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At least 235 records · Page 13Linked to original sources
PubMed2000

Proprioceptive population coding of two-dimensional limb movements in humans: II. Muscle-spindle feedback during "drawing-like" movements.

It was proposed to study the proprioceptive sensory coding of movement trajectories during the performance of two-dimensional "drawing-like" movements imposed on the tip of the foot. For this purpose, the activity of the muscle-spindle afferents from the Extensor digitorum longus, Tibialis anterior, Extensor hallucis longus, and Peroneus lateralis muscles was recorded from the lateral peroneal nerve using the microneurographic technique. The drawing movements, describing geometrical shapes such as squares, triangles, ellipses, and circles, were imposed at a constant velocity in both the clockwise and counterclockwise directions. A total number of 44 muscle-spindle afferents were tested, 36 of which were identified as primary and eight as secondary afferents. Whatever the shape of the imposed foot movement, the primary endings from one muscle never discharged throughout the whole trajectory (on average, they discharged for only 49.2% of the length of the trajectory), whereas all the secondary endings discharged for most part of the drawing trajectories (average: 84.8%). The relationship between afferent discharge rate and direction could be described with a cosine-shaped tuning function. The peak of this function corresponded to the preferred sensory direction of the receptor-bearing muscles. The whole path of a given geometrical drawing movement was found to be coded in turn by each of the primary afferents originating from each of the muscles successively stretched. The contribution of each population of muscle afferents from each ankle muscle was represented by a "population vector", whose orientation was the preferred direction of the muscle under consideration and whose length was the mean instantaneous frequency of the afferent population. The "sum vector" corresponding to the sum of all these weighted "population vectors" was found to point in the instantaneous direction of the drawing trajectory, i.e., the tangent to the trajectory. These findings suggest that trajectory information is already encoded at the peripheral level on the basis of the integrated inputs provided by sets of receptors belonging to all the muscles acting on a given joint.

Adult↗
PubMed1978

Human fetal breathing movements and gross fetal body movements at weeks 34 to 35 of gestation.

Human fetal breathing movements in utero at 34 to 35 weeks' gestational age were measured using a real-time ultrasonic scanner. Fetal breathing movements were episodic and occurred 31.8 per cent of the time. Aanalysis of continuous recordings in 10 fetuses from 09:00 to 17:00 hours demonstrated that the percentage of time spent breathing per hour was greater in the afternoon than in the morning. The number of gross fetal body movements was also greater in the afternoon than in the morning. The percentage of time spent breathing was significantly greater during the hour following the noon meal than during the hour preceding the noon meal. It was concluded that real-time ultrasonic scanning permits identification of fetal breathing movements and that between 09:00 and 17:00 hours the character of these movements is related to the time of the day and to the ingestion of food by the mother.

Adolescent↗
PubMed1986

Discharges of Purkinje cells in monkey's flocculus during smooth-pursuit eye movements and visual stimulus movements.

Modulations in discharges of Purkinje cells (P cells) associated with movements of visual patterns were studied in the flocculus of monkeys trained to execute smooth-pursuit eye movements and to suppress optokinetic nystagmus. One class of P cells responded to the movements of visual stimulus regardless of whether the eyes remained stationary (produced retinal-slip velocity) or moved with the stimulus produced eye velocity). These P cells processed high-order information concerning the absolute velocity of stimulus movements and thereby the eye velocity had already been incorporated in the visual responses (visuomotor P cells). The other class of P cells responded to visual inputs resulting from the retinal slip (visual P cells). The majority of visual P cells (82%) also modulated their activities during smooth pursuit. When sinusoidal trackings were executed against a stationary visual background, various types of interactions occurred in the P-cell responses between the converging visual and oculomotor inputs. The type of interaction was related to the preferred direction for the P cell during eye movements and the side of the peripheral receptive field.

Animals↗
PubMed1984

A kinematic investigation of mandibular border movement by means of an electronic measuring system. Part II: A study of the Bennett movement.

