Distinct consolidation outcomes in a visuomotor adaptation task: Off-line leaning and persistent after-effect

Consolidation is a time-dependent process responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. In two experiments, we sought to determine whether one’s performance influences the outcome of the consolidation process. We used a visuomotor adaptation task in which the cursor moved by the participants was rotated 30° clockwise. Thus, participants had to learn a new internal model to compensate for the rotation of the visual feedback. The results indicated that when participants showed good adaptation in the first session, consolidation resulted in a persistent after-effect in a no-rotation transfer test; they had difficulty returning to their normal no-rotation internal model. However, when participants showed poor adaptation in the first session, consolidation led to significant off-line learning (between sessions improvement) but labile after-effects. These observations suggest that distinct consolidation outcomes (off-line learning and persistent after-effect) may occur depending on the learner’s initial performance.     

Alternate response preparation in a visuomotor serial task

The preparation of a particular motor pattern is related to the information available that enables the actor to predict the correct response to a forthcoming stimulus. In many situations, however, prediction is not possible. In such cases, the individual can guess the probable parameters of the next stimulus. The authors attempted to establish the bias in the motor intention for movement and its interaction with a possible memory trace of the stimulus-response mapping produced by the preceding stimulus. Two letters were presented bilaterally, and participants (N=21) had to discriminate the target letter and respond with the compatible hand. The present findings support the existence of a memory trace of the previous stimulus-response mapping.     

Concurrent task performance enhances low-level visuomotor learning

Visuomotor association learning involves learning to make a motor response to an arbitrary visual stimulus. This learning is essential for visual search and discrimination performance and is reliant upon a well-defined neural circuit in the brain that includes the prefrontal cortex and the hippocampal formation. In the present study, we investigated the possible role of attentional processes during such learning using dual-task interference. A motor, verbal, or perceptual concurrent task was performed during the learning/training block of a simple visual discrimination task. Contrary to expectation, the dual-task groups showed improved learning and learning-dependent performance compared with untrained control and non-dual-task trained groups. A second experiment revealed that this effect did not appear to be due to increased arousal level; the inclusion of alerting tones during learning did not result in facilitation. These findings suggest that the engagement of attention, but not arousal, during the acquisition of a visuomotor association can facilitate this learning and its expression.     

Postdecision consolidation in a trend prediction task

To be able to learn from experience it is necessary to correctly apprehend experienced feedback and the situation in which it is provided. The results indicate how post-decision consolidation in complex domains may affect learning. The problem may be particularly pertinent in recurrent decision making where considerable risk is involved. The study explores the changes in aspect (signal) importance from pre- to postdiction as a function of outcome information. By postdiction we mean the remembering of an earlier prediction (cf. Hawkins & Hastie, 1990). Subjects were asked to decide on which of four alternative future price developments would follow a historical price trajectory for different commodities, and to rate the importance of each of the chosen alternative's corresponding aspects. The subjects revealed a bias in their support ratings of aspects--seeing support in aspects that traditionally (by themselves and in many contexts) would be seen as neutral or even counter-indicative of the alternative chosen. After an intermission, the subjects were also given information about what was indicated to be the actual development of the market. One group was told that their decisions were correct (irrespective of what the decisions were), another group that they were incorrect but close, a third group that they were incorrect by far, while a fourth group served as a control. Following this information the subjects were again asked to judge the importance of the aspects for their own prior decision on the most likely future development. The results indicated that outcome feed-back had an effect on post decision restructuring of facts. Subjects in the correct condition showed an average consolidation that increased the support, while the wrong conditions lead to negative consolidation (in retrospect indicating that they never found as much support for their decision in the past as they actually did). Thus, in a choice between consolidating their own initial prediction and the price trajectory they would have to live with, the decision makers consolidated the outcome. Therefore, the results of the study were related to the hindsight bias phenomenon (Fischhoff, 1975) and to Kahneman and Miller's (1986) mutability concept.     

Judgments of reachability are independent of visuomotor adaptation

The furthest distance that is judged to be reachable can change after participants have used a tool or if they are led to misjudge the position of their hand. Here we investigated how judged reachability changed when visual feedback about the hand was shifted. We hoped to distinguish between various ways in which visuomotor adaptation could influence judged reachability. Participants had to judge whether they could reach a virtual cube without actually doing so. They indicated whether they could reach this virtual cube by moving their hand. During these hand movements, visual feedback about the position of the hand was shifted in depth, either away from or toward the participant. Participants always adapted to the shifted feedback. In a session in which the hand movements in the presence of visual feedback were mainly in depth, perceived reachability shifted in accordance with the feedback (more distant cubes were judged to be reachable when feedback was shifted further away). In a second session in which the hand movements in the presence of visual feedback were mainly sideways, for some participants perceived reachability shifted in the opposite direction than we expected. The shift in perceived reachability was not correlated with the adaptation to the shift in visual feedback. We conclude that reachability judgments are not directly related to visuomotor adaptation.     

