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PubMed1978

Central control insufficiency. III. Disturbed motor control and sensation: a treatment approach emphasizing upper extremity orthoses.

In the discussion of the problems, the selection of patients, and some of the approaches to treatment, three major areas need emphasis. 1. Guidelines are necessary to select patients who require and can respond to treatment. The patients who will benefit the most must be identified and provided with structured therapy programs. 2. Effective bracing of the severely spastic wrist and hand may not be possible. The orthoses described are used to prevent deformity and relieve pain. 3. All motor control available to a patient must be incorporated immediately into the patient's daily activities.

Activities of Daily Living↗

PubMed2004

Earlier age of first diagnosis in schizophrenia is related to impaired motor control.

We examined the control of motor behavior in relation to age of first diagnosis (AFD; an approximation of age of onset) in schizophrenia. We hypothesized that earlier AFD reflects increased vulnerability to the disorder, vulnerability that may be indexed by elevated levels of motor abnormality. AFD, symptom and demographic features, motor performance on a line drawing task, and the presence and severity of dyskinesia and extrapyramidal side effects were evaluated in 65 chronic schizophrenia subjects. More severely impaired motor control was significantly related to an earlier age of diagnosis. Potential confounds, including age, gender, education, length of illness, current medication dosage, symptom status, and motor side effects, did not appear to influence this relationship, although greater chronicity appeared to be independently related to more severely impaired motor control. In summary, the data are consistent with the hypothesis that an earlier AFD is associated with more pronounced motor impairment.

Adolescent↗

PubMedDate not supplied

Motor control of schizophrenics--I. Oculomotor control of schizophrenics: a deficit in sensory processing, not strictly in motor control.

An in-depth analysis of eye movements of schizophrenics has demonstrated defects in several oculomotor subsystems, likely due to processing of sensory information and not to problems in the motor system itself. Schizophrenic subjects made more pursuit tracking errors, due to higher RMS errors, larger phase lag, and more saccades in pursuit. When making saccadic movements they had normal reaction times, saccade velocity and intersaccadic pause, but made more double-jump saccades and overshot the target. Only some had inability to hold steady fixation, but all had an attentional problem in restraining an inappropriate eye movement. The multiple defects suggest a processing problem that is not strictly motor and does not fit any standard definition of attention.

Adult↗

PubMed2002

The influence of computer experience on visuo-motor control: implications for visuo-motor testing in Parkinson's disease.

Abnormalities in visuo-motor control have repeatedly been reported in Parkinson's disease (PD) patients. In the more recent studies, tasks measuring visuo-motor performance are usually computerised tasks requiring the use of a mouse-like manipulandum. In healthy subjects, previous computer mouse experience can influence performance in computerised visuo-motor tasks. We, therefore, investigated the potential confounding effect of mouse experience in a visuo-motor task used in PD patients, the visuo-motor testing (VMT) system, and its concurrent usefulness in the diagnosis of PD. Our study population included 49 early PD patients and 31 controls. The VMT system involves moving a pointer over a sinusoidal path displayed on a computer screen by moving an unseen digitiser mouse over a tablet. In both PD patients and controls, subjects with low mouse experience scored worse than subjects with high mouse experience on variables measuring movement accuracy, direction and speed. After correction for mouse experience the aforementioned deficits were still present in PD patients with low mouse experience. However, PD patients with high mouse experience only showed deficits in movement accuracy. It would seem that previous mouse experience can at least partly compensate for deficits in directional control and speed in PD patients, implying a possible role for training in the treatment of functional motor impairments in PD. Future studies using computerised psychomotor tasks should take sufficient precautions to avoid potential confounding effects of mouse experience. The present data further suggest that only accuracy of visuo-motor control might be a useful parameter in the (early) diagnosis of PD.

Aged↗

PubMed1981

Deficits in contralateral and ipsilateral forepaw motor control following unilateral motor cortical ablations in rats.

Two force transducers which were interfaced with a minicomputer were used as operant manipulanda to assess changes in peak force and rate of response produced by unilateral motor cortical lesions in rats. Spatial arrangement of the manipulanda permitted a subject to respond on Transducer I exclusively with his left forepaw and on Transducer II exclusively with his right. Permanent deficits as measured by both force and rate of response were observed for the limb contralateral to the lesion. In the forelimb ipsilateral to the lesion rate of response was severely depressed immediately following the lesion and, although there was marked recovery during the 10-12 days following surgery, post-lesion rates never attained pre-lesion levels.

