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Statistics of natural movements are reflected in motor errors.

Howard IS, Ingram JN, Körding KP, Wolpert DM - J. Neurophysiol. (2009)

Bottom Line: We developed a portable motion-tracking system that could be worn by subjects as they went about their daily routine outside of a laboratory setting.Specifically, symmetric and antisymmetric movements are predominant at low frequencies, whereas only symmetric movements are predominant at high frequencies.Moreover, the statistics of natural movements, that is, their relative incidence, correlated with subjects' performance on a laboratory-based phase-tracking task.

View Article: PubMed Central - PubMed

Affiliation: Computational and Biological Learning Laboratory, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK. ish22@cam.ac.uk

ABSTRACT
Humans use their arms to engage in a wide variety of motor tasks during everyday life. However, little is known about the statistics of these natural arm movements. Studies of the sensory system have shown that the statistics of sensory inputs are key to determining sensory processing. We hypothesized that the statistics of natural everyday movements may, in a similar way, influence motor performance as measured in laboratory-based tasks. We developed a portable motion-tracking system that could be worn by subjects as they went about their daily routine outside of a laboratory setting. We found that the well-documented symmetry bias is reflected in the relative incidence of movements made during everyday tasks. Specifically, symmetric and antisymmetric movements are predominant at low frequencies, whereas only symmetric movements are predominant at high frequencies. Moreover, the statistics of natural movements, that is, their relative incidence, correlated with subjects' performance on a laboratory-based phase-tracking task. These results provide a link between natural movement statistics and motor performance and confirm that the symmetry bias documented in laboratory studies is a natural feature of human movement.

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A: front view of subject showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and z-axis. Dotted line shows the midsagittal plane. The directions of symmetric movements are shown by corresponding pairs of either open arrowheads on both sides or filled arrowheads on both sides. The directions of antisymmetric movements are shown by corresponding pairs of open arrowheads on one side with filled arrowheads on the other. B: top view of subject, as in A, showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and y-axis. C: the transmitter and sensor locations shown for the right arm with S1 located on the upper arm and S2 on the lower arm near the wrist. The transmitter is mounted on the chest over the sternum and defines the coordinate system for position and orientation of the sensors. Sensors S3 and S4 (not shown) are similarly located on the left arm. D: details of the joint center analysis showing sensors proximal and distal to the elbow joint with rotations (R1 and R2 for sensors 1 and 2, respectively) and translations (T1 and T2) relative to transmitter. The vectors D1 and D2 describe the location of the joint center relative to the upper and lower sensors, respectively. E: experimental setup for the phase-tracking task. The coordinate system is marked on the figure and the tracking movements were made along the y-axis.
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f1: A: front view of subject showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and z-axis. Dotted line shows the midsagittal plane. The directions of symmetric movements are shown by corresponding pairs of either open arrowheads on both sides or filled arrowheads on both sides. The directions of antisymmetric movements are shown by corresponding pairs of open arrowheads on one side with filled arrowheads on the other. B: top view of subject, as in A, showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and y-axis. C: the transmitter and sensor locations shown for the right arm with S1 located on the upper arm and S2 on the lower arm near the wrist. The transmitter is mounted on the chest over the sternum and defines the coordinate system for position and orientation of the sensors. Sensors S3 and S4 (not shown) are similarly located on the left arm. D: details of the joint center analysis showing sensors proximal and distal to the elbow joint with rotations (R1 and R2 for sensors 1 and 2, respectively) and translations (T1 and T2) relative to transmitter. The vectors D1 and D2 describe the location of the joint center relative to the upper and lower sensors, respectively. E: experimental setup for the phase-tracking task. The coordinate system is marked on the figure and the tracking movements were made along the y-axis.

Mentions: One feature of movement performance, which has been extensively studied in the laboratory, is the phase relation between left and right body parts during rhythmic movements (Kelso 1984, 1995; Li et al. 2005; Mechsner et al. 2001; Schmidt et al. 1993; Swinnen et al. 1998, 2002). In this context, bimanual movements can be described in terms of the phase relation between the left and right arms (see Fig. 1, A and B). In common with previous studies, we use the convention that a 0° phase difference between the two arms corresponds to their moving in a mirror-symmetric way in extrinsic space with respect to the midsagittal plane. In muscle-based definitions of symmetry, such 0° phase differences correspond to the use of homologous muscles (Kelso 1984).


Statistics of natural movements are reflected in motor errors.

