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PubMedDate not supplied

The effects of eye and limb movements on working memory.

Three experiments examined the role of eye and limb movements in the maintenance of information in spatial working memory. In Experiment 1, reflexive saccades interfered with memory span for spatial locations but did not interfere with memory span for letters. In Experiment 2, three different types of eye movements (reflexive saccades, pro-saccades, and anti-saccades) interfered with working memory to the same extent. In all three cases, spatial working memory was much more affected than verbal working memory. The results of these two experiments suggest that eye movements interfere with spatial working memory primarily by disrupting processes localised in the visuospatial sketchpad. In Experiment 3, limb movements performed while maintaining fixation produced as much interference with spatial working memory as reflexive saccades. These results suggest that the interference produced by eye movements is not the result of their visual consequences. Rather, all spatially directed movements appear to have similar effects on visuospatial working memory.

Extremities↗
PubMed1999

The cognate coat protein is required for cell-to-cell movement of a chimeric brome mosaic virus mediated by the cucumber mosaic virus movement protein.

Cucumber mosaic cucumovirus (CMV) and brome mosaic bromovirus (BMV) have many similarities, including the three-dimensional structure of virions, genome organizations, and requirement of the coat protein (CP) for cell-to-cell movement. We have shown that a chimeric BMV with the CMV 3a movement protein (MP) gene instead of its own cannot move from cell to cell in Chenopodium quinoa, a common permissive host for both BMV and CMV. Another chimeric BMV was constructed by replacing both MP and CP genes of BMV with those of CMV (MP/CP-chimera) and tested for its infectivity in C. quinoa, to determine whether the CMV CP has some functions required for the CMV MP-mediated cell-to-cell movement and to exhibit functional difference between CPs of BMV and CMV. Cell-to-cell movement of the MP/CP-chimera occurred, and small local lesions were induced on the inoculated leaves. A frameshift mutation introduced in the CMV CP gene of the MP/CP-chimera resulted in a lack of cell-to-cell movement of the chimeric virus. These results indicate that the viral movement mediated by the CMV MP requires its cognate CP. Deletion of the amino-terminal region in CMV CP, which is not obligatory for CMV movement, also abolished cell-to-cell movement of the MP/CP-chimera. This may suggest some differences in cell-to-cell movement of the MP/CP-chimera and CMV. On the other hand, the sole replacement of BMV CP gene with that of CMV abolished viral cell-to-cell movement, suggesting a possibility that the viral movement mediated by the BMV MP may also require its cognate CP. Functional compatibility between MP and CP in viral cell-to-cell movement is discussed.

Amino Acid Sequence↗
PubMed1993

Measurement of fetal movements using multichannel ultrasound pulsed Doppler: autorecognition of fetal movements by maximum entropy method.

Changes in fetal movements indicate biophysical conditions and functional development. The precise evaluation of fetal movements in clinical medicine requires the development of a continuous automated monitoring technique. A basic study of the measurement of fetal movements was carried out by modifying the Doppler ultrasound module of a cardiotocograph to produce low-frequency Doppler signals and five simultaneous outputs at various depths. These outputs represent displacement inside tissue at the various depths. Signal processing was executed on a 32-bit computer with a high-accuracy displacement estimation technique using the arctangent method. Results showed successful tracking of minute movements, such as fetal breathing movements (FBM), while rejecting other movements derived from maternal breathing etc. Using spectral analysis by the maximum entropy method (MEM), fetal movements were classified in three groups (FBM, fetal gross movements (FGM) and fetal heart movements (FHM), based on the character of their special peak frequencies. The order of movement recognition was first FGM, then FBM and lastly FHM. FBM were more successfully recognised by MEM than by conventional B-mode observation methods. Small body movements were difficult to recognise as FGM by MEM in some cases. Although further studies are required for clinical application, it appears that automated assessments of fetal movements should be possible with this technique.

Female↗
PubMed2000

A systematic directional error in 2-D arm movements increases with increasing delay between visual target presentation and movement execution.

