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.     

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.     

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.     

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.     

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.     

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).     

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.     

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.     

Representations underlying skill in the discrete sequence production task: effect of hand used and hand position

Various studies suggest that movement sequences are initially learned predominantly in effector-independent spatial coordinates and only after extended practice in effector-dependent coordinates. The present study examined this notion for the discrete sequence production (DSP) task by manipulating the hand used and the position of the hand relative to the body. During sequence learning in Experiment 1, in which sequences were executed by reacting to key-specific cues, hand position appeared important for execution with the practiced but not with the unpracticed hand. In Experiment 2 entire sequences were executed by reacting to one cue. This produced similar results as in Experiment 1. These experiments support the notion that robustness of sequencing skill is based on several codes, one being a representation that is both effector and position dependent.     

Nonword repetition in children and adults: effects on movement coordination

Hearing and repeating novel phonetic sequences, or novel nonwords, is a task that taps many levels of processing, including auditory decoding, phonological processing, working memory, speech motor planning and execution. Investigations of nonword repetition abilities have been framed within models of psycholinguistic processing, while the motor aspects, which also are critical for task performance, have been largely ignored. We focused our investigation on both the behavioral and speech motor performance characteristics of this task as performed in a learning paradigm by 9‐ and 10‐year‐old children and young adults. Behavioral (percent correct productions) and kinematic (movement duration, lip aperture variability – an index of the consistency of inter‐articulator coordination on repeated trials) measures were obtained in order to investigate the short‐term (Day 1, first five vs. next five trials) and longer‐term (Day 1 vs. Day 2, first five vs. next five trials) changes associated with practice within and between sessions. Overall, as expected, young adults showed higher levels of behavioral accuracy and greater levels of coordinative consistency than the children. Both groups, however, showed a learning effect, such that in general, later Day 1 trials and Day 2 trials were shorter in duration and more consistent in coordination patterns than Day 1 early trials. Phonemic complexity of the nonwords had a profound effect on both the behavioral and speech motor aspects of performance. The children showed marked learning effects on all nonwords that they could produce accurately, while adults’ performance improved only when challenged by the more complex nonword stimuli in the set. The findings point to a critical role for speech motor processes within models of nonword repetition and suggest that young adults, similar to children, show short‐ and longer‐term improvements in coordinative consistency with repeated production of complex nonwords. There is also a clear developmental change in nonword production performance, such that less complex novel sequences elicit changes in speech motor performance in children, but not in adults.     

The learning of two similar complex movement sequences: does practice insulate a sequence from interference?

Panzer et al. [Panzer, S., Wilde, H., & Shea, C. H. (2006). The learning of two similar complex movement sequences: Proactive and retroactive effects on learning. Journal of Motor Behavior, 38, 60-70] found evidence to indicate that the memory state(s) underpinning the production of a movement sequence that was practiced for one day was essentially "overwritten" when another similar sequence was subsequently practiced on the next day. An interference paradigm was used to determine if additional practice on the first sequence would insulate it from retroactive interference arising from learning a new similar sequence. Participants produced the sequences by moving a lever with their right arm/hand to sequentially presented target locations. The experimental group practiced one 16-element movement sequence (S1) for two consecutive days. A second 16-element sequence (S2) was practiced on Day 3. The sequence practiced on Day 3 was created by switching the positions of 2 of 16 elements in the sequence practiced on the first day. Control groups received either two days of practice on S1 or one day of practice on S2. Contrary to our earlier findings (Panzer, Wilde, & Shea, 2006) of strong retroactive interference when S1 was only practiced for one day, we found no evidence of retroactive interference when S1 was practiced for two days prior to the switch to S2 practice. Interestingly, but also contrary to our earlier findings, we found the learning of S2 was facilitated by the prior practice of S1. This proactive facilitation was observed in S2 acquisition and on the S2 retention test.     

Learning a keying sequence you never executed: Evidence for independent associative and motor chunk learning

A substantial amount of research has addressed how people learn and control movement sequences. Recent results suggested that practice with discrete key pressing sequences results in two types of sequence learning: associative learning and motor chunk development (Verwey & Abrahamse, 2012). In the present study, we addressed whether in keying sequences of limited length associative learning develops also when the use of the chunking mode is prevented by introducing during practice random deviants. In line with the notion of two different learning mechanisms, the present results indicate that associative sequence learning develops when motor chunks cannot be developed during practice. This confirms the notion that motor chunks do not rely on these associations. In addition, experience with a particular execution mode during the practice phase seems to benefit subsequent use of that mode with unfamiliar and random sequences. Also, participants with substantial video-gaming experience were faster in executing discrete keying sequences in the chunking mode. These last two results may point to the development of a general ability to produce movement sequences in the chunking mode.     

Hand preference, practice order, and spatial assimilations in rapid bimanual movement

When subjects make rapid bimanual aiming movements over different distances, spatial assimilations are shown; the shorter distance limb overshoots when paired with a longer distance limb. Recent research has also shown spatial assimilations to be greater in the nonpreferred left limb of right-handed subjects, but it is not known whether the increased spatial assimilations represent a handedness effect or one of hemispheric lateralization of motor control. To determine the nature of the asymmetric effect, left- (n = 32) and right- (n = 60) handed subjects part practiced, then whole practiced, short (20 degrees ) and long 60 degrees ) reversal movements. During whole practice, both groups showed spatial assimilations in the shorter distance limb, particularly when the left limb performed the short movement. This asymmetry was greatest for right-handed subjects, but left-handed subjects showed smaller, but systematic effects, providing moderate support for the hypothesis that the asymmetric effect is due to hemispheric lateralization of motor control. All interlimb differences in spatial accuracy for the short and long movements were eliminated with practice, however, suggesting the asymmetric effect was temporary as well. In addition, subjects who part practiced the long movement just prior to whole practice showed greater overshooting in the short distance limb compared with subjects who followed the other practice order throughout whole practice and the no-KR retention trials. Such findings suggest that the part-practice order of bimanual tasks can directionally bias whole-task performance.     

