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Biomedical subjects

Alan M Wing

Publications and source records attributed to Alan M Wing.

14 recordsLinked to original sources
PubMed2006

Time-based prediction in motor control: evidence from grip force response to external load perturbations.

An object held in precision grip creates predictable load forces on the hand during voluntary hand movement and these are associated with anticipatory modulation of grip force. Conflicting results have been obtained over whether predictable external load perturbations result in anticipatory grip force responses (e.g. Blakemore et al. in J Neurosci 18(18):7511-7518, 1998; Weeks et al. in Exp Brain Res 132:404-410, 2000). This paper investigated whether the discrepancies reflect differences in the methods used in estimating the time delay. Subjects held a manipulandum that delivered load force perturbations in the form of pulses of variable duration and interval or periodic 0.5 and 1 Hz square waves or sinusoids. The grip forces exerted by the subjects were measured. Two methods were used to assess the time delay of the grip force in relation to the load force: (1) cross-spectral analysis, (2) a single threshold method applied on time-locked averaged data. Despite a phase lag shown by the cross-spectral analysis, the threshold method revealed grip force increased 264.8+/-40.2 ms before the onset of the load force when 0.5 Hz square waves were used as the load force perturbation and 70.2+/-17.0 ms before the load force when 1 Hz square waves were used. Computer simulations indicated that the single threshold method gives a more sensitive estimate of the onset time than the cross-spectral analysis. We conclude that discrepancies in previous studies reflect differences in the methods used to assess the time-delay and that there is an anticipatory component in the grip force response to predictable external load perturbation.

Adult↗
PubMed2006

The synchronisation of lower limb responses with a variable metronome: the effect of biomechanical constraints on timing.

Stepping in time with a metronome has been reported to improve pathological gait. Although there have been many studies of finger tapping synchronisation tasks with a metronome, the specific details of the influences of metronome timing on walking remain unknown. As a preliminary to studying pathological control of gait timing, we designed an experiment with four synchronisation tasks, unilateral heel tapping in sitting, bilateral heel tapping in sitting, bilateral heel tapping in standing, and stepping on the spot, in order to examine the influence of biomechanical constraints on metronome timing. These four conditions allow study of the effects of bilateral co-ordination and maintenance of balance on timing. Eight neurologically normal participants made heel tapping and stepping responses in synchrony with a metronome producing 500 ms interpulse intervals. In each trial comprising 40 intervals, one interval, selected at random between intervals 15 and 30, was lengthened or shortened, which resulted in a shift in phase of all subsequent metronome pulses. Performance measures were the speed of compensation for the phase shift, in terms of the temporal difference between the response and the metronome pulse, i.e. asynchrony, and the standard deviation of the asynchronies and interresponse intervals of steady state synchronisation. The speed of compensation decreased with increase in the demands of maintaining balance. The standard deviation varied across conditions but was not related to the compensation speed. The implications of these findings for metronome assisted gait are discussed in terms of a first-order linear correction account of synchronisation.

Adult↗
PubMed2006

Force and time control in the production of rhythmic movement sequences in Parkinson's disease.

This study investigated force and time control in rhythm production in Parkinson's disease. Patients and age-matched controls reproduced rhythms consisting of equal (600 ms) or alternating (400 and 800 ms) intervals, produced with equal (12 N) or alternating (8 and 16 N) forces, under paced (synchronization) and unpaced (continuation) conditions. Performance was assessed in terms of accuracy and variability. Reproduction of force amplitudes was less accurate in patients than in controls when either time or force alternated but did not deteriorate further when force and time alternated. In contrast, interval timing was least accurate in patients compared with controls when rhythm alternated on both dimensions. The ratio between alternating force levels was better maintained by controls than by patients, without influence of timing requirements in either group. In contrast, the ratio between alternating intervals was relatively preserved in patients when force remained constant but was severely compromised when force alternated. Timing variability was greater in the patient group, especially in the more affected side, but there was no difference in timing variability between groups as a function of rhythm, and there were no differences between groups in variability of force. The results show that force and time control in patients are affected in different ways. We interpret the preserved timing of rhythms with alternation on one dimension as evidence of intact ability to organize movements in a sequence. The data are compatible with a basal ganglia role in the coregulation of time and force, but do not support a general timing function of the basal ganglia.

Aged↗
PubMed2005

Low frequency rTMS effects on sensorimotor synchronization.

