Adolescent development of motor imagery in a visually guided pointing task

The development of action representation during adolescence was investigated using a visually guided pointing motor task (VGPT) to test motor imagery. Forty adolescents (24 males; mean age 13.1 years) and 33 adults (15 males; mean age 27.5 years) were instructed to both execute and imagine hand movements from a starting point to a target of varying size. Reaction time (RT) was measured for both Execution (E) and Imagery (I) conditions. There is typically a close association between time taken to execute and image actions in adults because action execution and action simulation rely on overlapping neural circuitry. Further, representations of actions are governed by the same speed-accuracy trade-off as real actions, as expressed by Fitts’ Law. In the current study, performance on the VGPT in both adolescents and adults conformed to Fitts’ Law in E and I conditions. However, the strength of association between E and I significantly increased with age, reflecting a refinement in action representation between adolescence and adulthood.     

The scaling of information to action in visually guided braking

Braking to avoid a collision can be controlled by keeping the deceleration required to stop (i.e., ideal deceleration) in the "safe" region below maximum deceleration, but maximum deceleration is not optically specified and can vary as conditions change. When brake strength was manipulated between participants using a simulated braking task, the ratio of ideal to maximum deceleration at brake onset was invariant across groups, suggesting that calibration involves scaling information about ideal deceleration in intrinsic units of maximum deceleration. Evidence of rapid recalibration was found when brake strength was manipulated within participants, and the presence of external forces that affect brake dynamics resulted in biases in performance. Discussion focuses on the role of calibration, internal models, and affordance perception in visually guided action.     

The learning of visually guided action: An information-space analysis of pole balancing

In cart-pole balancing, one moves a cart in 1 dimension so as to balance an attached inverted pendulum. We approached perception-action and learning in this task from an ecological perspective. This entailed identifying a space of informational variables that balancers use as they perform the task and demonstrating that they improve by traversing the space to the loci of more useful variables. We presented a novel information space-including fractional derivatives of pendulum angle (e.g., halfway between angle and angular velocity)-as possible information for balancing. Fourteen college students tried to meet a criterion of balancing the pole for 30 s on 3 of 5 successive trials, up to a maximum of 150 attempts. Loci in the fractional derivative space predicted the time series of force production well. Systematic differences were seen in loci as a function of success, and systematic changes in locus were seen with learning. The fractional derivatives were shown to predict pole angles a short time interval into the future, allowing balancers to prospectively control the action and thereby nullify visuomotor delay. In addition to loci in the information space, we analyzed loci in a calibration space, reflecting the gain relating force to information. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Time course of planning for object and action parameters in visually guided manipulation

Under visual guidance, subjects reached for and manipulated an object that variedin weight and surface texture (slipperiness). The manipulatory action was either grasping, lifting, or posting in a slot. The task was constrained or unconstrained with respect to speed, grasp pattern, and contact force. Initiation time (pre-reach), movement time (reach), and post-contact errors were measured, to examine planning for task performance at three points in time. Results indicate that in the constrained task, the manipulatory action was planned during the initiation time, but planning for object parameters was deferred until the reach interval. With relaxed task constraints, initiation times increased,and texture and manipulatory action had independent effects on premovement planning. Errors were affected interactively by all variables. The results suggest a planning process that unfolds over time, incorporating in turn the manipulatory action, object texture, and object weight. This unfolding accommodates variables proximate to the time where they will affect physical action.     

Asymmetrical neural adaptation in lower leg muscles as a consequence of stereotypical motor training

Despite well-authorized facts regarding asymmetrical architectural changes between different limbs after persistent participation in particular motor training, no studies have addressed the neural aspects to the present. The authors undertook the study to elucidate the possibility of neural adaptation on a limb-by-limb basis after repetitive engagement in a particular motor training routine. We investigated lower leg muscles in endurance-trained track runners who have been trained by routinely running on a track in counterclockwise direction on curved paths. Stretch reflex responses in the plantarflexor muscles (soleus [SOL], medial [MG], and lateral head of the gastrocnemius muscle) were evaluated bilaterally with participants sitting at rest. Comparisons were made between homonymous muscles of the right (corresponding to outside leg for track running) and left leg (inside leg, likewise) and with a group of nontrained controls. The result clearly demonstrated that the responses were prominently different between the legs (thus, asymmetrical) in the MG muscles and partially in the SOL muscles in the trained group. In contrast, no such differences were obtained in the nontrained control group. The result demonstrated that neural adaptation took place asymmetrically and that could be attributable to their repetitive engagement in the stereotypical motor task.     