Forty-seven normal subjects performed two-dimensional arm movements on a digitizer board using a mouse device. The movements were projected on a computer monitor. Subjects were instructed to move the mouse using the whole arm from a center position to a peripheral target so that the projected movement would pass over the target without stopping on the target. A large number of targets (360) were used to cover the entire directional continuum. The direction of the arm movement was the parameter of interest, which was measured at an initial position, at one third of the distance towards the target, and at the vicinity of the target. Four conditions of delay between target presentation and movement execution were used (0, 2, 4, 6 s). A systematic directional error was observed at the initial portion of the trajectory. This error resulted from a clustering of movement directions on an axis that was perpendicular to the axis of the resting forearm before movement onset. This pattern of errors can be explained by the initial inertial anisotropy of the arm. As the trajectory evolved, a different directional error emerged, resulting from a clustering of movement directions in two orthogonal axes. This pattern of directional error increased in amplitude as the delay increased, in contrast to the error at the initial portion of the trajectory which remained invariant with increasing delay. Finally, the information transmitted by the movement direction was shown to increase with the evolution of the trajectory. The increase in delay resulted in a decrease in directional-information transmission. It is proposed that the directional bias towards the end of the movement trajectory might reflect the action of "movement primitives", that is patterns of muscle activation resulting from spinal interneuronal activation. It is further proposed that the directional bias observed at the vicinity of the target might reflect a loss of cortical directional information with increasing delay between target presentation and movement onset.

Acceleration↗
PubMed2000

Self-initiated versus externally triggered movements. II. The effect of movement predictability on regional cerebral blood flow.

Event-related potential studies in man suggest a role for the supplementary motor area (SMA) in movement preparation, particularly when movements are internally generated. In a previous study combining PET with recording of movement-related cortical potentials, we found similar SMA activation and early pre-movement negativity during self-initiated and predictably paced index finger extensions. Early pre-movement negativity was absent when finger movements were paced by unpredictable cues. We postulated that preparation preceding self-initiated and predictably cued movements was responsible for equivalent levels of SMA activation in these two conditions. To test this, we have performed further studies on six normal volunteers with H2(15)O-PET. Twelve measurements of regional cerebral blood flow were made in each subject under three conditions: rest; self-initiated right index finger extension at a variable rate of once every 2-7 s; and finger extension triggered by pacing tones at unpredictable intervals (at a rate yoked to the self-initiated movements). Activation associated with these conditions was compared using analysis of covariance and t statistics. Compared with rest, unpredictably cued movements activated the contralateral primary sensorimotor cortex, caudal SMA and contralateral putamen. Self-initiated movements additionally activated rostral SMA, adjacent anterior cingulate cortex and bilateral dorsolateral prefrontal cortex (DLPFC). Direct comparison of the two motor tasks confirmed significantly greater activation of these areas and of caudal SMA in the self-initiated condition. These results, combined with our previous data, suggest that rostral SMA plays a primary role in movement preparation while caudal SMA is a motor executive area. In this experiment and in our earlier study, DLPFC was activated only during the self-initiated task, in which decisions were required about the timing of movements.

Adult↗
PubMed1990

[Eye movements in schizophrenia--relationships among eye movements under three experimental conditions; closed-eye, pursuit, and exploratory].

