Human supplementary motor area contribution to predictive motor planning

The supplementary motor area (SMA) is involved in planning limb movements. An important component of such planning is the prediction of the sensory consequences of action. The authors used transcranial magnetic stimulation (TMS) to probe the contribution of SMA to motor planning during a predictive load-bearing task. Single TMS pulses were delivered over the SMA after a cue instructing the participant to release a platform supporting his or her right hand, which in turn held a 2 kg mass. Participants were less able to bear the load successfully when TMS was delivered 400-500 ms prior to the response. This result suggests that the SMA contributes to the prediction of the sensory consequences of movement well before movement onset.     

Disrupting somatosensory processing impairs motor execution but not motor imagery

While motor imagery (MI) is thought to be ‘functionally equivalent’ with motor execution (ME), the equivalence of feedforward and feedback mechanisms between the two modalities is unexplored. Here, we tested the equivalence of these mechanisms between MI and ME via two experiments designed to probe the role of somatosensory processing (Exp 1), and cognitive processing (Exp 2). All participants were engaged in a previously established force-matching task adapted for MI. A reference force was applied (on scale of 1–10, with higher numbers indicative of greater force) to one index finger while participants matched the force with their opposite index finger via ME or MI (control conditions). Participants then rated the force on the same scale of 1–10. Exp 1: Participants (N = 27) performed the task with tactile stimulation (ME+TAC, MI+TAC) in addition to control conditions. Exp 2: Participants (N = 26) performed the task in dual-task conditions (ME+COG, MI+COG) in addition to control conditions. Results indicate that (Exp 1) tactile stimulation impaired performance in ME but not MI. Dual-task conditions (Exp 2) were not shown to impair performance in either practice modality. Findings suggest that while somatosensory processing is critical for ME, it is not for MI. Overall we indicate a functional equivalence between feedforward/back mechanisms in MI and ME may not exist.     

Modular motor learning

An interesting theory of sensorimotor control has been recently extended and simulated. The simulation can learn to control an arm in several mutually exclusive 'contexts', situations where the arm carries one of four objects with different mechanical properties. It provides a good theoretical framework for testing biological motor systems.     

Shifts in attention demands and motor program utilization during motor learning

The relationship between changes in the level of motor program utilization and attention demand during the learning of a motor task was examined. The primary task involved an 86-cm horizontal arm movement which subjects attempted to complete coincident with the end of a 360 degrees sweep of a clock hand. A secondary task performed with the opposite limb required a rapid button press to an auditory probe stimulus presented at various temporal locations within each trial. Control subjects performed either the primary task or the secondary task alone, while experimental subjects performed both tasks in combination. Schmidt's (1972) index of preprogramming was used to measure the level of motor program utilization, while probe reaction time reflected the attention demand of the primary task. There was a stable level of motor programming over four consecutive days of practice (100 trials a day), but a general decrease in attention demand. Implications for an expansion of the concept of the motor program were discussed.     

Sleep dependent consolidation of gross motor sequence learning with motor imagery

Acquisition of gross motor sequence learning with physical and mental training elicits gains in performance. However, the effects of sleep or daytime consolidation after both types of practice remain unclear, especially the effects upon the goal- and movement-based components of a gross motor sequential task. The main purpose of this study was to test the effect of physical practice (PP) and motor imagery practice (MIP) on the acquisition and consolidation processes of gross motor sequence learning.Seventy-six participants were tested before and after PP or MIP on a whole-body sequential paradigm, following either a night of sleep (PP_sleep and MIP_sleep groups) or an equivalent daytime period (PP_day and MIP_day groups). Control groups without training were tested following similar timespans (CTRL_sleep and CTRL_day groups). The number of sequential movements and the centre of mass displacement – corresponding to goal and movement-based components, respectively – were assessed.Results showed that relative to the CTRL groups, the PP and MIP groups improved performance during acquisition. Importantly, only the MIP_sleep group further improved performance after a night of sleep; participants of other groups stabilised their performance after consolidation. Additionally, the number of sequential movements and the centre of mass displacement evolved conjointly without being influenced by the type of training or the nature of the consolidation.To conclude, these results confirm that sleep contributes to the consolidation of gross motor sequence learning acquired with MIP but not PP. The relationship between the goal- and movement-based components of a gross motor sequential task is discussed.     