Analyzing a complex visuomotor tracking task with brain-electrical event related potentials

Non-invasive techniques such as neuroimaging and event-related potential (ERP) methods have dramatically enhanced our understanding of the human brain. According to the requirements of the applied method, it is useful to simplify tasks for methodological reasons. In the present study we tested whether ERP measures are also suitable for analyzing complex tasks. In order to do this, we developed an analysis strategy based on the post hoc analysis of the behavioural data. We applied this method to a pursuit-tracking task of 25 s trial duration, consisting of repeated and non-repeated waveforms, where subjects had to track a target cross with a mouse-controlled cursor cross. An EEG was recorded from 62 channels. Response-locked ERPs were computed for two types of error correction: the correction of errors induced externally by the change of target direction and of internal errors generated by the subject itself. We found several ERP components that could be assigned to different feedback and feedforward controlled processing steps in the frontoparietal circuitry underlying visuomotor control, such as movement planning, movement execution (motor potential), reafferent activity, visuospatial analysis, and attentional (P300) processes. Our results support newer models that propose a role for the posterior parietal cortex in integrating multimodal sensory information. In addition, fast (about 180 ms and probably facilitated by anticipation) and slow (about 230-260 ms) error corrections could be differentiated by the time course of ERP activity. Our results show that complex (motor) tasks can be investigated with ERPs. This opens fruitful perspectives for future research on motor control in an ecological setting.     

Performance of a visuomotor walking task in an augmented reality training setting

Visual cues can be used to train walking patterns. Here, we studied the performance and learning capacities of healthy subjects executing a high-precision visuomotor walking task, in an augmented reality training set-up. A beamer was used to project visual stepping targets on the walking surface of an instrumented treadmill. Two speeds were used to manipulate task difficulty. All participants (n = 20) had to change their step length to hit visual stepping targets with a specific part of their foot, while walking on a treadmill over seven consecutive training blocks, each block composed of 100 stepping targets. Distance between stepping targets was varied between short, medium and long steps. Training blocks could either be composed of random stepping targets (no fixed sequence was present in the distance between the stepping targets) or sequenced stepping targets (repeating fixed sequence was present). Random training blocks were used to measure non-specific learning and sequenced training blocks were used to measure sequence-specific learning. Primary outcome measures were performance (% of correct hits), and learning effects (increase in performance over the training blocks: both sequence-specific and non-specific). Secondary outcome measures were the performance and stepping-error in relation to the step length (distance between stepping target). Subjects were able to score 76% and 54% at first try for lower speed (2.3 km/h) and higher speed (3.3 km/h) trials, respectively. Performance scores did not increase over the course of the trials, nor did the subjects show the ability to learn a sequenced walking task. Subjects were better able to hit targets while increasing their step length, compared to shortening it. In conclusion, augmented reality training by use of the current set-up was intuitive for the user. Suboptimal feedback presentation might have limited the learning effects of the subjects.     

Simultaneous visuomotor adaptation to optical tilt and displacement

Change in visuomotor direction and orientation was measured following simultaneous exposure to optical displacement and tilt. Adaptation to both transforms simultaneously was not different from adaptation to each transform separately. These results are consistent with previous work involving purely visual change, and suggest that the two kinds of adaptation involve independent processes for locus-specific and relational analysis.

     

Chunking in task sequences modulates task inhibition

In a study of the formation of representations of task sequences and its influence on task inhibition, participants first performed tasks in a predictable sequence (e.g., ABACBC) and then performed the tasks in a random sequence. Half of the participants were explicitly instructed about the predictable sequence, whereas the other participants did not receive these instructions. Task-sequence learning was inferred from shorter reaction times (RTs) in predictable relative to random sequences. Persisting inhibition of competing tasks was indicated by increased RTs in n- 2 task repetitions (e.g., ABA) compared with n- 2 nonrepetitions (e.g., CBA). The results show task-sequence learning for both groups. However, task inhibition was reduced in predictable relative to random sequences among instructed-learning participants who formed an explicit representation of the task sequence, whereas sequence learning and task inhibition were independent in the noninstructed group. We hypothesize that the explicit instructions led to chunking of the task sequence, and that n- 2 repetitions served as chunk points (ABA-CBC), so that within-chunk facilitation modulated the inhibition effect.     