In order to investigate the pathophysiology of schizophrenia using psychophysiological indicators of eye movements, this study was conducted to clarify relations among eye movements under three experimental conditions; closed-eye, pursuit, and exploratory eye movements. Thirty-five chronic schizophrenic patients diagnosed by DSM-III-R criteria and 32 normal controls were examined. Horizontal eye movements were recorded electrooculographically with the subjects under two experimental conditions; one with eyes closed ("Closed-eye Eye Movement," Closed-eye EM), and the other with visually tracking a moving pendulum ("Pursuit Eye Movement," Pursuit EM). The closed-eye condition was further divided into two sub-conditions; one with the subjects awake and at rest, and the other with the subjects in the presence of a repetitive sound. Exploratory eye movements were recorded with an eye-mark recording system while the subjects viewing "S"-shaped geometric figures ("Exploratory Eye Movement," Exploratory EM). Indicators of eye movements under the three experimental conditions described above were measured and the correlations among them were investigated. Clinical symptoms in schizophrenics were assessed by BPRS, SANS and SADS and studied with the Factor Analysis method. In the Closed-eye EM, rapid eye movements appeared significantly more frequently and slow ones were less frequent in schizophrenics than in normals under both sub-conditions. The results for schizophrenics did not change significantly with the addition of sound stimuli. In the Pursuit EM, both the number and amplitude ratio of saccades were significantly larger in schizophrenics than in normals, although these indicators gradually decreased in both groups when tasks requiring concentration were demanded. In the Exploratory EM, the number of eye fixations, the total eye scanning length, and the "Responsive Search Score (RSS)," which is the total number of sections on which the eyes fixed during the response to the confirmative question, were all significantly smaller in schizophrenics than in normals. In schizophrenics, there were significant negative correlations between the RSS of the Exploratory EM and the number of rapid eye movements of the Closed-eye EM, the RSS and the number, amplitude ratio of saccades of the Pursuit EM, respectively. On the contrary, in normals, significant positive correlations were found between the number of rapid eye movements and the number of saccades.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

A computational theory for movement pattern recognition based on optimal movement pattern generation.

We have previously proposed an optimal trajectory and control theory for continuous movements, such as reaching or cursive handwriting. According to Marr's three-level description of brain function, our theory can be summarized as follows: (1) The computational theory is the minimum torque-change model; (2) the intermediate representation of a pattern is given as a set of via-points extracted from an example pattern; and (3) algorithm and hardware are provided by FIRM, a neural network that can generate and control minimum torque-change trajectories. In this paper, we propose a computational theory for movement pattern recognition that is based on our theory for optimal movement pattern generation. The three levels of the description of brain function in the recognition theory are tightly coupled with those for pattern generation. In recognition, the generation process and the recognition process are actually two flows of information in opposite directions within a single functional unit. In our theory, if the input movement trajectory data are identical to the optimal movement pattern reconstructed from an intermediate representation of some symbol, the input data are recognized as that symbol. If an error exists between the movement trajectory data and the generated trajectory, the putative symbol is corrected, and the generation is repeated. In particular, we present concrete computational procedures for the recognition of connected cursive handwritten characters, as well as for the estimation of phonemic timing in natural speech. Our most important contribution is to demonstrate the computational realizability for the 'motor theory of movement pattern perception': the movement-pattern recognition process can be realized by actively recruiting the movement-pattern formation process. The way in which the formation process is utilized in pattern recognition in our theory suggests a duality between movement pattern formation and movement pattern perception.

Algorithms↗
PubMed1996

Movement-related potentials associated with movement preparation and motor imagery.

Movement-related potentials (MRPs), reflecting cortical activity associated with voluntary movement, typically show a slowly increasing negative potential beginning between 1 and 2 s prior to movement, which most likely reflects motor preparatory processes. Studies of regional cerebral blood flow implicate the supplementary motor area in such preparatory processes; however, the contribution of the supplementary motor area to premovement activity observed in MRPs is debated. It is possible to examine MRPs relating to movement preparation alone, in the absence of movement execution, by recording MRPs associated with imagined movements. In this study, MRPs were recorded from 11 healthy control subjects while performing a sequential button-pressing task in response to external cues, and while imaging performance of the same task in response to the same cues. The early component of MRPs was found not to differ in amplitude, onset time, or topography when performing compared with imagining movement, indicating that both movement execution and motor imagery involve similar pre-movement preparatory processes generated in the same cortical area-most likely the supplementary motor area. It is therefore concluded that the early component of the MRP reflects activity arising pre-dominantly from the supplementary motor area and is associated with pre-movement motor preparatory processes which occur relatively independently of actual movement execution.

