Simulated practice effects on the transfer and retention of gait sequences from the upper to the lower extremity.

This study investigated transfer of training from upper extremity limbs (the index fingers) to the lower extremity limbs (the legs) for performance of three gait sequences of different difficulty. Fifteen subjects participated in the study. Subjects in an iPad training group practiced by sequentially moving their left-and right-hand index fingers across tiles to each of three targets displayed on an iPad for 20 trials. Subjects in a gait training group practiced by sequentially walking across tiles to each of the 3 targets displayed on a screen for 20 trials. A no practice group did not receive practice trials. Immediately following practice of each level of difficulty, a transfer test (20 trials) was given for which subjects walked to the target just practiced. A retention test of 36 trials (12 trials at each difficulty level) was administered 20 min following performance of the last transfer test trial. The retention test showed that reaction times were shorter for the iPad training than gait training and no training groups; anticipatory postural adjustment times were equivalent for the iPad and gait training groups, but shorter than for the no training group; and movement times were shorter for the iPad training group than for the gait training and no training groups. These results suggest that iPad training (upper extremity) followed by performance of gait training (lower extremity) had greater benefits for learning (as measured by the delayed retention test) the gait sequences than practicing the actual gait sequences themselves.

Target position and avoidance margin effects on path planning in obstacle avoidance.

This study examined how people choose their path to a target, and the visual information they use for path planning. Participants avoided stepping outside an avoidance margin between a stationary obstacle and the edge of a walkway as they walked to a bookcase and picked up a target from different locations on a shelf. We provided an integrated explanation for path selection by combining avoidance margin, deviation angle, and distance to the obstacle. We found that the combination of right and left avoidance margins accounted for 26%, deviation angle accounted for 39%, and distance to the obstacle accounted for 35% of the variability in decisions about the direction taken to circumvent an obstacle on the way to a target. Gaze analysis findings showed that participants directed their gaze to minimize the uncertainty involved in successful task performance and that gaze sequence changed with obstacle location. In some cases, participants chose to circumvent the obstacle on a side for which the gaze time was shorter, and the path was longer than for the opposite side. Our results of a path selection judgment test showed that the threshold for participants abandoning their preferred side for circumventing the obstacle was a target location of 15 cm to the left of the bookcase shelf center.

Pupil diameter as a biomarker of effort in goal-directed gait.

Subjects' eye movement behavior related to cognitive effort during gait was measured as subjects walked to perform low and high cognitive load tasks. We found that all pupil diameter measures, fixation durations, and the proportion of blink duration changed significantly during gait as a function of task load. In contrast, the number of fixations, saccade durations and travel time did not change significantly as a function of task load. Findings showed that pupil diameter was the best predictor of task load during one's gait preceding the performance of the task. While other studies have demonstrated the importance of eye fixation characteristics during gait, our findings showed that eye measures related to pupil diameter were better at detecting cognitive load while walking to perform a task compared to eye fixation data. We also found that cognitive effort was not limited to just the performance of the task, but that it was also exerted during one's gait preceding the performance of the task. Therefore, the additional attention demand caused by an increase in task complexity may result in less attentional resources being available to adequately handle distractions (such as obstacle avoidance) while walking to perform the task. Consequently, this may increase the likelihood of falls in those individuals with lower attentional capacity.

Hierarchical goal effects on center of mass velocity and eye fixations during gait.

The purpose of this study was to determine the effect of hierarchical goal structure of a yet-to-be performed task on gait and eye fixation behavior while walking to the location of where the task was to be performed. Subjects performed different goal-directed tasks representing three hierarchical levels of planning. The first level of planning consisted of having the subject walk to a bookcase on which an object (a cup) was located in the middle of a shelf. The second level of planning consisted of walking to the bookcase and picking up the cup which was in the middle, on the right side, or on the left side of the bookcase shelf. The third level of planning consisted of walking to the bookcase, picking up the cup which was located in the middle of the bookcase shelf, and moving it to a higher shelf. Findings showed that hierarchal goals do affect center of mass velocity and eye fixation behavior. Center of mass velocity to the bookcase increased with an increase in the number of goals. Subjects decreased gait velocity as they approached the bookcase and adjusted their last steps to accommodate picking up the cup. The findings also demonstrated the important role of vision in controlling gait velocity in goal-directed tasks. Eye fixation duration was more important than the number of eye fixations in controlling gait velocity. Thus, the amount of information gained through object fixation duration is of greater importance than the number of fixations on the object for effective goal achievement.

