Observation and physical practice: Coding of simple motor sequences

An experiment was conducted to determine the coordinate system used in the development of movement codes during observation and utilized on later physical practice performance of a simple spatial–temporal movement sequence. The task was to reproduce a 1.3-s spatial–temporal pattern of elbow flexions and extensions. An intermanual transfer paradigm with a retention test and two transfer tests was used: a mirror transfer test where the same pattern of muscle activation and limb joint angles was required and a nonmirror transfer test where the visual–spatial pattern of the sequence was reinstated on the transfer test. The results indicated a strong advantage for participants in the physical practice condition when transferred to the mirror condition in which the motor coordinates (e.g., pattern of muscle activation and joint angles) were reinstated relative to transfer performance when the visual–spatial coordinates were reinstated (visual and spatial location of the target waveform). The observation group, however, demonstrated an advantage when the visual–spatial coordinates were reinstated. These results demonstrate that codes based in motor coordinates can be developed relatively quickly for simple rapid movement sequences when participants are provided physical practice, but observational practice limits the system to the development of codes based in visual–spatial coordinates. Performances of control participants, who were not permitted to practise or observe the task, were quite poor on all tests.     

Scheduling observational and physical practice: influence on the coding of simple motor sequences

The main purpose of the present experiment was to determine the coordinate system used in the development of movement codes when observational and physical practice are scheduled across practice sessions. The task was to reproduce a 1,300-ms spatial-temporal pattern of elbow flexions and extensions. An intermanual transfer paradigm with a retention test and two effector (contralateral limb) transfer tests was used. The mirror effector transfer test required the same pattern of homologous muscle activation and sequence of limb joint angles as that performed or observed during practice, and the non-mirror effector transfer test required the same spatial pattern movements as that performed or observed. The test results following the first acquisition session replicated the findings of Gruetzmacher, Panzer, Blandin, and Shea (2011) . The results following the second acquisition session indicated a strong advantage for participants who received physical practice in both practice sessions or received observational practice followed by physical practice. This advantage was found on both the retention and the mirror transfer tests compared to the non-mirror transfer test. These results demonstrate that codes based in motor coordinates can be developed relatively quickly and effectively for a simple spatial-temporal movement sequence when participants are provided with physical practice or observation followed by physical practice, but physical practice followed by observational practice or observational practice alone limits the development of codes based in motor coordinates.     

Coding of on-line and pre-planned movement sequences

Recent experiments have demonstrated that complex multi-element movement sequences were coded in visual-spatial coordinates even after extensive practice, while relatively simple spatial-temporal movement sequences are coded in motor coordinates after a single practice session. The purpose of the present experiment was to determine if the control process rather than the difficulty of the sequence played a role in determining the pattern of effector transfer. To accomplish this, different concurrent feedback conditions were provided to two groups of participants during practice of the same movement sequence. The results indicated that when concurrent visual feedback was provided during the production of the movement, which was thought to encourage on-line control, the participants performed transfer tests with the contra-lateral limb better when the visual-spatial coordinates were reinstated than when the motor coordinates were reinstated. When concurrent visual feedback was not provided, which was thought to encourage pre-planned control, the opposite was observed. The data are consistent with the hypothesis that the mode of control dictates the coordinate system used to code the movement sequence rather than sequence difficulty or stage of practice as has been proposed.     

Inter-manual transfer and practice: Coding of simple motor sequences

Previous research suggests that movements are represented early in practice in visual-spatial coordinates/codes, which are effector independent, and later in practice in motor coordinates/codes (e.g., joint angles, activation patterns), which are effector dependent. In the present experiments, the task was to reproduce 1.3 s patterns of elbow flexions and extensions. An inter-manual transfer paradigm was used in Experiment 1 and an inter-manual practice paradigm was used in Experiment 2. The present results clearly indicated a strong advantage of effector transfer when the motor coordinates available during acquisition were reinstated (Experiment 1) and demonstrate that inter-manual practice with the same motor coordinates results in enhanced retention performance relative to transfer and practice where the same visual-spatial coordinates are used. These results demonstrate that the more effective movement code (motor or visual-spatial) is dependent on the movement sequence characteristics (e.g., difficulty, number of elements, and mode of control [preplanned or on-line]). These results are also interesting because they indicate, contrary to previous findings with more complex movement sequences, that an effective motor code can be developed relatively early in practice for rapid movement sequences.     

