Explicit and implicit motor sequence learning in children and adults; the role of age and visual working memory

Online Anticipatory Cues During Practice Disrupt Intentional and Incidental Sequence Learning

In the Serial Reaction Time Task, participants respond to several stimuli usually being unaware that the stimuli follow a predefined sequence while still learning the sequence. In the present study, we aimed to clearly separate explicit intentional learning from implicit incidental learning by either informing participants about all details of the sequence or not informing participants about the existence of the sequence. Further, we explored the influence of anticipatory cues during practice while anticipatory cues were either presented (extrinsically triggered anticipation) or not presented (self-reliant intrinsic anticipation). Participants were tested before and after practice in the Practice Sequence and a Control Sequence. To test automatization, tests were performed in Single-Task and Dual-Task Blocks. Results showed that after learning with explicit instructions, participants memorized the sequence more deeply and executed the sequence faster than after learning without explicit instructions. Further, by learning with anticipatory cues, participants memorized the sequence less deeply and executed the sequence slower than by learning without anticipatory cues. Unexpectedly, automatization was sequence-unspecific and independent of the practice conditions. In conclusion, detailed explicit prior information about the sequence facilitates sequence learning while anticipatory online cues during practice hamper sequence learning.

Children exhibit a developmental advantage in the offline processing of a learned motor sequence

Changes in specific behaviors across the lifespan are frequently reported as an inverted-U trajectory. That is, young adults exhibit optimal performance, children are conceptualized as developing systems progressing towards this ideal state, and older adulthood is characterized by performance decrements. However, not all behaviors follow this trajectory, as there are instances in which children outperform young adults. Here, we acquired data from 7-35 and >55 year-old participants and assessed potential developmental advantages in motor sequence learning and memory consolidation. Results revealed no credible evidence for differences in initial learning dynamics among age groups, but 7- to 12-year-old children exhibited smaller sequence-specific learning relative to adolescents, young adults and older adults. Interestingly, children demonstrated the greatest performance gains across the 5 h and 24 h offline periods, reflecting enhanced motor memory consolidation. These results suggest that children exhibit an advantage in the offline processing of recently learned motor sequences.

Short-Term Modulation of Online Monocular Visuomotor Function

Previous literature suggests that correcting ongoing movements is more effective when using the dominant limb and seeing with the dominant eye. Specifically, individuals are more effective at adjusting their movement to account for an imperceptibly perturbed or changed target location (i.e., online movement correction), when vision is available to the dominant eye. However, less is known if visual-motor functions based on monocular information can undergo short-term neuroplastic changes after a bout of practice, to improve online correction processes. Participants (n = 12) performed pointing movements monocularly and their ability to correct their movement towards an imperceptibly displaced target was assessed. On the first day, the eye associated with smaller correction amplitudes was exclusively trained during acquisition. While correction amplitude was assessed again with both eyes monocularly, only the eye with smaller correction amplitudes in the pre-test showed significant improvement in delayed retention. These results indicate that monocular visuomotor pathways can undergo short-term neuroplastic changes.

Atypical procedural learning skills in children with Developmental Coordination Disorder

We investigated the procedural learning deficit hypothesis in Developmental Coordination Disorder (DCD) while controlling for global performance such as slower reaction times (RTs) and variability. Procedural (sequence) learning was assessed in 31 children with DCD and 31 age-matched typically developing (TD) children through a serial reaction time task (SRTT). Sequential and random trial conditions were intermixed within five training epochs. Two repeated measures ANOVAs were conducted on a Sequence-Specific Learning Index (SSLI) and a Global Performance Index (GPI, speed/accuracy measure) with Epoch (for SSLI and GPI) and Condition (for GPI) as within-subjects factors, and Group as between-subjects factor. Controlling for RTs differences through normalized RTs, revealed a global reduction of SSLI in children with DCD compared with TD peers suggesting reduced sequence learning skills in DCD. Still, a significant Group x Condition interaction observed on GPI indicated that children from both groups were able to discriminate between sequential and random trials. DCD presented reduced procedural learning skills after controlling for global performance. This finding highlights the importance of considering the general functioning of the child while assessing learning skills in patients.