Previous studies using low frequency (1 Hz) rTMS over the motor and premotor cortex have examined repetitive movements, but focused either on motor aspects of performance such as movement speed, or on variability of the produced intervals. A novel question is whether TMS affects the synchronization of repetitive movements with an external cue (sensorimotor synchronization). In the present study participants synchronized finger taps with the tones of an auditory metronome. The aim of the study was to examine whether motor and premotor cortical inhibition induced by rTMS affects timing aspects of synchronization performance such as the coupling between the tap and the tone and error correction after a metronome perturbation. Metronome sequences included perturbations corresponding to a change in the duration of a single interval (phase shifts) that were either small and below the threshold for conscious perception (10 ms) or large and perceivable (50 ms). Both premotor and motor cortex stimulation induced inhibition, as reflected in a lengthening of the silent period. Neither motor nor premotor cortex rTMS altered error correction after a phase shift. However, motor cortex stimulation made participants tap closer to the tone, yielding a decrease in tap-tone asynchrony. This provides the first neurophysiological demonstration of a dissociation between error correction and tap-tone asynchrony in sensorimotor synchronization. We discuss the results in terms of current theories of timing and error correction.

Acoustic Stimulation↗
PubMed2005

Force related activations in rhythmic sequence production.

Brain imaging studies have implicated the basal ganglia in the scaling of movement velocity. Basal ganglia activation has also been reported for movement timing. We investigated the neural correlates of scaling of force and time in the production of rhythmic motor sequences using functional magnetic resonance imaging (fMRI) of the human brain. Participants (N = 13) were imaged while squeezing a rigid force transducer in a near isometric manner between thumb and index finger, to reproduce four different rhythmic sequences. The responses were separated by either equal (600 ms) or alternating (400, 800 ms) intervals, and produced with either equal (12 N) or alternating (8, 16 N) forces pulses. Intervals and force levels were balanced across each condition. The primary motor cortex (M1), supplementary motor area (SMA), basal ganglia, thalamus, and cerebellum were activated during the production of sequences marked by equal interval and force. There was no reliable main effect of alternating interval. In contrast, greater activation of these regions was associated with the extra demands of responding with alternating force pulses. We interpret the data as identifying a significant role of the BG in the control of force. In addition, the results indicate the importance of monitoring force when studying brain activation associated with motor timing.

Acoustic Stimulation↗
PubMed2005

Temporal constraints on interactions across kinaesthetic channels.

We investigated the effect of correlation in background noise on the ability of participants to detect a kinaesthetic target on the index fingers of their hands. Participants had to judge whether the target (a smoothed ramp with quarter-sine onset and offset), was on the left or right finger (experiments 1 and 2). These targets were embedded in noise generated by pseudo-random up-down movements of both the left and right fingers. Positive correlation between the noise on the left and right fingers aided discrimination of the target signal relative to when the noise was uncorrelated. However, this benefit of positive correlation was subject to temporal limitations and diminished with increasing lag between the noise on the fingers (experiment 2). Tests of explicit detection of correlation in kinaesthetic noise (experiment 3) showed a similar pattern, with detection of correlation decreasing with the temporal lag between the noise on the fingers. The results suggest that kinaesthetic signal detection involves sensory integration across the fingers within a limited temporal window.

Adult↗
PubMed2005

Action modulates object-based selection.

Cueing attention to one part of an object can facilitate discrimination in another part (Experiment 1 [Duncan, J. (1984). Selective attention and the organization of visual information. Journal of Experimental Psychology: General, 113, 501-517]; [Egly, R., Driver, J., & Rafal, R. D. (1994). Shifting visual attention between objects and locations: evidence from normal and parietal lesion subjects. Journal of Experimental Psychology: Human Perception and Performance, 123, 161-177]). We show that this object-based mediation of attention is disrupted when a pointing movement is prepared to the cued part; when a pointing response is prepared to a part of an object, discrimination does not differ between (i) stimuli at locations in the same object but distant to the part where the pointing movement is programmed and (ii) stimuli at locations equidistant from the movement but outside the object (Experiment 2). This remains true even when the pointing movement cannot be performed without first coding the whole object (Experiment 3). Our results indicate that pointing either (i) emphasizes spatial selection at the expense of object-based selection, or (ii) changes the nature of the representation(s) mediating perceptual selection. In addition, the results indicate that there can be a distinct effect on attention of movement to a specific location, separate from the top-down cueing of attention to another position (Experiment 3). Our data highlight the interactivity between perception and action.

Adolescent↗
PubMed2005

Interlimb coordination deficits during cyclic movements in cerebellar hemiataxia.

The authors report a 35-year-old man whose unilateral cerebellar lesion resulted in marked deficits in coordinating simultaneous cyclic movements of the arm and leg on his ipsilesional side. He exhibited no such deficits when making simultaneous movements of the contralesional limbs or when moving paired left and right limbs. Thus, the cerebellum, which is already known to underlie within-limb interjoint coordination, also contributes to coordination between limbs.

