The “Motor” in Implicit Motor Sequence Learning: A Foot-stepping Serial Reaction Time Task

The overall goal of this experiment is to study how people learn a sequence of actions that mimic daily activities, and to elucidate the cognitive processes, specifically the explicit process operating an implicit motor sequence learning. This task provides a novel way to review the progress of development of the explicit wellness during implicit motor sequence learning. Using this task can help answer key questions in the motor learning and the developmental field, such as implicit motor sequence learning and its age-related development.

The key advantage of this technique is that compared to the classic SRT task, the foot-stepping in task involves greater motor control complexity and it allows us to better understand the learning of sequential skills in daily life, such as dancing, playing musical instruments, or playing sports. The implications of this technique extend to helping us understand children with movement difficulties, particularly the learning of motor sequences by children with something called developmental coordination disorder or DCD. We had first got the idea for this method when we watched one of our children, who we were studying, who had DCD, as he practiced the Wii game, Dance Dance Revolution”He was able to learn the sequence, despite the problems he was having with his motor control and his postural challenges.

Demonstrating the procedural will be Elizabeth Bell and Mia Caminita, graduate students from the neuromechanics laboratory. Begin by insuring proper function of the motion capture system to ensure accurate collection of 3D data from reflective markers. For dynamic calibration, wave the calibration wand supplied with the motion capture system through the space where all reflective markers would move when participants perform the SRT task.

For static calibration, place the calibration wand on the floor with the position and orientation, which can be used as the origin of the coordination system of the motion capture system. Run the motion capture system to set the origin. In the motion capture system, assign each marker a name and create segments by connecting markers together.

Link all segments to finalize the skeleton template. Upon arrival, ask participants to carefully read and sign the consent form. Hi Mia, thanks for volunteering to complete this study.

This consent form will give you better detail on exactly what we’re going to do today. If you will agree to participate, can you just initial each page and then sign the last? After this, there’s just a few questionnaires that we will go through.

Screen for study eligibility using such questionnaires as the hand dominance questionnaire, global physical activity level questionnaire, and neurological health questionnaire. Ask the participant to take off their shoes and socks. Okay, great, now we’re ready for motion capture.

If I could just have you take off your shoes and socks, we’ll be good to go.Okay. Then use double-sided, hypoallergenic, adhesive tape and pre-wrapping tape to attach 38 spherical reflective markers, each 50 millimeters in diameter, to the skin at predetermined significant bony landmarks. This marker setup is the same as the customized skeleton template shown here.

Clear all unwanted reflections other than those 38 markers from the participant’s body. Run a calibration trial by instructing participants to stand quietly on the home position in a T-pose and run the motion capture system to capture all markers for two to ten seconds. Before each participant starts the task, set up the parameters, including but not limited to, participant ID, group ID, number of learning blocks, the time length of stimulus presentation, and the interstimulus interval or response stimulus interval, to control the time interval between the completion of movement and the onset of the next stimulus.

Ask the participant to stand on the home position. Okay, if you could step into the dark blue rectangles, this will be your home position. And adjust the distance of the home position so that participants can comfortably step on to all six targets on the floor.

Have the participant quickly step on to each target several times. And back behind your left foot, great. And mark the distance from the home position to each target at the most comfortable stepping length for each participant.

Tell the participant that once a stimulus appears at one of six locations shown on the monitor, they need to step as quickly and accurately as possible to the corresponding target on the floor and then return to the home position. Once the stimulus appears at one of the six locations shown on the monitor, you will step as quickly and accurately as possible to the corresponding target on the floor and then return to the home position. Then, tell the participant to step with the right foot to the three targets located on the right side and the left foot to the other three targets.

You will step with your right foot for the three targets on the right side of the screen and your left foot for the three targets on the left. Instruct the participants to keep their elbows by their side and bent at a 90 degree angle when they perform the task so that the cameras can see the markers placed on the hip. Please keep your hands by your side and your elbows bent at a 90 degree angle.

Run a practice block that consist of 36 steps so that participants are familiar with the task. Stimuli on this block appear in random order. After the practice block, start the experimental blocks.

In this protocol, there are six blocks, and each experimental block is comprised of 100 steps per stimulus. Set the specific order of visual stimuli as per experimental purposes. Stimuli follow either a specified or random sequence.

The presentation of stimulus order is unknown to participants. Give participants a mandatory three minute break after each block. Before each experimental block, remind participants to respond to stimuli as quickly and accurately as they can.

So we’re going to repeat the same task. It’s important to respond to stimuli as quickly and accurately as you can. Given a possible speed accuracy trade-off, instructing the subject to be as fast and accurate as possible, at the same time before each learning block is critical.

Upon completion of all learning blocks, ask participants to complete a post-test that consists of widely used recall and recognition tests described in the literature. This figure illustrates 12 young adults’mean response times across six learning blocks. The response time to a novel sequence is significantly lower in block five compared with the learned sequence in block four, indicating learning of the sequence.

Mean reaction time exhibits the same pattern as response time. In particular, reaction time in block five is slower than that in block four. Unlike response time and reaction time, movement time is comparable between blocks four and five.

In addition to the time measurement focused in the classic SRT task, the whole body movement, especially the center of mass movement, can also be measured in the foot-stepping SRT task. This figure shows one participant’s data of movement trajectories of the center of mass that occur 100 milliseconds before the stimuli appear. This figure shows the directions of the anticipatory center of mass movement.

The anticipatory movement direction for each stimulus is very inconsistent at the beginning and became more consistent as learning progressed across blocks. This figure shows the significant changes in the movement direction variability across blocks at the group level. Specifically, the variability increased from block four to five, indicating that the center of mass movement direction would be an evident sign of motor sequence learning in the SRT task.

More importantly, the anticipatory center of mass movement is likely to reflect the explicit process operating in implicit motor sequence learning. The increased variability from block four to five was demonstrated only in participants who required the explicit knowledge of the sequence, but not in participants who did not show explicit knowledge. Moreover, the change in variability from block four to five is significantly correlated to the amount of explicit knowledge acquired by participants.

After watching this video, you should have a good understanding of the advantages of this foot-stepping task, that compliment the classic key-pressing SRT task. First, it better mimics impulse sequence learning in daily sequenced activities. Second, this modified SRT task offers a unique ability to examine the temporal evolution of explicit awareness that operates in implicit motor sequence learning.

Last, using this tasks, other information, like continuous movement trajectories, can be recorded and examined. The measurement of temporal dynamics of movement could be used to review hidden cognitive process in future sequence learning studies.