Tau as a potential control variable for visually guided braking

D. N. Lee (1976) described a braking strategy based on optical expansion in which the driver brakes so that the target's time-to-contact declines around a constant slope in the range -0.5 < or = tau < 0. The present results from a series of braking simulations confirm and extend earlier reports (E. H. Yilmaz & W. H. Warren, 1995) that performance is broadly compatible with the tau hypothesis. However, performance was not enhanced in situations that favored the estimation of tau, and unlike in earlier reports, performance deteriorated in the absence of a ground plane that provided information about speed and target distance. This finding suggests that the tau hypothesis does not provide a complete account of braking control.     

Observing or producing a motor action improves later perception of biological motion: Evidence for a gender effect

Two experiments are presented addressing the issue of whether observing (visual priming) or producing (motor priming) a running activity during a very short period (30 s) facilitates the perception of the direction of a point-light runner embedded in a dense dynamical mask. Experiment 1 showed that perceptual judgements improved and response time increased in the visual priming compared to the neutral priming condition (video of a moving car) in which judgements were at random. Because this effect was observed for male participants only, we performed a second experiment with the aim of evaluating the role of gender congruency in the visual priming condition. Results confirmed the facilitation effect and demonstrated that this effect was strictly dependent on the gender congruency between the perceiver and the priming information. Moreover, we found that actually producing a motor activity similar to the one presented in the video sequence improved to the same extent participants’ judgement of the direction of the point-light runner, without any gender effect. As a whole, these findings argue in favour of common representation for the perception and the production of human movement and showed that the perception of biological motion can be improved by prior motor activity either performed or observed. However, the gender-dependent effect of visual priming suggested that motor repertoire differed in males and females.     

Perceptual delay: a consequence of metacontrast and apparent motion

Temporal-order judgments were used to demonstrate that a later visual stimulus can delay the perception of an earlier one when the two stimuli together produce the phenomenon of metacontrast or of apparent motion. The perceptual delay is the same for movement and metacontrast and for one or two characters appearing to move or to be masked.     

An action sequence withheld in memory can delay execution of visually guided actions: the generalization of response compatibility interference

Withholding an action plan in memory for later execution can delay execution of another action, if the actions share a similar (compatible) action feature (i.e., response hand). This phenomenon, termed compatibility interference (CI), was found for identity-based actions that do not require visual guidance. The authors examined whether CI can generalize to both identity-based and location-based actions that require visual guidance. Participants withheld a planned action based on the identity of a stimulus and then immediately executed a visually guided action (touch response) to a 2nd stimulus based on its color identity (Experiment 1), its spatial location (Experiment 2), or an intrinsic spatial location within an object (Experiment 3). Results showed CI for both left- and right-hand responses in Experiment 1. However, CI occurred for left- but not right-hand responses in Experiment 2 and 3. This suggests that CI can generalize to visually guided actions under cognitive control but not to actions that invoke automatic visual-control mechanisms where the left hemisphere may play a special role (C. Gonzalez, T. Ganel, & M. Goodale, 2006). The code occupation account for CI (G. Stoet & B. Hommel, 2002) is also discussed.     

Free-time as a consequence for behavior in classroom settings: A critical review

Osborne (1969) presented adolescent hearing impaired students with five minutes of free- time contingent upon remaining seated for 15 minutes in the classroom. This procedure substantially reduced the frequency of out- of- seat behavior. Since the publication of this seminal work, 49 studies have used free- time as a consequence to change behavior. This review critically examines these 49 studies. The review shows that free-time has been used effectively with a variety of different behaviors and student populations, and with different methods of delivery. Based on a synthesis of information from the review, optimal methods for the use of free-time are suggested. Finally, it is concluded that additional research is needed, especially to answer the question of why free-time is effective.     

Risky choice: An examination of information acquisition behavior

The monitoring of information acquisition behavior, along with other process tracing measures such as response times, was used to examine how individuals process information about gambles into a decision. Subjects indicated preferences among specially constructed three-outcome gambles. The number of alternatives available was varied across the sets of gambles. A majority of the subjects processed information about the gambles in ways inconsistent with compensatory models of risky decision making, such as information integration (Anderson & Shanteau, 1970). Furthermore, the inconsistency between observed information acquisition behavior and such compensatory rules increased as the choice task became more complex. Alternative explanations of risky choice behavior are considered.     