Animals↗

PubMed2000

Motor control: Mechanisms of motor equivalence in handwriting.

Handwriting is a classic example of how the details of movement can be scale and plane invariant: letter forms reflecting personal style are unchanged, whether one is writing on a piece of paper, on a blackboard or in the sand using the foot. Recent research points to a role for the parietal cortex in such motor equivalence.

Handwriting↗

PubMed1999

Cognitive motor control in human pre-supplementary motor area studied by subdural recording of discrimination/selection-related potentials.

To clarify the functional role of human pre-supplementary motor area (pre-SMA) in 'cognitive' motor control as compared with other non-primary motor cortices (SMA-proper and lateral premotor areas) and prefrontal area, we recorded epicortical field potentials by using subdural electrodes in five epileptic patients during presurgical evaluation, whose pre-SMA, SMA-proper, prefrontal and lateral premotor areas were defined by electric cortical stimulation and recent anatomical orientations according to the bicommissural plane and callosal grid system. An S1-Go/NoGo choice and delayed reaction task (S1-choice paradigm) and a warned choice Go/NoGo reaction task (S2-choice paradigm) with inter-stimulus intervals of 2 s were employed. The results showed (i) transient potentials with onset and peak latencies of about 200 and 600 ms, respectively, after S1 in the S1-choice paradigm mainly at pre-SMA and to a lesser degree at the prefrontal and lateral premotor areas, but not in the S2-choice paradigm. At SMA-proper, a similar but much smaller potential was seen after S1 in both S1- and S2-choice paradigms and (ii) slow sustained potentials between S1 and S2 in both S1- and S2-choice paradigms in all of the non-primary motor areas investigated (pre-SMA, SMA-proper and lateral premotor areas) and prefrontal area. It is concluded that pre-SMA plays a more important role in cognitive motor control which involves sensory discrimination and decision making or motor selection for the action after stimuli, whereas SMA-proper is one of the main generators of Bereitschaftspotential preceding self-paced, voluntary movements. In the more general anticipation of and attention to the forthcoming stimuli, non-primary motor cortices including pre-SMA, SMA-proper and lateral premotor area, and the prefrontal area are commonly involved.

Adult↗

PubMed1993

A neural-network model enabling sensorimotor learning: application to the control of arm movements and some implications for speech-motor control and stuttering.

Low-level motor control is defined as adapting an organism to the unique physical properties of its own limbs. The two-jointed arm serves to exemplify that effective low-level motor control demands a neurally medicated inversion of the dynamics, as well as of the kinematics, of a limb system. Reflex-like processing--that is, feedforword of either actual or predicted proprioceptive signals--is thereby assumed to be the principle of the dynamics control. As regards speech-motor control, the overall tool transformation is assumed to transform the force pattern of the articulatory muscles into speech sounds. Like the arm model, the vocal-tract transformation thus defined is also divided into two parts, namely the transformation relating the muscle forces to the mechanospatial states of the vocal tract (which is analogous to the forward dynamics including natural interarticulatory couplings), and the transformation relating the mechanospatial states to the speech sounds. Low-level speech-motor control, then, needs to invert both transformations, each of which can be learned by means of the self-imitation algorithm. Erroneous learning can fail to decouple interarticulatory coupling and therefore lead to abnormal feedback loops through the reflex-like operating neural network, which in turn can cause stuttering if audiophonatoric coupling is involved in learning.

Algorithms↗

PubMed1991

Laterality and motor control.

Lateralization in motor control, exemplified by handedness, is a publically observable lateral asymmetry. The understanding of causation of lateral asymmetry in movement is poor for two major reasons. First, structural limitations underlying lateral bias cannot be compelling in the sense that laterality is completely specified. Second, interacting sources of lateral bias are probably represented at several levels of the central nervous system, with some sources being many steps removed from the executing motor structures. Both factors permit flexibility in terms of which side does what. I suggest two approaches to improve understanding of mechanism. First, use of bimanual tasks which reduce flexibility in lateral expression and therefore provide more information than unimanual tasks. Second, analysis of task performances in terms of what levels of lateral specialization are likely to be involved. Such analyses will be especially useful in the understanding of hand use in left-handers who perform different skilled tasks with different hands.