Aging effect on step adjustments and stability control in visually perturbed gait initiation.

Gait adaptability is essential for fall avoidance during locomotion. It requires the ability to rapidly inhibit original motor planning, select and execute alternative motor commands, while also maintaining the stability of locomotion. This study investigated the aging effect on gait adaptability and dynamic stability control during a visually perturbed gait initiation task. A novel approach was used such that the anticipatory postural adjustment (APA) during gait initiation were used to trigger the unpredictable relocation of a foot-size stepping target. Participants (10 young adults and 10 older adults) completed visually perturbed gait initiation in three adjustment timing conditions (early, intermediate, late; all extracted from the stereotypical APA pattern) and two adjustment direction conditions (medial, lateral). Stepping accuracy, foot rotation at landing, and Margin of Dynamic Stability (MDS) were analyzed and compared across test conditions and groups using a linear mixed model. Stepping accuracy decreased as a function of adjustment timing as well as stepping direction, with older subjects exhibited a significantly greater undershoot in foot placement to late lateral stepping. Late adjustment also elicited a reaching-like movement (i.e. foot rotation prior to landing in order to step on the target), regardless of stepping direction. MDS measures in the medial-lateral and anterior-posterior direction revealed both young and older adults exhibited reduced stability in the adjustment step and subsequent steps. However, young adults returned to stable gait faster than older adults. These findings could be useful for future study of screening deficits in gait adaptability and preventing falls.

Steps to Health in Cognitive Aging: Effects of Physical Activity on Spatial Attention and Executive Control in the Elderly.

The purpose of this study was to investigate whether physical activity (PA) habits may positively impact performance of the orienting and executive control networks in community-dwelling aging individuals and diabetics, who are at risk of cognitive dysfunction. To this aim, we tested cross-sectionally whether age, ranging from late middle-age to old adulthood, and PA level independently or interactively predict different facets of the attentional performance. Hundred and thirty female and male individuals and 22 adults with type 2 diabetes aged 55-84 years were recruited and their daily PA (steps) was objectively measured by means of armband monitors. Participants performed a multifunctional attentional go/no-go reaction time (RT) task in which spatial attention was cued by means of informative direct cues of different sizes followed by compound stimuli with local and global target features. The performance efficiency of the orienting networks was estimated by computing RT differences between validly and invalidly cued trials, that of the executive control networks by computing local switch costs that are RT differences between switch and non-switch trials in mixed blocks of global and local target trials. In regression analyses performed on the data of non-diabetic elderlies, overall RTs and orienting effects resulted jointly predicted by age and steps. Age predicted overall RTs in low-active individuals, but orienting effects and response errors in high-active individuals. Switch costs were predicted by age only, with larger costs at older age. In the analysis conducted with the 22 diabetics and 22 matched non-diabetic elderlies, diabetic status and daily steps predicted longer and shorter RTs, respectively. Results suggest that high PA levels exert beneficial, but differentiated effects on processing speed and attentional networks performance in aging individuals that partially counteract the detrimental effects of advancing age and diabetic status. In conclusion, adequate levels of overall PA may positively impinge on brain efficiency and attentional control and should be therefore promoted by actions that support lifelong PA participation and impact the built environment to render it more conducive to PA.

Probing attention prioritization during dual-task step initiation: a novel method.