Adult↗
PubMed1988

Kinematic variability of grasp movements as a function of practice and movement speed.

Grasp movements were studied in six female subjects to determine the effects of practice and movement speed on kinematics and movement variability. Subjects performed four-joint pinch movements of the index finger and thumb, with 200 repetitions at each of three durations (100, 200, and 400 ms). As observed previously, movements of high velocity were performed with bell-shaped, single-peaked velocity profiles. In contrast, slower movements (approximately 200, 400 ms) were performed as a series of two to four submovements with multiple peaks in the associated joint angular velocity profiles. With practice, only the slowest movements (400 ms duration) showed significant reductions in variability of joint end-positions. Surprisingly, variability of finger and thumb joint end-positions did not increase with increasing movement speed as has been observed for arm pointing movements. This was apparently due to reductions in positional variability during deceleration of the movement which offset increases in positional variability during acceleration. Neither practice nor movement speed affected variability of the location of fingertip contact on the thumb, which always occurred on the thumb distal pulpar surface.

Adolescent↗
PubMed1975

Prophase chromosome movements in living house cricket spermatocytes and their relationship to prometaphase, anaphase and granule movements.

Chromosome and granule movements in meiotic prophase and prometaphase have been studied by time-lapse cinemicrography in live spermatocytes of the house cricket, Acheta domesticus. Chromosome movements in prophase cells, up to one hour or more before breakdown of the nuclear envelope, are described. These movements are frequent but saltatory; are based mostly at chromosome ends but also at kinetochores; occur in very intimate association with the inside of the nuclear envelope; are directed towards and away from the extranuclear centres (centrioles); tend weakly to accumulate bivalents round the two centres and reach a velocity of 0.65 micron/sec. Saltatory movements in granules associated with extranuclear asters are remarkably similar to basic characteristics to the intranuclear chromosome movements. Surprisingly, the chromosome movements (and those granules) are reversably blocked by colcemid (but not lumi-colcemid), and yet occur in the apparent absence of an intranuclear envelope. However, kinetochore movements in very early prometaphase are similar in velocity and other respects to prophase movements; later prometaphase movements are clearly slower, and those of anaphase very much slower still. -The prophase movements suggest a two component model for motion: a non-microtubule, linear force producer together withrotubules with a skeletal, orientational role. Arguably, both these components are also necessary for chromosome movements in prometaphase and anaphase.

Animals↗
PubMed2002

Hand-eye coordination for rapid pointing movements. Arm movement direction and distance are specified prior to saccade onset.

Visually guided arm movements such as reaching or pointing are accompanied by saccadic eye movements that typically begin prior to motion of the arm. In the past, some degree of coupling between the oculomotor and limb motor systems has been demonstrated by assessing the relative onset times of eye and arm movement, and by the demonstration of a gap effect for arm movement reaction times. However, measures of limb movement onset time based on kinematics are affected by factors such as the relatively high inertia of the limb and neuromechanical delays. The goal of the present study was thus to assess the relative timing of rapid eye and arm movements made to visual targets by examining electromyographic (EMG) activity of limb muscles in conjunction with eye and arm position measures. The observation of a positive correlation between eye and limb EMG onset latencies, and the presence of a gap effect for limb EMG onset times (a reduction in reaction time when a temporal gap is introduced between the disappearance of a central fixation point and the appearance of a new target) both support the idea that eye and arm movement initiation are linked. However, limb EMG onset in most cases precedes saccade onset, and the magnitude of EMG activity prior to eye movement is correlated with both the direction and amplitude of the upcoming arm movement. This suggests that, for the rapid movements studied here, arm movement direction and distance are specified prior to the onset of saccades.

Arm↗
PubMed2006

The Ia afferent feedback of a given movement evokes the illusion of the same movement when returned to the subject via muscle tendon vibration.