Age-related effects in interlimb practice on coding complex movement sequences

Hikosaka et al. (1999) proposed that sequential movements are acquired in independent visual-spatial and motor coordinate systems with coding initially represented in visual-spatial coordinates, and later after extended practice in motor coordinates. One aspect of sequence learning that has not been systematically studied, however, is the question of whether or not older adults show the same pattern of coding in inter-limb practice as younger learners. In the present experiment an inter-limb practice paradigm was designed to determine the role that visual-spatial (Cartesian) and motor (joint angles, activation patterns) coordinates play in the coding and learning of a complex movement sequence. Younger and older adults practiced a 16-element movement sequence with one limb on Day 1 and the contra-lateral limb on Day 2. Practice involved the same sequence with either the same visual-spatial or motor coordinates on the two days. Retention tests were conducted on Day 3. Results indicated that keeping the visual-spatial coordinates the same during acquisition resulted in superior retention only for younger adults. Results also indicated the overall slowing of sequential movement production for older adults which appears to result from these participants inability to impose a structure on the sequence. This provides strong evidence that the visual-spatial code plays a dominant role in complex movement sequences and this code is represented in an effector-independent manner for younger adults, but not for older adults.     

Representation of movement sequences is related to task characteristics

Recent experiments have produced mixed results in terms of performance when, after learning a sequential task, the same visual-spatial coordinates or the same motor coordinates were reinstated on a subsequent effector transfer test. Given the diversity of tasks and especially sequence characteristics used in previous experiments, the cross-experimental comparison makes inferences and unambiguous interpretations difficult. The purpose of the present experiment was to determine in a principled manner how the spatio-temporal structure of a sequence influences the way the sequence is represented. The results indicated that after limited amount of practice relatively more simple sequences (S1) are coded more efficiently in a mirror (motor) representation which requires the same pattern of homologous muscle activation. Conversely, relatively more complex sequences (S2) are more efficiently coded in a visual-spatial coordinate system which requires movements to the same spatial locations as during acquisition. The data are also consistent with the notion that sequences with different spatio-temporal structures rely to a different degree on distinct control mechanisms (pre-planned vs. on-line, respectively).     

Scheduling observational and physical practice: Influence on the coding of simple motor sequences

The main purpose of the present experiment was to determine the coordinate system used in the development of movement codes when observational and physical practice are scheduled across practice sessions. The task was to reproduce a 1,300-ms spatial–temporal pattern of elbow flexions and extensions. An intermanual transfer paradigm with a retention test and two effector (contralateral limb) transfer tests was used. The mirror effector transfer test required the same pattern of homologous muscle activation and sequence of limb joint angles as that performed or observed during practice, and the nonmirror effector transfer test required the same spatial pattern movements as that performed or observed. The test results following the first acquisition session replicated the findings of Gruetzmacher, Panzer, Blandin, and Shea (2011) Gruetzmacher, N., Panzer, S., Blandin, Y. and Shea, C. H. 2011. Observation and coding of simple motor sequences. Quarterly Journal of Experimental Psychology, 64: 1111–1123. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. The results following the second acquisition session indicated a strong advantage for participants who received physical practice in both practice sessions or received observational practice followed by physical practice. This advantage was found on both the retention and the mirror transfer tests compared to the nonmirror transfer test. These results demonstrate that codes based in motor coordinates can be developed relatively quickly and effectively for a simple spatial–temporal movement sequence when participants are provided with physical practice or observation followed by physical practice, but physical practice followed by observational practice or observational practice alone limits the development of codes based in motor coordinates.     