The present study investigated the attention allocation during reactive stepping using a continuous finger-tapping task. Ten healthy young subjects were recruited to participate in this study. Subjects were required to perform a rapid voluntary step with either left or right leg after hearing an auditory tone while tapping their right index finger on a handhold numeric keypad. Step initiation conditions included simple and choice reaction forward stepping with three variants of continuous tapping task that were: (1) single task--no concurrent finger-tapping task; (2) dual task easy--one-button tapping task; (3) dual task hard--four-button tapping task. Types of anticipatory postural adjustment (APA) were determined by the center of pressure trajectory. Reaction time, APA duration, and stepping latency were compared between APA types and various dual-task conditions. Wavelet analysis was performed on the stimulus-locked finger-tapping data to determine the frequency change of tapping speed related to reactive stepping. Results showed that postural performance was negatively affected only by the high-attention-demanding cognitive task. Significant reduction of finger-tapping speed post-stimulus presentation was observed across all test conditions, indicating attention shift during the execution of a step. In addition, the DTH condition induced early postural prioritization in choice reaction stepping when different motor programs needed to be planned and executed. Error APA also triggered larger deterioration of tapping performance compared to correct APA, indicating the perceived error and the remedial action require additional attentional resources.

MOTOR IMAGERY, PHYSICAL PRACTICE, AND MEMORY: THE EFFECTS ON PERFORMANCE AND WORKLOAD.

-The theoretical explanations used to explain changes in performance during motor imagery and physical practice conditions are inconsistent when memory retrieval is and is not required. This study measured performance time and workload during acquisition, a retention test requiring memory retrieval, and a retention test not requiring memory retrieval using a key-pressing task. The participants were assigned to physical practice with or without instructions to learn or motor imagery with or without instructions to learn. A diagram of the keys was presented during the practice trials and the first retention test, but was not presented during the second test. The results revealed no effect for the learning instructions or performance changes during the practice phases. However, during both retention tests participants in the physical practice conditions performed significantly faster than those in the motor imagery conditions. Also, higher levels of workload were reported for the motor imagery conditions when the retention test required memory retrieval compared to the other phases. A discussion of the implications of workload on performance is presented with respect to varying practice conditions.

The posterior shift anticipatory postural adjustment in choice reaction step initiation.

The ability to step quickly in response to a perturbation has been shown to be critical for prevention of falls. The cognitive processing, weight shifting, and locomotion must be well timed to execute a successful step. The purpose of this study was to compare the response preparation and response execution processes between a simple (SRST) and a choice reaction stepping task (CRST). Nine healthy young subjects were recruited to participate in this study. Subjects were required to stand on a forceplate and maintain their balance, and step forward on a second forceplate with either the left or right foot after hearing an auditory tone. The center of pressure (COP) was analyzed to determine the types of anticipatory postural adjustment (APA) prior to a step. The APA phase and stepping phase timing was calculated based on the COP trajectory. Findings showed that reaction time (RT), APA phase and overall stepping latency were slower for CRST than for SRST. We also identified an intermediate type of APA response (posterior shift APA) in addition to the correct and error APA response, and found the posterior shift APA response had the fastest execution time for CRST, and may be beneficial for falls prevention.

Effects of mental practice in novice learners in a serial positioning skill acquisition.

The effects of mental practice in novices were investigated. University students (N = 60) performed a serial aiming task, distributed in 5 groups of 12: mental practice, physical practice, mental-physical practice (first mental then physical practice), physical-mental practice (first physical then mental practice), and a control group that only performed the tests. Participants transported three tennis balls among six containers in a pre-established sequence in a target time. In the acquisition phase and retention test (24 hr. later), the task was the same; in the transfer test, 5 min. after the acquisition phase, sequence and time changed. Six trials were performed in the acquisition phase, and each test consisted of 9 trials. The performance measures were absolute error, constant error, and variable error; a t test and a two-way ANOVA were used to compare the acquisition phase and tests, respectively. Physical practice and both groups of combined conditions presented better performance in tests than the mental practice and control groups. Mental practice without motor experience in the task did not improve motor learning. Prior physical performance is desirable before conducting mental practice.

A two process memory-based account for mental and physical practice differences.