The aim of the present study was to further investigate the contribution of primary muscle spindle feedback to proprioception and higher brain functions, such as movement trajectory recognition. For this purpose, complex illusory movements were evoked in subjects by applying patterns of muscle tendon vibration mimicking the natural Ia afferent pattern. Ia afferent messages were previously recorded using microneurographic method from the six main muscle groups acting on the ankle joint during imposed "writing like" movements. The mean Ia afferent pattern was calculated for each muscle group and used as a template to pilot each vibrator. Eleven different vibratory patterns were applied to ten volunteers. Subjects were asked both to copy the perceived illusory movements by hand on a digitizing tablet and to recognize and name the corresponding graphic symbol. The results show that the Ia afferent feedback of a given movement evokes the illusion of the same movement when it is applied to the subject via the appropriate pattern of muscle tendon vibration. The geometry and the kinematic parameters of the imposed and illusory movements are very similar and the so-called "two-thirds power law" is present in the reproduction of the vibration-induced illusory movements. Vibrations within the "natural" frequency range of Ia fibres firing (around 30 Hz) produce clear illusions of movements in all the tested subjects. In addition, increasing the mean frequency of the vibration patterns resulted in a linear increase in the size of the illusory movements. Lastly, the subjects were able to recognize and name the symbols evoked by the vibration-induced primary muscle spindle afferent patterns in 83% of the trials. These findings suggest that the "proprioceptive signature" of a given movement is associated with the corresponding "perceptual signature". The neural mechanisms possibly underlying the sensory to perceptual transformation are discussed in the general framework of "the neuronal population vector model".

Adult↗
PubMed1993

Movement-related potentials associated with single and repetitive movements recorded from human supplementary motor area.

To clarify the differences of movement-related potentials (MRPs) between single and repetitive movements, MRPs with finger movements were recorded from subdural electrodes chronically implanted on the supplementary motor area (SMA) in 2 patients, and MRPs with foot movements were recorded simultaneously from the SMA and the primary motor foot area in 1 patient. Repetitive movements did not elicit larger pre-movement potentials in the SMA as compared with single movements in all 3 patients. In the negative motor area, where electrical stimulation elicited inhibitory responses of voluntary movements and which is located at the rostral part of the SMA, pre-movement potentials to either single or repetitive movements were of approximately equal amplitude in 1 out of 3 patients. It is, therefore, most likely that the SMA plays an equally significant role in preparation for single and repetive voluntary movements.

Adult↗
PubMed1994

Movement-related cortical potentials preceding sequential and goal-directed finger and arm movements in patients with cerebellar atrophy.

To determine the influence of cerebellar involvement on the preparatory state of the cerebral cortex for voluntary movements, we studied the movement-related cortical potentials (Bereitschaftspotential, BP) preceding sequential and goal-directed finger and arm movements in patients with cerebellar atrophy (CA). The first task (paradigm 1) consisted of a sequential finger movement at a self-paced rate of every 3 sec or longer, in which patients and control subjects pushed rapidly 7 keys on a keyboard in a sequence visually predetermined on a screen. The second task (paradigm 2) consisted of a goal-directed self-paced movement with visual feedback on a screen. In both paradigms, control subjects and patients had distinct movement-related cortical potentials, but peak amplitudes (close to movement onset) were reduced in the patient group (paradigm 2), whereas in the overall analysis the mean amplitude 600-800 msec before movement onset (NS1) was larger in the patient group (paradigms 1 and 2). Accordingly, the difference (NS2) between peak amplitude and NS1 was smaller in the patient group (paradigms 1 and 2). Whereas control subjects' peak amplitude (paradigm 2) and NS2 (paradigm 1) were focused at Cz, this topographical differentiation was abolished in the patient group. The onset of the BP was earlier in the patients than in the control subjects (paradigms 1 and 2). Our results suggest that pathways from the cerebellum to the cortex do play a role in generating movement-related cortical potentials. A strong input from the cerebellum seems to be crucial for the generation of a normal motor potential close to the movement onset, reflecting a specific deficit in patients with CA. Patients with CA may try to compensate for their motor deficits by a longer cortical activation preceding voluntary movements (earlier onset of the BP). The increased NS1 could be the result of larger effort, by which patients try to compensate for their motor deficits as well.