Howard IS, Ingram JN, Körding KP, Wolpert DM - J. Neurophysiol. (2009)

A: front view of subject showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and z-axis. Dotted line shows the midsagittal plane. The directions of symmetric movements are shown by corresponding pairs of either open arrowheads on both sides or filled arrowheads on both sides. The directions of antisymmetric movements are shown by corresponding pairs of open arrowheads on one side with filled arrowheads on the other. B: top view of subject, as in A, showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and y-axis. C: the transmitter and sensor locations shown for the right arm with S1 located on the upper arm and S2 on the lower arm near the wrist. The transmitter is mounted on the chest over the sternum and defines the coordinate system for position and orientation of the sensors. Sensors S3 and S4 (not shown) are similarly located on the left arm. D: details of the joint center analysis showing sensors proximal and distal to the elbow joint with rotations (R1 and R2 for sensors 1 and 2, respectively) and translations (T1 and T2) relative to transmitter. The vectors D1 and D2 describe the location of the joint center relative to the upper and lower sensors, respectively. E: experimental setup for the phase-tracking task. The coordinate system is marked on the figure and the tracking movements were made along the y-axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2746767&req=5

f1: A: front view of subject showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and z-axis. Dotted line shows the midsagittal plane. The directions of symmetric movements are shown by corresponding pairs of either open arrowheads on both sides or filled arrowheads on both sides. The directions of antisymmetric movements are shown by corresponding pairs of open arrowheads on one side with filled arrowheads on the other. B: top view of subject, as in A, showing movements at the elbow in joint space and at the hands in extrinsic space for the x-axis and y-axis. C: the transmitter and sensor locations shown for the right arm with S1 located on the upper arm and S2 on the lower arm near the wrist. The transmitter is mounted on the chest over the sternum and defines the coordinate system for position and orientation of the sensors. Sensors S3 and S4 (not shown) are similarly located on the left arm. D: details of the joint center analysis showing sensors proximal and distal to the elbow joint with rotations (R1 and R2 for sensors 1 and 2, respectively) and translations (T1 and T2) relative to transmitter. The vectors D1 and D2 describe the location of the joint center relative to the upper and lower sensors, respectively. E: experimental setup for the phase-tracking task. The coordinate system is marked on the figure and the tracking movements were made along the y-axis.
Mentions: One feature of movement performance, which has been extensively studied in the laboratory, is the phase relation between left and right body parts during rhythmic movements (Kelso 1984, 1995; Li et al. 2005; Mechsner et al. 2001; Schmidt et al. 1993; Swinnen et al. 1998, 2002). In this context, bimanual movements can be described in terms of the phase relation between the left and right arms (see Fig. 1, A and B). In common with previous studies, we use the convention that a 0° phase difference between the two arms corresponds to their moving in a mirror-symmetric way in extrinsic space with respect to the midsagittal plane. In muscle-based definitions of symmetry, such 0° phase differences correspond to the use of homologous muscles (Kelso 1984).

Bottom Line: We developed a portable motion-tracking system that could be worn by subjects as they went about their daily routine outside of a laboratory setting.Specifically, symmetric and antisymmetric movements are predominant at low frequencies, whereas only symmetric movements are predominant at high frequencies.Moreover, the statistics of natural movements, that is, their relative incidence, correlated with subjects' performance on a laboratory-based phase-tracking task.

View Article: PubMed Central - PubMed

Affiliation: Computational and Biological Learning Laboratory, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK. ish22@cam.ac.uk

ABSTRACT
Humans use their arms to engage in a wide variety of motor tasks during everyday life. However, little is known about the statistics of these natural arm movements. Studies of the sensory system have shown that the statistics of sensory inputs are key to determining sensory processing. We hypothesized that the statistics of natural everyday movements may, in a similar way, influence motor performance as measured in laboratory-based tasks. We developed a portable motion-tracking system that could be worn by subjects as they went about their daily routine outside of a laboratory setting. We found that the well-documented symmetry bias is reflected in the relative incidence of movements made during everyday tasks. Specifically, symmetric and antisymmetric movements are predominant at low frequencies, whereas only symmetric movements are predominant at high frequencies. Moreover, the statistics of natural movements, that is, their relative incidence, correlated with subjects' performance on a laboratory-based phase-tracking task. These results provide a link between natural movement statistics and motor performance and confirm that the symmetry bias documented in laboratory studies is a natural feature of human movement.

Show MeSH