Short and long-term motor skill learning in an accelerated rotarod training paradigm

Rodent models of motor skill learning include skilled forelimb reaching and acrobatic locomotor paradigms. This study characterizes motor skill learning in the accelerated rotarod task. Thirty Long-Evans rats (300-400 g) were trained on an accelerated rotarod (1cm/s(2)) over eight consecutive sessions (=days, 20 trials each). Improvement in rotarod velocities mastered before falling off the rod was observed within and between sessions (plateau after five sessions). Intrasession improvement was incompletely retained at the beginning of the next day's session. Over several training sessions, intrasession improvement diminished, suggesting a ceiling effect. After 1 week of pause, the rotarod skill was retained. Locomotor exercise in a running wheel for 30 min before the first rotarod session did not affect intrasession improvement. Running-wheel exposure for 6 days did not diminish the rate of rotarod skill learning (steepness of the learning curve) but improved overall performance (upward shift of curve). Video analysis of gait on the rotarod showed that rats developed a motor strategy by modifying their gait patterns during training. The data demonstrate that rotarod improvement is not the result of enhanced general locomotor ability or fitness, which are trained in the running wheel, but requires a change in the motor strategy to master the task. Accelerated rotarod training can be regarded a valid paradigm for motor skill learning over short (intrasession, minutes) and long time frames (intersession, days).     

The planning and execution of sequential eye movements: saccades do not show the one target advantage

The present experiment examined the one-target advantage (OTA) with regard to saccadic eye movements. The OTA, previously found with manual pointing responses, refers to the finding that movements are executed faster when the limb is allowed to stop on the target compared to the situation where it has to proceed and hit a second target. Using an adapted limb movement OTA task, saccades of 5 degrees and 15 degrees were made to (a) a single target (one-target), (b) one target and immediately to another target without a change in direction (two-target-extension), and (c) one target and immediately back to the start location (two-target-reversal). Unlike manual movements, the movement times for the initial saccade in the two-target-extension condition were not prolonged compared to either of the other two conditions. Moreover, this pattern of results was found for both the shorter and longer amplitude saccades. The results indicate that the OTA does not occur in the oculomotor system and therefore is not a general motor control phenomenon.     

Multiple aspects in the sense of agency

Recent significant research in a number of disciplines centers on the concept of the sense of agency. Because many of these studies cut across disciplinary lines there is good reason to seek a clear consensus on what ‘sense of agency’ means. In this paper I indicate some complexities that this consensus might have to deal with. I also highlight an important phenomenological distinction that needs to be considered in any discussion of the sense of agency, regardless of how it gets defined. Finally, I suggest that the sense of agency has an ambiguous phenomenology and I offer some critical comments on current models that fail to notice this ambiguity.     

But I can’t pass that far! The influence of motor skill on decision making

Objectives

The influence of motor skill on perceptual-cognitive and perceptual-motor decision making has been theorised but not verified empirically.

Method

Expert (n = 19), developmental (n = 20), and lesser-skilled netballers (n = 19) completed tests designed to evaluate three different components of domain-specific expertise: (i) motor skill-execution; (ii) perceptual-cognitive decision making; and (iii) perceptual-motor decision making.

Results

Each of the three measures was found to improve commensurate with domain-specific skill. Decisions requiring movements (perceptual-motor) elicited more accurate decision making than simple verbal responses (perceptual-cognitive), irrespective of participant skill. Although motor skill was found to be related to the successful execution of a most appropriate movement in a game situation, it was not found to limit the nature of the decision made by participants. No evidence was found to support the supposition that lesser-skilled participants bias their perceptual-cognitive decisions towards ones supported by their motor ability.

Conclusions

Results fail to comprehensively support the contemporary models for the development of perceptual-cognitive and perceptual-motor skill in sport.     

Stopping speech suppresses the task-irrelevant hand

Some situations require one to quickly stop an initiated response. Recent evidence suggests that rapid stopping engages a mechanism that has diffuse effects on the motor system. For example, stopping the hand dampens the excitability of the task-irrelevant leg. However, it is unclear whether this ‘global suppression’ could apply across wider motor modalities. Here we tested whether stopping speech leads to suppression of the task-irrelevant hand. We used Transcranial Magnetic Stimulation over the primary motor cortex with concurrent electromyography from the hand. We found that when speech was successfully stopped the motor evoked potential from the task-irrelevant hand was significantly reduced compared to when the participant failed to stop speaking, or responded on non stop signal trials, or compared to baseline. This shows that when speech is quickly stopped, there is a broad suppression across the motor system. This has implications for the neural basis of speech control and stuttering.     