Differential features of early childhood motor skill development and working memory processing: evidence from fNIRS

Objective

The study investigated the differential characteristics associated with motor skill development and working memory processing during early childhood, thereby providing insights for understanding motor learning and cognitive development in young children.

Methods

In total, 101 preschool children (age: 4-6 years) were recruited for this study. The motor skill development level and the working memory capacity of the children were assessed using the MOBAK Motor Development Assessment Scale and a block task paradigm, respectively. Functional near-infrared spectroscopy brain imaging technology was used to monitor hemodynamic signals in the prefrontal cortex (PFC) of the children while they completed different memory tasks. MATLAB software and the Homer2 plugin were used to calculate the oxygenated hemoglobin (Oxy-Hb) concentration in relevant brain regions during the tasks.

Results

(1) The low motor skill group exhibited significantly lower accuracy during the three-memory load condition than during the two-memory load condition. Under both two-memory and three-memory load conditions, the high motor skill group exhibited significantly higher accuracy than the low motor skill group. (2) Significant differences in the Oxy-Hb concentration were observed in the left dorsolateral PFC (L-DLPFC), and right and left triangular part of the Broca's area (R-PTBA and L-PTBA, respectively) between the two memory difficulty levels for the high motor skill group. The Oxy-Hb concentration was significantly higher during the three-memory load condition than during the two-memory load condition. Under the two-memory load condition, the high motor skill group exhibited significantly higher Oxy-Hb concentration in the L-DLPFC and L-PTBA regions than in the low motor skill group. Under the three-memory load condition, the high motor skill group exhibited significantly higher Oxy-Hb concentration in the L-DLPFC, R-PTBA, and L-PTBA regions than the low motor skill group.

Conclusion

A close association was observed between the motor skill levels and working memory in young children, with higher motor skill levels being associated with more pronounced brain activation patterns during working memory tasks.

Human-machine interface for two-dimensional steering control with the auricular muscles

Human-machine interfaces (HMIs) can be used to decode a user's motor intention to control an external device. People that suffer from motor disabilities, such as spinal cord injury, can benefit from the uses of these interfaces. While many solutions can be found in this direction, there is still room for improvement both from a decoding, hardware, and subject-motor learning perspective. Here we show, in a series of experiments with non-disabled participants, a novel decoding and training paradigm allowing naïve participants to use their auricular muscles (AM) to control two degrees of freedom with a virtual cursor. AMs are particularly interesting because they are vestigial muscles and are often preserved after neurological diseases. Our method relies on the use of surface electromyographic records and the use of contraction levels of both AMs to modulate the velocity and direction of a cursor in a two-dimensional paradigm. We used a locking mechanism to fix the current position of each axis separately to enable the user to stop the cursor at a certain location. A five-session training procedure (20-30 min per session) with a 2D center-out task was performed by five volunteers. All participants increased their success rate (Initial: 52.78 ± 5.56%; Final: 72.22 ± 6.67%; median ± median absolute deviation) and their trajectory performances throughout the training. We implemented a dual task with visual distractors to assess the mental challenge of controlling while executing another task; our results suggest that the participants could perform the task in cognitively demanding conditions (success rate of 66.67 ± 5.56%). Finally, using the Nasa Task Load Index questionnaire, we found that participants reported lower mental demand and effort in the last two sessions. To summarize, all subjects could learn to control the movement of a cursor with two degrees of freedom using their AM, with a low impact on the cognitive load. Our study is a first step in developing AM-based decoders for HMIs for people with motor disabilities, such as spinal cord injury.

Motor memory consolidation in children: The role of awareness and sleep on offline general and sequence-specific learning

Study aim: The purpose of this study was to investigate the role of sleep and awareness on consolidation of general and Sequence-Specific learning in children.

Material and methods: Male participants (n = 48, 10 to 12 years old) were assigned to one of four groups based on awareness and sleep. Acquisition phase took place in the morning (wake groups, 8 ± am) or in the evening (sleep groups, 8 ± pm) followed by a 12 hours retention interval and a subsequent delayed retention test (1 week). Children in the explicit groups were informed about the presence of the sequence, while in the implicit groups were not informed about it. For data analysis in consolidation of general sequence learning and Sequence-Specific Consolidation phases, 2 × 2 × 2 and 2 × 2 × 3 ANOVA with repeated measures on block tests were used respectively.