Implicit and explicit components of dual adaptation to visuomotor rotations

Concurrent adaptation to two different visuomotor transformations has been shown to be possible as long as discriminative contextual cues are available. The authors examined explicit and implicit components of visually cued dual adaptation in younger and older adults. They found that only young adults, but not old adults, produced appropriate adaptive shifts of hand-movement direction to compensate for the visuomotor rotations. Aftereffects, conceived as a measure of implicit knowledge, were only poorly developed. Furthermore, only participants in the younger group exhibited systematic explicit knowledge of the visuomotor rotations. Subsequent analyses revealed strong correlations between the quality of explicit knowledge and the overall visuomotor adaptation. Thus, visually cued dual adaptation to two opposite visuomotor rotations is primarily mediated by conscious strategic corrections based on explicit knowledge of the transformations, a process, which is selectively impaired in older adults.     

The visuomotor mental rotation task: visuomotor transformation times are reduced for small and perceptually familiar angles

In the visuomotor mental rotation (VMR) task, participants point to a location that deviates from a visual cue by a predetermined angle. This task elicits longer reaction times (RT) relative to tasks wherein the visual cue is spatially compatible with the movement goal. The authors previously reported that visuomotor transformations are faster and more efficient when VMR responses elicit a degree of dimensional overlap (i.e., 0° and 5°) or when the transformation involves a perceptually familiar angle (i.e., 90° or 180°; K. A. Neely & M. Heath, 2010b). One caveat to this finding is that standard and VMR responses were completed in separate blocks of trials. Thus, between-task differences not only reflect the temporal demands of the visuomotor transformations, but also reflect the temporal cost of response inhibition. The goal of this study was to isolate the time cost of visuomotor transformations in the VMR task. The results demonstrated that visuomotor transformations are more efficient and effective when the response entails a degree of dimensional overlap between target and response (i.e., when the angular disparity between the responses is small) or when the transformation angle is perceptually familiar.     

Temporal expectancy modulates inhibition of return in a discrimination task

This research examined the influence of cue temporal predictability on inhibition of return (IOR) in a discrimination task. In exogenous attention experiments, the cue that summons attention is noninformative as to where the target will appear. However, it is predictive as to when it will appear. In previous work, it was demonstrated that temporal predictability does not influence IOR in detection tasks. In this work, it is shown that IOR is influenced by temporal predictability in discrimination tasks. Predictability was manipulated by using three stimulus onset asynchrony distributions: nonaging, aging, and accelerated aging. IOR was found when the cue predicted target appearance and was modulated by temporal information. In the nonaging distribution (in which the cue did not predict target appearance), there was no IOR.     

Concurrent cognitive task modulates coordination dynamics

Does a concurrent cognitive task affect the dynamics of bimanual rhythmic coordination? In‐phase coordination was performed under manipulations of phase detuning and movement frequency and either singly or in combination with an arithmetic task. Predicted direction‐specific shifts in stable relative phase from 0° due to detuning and movement frequency were amplified by the cognitive task. Nonlinear cross‐recurrence analysis suggested that this cognitive influence on the locations of the stable points or attractors of coordination entailed a magnification of attractor noise without a reduction in attractor strength. An approximation to these findings was achieved through parameter changes in a motion equation in relative phase. Results are discussed in terms of dual‐task performance as limited resources, dynamics rather than chronometrics, and reparameterization rather than degradation.     

Laterality briefed: laterality modulates performance in a numerosity-congruity task

It is widely agreed that irrelevant numerical values are automatically activated. However, automatic and intentional activations may give rise to different numerical representations. We examined processing of symbolic and non-symbolic (i.e., numerosity) representations asking whether they differ in automatic and intentional processing. Participants were presented with two-dimensional displays containing repetitions of a digit and were asked to report, in different blocks, whether the digit or numerosity was smaller or larger than 5. Incongruent trials differed either in laterality between the relevant and irrelevant dimensions (i.e., the location of both dimensions in reference to the midpoint 5) or in numerical distance between dimensions. Congruency affected performance regardless of symbolic or non-symbolic presentation. For incongruent trials, laterality (not distance) affected performance, again regardless of presentation. This implies that automaticity does not mean similar processing of relevant and irrelevant dimensions. Specifically, the relevant dimension is processed elaborately whereas the irrelevant dimension is processed crudely.     