Fifty adults with orthognathic maxillomandibular relationships were selected as the test group. The movement of the working condyle was examined during lateral movement of the mandible with an electronic system capable of measuring six degrees of freedom of the mandible with an accuracy of +/- 0.06 mm. The results were: Orbits of the points on the terminal hinge axis d mm from the midpoint during lateral movement of the mandible varied appreciably as the value of d changed. The orbits more affected were the working side on the horizontal and frontal planes. The point on the working side moved forward, laterally, and downward as the value of d was small; and it moved backward, laterally, and upward as the value of d increased. Depending on the value of d, orbits moved in opposite directions. As the value of d varied from small to large, the point on the working side moved only laterally along the terminal hinge axis when d was 55 mm. From this observation, the Bennett movement is explained as the lateral shift of the working condyle along the terminal hinge axis. Reports concerning the directions and mode of motion of the Bennett movement differ because of the lack of specification of location of the positions (targets) assigned for measurement.

Adult↗
PubMed1991

The effects of maternal hyperoxia on fetal breathing movements, body movements and heart rate variation in growth retarded fetuses.

In hypoxemic intrauterine growth-retarded fetuses (IUGR) there is a reduction in the incidence of fetal movements and in fetal heart rate variation. A causal relationship with the impairment of fetal oxygenation has been suggested. In 16 IUGR fetuses and in 13 normally grown fetuses maternal hyperoxygenation was applied for 40 min to increase fetal PO2 levels. All IUGR fetuses had abnormal Doppler blood velocity waveforms of the umbilical artery suggesting an impaired uteroplacental exchange. The effect of hyperoxygenation on fetal breathing and body movements and on fetal heart rate was evaluated. In the IUGR fetuses there was a significant increase in fetal breathing and body movements and in heart rate variation during hyperoxygenation as compared to the preceding control period of 40 min. No significant changes in fetal breathing and body movements were found in the normally grown control fetuses. A surprising observation was the increase of the number of heart rate decelerations after discontinuation of the maternal hyperoxygenation. It is concluded that in IUGR fetuses the increase in fetal heart rate variation and the increase in the incidence of breathing and body movements during maternal hyperoxygenation substantiates the relationship between these variables and the oxygenation status of the fetus.

Female↗
PubMed2004

fMRI signal decreases in ipsilateral primary motor cortex during unilateral hand movements are related to duration and side of movement.

Interactions between the primary motor cortices of each hemisphere during unilateral hand movements appear to be inhibitory, although there is evidence that the strengths of these interactions are asymmetrical. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate the effects of motor task duration and hand used on unilateral movement-related BOLD signal increases and decreases in the hand region of primary motor cortex (M1) of each hemisphere in six right-handed volunteers. Significant task-related BOLD signal decreases were observed in ipsilateral M1 during single and brief bursts of unilateral movements for both hands. However, these negative-to-baseline responses were found to intensify with increasing movement duration in parallel with greater task-related increases in contralateral M1. Movement-related BOLD signal decreases in ipsilateral M1 were also stronger for the right, dominant hand than for the left hand in our right-handed subjects. These findings would be consistent with the existence of interhemispheric interactions between M1 of each hemisphere, whereby increased neuronal activation in M1 of one hemisphere induces reduced neuronal activity in M1 of the opposite hemisphere. The observation of a hemispheric asymmetry in inhibition between M1 of each hemisphere agrees well with previous neuroimaging and electrophysiological data. These findings are discussed in the context of current understanding of the physiological origins of negative-to-baseline BOLD responses.

Adult↗
PubMed2005

Mutational analysis of the RNA-binding domain of the Prunus necrotic ringspot virus (PNRSV) movement protein reveals its requirement for cell-to-cell movement.

The movement protein (MP) of Prunus necrotic ringspot virus (PNRSV) is required for cell-to-cell movement. MP subcellular localization studies using a GFP fusion protein revealed highly punctate structures between neighboring cells, believed to represent plasmodesmata. Deletion of the RNA-binding domain (RBD) of PNRSV MP abolishes the cell-to-cell movement. A mutational analysis on this RBD was performed in order to identify in vivo the features that govern viral transport. Loss of positive charges prevented the cell-to-cell movement even though all mutants showed a similar accumulation level in protoplasts to those observed with the wild-type (wt) MP. Synthetic peptides representing the mutants and wild-type RBDs were used to study RNA-binding affinities by EMSA assays being approximately 20-fold lower in the mutants. Circular dichroism analyses revealed that the secondary structure of the peptides was not significantly affected by mutations. The involvement of the affinity changes between the viral RNA and the MP in the viral cell-to-cell movement is discussed.

Amino Acid Sequence↗
PubMed1997

Steady-state movement-related cortical potentials: a new approach to assessing cortical activity associated with fast repetitive finger movements.

