The interplay of perceptual processing demands and practice in modulating voluntary and involuntary motor responses.

Understanding how sensory processing demands affect the ability to ignore task-irrelevant, loud auditory stimuli (LAS) during a task is key to performance in dynamic environments. For example, tennis players must ignore crowd noise to perform optimally. We investigated how practice affects this ability by examining the effects of delivering LASs during preparatory phase of an anticipatory timing (AT) task on the voluntary and reflexive responses in two conditions: lower and higher visual processing loads.

Evolving changes in cortical and subcortical excitability during movement preparation: A study of brain potentials and eye-blink reflexes during loud acoustic stimulation.

During preparation for action, the presentation of loud acoustic stimuli (LAS) can trigger movements at very short latencies in a phenomenon called the StartReact effect. It was initially proposed that a special, separate subcortical mechanism that bypasses slower cortical areas could be involved. We sought to examine the evidence for a separate mechanism against the alternative that responses to LAS can be explained by a combination of stimulus intensity effects and preparatory states.

Premovement inhibition can protect motor actions from interference by response-irrelevant sensory stimulation.

Key Points: Suppression of corticospinal excitability is reliably observed during preparation for a range of motor actions, leading to the belief that this preparatory inhibition is a physiologically obligatory component of motor preparation. The neurophysiological function of this suppression is uncertain. We restricted the time available for participants to engage in preparation and found no evidence for preparatory inhibition.

Acoustic stimulation increases implicit adaptation in sensorimotor adaptation.

Sensorimotor adaptation is an important part of our ability to perform novel motor tasks (i.e., learning of motor skills).

Preparatory suppression and facilitation of voluntary and involuntary responses to loud acoustic stimuli in an anticipatory timing task.

In this study, we sought to characterize the effects of intense sensory stimulation on voluntary and involuntary behaviors at different stages of preparation for an anticipated action. We presented unexpected loud acoustic stimuli (LAS) at-rest and at three critical times during active movement preparation (-1,192, -392, and 0 ms relative to expected voluntary movement onset) to probe the state of the nervous system, and measured their effect on voluntary and involuntary motor actions (finger-press and eye-blink startle reflex, respectively). Voluntary responses were facilitated by LAS presented during active preparation, leading to earlier and more forceful responses compared to control and LAS at-rest.

Cumulative distribution functions: An alternative approach to examine the triggering of prepared motor actions in the StartReact effect.

There has been much debate concerning whether startling sensory stimuli can activate a fast-neural pathway for movement triggering (StartReact) which is different from that of voluntary movements. Activity in sternocleidomastoid (SCM) electromyogram is suggested to indicate activation of this pathway. We evaluated whether SCM activity can accurately identify trials which may differ in their neurophysiological triggering and assessed the use of cumulative distribution functions (CDFs) of reaction time (RT) data to identify trials with the shortest RTs for analysis.

Neural gain induced by startling acoustic stimuli is additive to preparatory activation.

Loud acoustic stimuli presented during movement preparation can shorten reaction time and increase response forcefulness. We examined how efferent connectivity of an agonist muscle to reticulospinal and corticospinal pathways, and the level of prepared movement force, affect reaction time and movement execution when the motor response is triggered by an intense acoustic stimulus. In Experiment 1, participants executed ballistic wrist flexion and extension movements of low and high force in response to visual stimuli.

Grasping at laws: Speed-accuracy trade-offs in manual prehension.

Most of human performance is subject to speed-accuracy trade-offs. For spatially constrained aiming, the trade-off is often said to take the specific form of Fitts' law, in which movement duration is predicted from a single factor combining target distance and target size. However, efforts to extend this law to the three-dimensional context of reaching to grasp (prehension) have had limited success.

Intercepting accelerated moving targets: effects of practice on movement performance.

When performing a rapid manual interception, targets moving under constant motion are often intercepted with greater accuracy when compared to targets moving under accelerated motion. Usually, accelerated targets are timed too late and decelerating ones too early. The present experiment sought to investigate whether these differences in performance when intercepting targets moving under constant and accelerated motions change after a short period of practice.

The effect of attention on the release of anticipatory timing actions.

A loud auditory stimulus (LAS) presented during movement preparation can result in an earlier than normal movement onset. This effect had initially been assumed to be independent of the sensorial modality people attended to trigger their responses. In 2 experiments, we tested whether this assumption was warranted.

The early release of actions by loud sounds in muscles with distinct connectivity.

The presentation of an unexpected and loud auditory stimulus (LAS) during action preparation can trigger movement onset much sooner than normal. Recent research has attributed this effect to the activation of reticulospinal connections to the target muscles. To our knowledge, no studies have investigated the effects of LAS presentation in tasks requiring the simultaneous activation of muscles with different connectivity to motor areas of the brain.

Corticospinal modulation induced by sounds depends on action preparedness.