Understanding social motor coordination

Recently there has been much interest in social coordination of motor movements, or as it is referred to by some researchers, joint action. This paper reviews the cognitive perspective’s common coding/mirror neuron theory of joint action, describes some of its limitations and then presents the behavioral dynamics perspective as an alternative way of understanding social motor coordination. In particular, behavioral dynamics’ ability to explain the temporal coordination of interacting individuals is detailed. Two experiments are then described that demonstrate how dynamical processes of synchronization are apparent in the coordination underlying everyday joint actions such as martial art exercises, hand-clapping games, and conversations. The import of this evidence is that emergent dynamic patterns such as synchronization are the behavioral order that any neural substrate supporting joint action (e.g., mirror systems) would have to sustain.     

Deluding the motor system

How do we know that our own actions belong to us? How are we able to distinguish self-generated sensory events from those that arise externally? In this paper, I will briefly discuss experiments that were designed to investigate these questions. In particular, I will review psychophysical and neuroimaging studies that have investigated how we recognise the consequences of our own actions, and why patients with delusions of control confuse self-produced and externally produced actions and sensations. Studies investigating the failure of this 'self-monitoring' mechanism in patients with delusions of control will be discussed in the context of the hypothesis that overactivity in the parietal cortex and the cerebellum contribute to the misattribution of an action to an external source.     

Metacognition in motor learning

Research on judgments of verbal learning has demonstrated that participants' judgments are unreliable and often overconfident. The authors studied judgments of perceptual-motor learning. Participants learned 3 keystroke patterns on the number pad of a computer, each requiring that a different sequence of keys be struck in a different total movement time. Practice trials on each pattern were either blocked or randomly interleaved with trials on the other patterns, and each participant was asked, periodically, to predict his or her performance on a 24-hr test. Consistent with earlier findings, blocked practice enhanced acquisition but harmed retention. Participants, though, predicted better performance given blocked practice. These results augment research on judgments of verbal learning and suggest that humans, at their peril, interpret current ease of access to a perceptual-motor skill as a valid index of learning.     

Reliability and motor memory

The generalizability framework was employed to estimate variance components and reliability of performance in a positioning task. The subjects (n =70) performed 16 trials at each of three target lengths of 25 cm, 45 cm, and 65 cm. The data were analyzed using a subjects x targets x trials repeated measures ANOVA. Two reliability coefficients were estimated. The first (R) provided an estimate of performance reliability generalized over targets and trials. The second (R') treated targets as a source of true-score variance and hence was generalized over trials alone. Both reliability coefficients were higher for algebraic error than for absolute error, and R1 provided higher reliability estimates than R for both dependent variables. Increasing the number of positioning trials from 2 to 16 at each target length did not appreciably alter either reliability coefficient. The overall low reliability of R appears to compound the dependent variables and statistical power problems associated with short-term motor-memory studies.     

The influence of motor expertise and motor experience on action and actor recognition

Two experiments examined whether different levels of motor and visual experience influence action perception and whether this effect depends on the type of perceptual task. Within an action recognition task (Experiment 1), professional basketball players and novice college students were asked to identify basketball dribbles from point-light displays. Results showed faster reaction times and greater accuracy in experts, but no advantage when observing either own or teammates’ actions compared with unknown expert players. Within an actor recognition task (Experiment 2), the same expert players were asked to identify the model actors. Results showed poor discrimination between teammates and players from another team, but a more accurate assignment of own actions to the own team. When asked to name the actor, experts recognised themselves slightly better than teammates. Results support the hypothesis that motor experience influences action recognition. They also show that the influence of motor experience on the perception of own actions depends on the type of perceptual task.     

The supplementary motor area in motor and perceptual time processing: fMRI studies

The neural bases of timing mechanisms in the second-to-minute range are currently investigated using multidisciplinary approaches. This paper documents the involvement of the supplementary motor area (SMA) in the encoding of target durations by reporting convergent fMRI data from motor and perceptual timing tasks. Event-related fMRI was used in two temporal procedures, involving (1) the production of an accurate interval as compared to an accurate force, and (2) a dual-task of time and colour discrimination with parametric manipulation of the level of attention attributed to each parameter. The first study revealed greater activation of the SMA proper in skilful control of time compared to force. The second showed that increasing attentional allocation to time increased activity in a cortico-striatal network including the pre-SMA (in contrast with the occipital cortex for increasing attention to colour). Further, the SMA proper was sensitive to the attentional modulation cued prior to the time processing period. Taken together, these data and related literature suggest that the SMA plays a key role in time processing as part of the striato-cortical pathway previously identified by animal studies, human neuropsychology and neuroimaging.     