The impact of concurrent visual feedback on coding of on-line and pre-planned movement sequences

The purpose of this study was to determine the extent to which participants could effectively switch from on-line (OL) to pre-planned (PP) control (or vice versa) depending on previous practice conditions and whether concurrent visual feedback was available during transfer testing. The task was to reproduce a 2000 ms spatial–temporal pattern of a sequence of elbow flexions and extensions. Participants were randomly assigned to one of two practice conditions termed OL or PP. In the OL condition the criterion waveform and the cursor were provided during movement production while this information was withheld during movement production for the PP condition. A retention test and two effector transfer tests were administered to half of the participants in each acquisition conditions under OL conditions and the other half under PP conditions. The mirror effector transfer test required the same pattern of muscle activation and limb joint angles as required during acquisition. The non-mirror transfer test required movements to the same visual–spatial locations as experienced during acquisition. The results indicated that when visual information was available during the transfer tests performers could switch from PP to OL. When visual information was withdrawn, they shifted from the OL to the PP-control mode. This finding suggests that performers adopt a mode of control consistent with the feedback conditions provided during testing.     

Role of action observation and action in sequence learning and coding

A complex sequence learning task was used to determine if the type of coding acquired through physical practice (PP), observation of the stimulus (Obs-S), or observation of stimulus and action (Obs-SA) differs between conditions and whether the type of observation influences subsequent learning of the task when physical practice was permitted. Participants in the Obs-S group were permitted to watch the sequentially illuminated stimuli on the screen. In the Obs-SA group participants could see both flexion-extension movements of the model's arm performing the sequence and the sequentially illuminated stimuli on the screen. Participants in the PP group actually performed the 16-element sequence with their dominant right arm. Delayed retention tests and two inter-manual transfer tests were completed following each of two acquisition sessions. First, the data indicated that learning the sequence structure, as revealed by response time per element, occurred similarly irrespective of the initial practice condition. Secondly, the movement sequence appeared to be coded in abstract visual-spatial coordinates resulting in effector-independent performance. Finally, observing the model's action and sequential stimuli allows participants to transfer the perceived aspects of the movement sequence into efficient coordination patterns when additional physical practice is permitted.     

Observing different model types interspersed with physical practice has no effect on consolidation or motor learning of an elbow flexion–extension task

We compared varied model types and their potential differential effects on learning outcomes and consolidation processes when observational practice was interspersed with physical practice. Participants (N = 75) were randomly assigned to one of five groups: (1) unskilled model observation, (2) skilled model observation, (3) mixed-model observation, (4) physical practice only, and (5) no observational or physical practice (control). All were tasked with learning a waveform-matching task. With exception of the control group not involved in acquisition sessions, participants were involved in one pre-test, two acquisition sessions, four retention tests (immediate-post acquisition 1, 24hr post acquisition 1, immediate-post acquisition 2, and approximate 7-day retention), as well as an approximate 7-day transfer test. No differences were demonstrated in consolidation processes or learning outcomes as all groups showed the same pattern of retention and transfer data. Our conclusion is that motor memory processes were not impacted differentially when different models types were used in observational practice that was intermixed with physical practice for the learning of a movement pattern with low task difficulty, and thus similar learning outcomes emerged for all groups.     

Effects of interlimb practice on coding and learning of movement sequences

An interlimb practice paradigm was designed to determine the role that visual–spatial (Cartesian) and motor (joint angles, activation patterns) coordinates play in the coding and learning of complex movement sequences. Participants practised a 16-element movement sequence by moving a lever to sequentially presented targets with one limb on Day 1 and the contralateral limb on Day 2. Practice involved the same sequence with either the same visual–spatial or motor coordinates on the two days. A unilateral practice condition (control) was also tested where both coordinate systems were changed but the same limb was used. Retention tests were conducted on Day 3. Regardless of the order in which the limbs were used during practice, results indicated that keeping the visual–spatial coordinates the same during acquisition resulted in superior retention. This provides strong evidence that the visual–spatial code plays a dominant role in complex movement sequences, and this code is represented in an effector-independent manner.     