Conflict adaptation depends on task structure

The dependence of the Simon effect on the correspondence of the previous trial can be explained by the conflict-monitoring theory, which holds that a control system adjusts automatic activation from irrelevant stimulus information (conflict adaptation) on the basis of the congruency of the previous trial. The authors report on 4 experiments showing that conflict adaptation is mediated by task structure as well as previous congruency. Experiment 1 showed that for 2 completely segregated sets of stimulus-response pairs there was no conflict adaptation across sets. However, if the stimulus sets overlapped for 2 separate response sets, conflict adaptation could be observed across the response sets. Experiment 2 showed that this effect was not due to the use of stimulus-response sets lateralized to 1 hemisphere each. Experiment 3 showed that if response sets are common for 2 separate stimulus sets, then conflict adaptation can again be observed across sets. Finally, Experiment 4 showed local control effects in the absence of confounding feature-overlap effects. These results indicate that deployment of control as evidenced by conflict adaptation reflects task structure.     

Stimulus conflict predicts conflict adaptation in a numerical flanker task

Conflict monitoring theory states that response conflict triggers conflict adaptation, resulting in reduced congruency effects after response-incongruent trials (Botvinick, Braver, Barch, Carter, & Cohen, 2001). Verbruggen, Notebaert, Liefooghe, and Vandierendonck (2006) observed conflict adaptation after stimulus-incongruent trials without any response conflict. In this study, we further explore the hypothesis that stimulus conflict is an important trigger for conflict adaptation. We propose a measure for stimulus conflict that adequately explains the data of Verbruggen et al. and new data from a numerical flanker task. We conclude that stimulus conflict and response conflict have dissociable effects on behavior Whereas response conflict is a good predictor of response times, stimulus conflict is a better predictor of the adaptation effect.     

Effect of response task on taste adaptation

Two experiments studied whether subjects reported complete adaptation of a taste sensation. Three tasks were chosen based on their use in other laboratories: hand lowering to connote stimulus absence, magnitude estimation, and cross-adaptation of a brief stimulus following a prolonged stimulus. In the first experiment, different groups of 9 subjects received the three different tasks; in the second experiment, all 20 subjects received all three tasks. In both experiments, subjects failed to demonstrate complete taste adaptation in at least 50% of adaptation trials. Response task did affect the likelihood of observing complete taste adaptation.     

Interlimb differences in visuomotor and dynamic adaptation during targeted reaching in children

While a number of studies have focused on movement (a)symmetries between the arms in adults, less is known about movement asymmetries in typically developing children. The goal of this study was to examine interlimb differences in children when adapting to novel visuomotor and dynamic conditions while performing a center-out reaching task. We tested 13 right-handed children aged 9–11 years old. Prior to movement, one of eight targets arranged radially around the start position was randomly displayed. Movements were made either with the right (dominant) arm or the left (nondominant) arm. The children participated in two experiments separated by at least one week. In one experiment, subjects were exposed to a rotated visual display (30° about the start circle); and in the other, a 1 kg mass (attached eccentrically to the forearm axis). Each experiment consisted of three blocks: pre-exposure, exposure and post-exposure. Three measures of task performance were calculated from hand trajectory data: hand-path deviation from the straight target line, direction error at peak velocity and final position error. Results showed that during visuomotor adaptation, no interlimb differences were observed for any of the three measures. During dynamic adaptation, however, a significant difference between the arms was observed at the first cycle during dynamic adaptation. With regard to the aftereffects observed during the post-exposure block, direction error data indicate considerably large aftereffects for both arms during visuomotor adaptation; and there was a significant difference between the arms, resulting in substantially larger aftereffects for the right arm. Similarly, dynamic adaptation results also showed a significant difference between the arms; and post hoc analyses indicated that aftereffects were present only for the right arm. Collectively, these findings indicate that the dominant arm advantage for developing an internal model associated with a novel visuomotor or dynamic transform, as previously shown in young adults, may already be apparent at 9 to 11-year old children.     

Preparation time modulates pro-active control and enhances task conflict in task switching

Performance in the Stroop task reflects two conflicts—informational (between the incongruent word and ink color) and task (between relevant color naming and irrelevant word reading). Neuroimaging findings support the existence of task conflict in congruent trials. A behavioral indication for task conflict—Stroop reverse facilitation—was found in previous studies under low task-control conditions. Task switching also causes reduction in task control because the task set frequently changes. We hypothesized that it would be harder to efficiently manage task conflicts in switching situations and, specifically, as cue–target interval (CTI) decreases. This suggestion was examined in two experiments using a combined Stroop task-switching design. We found a large interference effect and reverse facilitation that decreased with elongation of CTI. Results imply that task switching reduces pro-active task control and thereby enhances the informational and the task conflicts. This calls for a revision of recent control models to include task conflict.