Traditionally, studies of movement-related cortical potentials have focused on the preparation of single self-paced movements performed slowly. We studied MRCPs elicited by metronome-paced, fast repetitive finger movements (2/s) with 28-channel (10 normal subjects) and 122-channel (two subjects) EEG. EMG-locked averaging of 500 ms time windows (300 ms before to 200 ms after each EMG onset) produced a distinct pattern of phasic MRCPs (steady-state MRCPs). The main components were a pre-movement peak (pre-MP), 57 ms before EMG onset, and a post-movement peak (post-MP), 93 ms after EMG onset. From timing information and topographic mapping results, we propose that the pre-MP is largely generated by a tangential source in the anterior bank of the central sulcus and reflects precentral motor processing, whereas the post-MP is generated in the posterior bank of the central sulcus and represents post-central feedback processing. Steady-state MRCPs require actual recording times of less than 10 min, and show excellent inter-session reproducibility. These characteristics may make them convenient for studying sensorimotor cortex activity experimentally and clinically.

Adult↗
PubMed1999

Mental representations of movements. Brain potentials associated with imagination of eye movements.

OBJECTIVE: Current research in motor imagery is focused on similarities between actual and imagined movements on a central and a peripheral level of the nervous system. The present study measured slow cortical potentials (DC-potentials) during execution and internal simulation of memorized saccadic eye movements. METHODS: In 19 healthy righthanded subjects DC-potentials were recorded from 28 electrodes during execution and during imagination of a sequence of memorized eye movements during a visual imagery condition. RESULTS: Both oculomotor conditions showed a similar global level and similar topography of performance related DC-potentials, both strongly differed from the visual imagery condition and were lateralized to the left hemisphere. CONCLUSION: This study therefore supports the hypothesis that cortical brain structures responsible for execution and imagination of memorized saccadic eye movements are similar. The observed left hemispheric lateralization is in contrast to a previous study using bimanual movements. This discrepancy is discussed in relation to recent observations in apractic patients with parietal lesions.

Adult↗
PubMed2000

Steady-state movement-related potentials evoked by fast repetitive movements.

We investigated steady-state movement-related cortical potentials elicited by fast repetitive movements (1/sec) with 50-channel EEG. The experimental design comprised a comparison (a) between unilateral movements of the digits and the toes and (b) between metronome-paced and self-paced initiation of the movements. A distinct biphasic pattern of electrical activity following movement onset was observed, namely a frontal negative peak at a latency of 90 ms (post-MP100) anda frontal positive peak at a latency of 310ms (post-MP300). Pacing exerted its effects mainly on the amplitude and on the latency of the post-MP300. Source analysis revealed that both peaks could be modelled by a single source. The source locations were highly reproducible across the metronome-paced and self-paced conditions, and, they followed the expected somatotopic organisation.

Adult↗
PubMed2005

The preparation of reach-to-grasp movements in adults, children, and children with movement problems.

This study explored the use of advance information in the control of reach-to-grasp movements. The paradigm required participants to reach and grasp illuminated blocks with their right hand. Four target blocks were positioned on a table surface, two each side of the mid-saggital plane. In the complete precue condition, advance information precisely specified target location. In the partial precue condition, advance information indicated target location relative to the midsaggital plane (left or right). In the null condition, the advance information was entirely ambiguous. Participants produced fastest responses in the complete precue condition, intermediate response times in the partial condition, and the slowest responses in the null condition. This result was observed in adults and four groups of children including a group aged 4-6 years. In contrast, children with Developmental Coordination Disorder (DCD, n=11, aged 7--13 years) showed no advantage of partial precueing. Movement duration was determined by target location but was unaffected by precue condition. Movement duration was a clear function of age apart from children in the DCD group who showed equivalent movement times to those of the youngest children. These findings provide important insights into the control of reach-to-grasp movements and highlight that partial cues are exploited by children as young as 4 years but are not used in situations of abnormal development.

Adolescent↗
PubMedDate not supplied

Independent coding of movement duration in a repetitive non-visually guided movement.