Anxiety and motor behavior: a review

Anxiety and related terms were defined by conceptually distinguishing between "state" and "trait" anxiety and between anxiety, stress and fear. The literature concerned with the anxiety-motor behavior relationship was reviewed using the state-trait anxiety distinction. After outlining the general notions of drive theory as related between the Taylor Manifest Anxiety Scale (MAS) and motor behavior in the absence or in the presence of a stressor, and on those studies using anxiety scales other than MAS. The accumulated evidence failed to reveal any consistent trends in these three areas. The use of drive theory and the MAS to predict motor behavior ws shown not to be a viable approach. Two alternative approaches were briefly outlined.     

Evidence for a common motion mechanism of luminance-modulated and contrast-modulated patterns: selective adaptation.

Selective adaptation effects were measured with contrast-modulated patterns and sine-wave gratings in order to determine the extent to which the two patterns are processed by common mechanisms. Direction-specific adaptation effects were measured for a contrast-modulated adapting pattern and a test pattern. The contrast-modulated adapting pattern was composed of a sine-wave grating of 8 cycles deg-1 whose contrast was spatially modulated by a sinusoid of 1 cycle deg-1 at one of four levels: 100%, 60%, 30%, or 0%. The results showed that contrast-modulation thresholds for contrast-modulated gratings were raised by 0.3 to 0.5 log units following adaptation to a contrast-modulated grating moving in the same direction as the test pattern, relative to thresholds obtained following adaptation to a contrast-modulated grafting moving in the opposite direction. Cross-adaptation effects were also measured with a sine-wave adapting pattern and a contrast-modulated test pattern. The sine-wave adapting pattern was a sine-wave grating of 1 cycle deg-1 whose contrast was set to one of three levels: 16.4%, 1.25%, or 0%. The contrast-modulated test pattern was a sine-wave grating of 8 cycles deg-1 whose contrast was modulated by a sinusoid of 1 cycle deg-1. The results revealed that contrast-modulation thresholds for contrast-modulated gratings were raised by approximately 0.25 log units following adaptation to moving sine-wave gratings, relative to thresholds obtained following adaptation to a uniform field. Cross-adaptation effects were also obtained with a contrast-modulated adapting pattern and a sine-wave test pattern. The results support the view that signals generated from luminance-domain stimuli and from contrast-domain stimuli are processed by a common motion mechanism.     

Talking and driving: applications of crossmodal action reveal a special role for spatial language

Talking reduces attention resulting in real-world crash risks to drivers that talk on a phone and drive. Driving is a behavior that is very demanding on spatial attention, suggesting potentially large interference by spatial codes in language. The current study investigated how different types of verbal codes influence visual attention during dual-task performance. In two experiments, participants performed a spatial or non-spatial verbal task while simultaneously performing a visual attention task. The results showed a larger decrement to visual attention performance when participants were concurrently engaged in a spatial verbal task. The results of the second experiment isolated this effect to the right cerebral hemisphere, consistent with a role for shared right parietal resources. These results are consistent with the idea that processing codes are an important component of coordinating talking and driving but generally inconsistent with a broad class of bottleneck approaches that describes dual-task decrements but treats component tasks as cognitively equivalent.     

Reaching beyond spatial perception: Effects of intended future actions on visually guided prehension

Three experiments examined whether manipulating actors' intentions, regarding forthcoming actions, influences the time course and kinematics of visually guided, reach‐to‐grasp movements. Subjects performed two‐step action sequences where the initial movement always involved reaching for and grasping cubes located at a constant distance. Demands of the second movement were systematically manipulated. Although the spatial parameters (cube size and distance) remained constant across all conditions, the durations of the initial movements differed substantially depending on the actions subjects intended to perform once the objects were in hand. Less time was required to engage a small (1 cm³) cube when the intention was to transport it to a new location on the workspace vs. a large (4 cm³) cube when the goal was to merely lift it above its current resting position (Experiment 1). This difference in duration of the initial movement reflects more time spent in the deceleration phase of the reach when the task does not require transporting the cube to a new location on the workspace. Further, this context effect is not related to accuracy demands (Experiment 2), or complexity (Experiment 3) of the intended second movement. These findings demonstrate that actions are determined both by the perceived spatial demands of the immediate movement as well as the intended goal of the entire action sequence.