral movements). We obtained MRCPs by averaging the EEG, using the visually determined EMG onset as a trigger signal. In all the movements, a slowly increasing, bilaterally widespread negativity starting 1.5 to 2.0 sec before the EMG onset (Bereitschaftspotential, or BP proper) was observed, with the maximum over the vertex region. The negative slope (NS') occurred about 300 to 700 msec before the EMG onset. The cortical maps of BP/NS' (BP and NS' combined), immediately prior to the mouth-opening and closing, showed a symmetrical distribution, whereas that for the lateral movements showed a tendency of predominance over the hemisphere ipsilateral to the direction of the movement. BP/NS' amplitudes at the onset of movement differed significantly or tended to do so between open, close, and lateral movements, suggesting that MRCP recordings may thus provide a means to explore the role of the cerebral cortex in the control of mandibular movements.

Adult↗