References for motor tasks--gender differences across age in motor performance: a meta-analysis

In 1985 we published a meta-analysis of gender differences across age in motor performance in Psychological Bulletin, but it did not include an indexing of each motor task to the references from which it was obtained. This paper provides a table listing the 20 motor tasks and the references from which data for each task were taken. The range of tasks was from fundamental movements (e.g., catching, jumping, running, throwing) to motor fitness (e.g., agility, arm hang, balance, grip strength) to perceptual-motor abilities (e.g., anticipation timing, fine eye-motor coordination, pursuit-rotor tracking, reaction time). The arm hang was represented in the fewest papers (n = 2) while the dash and long jump were most frequently referenced (n = 21).     

Diminished motor skill development in elderly: Indications for limited motor chunk use

The present study examined whether elderly use motor chunks after practicing discrete keying sequences, just like young adults, or whether they perhaps learn these movement patterns in a different way. To that end, elderly (75-88) and young adults (18-28) practiced as part of the discrete sequence production (DSP) task two fixed series of three and six key presses. The results demonstrate that elderly did improve with practice but this improvement was largely sequence-unspecific. Detailed analyses showed that, in contrast to young adults, most elderly did not use motor chunks, had little explicit sequence knowledge, and remained highly dependent on external stimuli. Still, elderly did show sequence-specific learning with a 6-key sequence that can be explained by an associative learning mechanism.     

基于fNIRS的运动执行与运动想象脑激活模式比较

使用《运动想象问卷−修订版》筛选出的30名被试(男女各半), 采用功能性近红外光谱成像技术(fNIRS)监测被试在执行实际举哑铃(男生, 4磅和8磅; 女生, 2磅和4磅)任务和想象举同等重量哑铃任务时, 其大脑皮层氧合血红蛋白浓度的变化。结果发现：男女被试在运动执行与运动想象任务下都激活了主运动皮层; 且运动执行的大脑激活水平高于运动想象。在执行实际运动任务时, 运动强度显著影响大脑皮层血氧浓度的变化, 表现出左半球偏侧化优势; 在执行想象运动任务时, 运动强度没有影响大脑皮层血氧浓度的变化, 且无偏侧化现象。     

Minimizing motor mimicry by myself: Self-focus enhances online action-control mechanisms during motor contagion

Ideomotor theory of human action control proposes that activation of a motor representation can occur either through internally-intended or externally-perceived actions. Critically, sometimes these alternatives of eliciting a motor response may be conflicting, for example, when intending one action and perceiving another, necessitating the recruitment of enhanced action-control to avoid motor mimicry. Based on previous neuroimaging evidence, suggesting that reduced mimicry is associated with self-related processing, we aimed to experimentally enhance these action-control mechanisms during motor contagion by inducing self-focus. In two within-subjects experiments, participants had to enforce their action intention against an external motor contagion tendency under heightened and normal self-focus. During high self-focus participants showed reduced motor mimicry, induced either by mirror self-observation or self-referential judgments. This indicates that a self-focus provoking situation can enhance online action-control mechanisms, needed to resist unintentional motor contagion tendencies and thereby enables a modulation of automatic mirroring responses.     

Timing processes in motor imagery

Previous research shows inconsistencies in the timing of imagined and actual actions. Little is known about the timing in imagery, or how it relates to other forms of timing. Two studies examined whether imagery timing followed Weber's law, where variations in judgements grow linearly as the interval duration increases, or Vierordt's law, where short durations are overestimated and longer durations underestimated. In Study 1 participants (n=22) mentally walked and estimated journey times for flat paths and stairways, with and without a load. The timing patterns that emerged did not conform to Weber's law. In Study 2 participants (n=20) completed imagery, reproduction, production, and estimation timing tasks. Timing errors for imagery along a straight path, reproduction, estimation, and production all showed “Vierordt-like” effects. However, when imagining walking in a square participants consistently overestimated. It was concluded that imagery and interval timing processes are similar, but imagery timing is task dependent.