Retrieval practice in motor learning

In this study we sought to determine whether testing promotes the generalization of motor skills during the process of encoding and/or consolidation. We used a dynamic arm movement task that required participants to reproduce a spatial-temporal pattern of elbow extensions and flexions with their dominant right arm. Generalization of motor learning was tested by the ability to transfer the original pattern (extrinsic transformation) or the mirrored pattern (intrinsic transformation) to the unpractised left arm. To investigate the testing effects during both encoding and consolidation processing, participants were administered an initial testing session during early practice before being evaluated on a post-practice testing session administered either 10 min (Testing-Encoding group) or 24 hr apart (Testing-Consolidation group), respectively. Control groups were required to perform a post-practice testing session administered after either a 10-min (Control-Encoding group) or 24-hr delay (Control-Consolidation group). The findings revealed that testing produced rapid, within-practice skill improvements, yielding better effector transfer at the 10-min testing for the Testing-Encoding group on both extrinsic and intrinsic transformation tests when compared with the Control-Encoding group. Furthermore, we found better performance for the Testing-Consolidation group at the 24-hr testing for extrinsic and intrinsic transformations of the movement pattern when compared with the Control-Consolidation group. However, our results did not indicate any significant testing advantage on the latent, between-session development of the motor skill representation (i.e., from the 10-min to the 24-hr testing). The testing benefits expressed at the 10-min testing were stabilised but did not extend during the period of consolidation. This indicates that testing contributes to the generalisation of motor skills during encoding but not consolidation.     

Generalization of action knowledge following observational learning

Both observational and physical practices support the acquisition of motor skill knowledge in the form of spatiotemporal coordination patterns. The current experiment examined the extent that observation and physical practice can support the transfer of spatiotemporal knowledge and amplitude knowledge associated with motor skills. Evidence from a multijoint limb task revealed that knowledge about spatiotemporal patterns (relative phase) acquired by observers and models can be generalized exceptionally well within the trained arm (right) and across to the untrained arm (left). Transfer of relative phase occurred even when untrained combinations of joint amplitudes were required. This indicates that observation and physical practice both lead to the development of an effector-independent representation of the spatiotemporal knowledge in this task. Both observers and models showed some transfer of the relative amplitude knowledge, with observers demonstrating superior transfer for both a trained and untrained-arm transfer test, while the models were limited to positive transfer on an untrained-arm transfer test. The representation of movement amplitude knowledge is effector-independent in this task, but the use of that knowledge is constrained by the specific practice context and the linkage between the elbow and wrist.     

Motor imagery effectiveness for mirror reversed movements

Physical practice is known to enhance motor adaptation skills, which refer to the individual ability to compensate for environmental changes. So far, it is still unknown whether a similar effect can be observed following motor imagery (MI). Thirty-nine participants were tested during a joystick tracking task under both normal and mirror conditions (i.e., the inductive direction of the joystick was reversed), before and after a physical practice or MI training phase. Eye movements and electromyographic activity were recorded during MI. Motor performance was also evaluated after a 6 h interval during daytime. As compared to the control group, the results revealed that both MI and physical practice improved motor performance in the mirror condition, during the post-training test. Furthermore, the time to complete the task was further reduced after 6 hours, both in the normal and mirror conditions. These results demonstrate the effectiveness of MI for learning mirror-reversed movements, and for the consolidation process that follows motor adaptation.     

Proportional and nonproportional transfer of movement sequences

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included 2 groups. One group practised a pattern in which targets were located at 20, 40, 60, and 80° from the start position (long sequence). The other group practised a pattern with targets at 20, 26.67, 60, and 80° (mixed sequence). Both groups were tested 24 hours later on the long, mixed, and short sequence. The short sequence was considered a proportional transfer for the long acquisition group because all the amplitudes between targets were reduced by the same proportion. Nonproportional transfer occurred when the amplitudes between targets did not have the same proportions as those for their practice sequence (e.g., long sequence to mixed sequence or vice versa). The results indicated that participants could effectively transfer to new target configurations regardless of whether the transfer required proportional or nonproportional spatial changes to the movement pattern. Experiment 2 assessed the effects of extended practice on proportional and nonproportional spatial transfer. The data indicated that while participants can effectively transfer to both proportional and nonproportional spatial transfer conditions after 1 day of practice, they are only effective at transferring to proportional transfer conditions after 4 days of practice. The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production.     