Female↗

PubMed2002

Effects of activity on axonal excitability: implications for motor control studies.

In many motor control studies, such as those involving H reflexes in human subjects, stimuli are delivered to nerves in which axons are or have recently been active. It is assumed that a constant stimulus intensity ensures that the same population of axons has been activated, particularly when there is little change in the M wave. However, the neurophysiological literature is replete with evidence that activity depresses axonal excitability. Indeed, some motor control studies have exploited this phenomenon to stimulate specific afferent populations selectively. This chapter will review studies performed in human subjects demonstrating that a voluntary contraction can have profound effects on the excitability of the active axons and on their ability to transmit impulses. These data need to be considered when interpreting human reflex studies.

Afferent Pathways↗

PubMed2000

Neural aspects of cognitive motor control.

Traditionally, motor and cognitive functions were studied separately; however, the investigation of processes at the interface between cognition and action has become more and more popular recently. Typical research goals include the identification of the processes involved using experimental psychological methods, and understanding the neural mechanisms underlying these processes using neurophysiological and functional neuroimaging methods. Specifically, there has been a special emphasis during the past few years on timing mechanisms, practice effects, and the application of rules in guiding action. New information concerning the neural mechanisms involved is being acquired at a rapid pace, albeit mostly within a descriptive framework. With respect to specific brain areas, a key finding has been the clear involvement of the primary motor cortex in complex tasks engaging diverse motor and cognitive dimensions.

Animals↗

PubMed2000

What and when: parallel and convergent processing in motor control.

Successful motor behavior requires making appropriate response (response selection) at the right time (timing adjustment). Earlier psychological studies have suggested that the response selection and timing adjustment processes are performed serially in separate stages. We tested this hypothesis using functional magnetic resonance imaging. The subjects performed a choice reaction time task in four conditions: two (on-line response selection required or not) by two (on-line timing adjustment required or not). We found that the neural correlates for the two processes were indeed separate: the anterior medial premotor cortex (presupplementary motor area) was selectively active in response selection, whereas the cerebellar posterior lobe was selectively active in timing adjustment. However, the functional separation was only partial in that the lateral premotor cortex and the intraparietal sulcus were active equally for response selection and timing adjustment. The lateral premotor cortex was most active when both processes were required, suggesting that it integrates the information on response selection and the information on timing adjustment; alternatively, it might contribute to the allocation of attentional resources during dual information processing. The intraparietal sulcus was equally active when either response selection or timing adjustment was required, suggesting that it modifies, rather than integrates, these processes. Furthermore, our results suggest that these activations related to response selection and timing adjustment were distinct from sensory or motor processes.

Adult↗

PubMed2005

Integrating visual cues for motor control: a matter of time.

The visual system continuously integrates multiple sensory cues to help plan and control everyday motor tasks. We quantified how subjects integrated monocular cues (contour and texture) and binocular cues (disparity and vergence) about 3D surface orientation throughout an object placement task and found that binocular cues contributed more to online control than planning. A temporal analysis of corrective responses to stimulus perturbations revealed that the visuomotor system processes binocular cues faster than monocular cues. This suggests that binocular cues dominated online control because they were available sooner, thus affecting a larger proportion of the movement. This was consistent with our finding that the relative influence of binocular information was higher for short-duration movements than long-duration movements. A motor control model that optimally integrates cues with different delays accounts for our findings and shows that cue integration for motor control depends in part on the time course of cue processing.

Cues↗

PubMed1986

Abnormalities of fine motor control in schizophrenia.

Response time and fine motor control during a classification task were examined in schizophrenics and nonschizophrenics. The task involved decisions about either the sensory characteristics of auditory and visual stimuli or the referential meanings of spoken words and viewed pictures. Nonschizophrenics responded more quickly and exhibited a smoother and faster motor response on all tasks. Response time and motor control were influenced by stimulus modality and the complexity of the classification task in both groups. In the analysis of motor control, the schizophrenics differed from the nonschizophrenics in exhibiting a pattern suggestive of a specific difficulty with decisions involving referential meaning. The observed motor control dysfunction in schizophrenics is a psychomotor deficit similar to previously reported abnormalities in smooth pursuit eye movement. Further, the interaction of group and task variables in the motor response suggests that decisions about the abstract referential meaning of words and pictures produce greater cognitive loads in schizophrenics than in nonschizophrenics.