Prism Adaptation During Target Pointing From Visible and Nonvisible Starting Locations

The performance of subjects whose starting limb location was visible when pointing to a sagittal target during exposure to prismatic displacement showed immediate target acquisition, but aftereffects of exposure were absent. When starting limb location was not visible, accurate exposure performance was slow to develop, but aftereffects were substantial. Visible starting location evoked a zeroing-in control strategy on the basis of relative-location coding, which rapidly reduced performance error but disabled detection of spatial misalignment between sensorimotor systems. When starting location was not visible, absolute-location coding of the displaced target initiated movement that had to be corrected subsequently by visual feedback. In this case, comparison of the initial erroneous movement code with the limb location that achieved the target enabled misalignment detection and consequent realignment.     

The effects of sequence difficulty and practice on proportional and nonproportional transfer

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 two groups. One group practised a relatively easy 16-element movement sequence (easy long). The other group practised a more difficult 16-element movement sequence (difficult long). Approximately 24 hours after practice with their respective sequence both groups were administered a retention and two transfer tests. The only difference between the retention and transfer tests was the location of the targets. The short transfer target configuration was considered a proportional transfer because all the amplitudes between targets were reduced by the same proportion. The mixed transfer configuration was considered a nonproportional transfer because the targets did not have the same proportional distances between targets as the sequence they practised. The results indicated that participants could effectively transfer the difficult long sequence to the new target configurations regardless of whether the transfer required proportional and nonproportional spatial changes to the movement pattern. However, the easy long sequence was only effectively transferred in the proportional transfer condition. Experiment 2 assessed the effects of extended practice of the easy long sequence on proportional and nonproportional spatial transfer. The data indicated that participants could again effectively transfer the easy long sequence to proportional but not the nonproportional spatial transfer conditions regardless of the amount of practice (1 or 4 days). 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 and how this process interacts with the difficulty of the sequence.     

Object-location binding across a saccade: A retinotopic spatial congruency bias

Despite frequent eye movements that rapidly shift the locations of objects on our retinas, our visual system creates a stable perception of the world. To do this, it must convert eye-centered (retinotopic) input to world-centered (spatiotopic) percepts. Moreover, for successful behavior we must also incorporate information about object features/identities during this updating – a fundamental challenge that remains to be understood. Here we adapted a recent behavioral paradigm, the “spatial congruency bias,” to investigate object-location binding across an eye movement. In two initial baseline experiments, we showed that the spatial congruency bias was present for both gabor and face stimuli in addition to the object stimuli used in the original paradigm. Then, across three main experiments, we found the bias was preserved across an eye movement, but only in retinotopic coordinates: Subjects were more likely to perceive two stimuli as having the same features/identity when they were presented in the same retinotopic location. Strikingly, there was no evidence of location binding in the more ecologically relevant spatiotopic (world-centered) coordinates; the reference frame did not update to spatiotopic even at longer post-saccade delays, nor did it transition to spatiotopic with more complex stimuli (gabors, shapes, and faces all showed a retinotopic congruency bias). Our results suggest that object-location binding may be tied to retinotopic coordinates, and that it may need to be re-established following each eye movement rather than being automatically updated to spatiotopic coordinates.     

What determines the impact of context on sequential action?

In the current study we build on earlier observations that memory-based sequential action is better in the original learning context than in other contexts. We examined whether changes in the perceptual context have differential impact across distinct processing phases (preparation versus execution of a motor chunk) within an ongoing movement sequence. Participants were trained on two discrete keying sequences, each of which was systematically presented in its own unique color during a practice session with either limited or extended practice. In a subsequent test session, sequences were performed with the same, with reversed, and with completely novel sequence-specific colors. The results confirm context-dependence in sequential action, the relevance of practice for its development, and its selective expression for the preparation but not the execution of highly practiced motor chunks. As such, the current study provides novel insights into the determinants of context-dependent sequential action. We finish by outlining the overall status of context-dependence in sequential motor behavior, and specify a general working model.     

Determination of target distance in a structured environment: Selection of visual information for action

In the literature relating to visuo-motor control, controversial data are found concerning the consequence of enriching the visual scene in the specification of the target's spatial coordinates. In this paper four experiments were carried out to unravel this issue. Based on spatio-temporal analysis of pointing movements carried out in an open loop condition, the effect of appending contextual elements in the vicinity of a visual target was investigated, taking into account (1) their location in the visual field, (2) the extent of the movement, and (3) their presence during the planning and/or execution period of the movement. Taken as a whole, results showed that enriching the visual scene gave rise to a decrease of perceptual underestimation of distance (with no effect on the direction parameter), as otherwise observed (dark environment). Though not deeply affecting reaction and movement time, this effect held whatever the target position, provided that the contextual elements were situated between the initial and terminal position of the hand trajectory. The magnitude of the effect was, however, dependent upon the space conferred to the visual context. Furthermore, a higher spatial performance was observed when the latter was provided during the planning of execution period of the movement. Both effects combined when contextual elements were provided during the entire movement, which suggests a continuous updating of target coordinates during the whole motor performance. Altogether these findings underline a dynamic aspect of space perception, originating, in part, in the functional use of contextual cues in the coding of target distance. They also suggest that, provided the visual environment is structured, the retinal signal is widely used in the perception of target distance in visuo-manual tasks.     

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.