A loud acoustic stimulus (LAS) presented during movement preparation can induce an early release of the prepared action. Because loud sound has been found to have an inhibitory effect on motor cortex excitability, it is possible that the motor cortex plays little role in the early release of prepared responses. We sought to shed new light on this suggestion by probing changes in corticospinal excitability after LAS presentation during preparation for an anticipatory action.

Responses to loud auditory stimuli indicate that movement-related activation builds up in anticipation of action.

Previous research using a loud acoustic stimulus (LAS) to investigate motor preparation in reaction time (RT) tasks indicates that responses can be triggered well in advance of the presentation of an imperative stimulus (IS). This is intriguing given that high levels of response preparation cannot be maintained for long periods (≈ 200 ms). In the experiments reported here we sought to assess whether response-related activation increases gradually over time in simple RT tasks.

Corticospinal excitability during preparation for an anticipatory action is modulated by the availability of visual information.

To intercept rapidly moving objects, people must predict the right time to initiate their actions. The timing of movement initiation in interceptions is thought to be determined when a perceptual variable specifying time to contact reaches a criterion value. If a response needs to be aborted, the performer must make a decision before this moment.

Continuous priming effects on discrete response choices.

When primed by backward-masked, target-like stimuli, discrete responses (e.g. button presses) to simple visual targets can be slower when prime and target match (compatible) than when they do not (incompatible).

The effect of priming on interceptive actions.

Time constraints in ball sports encourage players to take advantage of any relevant advance information available to prepare their actions. Advance information, therefore, can serve to prime movement parameters (e.g.

Delayed inhibition of an anticipatory action during motion extrapolation.

Background: Continuous visual information is important for movement initiation in a variety of motor tasks. However, even in the absence of visual information people are able to initiate their responses by using motion extrapolation processes. Initiation of actions based on these cognitive processes, however, can demand more attentional resources than that required in situations in which visual information is uninterrupted.

The time course of direction specification in brief interceptive actions.

In fastball sports such as baseball and tennis people are required to produce accurate responses following brief observations of the ball. This limits the time available to prepare the movement. To cope with constrained viewing periods which precede the interception of fast approaching balls, performers are likely to prepare their responses in advance.

Real-time error detection but not error correction drives automatic visuomotor adaptation.

We investigated the role of visual feedback of task performance in visuomotor adaptation. Participants produced novel two degrees of freedom movements (elbow flexion-extension, forearm pronation-supination) to move a cursor towards visual targets. Following trials with no rotation, participants were exposed to a 60 degrees visuomotor rotation, before returning to the non-rotated condition.

Preparation and inhibition of interceptive actions.

Two experiments aimed to provide an estimate of the last moment at which visual information needs to be obtained in order for it to be used to initiate execution of an interceptive movement or to withhold execution of such a movement. In experiment 1, we sought to estimate the minimum time required to suppress the movement when the participants were first asked to intercept a moving target. In experiment 2, we sought to determine the minimum time required to initiate an interceptive movement when the participants were initially asked to keep stationary.

The utilisation of visual information in the control of rapid interceptive actions.

When intercepting a moving target, accurate timing depends, in part, upon starting to move at the right moment. It is generally believed that this is achieved by triggering motor command generation when a visually perceived quantity such as the target's time-to-arrival reaches a specific criterion value. An experimental method that could be used to determine the moment when this visual event happens was introduced by Whiting and coworkers in the 1970s, and it involves occluding the vision of the target at different times prior to the time of movement onset (MO).

The efficacy of colour cues in facilitating adaptation to opposing visuomotor rotations.

We investigated visuomotor adaptation using an isometric, target-acquisition task. Following trials with no rotation, two participant groups were exposed to a random sequence of 30 degrees clockwise (CW) and 60 degrees counter-clockwise (CCW) rotations, with (DUAL-CUE), or without (DUAL-NO CUE), colour cues that enabled each environment (non-rotated, 30 degrees CW and 60 degrees CCW) to be identified. A further three groups experienced only 30 degrees CW trials or only 60 degrees CCW trials (SINGLE rotation groups) in which each visuomotor mapping was again associated with a colour cue.

Generalisation between opposing visuomotor rotations when each is associated with visual targets and movements of different amplitude.

Previous studies have attempted to identify sources of contextual information which can facilitate dual adaptation to two variants of a novel environment, which are normally prone to interference. The type of contextual information previously used can be grouped into two broad categories: that which is arbitrary to the motor system, such as a colour cue, and that which is based on an internal property of the motor system, such as a change in movement effector. The experiments reported here examined whether associating visuomotor rotations to visual targets and movements of different amplitude would serve as an appropriate source of contextual information to enable dual adaptation.

The time course of amplitude specification in brief interceptive actions.

The interception of fast moving objects typically allows the object to be seen for only a short period of time. This limits the time available to prepare the movement. To deal with short preparation intervals, performers are likely to prepare a motor program in advance.