Proportional and nonproportional transfer of movement sequences

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included 2 groups. One group practised a pattern in which targets were located at 20, 40, 60, and 80° from the start position (long sequence). The other group practised a pattern with targets at 20, 26.67, 60, and 80° (mixed sequence). Both groups were tested 24 hours later on the long, mixed, and short sequence. The short sequence was considered a proportional transfer for the long acquisition group because all the amplitudes between targets were reduced by the same proportion. Nonproportional transfer occurred when the amplitudes between targets did not have the same proportions as those for their practice sequence (e.g., long sequence to mixed sequence or vice versa). The results indicated that participants could effectively transfer to new target configurations regardless of whether the transfer required proportional or nonproportional spatial changes to the movement pattern. Experiment 2 assessed the effects of extended practice on proportional and nonproportional spatial transfer. The data indicated that while participants can effectively transfer to both proportional and nonproportional spatial transfer conditions after 1 day of practice, they are only effective at transferring to proportional transfer conditions after 4 days of practice. The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production.     

Sex differences in visual-spatial working memory: A meta-analysis

Visual-spatial working memory measures are widely used in clinical and experimental settings. Furthermore, it has been argued that the male advantage in spatial abilities can be explained by a sex difference in visual-spatial working memory. Therefore, sex differences in visual-spatial working memory have important implication for research, theory, and practice, but they have yet to be quantified. The present meta-analysis quantified the magnitude of sex differences in visual-spatial working memory and examined variables that might moderate them. The analysis used a set of 180 effect sizes from healthy males and females drawn from 98 samples ranging in mean age from 3 to 86 years. Multilevel meta-analysis was used on the overall data set to account for non-independent effect sizes. The data also were analyzed in separate task subgroups by means of multilevel and mixed-effects models. Results showed a small but significant male advantage (mean d = 0.155, 95 % confidence interval = 0.087-0.223). All the tasks produced a male advantage, except for memory for location, where a female advantage emerged. Age of the participants was a significant moderator, indicating that sex differences in visual-spatial working memory appeared first in the 13-17 years age group. Removing memory for location tasks from the sample affected the pattern of significant moderators. The present results indicate a male advantage in visual-spatial working memory, although age and specific task modulate the magnitude and direction of the effects. Implications for clinical applications, cognitive model building, and experimental research are discussed.     

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.     

Motor priming by movement observation with contralateral concurrent action execution

In the present study, the influence of simultaneous action execution on motor priming was investigated during movement observation using a simple-reaction task. Although previous studies have reported various effects of priming on motor performance, it has not yet been clarified how an additional source conveying kinetic information would modulate the priming effects. In the experiment, participants were asked to respond to an auditory cue by flexing their wrist while observing a line movement, which was slowly swinging like an inverted pendulum. In addition to the observation of line movement, the participants executed wrist flexion-extension actions synchronizing with line movement. The hand involved in pre-response wrist action varied with the priming condition: no movement execution (observation only), contralateral hand, and ipsilateral hand. In the contralateral condition, the stimulus-response congruency of movement direction was conflicted depending on the frame of reference (visual vs. anatomical coordinates). We found that all three priming conditions produced the compatibility effect, and the effect size did not differ between them. Importantly, in the contralateral condition, participants responded faster when the direction of line movement was congruent with the response movement in the anatomical coordinates. That is, the reaction time was shorter when pre-response action execution was in the flexion phase, even though the direction of observed movement and the response action were incongruent from the participants’ view. These results suggest that kinetic information has a great contribution to the motor priming system, which can reverse the vision-based compatibility effect.     

Does hand dominance affect the use of motor abundance when reaching to uncertain targets?

This study investigated hemispheric differences in utilizing motor abundance to achieve flexible patterns of joint coordination when reaching to uncertain target locations. Right-handed participants reached with each arm to the same central target when its final location was certain or when there was a 66% probability that its location could change after movement initiation. Use of greater motor abundance was observed when participants reached to the central target under target location uncertainty regardless of the arm used to reach. Joint variance associated with variability of movement direction was larger when reaching with the left, non-dominant arm. This arm also exhibited higher hand path variability compared to the dominant arm. These arm differences were not found when the final (central) target location was known in advance. The results provide preliminary evidence for a greater ability of the dominant (right) arm/left hemisphere to decouple directions in joint space. That is, to increase the use of motor abundance without simultaneously inducing unwanted hand path variability requires that joint variations be restricted to a limited subspace of joint space. Hemispheric differences in motor planning did not appear to account for arm differences related to the use of motor abundance.