The authors investigated the underlying processing structures for mental and physical practice. Participants mentally or physically performed 4 tasks during practice. Halfway through practice, 2 tasks were switched from mental to physical practice, or vice versa. After completing practice trials, participants performed 2 retention tests. The first retention test required memory retrieval and the second retention test reinstated the practice context and did not require memory retrieval. Measures of response initiation and execution showed discrepant findings suggesting that different processing structures underlie response initiation and execution during mental and physical practice. Findings for the switch conditions supported this interpretation suggesting that different neural structures may facilitate processing related to mental and physical practice.

Effects of auditory feedback on movement time in a Fitts task.

The purpose of the present experiment was to investigate the role of auditory feedback and its impact on movement time in a standard Fitts task. Feedback was given at the moment of target acquisition. A 2-way analysis of variance found significant differences between feedback groups at all three indexes of difficulty (F(2, 40) = 156.02, p < .001). Results from a mixed-model multivariate analysis of variance for kinematic factors show significant differences in peak velocity and the location of peak velocity when comparing feedback groups. In general, the addition of auditory feedback decreased the task ID by .5.

Repeated retention testing effects do not generalize to a contextual interference protocol.

Three experiments examined repeated retention testing effects in a contextual interference (CI) protocol. Retention was assessed at 10 min and 24 hr following acquisition or at just 24-hr for the one-test conditions. Experiments 1 and 2 used speeded-response key-pressing tasks. Dependent measures were total time and errors. Experiment 3 used sequential-timing tasks. Dependent measures were absolute error and absolute constant error Results revealed CI effects in each experiment. Repeated retention testing effects were not found in Experiments 1 and 3. Experiment 2 revealed superior performance by the two-test condition compared to the one-test condition. This result was qualified by possible practice effects during the 10-min test. It was concluded that repeated retention testing does not present problems for most studies of CI.

The effects of a single reminder trial on retention of a motor skill.

Two experiments investigated the effects of a single reminder trial on immediate and delayed retention. Experiment 1 determined if beneficial effects of a reminder trial were a function of task order immediate retention performance benefited only when the reminder trial was practiced in the first block of trials. Experiment 2 added a 24-hr delayed retention test to examine the long-term benefits of a reminder trial. Retention performance was enhanced over both delay intervals. The long-term effect extended previous research (Shea & Titzer, 1993) that documented effects after 10 min. The use of a single reminder trial established that intertask comparisons between multiple reminder trials were not a precondition for the reminder trial effect as postulated by Shea and Titzer.

Effects of repeated retention tests on learning a single timing task.

The purpose of the present study was to investigate the possibility that administering an initial retention test would influence any subsequent retention tests administered to the same participants. Participants performed 40 practice trials of a four-segment key-pressing task with a movement time goal of 925 ms. Participants were then administered either two retention tests (Day 1-Day 1 group, 10 min and 20 min after practice; Day 1-Day 2 group, 10 min and 24 hr after practice; Day 2-Day 2 group, 23 hr 50 min and 24 hr after practice) or one retention test (Day 1-Control group, 20 min after practice; Day 2-Control group, 24 hr after practice). The first test had a deleterious effect on performing the second test for the Day 2-Day 2 group, which would be expected if the task representation was updated and re-encoded at the time of recall using diminished information. This finding suggests that researchers should be cautious about using repeated retention tests that are administered 1 day after practice. In addition, teachers and coaches should consider administering a test under gamelike conditions following practice of a new technique. Otherwise, performance of the new technique may be degraded or perturbed at the time of later performances.

Differential transfer benefits of increased practice for constant, blocked, and serial practice schedules.

The effects of practice schedule and amount of practice on the development of the generalized motor program (GMP) and on parameter estimation were investigated. Participants (N = 108) practiced the same relative timing but different absolute durations of a multisegment timing task. Practice schedules (constant, blocked, or serial) were crossed with amounts of practice (low and high). Inclusion of a constant practice condition allowed the authors to investigate the variability of practice prediction. Participants practiced the same proportional durations in a serial or a blocked schedule, which enabled the authors to examine contextual interference. A constant practice schedule enhanced GMP performance when task parameters remained the same, but varied practice schedules were beneficial when task parameters changed. A serial as opposed to a blocked practice schedule was superior when the performance of a task governed by a different GMP was required. Increased practice led to a consolidated task representation that was unavailable for updating.