Results: The data provides evidence of offline enhancement of general motor learning after 12 hours which was dependent on sleep and awareness. Moreover, the information persistence after 1-week was significant only in sleep groups. The results also indicated that consolidation of sequence-specific learning was only observed after 12 hours in element duration and it was related to sleep and awareness.

Conclusions: The results revealed that sleep wasn’t only an essential factor in enhancement of off-line sequence learning task after 12 hours in children, but performance of the children was dependent on awareness and sleep.

Specific Cues Can Improve Procedural Learning and Retention in Developmental Coordination Disorder and/or Developmental Dyslexia

The present study investigates procedural learning of motor sequences in children with developmental coordination disorder (DCD) and/or developmental dyslexia (DD), typically-developing children (TD) and healthy adults with a special emphasis on (1) the role of the nature of stimuli and (2) the neuropsychological functions associated to final performance of the sequence. Seventy children and ten adults participated in this study and were separated in five experimental groups: TD, DCD, DD, and DCD + DD children and adults. Procedural learning was assessed with a serial reaction time task (SRTT) that required to tap on a specific key as accurately and quickly as possible when stimuli appeared on the screen. Three types of stimuli were proposed as cues: the classical version of the SRTT with 4 squares aligned horizontally on the screen, giving visuospatial cues (VS cues), and two modified versions, with 4 letters aligned horizontally on the screen (VS + L cues) and letters at the center of the screen (L cues). Reaction times (RT) during the repeated and random blocks allowed assessing three phases of learning: global learning, specific learning and retention of the sequence. Learning was considered as completed when RT evolved significantly in the three phases. Neuropsychological assessment involved, among other functions, memory and attentional functions. Our main result was that learning and retention were not influenced by the available cues in adults whereas learning improved with specific cues in children with or without neurodevelopmental disorders. More precisely, learning was not completed with L cues in children with neurodevelopmental disorders. For children with DD, learning was completed with the VS and VS + L cues whereas for children with DCD (with or without DD), learning was completed with combined VS + L cues. Comorbidity between DD and DCD had no more impact on procedural learning than DCD alone. These results suggest that learning depends on the nature of cues available during practice and that cues allowing learning and retention depend on the type of disorder. Moreover, selective attention was correlated with RT during retention, suggesting that this neuropsychological function is important for procedural learning whatever the available cues.

The Role of Movement Representation Techniques in the Motor Learning Process: A Neurophysiological Hypothesis and a Narrative Review

We present a neurophysiological hypothesis for the role of motor imagery (MI) and action observation (AO) training in the motor learning process. The effects of movement representation in the brain and those of the cortical–subcortical networks related to planning, executing, adjusting, and automating real movements share a similar neurophysiological activity. Coupled with the influence of certain variables related to the movement representation process, this neurophysiological activity is a key component of the present hypothesis. These variables can be classified into four domains: physical, cognitive–evaluative, motivational–emotional, and direct-modulation. The neurophysiological activity underlying the creation and consolidation of mnemonic representations of motor gestures as a prerequisite to motor learning might differ between AO and MI. Together with variations in cognitive loads, these differences might explain the differing results in motor learning. The mirror neuron system appears to function more efficiently through AO training than MI, and AO is less demanding in terms of cognitive load than MI. AO might be less susceptible to the influence of variables related to movement representation.

Working memory affects anticipatory behavior during implicit pattern learning

We investigated the relation between implicit sequence learning and individual differences in working memory (WM) capacity. Participants performed an oculomotor version of the serial reaction time (SRT) task and three computerized WM tasks. Implicit learning was measured using anticipation measures only, as they represent strong indicators of learning. Our results demonstrate that anticipatory behavior in the SRT task changes as a function of WM capacity, such that it increases with decreased WM capacity. On the other hand, WM capacity did not affect the overall number of correct anticipations in the task. In addition, we report a positive relation between WM capacity and the number of consecutive correct anticipations (or chunks), and a negative relation between WM capacity and the overall number of errors, indicating different learning strategies during implicit sequence learning. The results of the current study are theoretically important, because they demonstrate that individual differences in WM capacity could account for differences in learning processes, and ultimately change individuals' anticipatory behavior, even when learning is implicit, without intention and awareness.