Temporal information is an embedded feature of our sensory and motor experiences. How is temporal information encoded in the brain? In the two-stage theory of timing, an explicit representation of timing is responsible for the movement initiation while movement duration is coded implicitly. We investigated the correlation of movement duration and amplitude in a repetitive one-dimensional non-visually guided movement to find out if temporal information could be coded independently from movement. Subjects were asked to learn the distance between two points by moving their hands repeatedly along the distance between two sticks, while they could not see their hands and hand path. After a training phase, a delay of either 2 or 20 s was imposed and the subjects were asked to reproduce the learned distance. There was no correlation between distance difference and time difference in either delay condition. In the 20 s delay experiment, in comparison to the 2 s delay experiment, there was a significant increase in distance reproduction error. However, there was no significant change in time differences in either of the experiments. In addition, the time difference between the training and test trials was independent from the direction of the distance difference (i.e., overshot, undershot, or accurate). In conclusion, time may be coded as an independent measure after the delay period, so it should be a kind of explicitly coded information.

Adult↗
PubMed2001

A neural network for recognizing movement patterns during repetitive self-paced movements of the fingers in opposition to the thumb.

A data glove is a typical input device to control a virtual environment. At the same time it measures movements of wrist and fingers. The purposes of this investigation were to assess the ability of BrainMaker, a neural network, to recognize movement patterns during an opposition task that consisted of repetitive self-paced movements of the fingers in opposition to the thumb. The neural network contained 56 inputs, 3 hidden layers of 20 neurons, and one output. The 5th glove '95 (5DT), a commercial glove especially designed for virtual reality games, was used for finger motion capture. The training of the neural network was successful for recognizing the thumb, the index finger and the ring finger movements during the repetitive self-paced movements and neural network performed well during testing.

Adult↗
PubMed2000

Bromovirus movement protein conditions for the host specificity of virus movement through the vascular system and affects pathogenicity in cowpea.

Previously, we reported that CCMV(B3a), a hybrid of bromovirus Cowpea chlorotic mottle virus (CCMV) with the 3a cell-to-cell movement protein (MP) gene replaced by that of cowpea-nonadapted bromovirus Brome mosaic virus (BMV), can form small infection foci in inoculated cowpea leaves, but that expansion of the foci stops between 1 and 2 days postinoculation. To determine whether the lack of systemic movement of CCMV(B3a) is due to restriction of local spread at specific leaf tissue interfaces, we conducted more detailed analyses of infection in inoculated leaves. Tissue-printing and leaf press-blotting analyses revealed that CCMV(B3a) was confined to the inoculated cowpea leaves and exhibited constrained movement into leaf veins. Immunocytochemical analyses to examine the infected cell types in inoculated leaves indicated that CCMV(B3a) was able to reach the bundle sheath cells through the mesophyll cells and successfully infected the phloem cells of 50% of the examined veins. Thus, these data demonstrate that the lack of long-distance movement of CCMV(B3a) is not due to an inability to reach the vasculature, but results from failure of the virus to move through the vascular system of cowpea plants. Further, a previously identified 3a coding change (A776C), which is required for CCMV(B3a) systemic infection of cowpea plants, suppressed formation of reddish spots, mediated faster spread of infection, and enabled the virus to move into the veins of inoculated cowpea leaves. From these data, and the fact that CCMV(B3a) directs systemic infection in Nicotiana benthamiana, a permissive systemic host for both BMV and CCMV, we conclude that the bromovirus 3a MP engages in multiple activities that contribute substantially to host-specific long-distance movement through the phloem.

Biological Transport↗
PubMed1988

1988 Volvo award in biomechanics. The triaxial coupling of torque generation of trunk muscles during isometric exertions and the effect of fatiguing isoinertial movements on the motor output and movement patterns.