One hand, two objects: emergence of affordance in contexts

Studies on affordances typically focus on single objects. We investigated whether affordances are modulated by the context, defined by the relation between two objects and a hand. Participants were presented with pictures displaying two manipulable objects linked by a functional (knife-butter), a spatial (knife-coffee mug), or by no relation. They responded by pressing a key whether the objects were related or not. To determine if observing other's actions and understanding their goals would facilitate judgments, a hand was: (a) displayed near the objects; (b) grasping an object to use it; (c) grasping an object to manipulate/move it; (d) no hand was displayed. RTs were faster when objects were functionally rather than spatially related. Manipulation postures were the slowest in the functional context and functional postures were inhibited in the spatial context, probably due to mismatch between the inferred goal and the context. The absence of this interaction with foot responses instead of hands in Experiment 2 suggests that effects are due to motor simulation rather than to associations between context and hand-postures.     

The cost of action miscues: hemispheric asymmetries

Adaptive behaviors require preparation and when necessary inhibition or alteration of actions. The right hemisphere has been posited to be dominant for preparatory motor activation. This experiment was designed to learn if there are hemispheric asymmetries in the control of altered plans of actions. Cues, both valid and invalid, which indicate the hand most likely to be called onto respond, as well as the imperative stimuli that indicate the actual response hand, were presented to either the right or left visual fields of 14 normal right handed participants. The delay after a miscue is dependent on the time taken to inhibit the premotor and motor systems of the incorrectly activated hemisphere, as well as to activate the motor systems of the opposite hemisphere, which might have been interhemispherically inhibited by this miscue. Analyses of reaction times revealed that miscues presented in left hemispace (right hemisphere) cost more time than those miscues presented in right hemispace (left hemisphere), suggesting that activation of the preparatory systems controlled by the right hemisphere may take longer to reverse than those controlled by the left hemisphere. This asymmetry may be related to asymmetries in the strength of hemispheric activation with contralateral inhibition.     

Processing prefixes and suffixes in handwriting production

Previous research showed that handwriting production is mediated by linguistically oriented processing units such as syllables and graphemes. The goal of this study was to investigate whether French adults also activate another kind of unit that is more related to semantics than phonology, namely morphemes. Experiment 1 revealed that letter duration and inter-letter intervals were longer for suffixed words than for pseudo-suffixed words. These results suggest that the handwriting production system chunks the letter components of the root and suffix into morpheme-sized units. Experiment 2 compared the production of prefixed and pseudo-prefixed words. The results did not yield significant differences. This asymmetry between suffix and prefix processing has also been observed in other linguistic tasks. In suffixed words, the suffix would be processed on-line during the production of the root, in an analytic fashion. Prefixed words, in contrast, seem to be processed without decomposition, as pseudo-affixed words.     

When two become one: Temporally dynamic integration of the face and voice

In everyday interactions with others, people have to deal with the sight of a face and sound of a voice at the same time. How the perceptual system brings this information together over hundreds of milliseconds to perceive others remains unclear. In 2 studies, we investigated how facial and vocal cues are integrated during real-time social categorization by recording participants' hand movements (via the streaming x, y coordinates of the computer mouse) en route to “male” and “female” responses on the screen. Participants were presented with male and female faces that were accompanied by a same-sex voice morphed to be either sex-typical (e.g., masculinized male voice) or sex-atypical (i.e., feminized male voice). Before settling into ultimate sex categorizations of the face, the simultaneous processing of a sex-atypical voice led the hand to be continuously attracted to the opposite sex-category response across construal. This is evidence that ongoing results from voice perception continuously influence face perception across processing. Thus, social categorization involves dynamic updates of gradual integration of the face and voice.     

Negative stimulus-response compatibility observed with a briefly displayed image of a hand

Manual responses can be primed by viewing an image of a hand. The left-right identity of the viewed hand reflexively facilitates responses of the hand that corresponds to the identity. Previous research also suggests that when the response activation is triggered by an arrow, which is backward-masked and presented briefly, the activation manifests itself in the negative priming effect. The present study showed that response activation, which is produced by an identity of a briefly presented image of a hand, can be similarly associated with a negative priming effect. However, in contrast to the previously reported negative priming effects, the hand stimuli produced negative priming even when the hand was not backward-masked and did not contain task-relevant information. The study supports the view that the automatic inhibition of motor activation triggered by briefly viewed objects is a general and basic functional principle in exogenous motor control processes.