Adult↗

PubMed1999

Serotonin transporter promoter polymorphism influences topography of inhibitory motor control.

The prefrontal cortex participates in motor control and is modulated by serotonergic activity. The serotonin transporter (5-HTT) is a major regulator of serotonergic neurotransmission and may thus influence motor control. The short allele (s) of the 5-HTT linked polymorphic region (5-HTTLPR) is associated with less 5-HTT expression and function than the long variant (l). The neurophysiological parameters termed 'Go- and NoGo- centroid location' represent characteristic brain electrical substrates of the execution and inhibition of motor response elicited by the Continuous Performance Test (CPT). In the present study, the impact of the 5-HTTLPR genotype on the centroid locations was investigated in 23 healthy subjects. The NoGo-centroid, but not the Go-centroid, was located significantly more anteriorly in the short allele group (mean electrode location in s/s and s/l, 2.86+/-0.37) compared to the group with two long alleles (l/l, 3.34+/-0.49; t=2.66, p<0.05). Age, gender, and test performance did not differ between groups. The results indicate that 5-HTTLPR genotype dependent 5-HTT function is associated with the neurophysiologically assessed topography of inhibitory motor control and provides further evidence for a genetic influence on central serotonergic and motor function.

Journal Article↗

PubMed1996

Motor control, excitement, and overarm throwing.

Although motor control has historically been an important discipline, it runs the risk of being overshadowed by other newer areas of neuroscience. One response would be to generate increased excitement in motor control, e.g., by more clearly defining the big questions, by discussing them in new audience-friendly formats, and by promoting them, perhaps in the context of applied motor control. One recent exciting development has been a shift to the study of natural multijoint movements in three dimensions. We are currently investigating one such multijoint movement, overarm throwing. The question we are asking is, What causes inaccuracies in overarm throws? Is it errors in the timing or in the velocity of joint rotations that produce the hand trajectory? Surprisingly, inaccuracies (high and low throws) do not result from errors in rotations of proximal joints; instead they result from variability in the timing of onset of finger opening. It remains to be determined whether the decreased accuracy in throwing in cerebellar patients is caused by an increase in this error or from disorder in some other multijoint coordinating mechanism.

Arm↗

PubMed2005

A meta-analytic review of stopping performance in attention-deficit/hyperactivity disorder: deficient inhibitory motor control?

This review discusses whether deficient inhibitory motor control is the core deficit of attention-deficit/hyperactivity disorder (ADHD). Inhibitory motor control is commonly assessed using the stop-signal paradigm. Since the last meta-analysis that was performed, 33 new studies have appeared. The current meta-analysis revealed a significant difference between ADHD patients and matched controls in stop latency (stop-signal reaction time) in both children and adults. Basic reaction time was significantly longer in children with ADHD, but not in adults, and there was a significant interaction between the elongation of the latency to stop and to respond in adults, but not in children. Deficient inhibitory motor control may be less crucial in children than in adults with ADHD.

Adolescent↗

PubMed1984

Motor control of schizophrenics--II. Manual control and tracking: sensory and motor deficits.

Manual control and tracking of 12 acute and chronic schizophrenics was tested for comparison with their performance in oculomotor tracking. Schizophrenics tended to be slower in a non-timed, non-tracking hand movement, and chronics made even slower movement when the experimental room was illuminated than when it was darkened. Chronics also had a significantly higher reaction time than normal controls. When tracking a constant-velocity visual target, all schizophrenics were significantly slower than normals to high-velocity (50 degrees and 60 degrees/s) targets only. When tracking a sinusoidally moving target, schizophrenics were not less accurate over-all but they showed less improvement than normals when room illumination gave visual information about background and hand position. This complex group of motor deficiencies of schizophrenics, along with their oculomotor control problems, suggests that they have sensory processing, attentional, and motor planning problems when performing orienting tasks.

Adult↗