Previous studies have shown that reduction of precise motor control accompanies local muscular fatigue. The effects of isodynamic fatiguing of flexion and extension trunk movements on the movement patterns and the motor output of the trunk were investigated. Twenty male subjects with no history of low-back pain for the past 6 months volunteered for the study. A triaxial dynamometer was used that simultaneously provided measurement of torque, angular position and velocity of each axis. Resistances were set independently for each axis by an interfaced computer. The subjects performed trunk flexion and extension movement against a sagittal plane resistance equal to 70% of their maximum isometric extension strength in the upright position. The minimum resistances in the coronal and transverse planes were set up at 7 Newton meters. The subjects were asked to perform trunk movement as quickly and as accurately as possible while exerting the maximum efforts until exhaustion. Analysis of variance, the MANOVA procedure with a repeated measure design, was performed among the selected parameters of the first, middle and last three repetition cycles. The selected parameters are the trunk motor output and movement patterns; the total angular excursion, range of motion, maximum and average torque and angular velocity of the trunk. All the selected parameters were significantly reduced in the sagittal plane. Subjects displayed significantly less motor control and greater range of motion in the coronal and transverse planes in performing the primary task of flexion and extension. The reduction in the functional capacity of the primary muscles performing the required task is compensated by secondary muscle groups and the spinal structure is loaded in a more injury prone pattern, as identified by finite element models. In addition it is suggested that the fatigued muscles would be less able to compensate any perturbation in the load or position of the trunk. The repetitive loading results in a weakening of the viscoelastic passive elements of the spineless structure. The loss of ability to protect these weakened passive elements makes the spine susceptible to industrial and recreational injuries.

Adult↗
PubMed1999

Effect of C-terminal deletions in the movement protein of cowpea chlorotic mottle virus on cell-to-cell and long-distance movement.

In order to elucidate the function of the C-terminal region of cowpea chlorotic mottle bromovirus (CCMV) movement protein (MP) in cell-to-cell movement, a set of deletions ranging from 10 to 80 amino acids (deltaMP10, deltaMP20, deltaMP33, deltaMP43, deltaMP60 and deltaMP80) was engineered into the MP gene encoded by the biologically active clone C3/deltaCP-EGFP, a variant of CCMV RNA3 that contained wild-type (wt) MP and the enhanced green fluorescent protein (EGFP) gene in place of the coat protein (CP). The effect of each MP deletion on cell-to-cell movement was examined in three susceptible host plants: Chenopodium quinoa, Nicotiana benthamiana and cowpea (Vigno sinensis cv. Black Eye). The results indicate that, except for mutant deltaMP43, infections resulting from the deletion mutants remained subliminal. Interestingly, infections resulting from inoculating mutant deltaMP43, which lacked the 43 most C-terminal amino acids, spread rapidly between cells and the number of infected cells expressing EGFP approached that of control inoculations made with C3/deltaCP-EGFP. To verify whether the presence of wt CP altered the movement behaviour of these mutants, each MP deletion was also incorporated into the genetic background of wt CCMV RNA3 (pCC3) and inoculated independently to all three hosts. The results suggest that the overall movement process exhibited by each MP mutant is influenced profoundly by the presence of CP and the particular host plant tested.

Bromovirus↗
PubMed2004

Compatibility of the movement protein and the coat protein of cucumoviruses is required for cell-to-cell movement.

For the cell-to-cell movement of cucumoviruses both the movement protein (MP) and the coat protein (CP) are required. These are not reversibly exchangeable between Cucumber mosaic virus (CMV) and Tomato aspermy virus (TAV). The MP of CMV is able to function with the TAV CP (chimera RT), but TAV MP is unable to promote the cell-to-cell movement in the presence of CMV CP (chimera TR). To gain further insight into the non-infectious nature of the TR recombinant, RNA 3 chimeras were constructed with recombinant MPs and CPs. The chimeric MP and one of the CP recombinants were infectious. The other recombinant CP enabled virus movement only after the introduction of two point mutations (Glu-->Lys and Lys-->Arg at aa 62 and 65, respectively). The mutations served to correct the CP surface electrostatic potential that was altered by the recombination. The infectivity of the TR virus on different test plants was restored by replacing the sequence encoding the C-terminal 29 aa of the MP with the corresponding sequence of the CMV MP gene or by exchanging the sequence encoding the C-terminal 15 aa of the CP with the same region of TAV. The analysis of the recombinant clones suggests a requirement for compatibility between the C-terminal 29 aa of the MP and the C-terminal two-thirds of the CP for cell-to-cell movement of cucumoviruses.

Amino Acid Substitution↗
PubMed1983

Ocular bobbing: abnormal eye movement or eye movement's abnormality?

Ocular bobbing is classified as an abnormal eye movement, resulting from pathological neuronal activity of the brain stem after bilateral pontine lesions. Clinical oculographic study of 5 patients suffering from ocular bobbing shows that upwards voluntary eye movements are abnormal. We suggest that ocular bobbing should not to be regarded as an abnormal eye movement, but, rather, as the only residual movement of patients which are totally deprived of both horizontal and upward movements.

Arterial Occlusive Diseases↗