Adult↗
PubMed2005

Movement precues in planning and execution of aiming movements in Parkinson's disease.

Two experiments tested how changing a planned movement affects movement initiation and execution in idiopathic Parkinson's disease (PD) patients. In Experiment 1, PD patients, elderly controls, and young adults performed discrete aiming movements to one of two targets on a digitizer. A precue (80% valid cue and 20% invalid cue of all trials) reflecting the subsequent movement direction was presented prior to the imperative stimulus. All groups produced slower reaction times (RTs) to the invalid precue condition. Only the subgroup of patients with slowest movement time showed a significant prolongation of movement for the invalid condition. This suggests that, in the most impaired patients, modifying a planned action also affects movement execution. In Experiment 2, two-segment aiming movements were used to increase the demand on movement planning. PD patients and elderly controls underwent the two precue conditions (80% valid, 20% invalid). Patients exhibited longer RTs than the controls. RT was similarly increased for the invalid condition in both groups. The patients, however, exhibited longer movement times, lower peak velocities, and higher normalized jerk scores of the first segment in the invalid condition compared to the valid condition. Conversely, the controls showed no difference between the valid and invalid cue conditions. Thus, PD patients demonstrated substantially pronounced movement slowness and variability when required to change a planned action. The results from both experiments suggest that modifying a planned action may continue beyond the initiation phase into the execution phase in PD patients.

Adult↗
PubMed1997

Time quantified detection of fetal movements using a new fetal movement algorithm.

Primarily, the objective is to develop an automated ultrasound fetal movement detection system that will better characterize fetal movements. Secondarily, the objective is to develop an improved method of quantifying the performance of fetal movement detectors. We recorded 20-minute segments of fetal movement on 101 patients using a UAMS-developed fetal movement detection algorithm (Russell algorithm) and compared this to a Hewlett-Packard (HP) M-1350-A. Movements were recorded on a second-per-second basis by an expert examiner reviewing videotaped real-time ultrasound images. Videotape (86,592 seconds) was scored and compared with the electronic movement-detection systems. The Russell algorithm detected 95.53% of the discrete movements greater than 5 seconds, while the HP system (M-1350-A) detected only 86.08% of the discrete movements (p = 0.012). Both devices were less efficient at detecting the short discrete movements, obtaining sensitivities of 57.39 and 35.22, respectively. Neither system fully identifies fetal movement based on the second-per-second system. Improved methods of quantifying performance indicated that the Russell algorithm performed better than the HP on these patients.

Adolescent↗
PubMed1988

Movement-related potentials and control of associated movements.

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

Adolescent↗
PubMed1986

[Comparison of triggered movement-related and self paced movement-related neuronal activities in the frontal agranular cortex].

To examine the functional differences in primate motor cortex (MC), premotor cortex (PM) and supplementary motor area (SMA), single cell activities in these areas were recorded from monkeys performing either visually triggered or self paced key press movement. EMG recordings made clear that activities in finger and hand flexor muscles preceding the triggered or self paced movement were identical and no limb and body muscles were active during performing the task. Neuronal activity changes preceding movement onsets were classified into two categories; a short lead type with the preceding time of less than 300 ms, a long lead type with longer preceding times. In MC, a majority of movement-related neurons (86%) was active phasically and therefore belonged to a short lead type. They exhibited similar activity changes regardless of whether triggered or self paced. In PM, 87% of movement-related neurons were of short lead type. About one third of them were triggered movement specific and another one third were triggered movement predominant. These preferential relation to triggered movement were characteristic in PM. Neurons of SMA were different from MC and PM cells in that as much as a half of them showed the long lead type of activity changes and almost all of these cells were classified into self paced movement dominant or specific. These results suggest that each of these areas have different functional characteristics. PM has more preferential relation to the triggered movement and SMA has more preferential relation to the self paced movement, whereas MC is involved equally in both.

Action Potentials↗