Adult↗
PubMed2004

Keeping with the beat: movement trajectories contribute to movement timing.

Previous studies of paced repetitive movements with respect to an external beat have either emphasised (a) the form of movement trajectories or (b) timing errors made with respect to the external beat. The question of what kinds of movement trajectories assist timing accuracy has not previously been addressed. In an experiment involving synchronisation or syncopation with an external auditory metronome we show that the nervous system produces trajectories that are asymmetric with respect to time and velocity in the out and return phases of the repeating movement cycle. This asymmetry is task specific and is independent of motor implementation details (finger flexion vs. extension). Additionally, we found that timed trajectories are less smooth (higher mean squared jerk) than unpaced ones. The degree of asymmetry in the flexion and extension movement times is positively correlated with timing accuracy. Negative correlations were observed between synchronisation timing error and the movement time of the ensuing return phase, suggesting that late arrival of the finger is compensated by a shorter return phase and conversely for early arrival. We suggest that movement asymmetry in repetitive timing tasks helps satisfy requirements of precision and accuracy relative to a target event.

Acoustic Stimulation↗
PubMed2003

Perceptual judgement, grasp point selection and object symmetry.

Object symmetry is a visual attribute that may contribute to perceptual judgement and to action. We evaluated the effects of varying the physical symmetry of planar objects (presence versus absence) on both aspects. In Experiment 1, subjects estimated the magnitude of visually perceived symmetry of the objects. The results confirmed the influence of physical symmetry on perceived symmetry, and supported our binary categorisation of stimulus objects in terms of presence versus absence of physical symmetry. In Experiment 2, participants used a precision grip to grasp and stably lift the same planar objects varying in degree of symmetry. Choice of grasp points was unrestricted. Participants selected a grasp axis (between thumb and middle finger) that limited the perpendicular distance from CM (i.e., grasp-axis error) to just a few millimetres. Moreover, they took advantage of visual cues to object symmetry to better determine CM, thus reducing their grasp-axis error for symmetric (vs. asymmetric) objects by 31%. We interpret these findings in terms of user and object-geometry constraints on grasp-point selection.

Adult↗
PubMed2003

Predictive and reactive co-ordination of grip and load forces in bimanual lifting in man.

We investigated the intra- and inter-manual coordination of grip force (GF) and load force (LF) during bimanual lifting and holding of a single object. In a voluntary task involving lifting a predictable load (Experiment 1), we showed scaling of GF to LF generated by either hand, similar to effects seen in previous unimanual studies. Moreover, the GF rates generated by the two hands were correlated. In part this correlation was due to the correlation between the LF rates. However, the GF rates remained correlated when the effects of the correlation in LF rates were partialled out. This novel finding suggests an additional co-ordinative constraint at the level of specification of GFs. As a contrast to the predictable loading in the first experiment, in the second experiment loading was temporally unpredictable and elicited reactive increases in GF. In Experiment 2, the intermanual correlation of GF rates was stronger than in Experiment 1. We speculate that this result reflects greater degrees of co-ordinative constraint at lower levels in the motor control hierarchy.

Adolescent↗
PubMed2003

Age-related changes in grip force and dynamics of hand movement.

The authors investigated whether older adults (n = 16; mean age = 65 years) increased grip force to compensate for load force fluctuations during up and down movements more than young adults did (n = 16; mean age = 24 years) and whether older and young adults exhibited similar adaptation of grip force to alterations in friction associated with changes in object surface texture. As previously reported, older adults used a higher level of grip force than young adults during static holding. Increased grip force was observed in the older group during movement. The increase was appropriate to the lower coefficient of friction estimated for the older group. In both groups, grip force was greater with a smooth than with a rough surface (the latter having the higher coefficient of friction) during static holding and during movement. Moreover, grip force modulation was equally well synchronized with load force fluctuation during movement in the two groups. The authors concluded that changes in organization of grip force with age are well adapted to change in hand-object interface properties. Elevated grip force in older adults does not necessarily signify a fundamental change in synchronizing grip force modulation with load force fluctuation.

Adolescent↗
PubMed2002

Voluntary timing and brain function: an information processing approach.

This article takes an information processing perspective to review current understanding of brain mechanisms of human voluntary timing. Theoretical accounts of timing of the production of isochronous tapping and rhythms and of bimanual responding repetitive responding are reviewed. The mapping of higher level temporal parameter setting and memory processes and of lower level motor implementation process onto cortical and subcortical brain structures is discussed in relation to evidence from selective lesions in a range of neurological motor disorders. Brain activation studies that have helped identify key brain structures involved in the control of timing are reviewed.

Brain↗