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Somatosensory comparison during haptic tracing.

Weiss EJ, Flanders M - Cereb. Cortex (2010)

Bottom Line: Active sensing involves memory retrieval and updating as well as mechanisms that trigger corrections to the ongoing exploratory movement.This short latency indicates that spinally mediated corrections are engaged during this task.The results support the hypothesis that during haptic exploration, the neural comparison between expected and actual somatosensory feedback takes places at multiple levels, including the spinal cord.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.

ABSTRACT
Active sensing involves memory retrieval and updating as well as mechanisms that trigger corrections to the ongoing exploratory movement. The present study examined this process in a task where human subjects moved the index fingertip clockwise around the circumference of a virtual sphere created by a robotic device. The fingertip pressed into the sphere during the movement, and the subjects were to report slight differences in sphere size (or surface curvature), which occurred from trial to trial. During each 2- to 3-s trial, subjects gradually adjusted their speed and pressure according to the current surface curvature, achieving a consistent level of contact force in the last half of the exploration. The results demonstrate that subjects were gradually accumulating haptic information about curvature and, at the same time, gradually changing the motor commands for the movement. When subjects encountered an unexpected transition in curvature (from circular to flat), they reacted by abruptly decreasing contact force at a latency of about 50 ms. This short latency indicates that spinally mediated corrections are engaged during this task. The results support the hypothesis that during haptic exploration, the neural comparison between expected and actual somatosensory feedback takes places at multiple levels, including the spinal cord.

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Related in: MedlinePlus

Schematic model of reactions to somatosensory input at the spinal (right), subcortical (middle), and cortical (left) levels. Loop a) is a feedback-based updating of the motor command at the highest level (target state). Loop b) represents the comparison of somatosensory feedback with efference copy used to update the inverse model (square). The gray circle represents forward model operations used to facilitate this comparison and to update the current state. Loop c) is a hypothetical comparison of somatosensory input with efference copy at the level of the spinal cord. This could give rise to functionally appropriate modifications to motor output at spinal reflex latencies.
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fig8: Schematic model of reactions to somatosensory input at the spinal (right), subcortical (middle), and cortical (left) levels. Loop a) is a feedback-based updating of the motor command at the highest level (target state). Loop b) represents the comparison of somatosensory feedback with efference copy used to update the inverse model (square). The gray circle represents forward model operations used to facilitate this comparison and to update the current state. Loop c) is a hypothetical comparison of somatosensory input with efference copy at the level of the spinal cord. This could give rise to functionally appropriate modifications to motor output at spinal reflex latencies.

Mentions: According to the currently popular view, during this process, arm and hand muscles receive descending motor commands (gray arrows in Fig. 8) that are approximately accurate due to experience. Somatosensory input (Fig. 8, far right) can act as feedback to update the ongoing commands (upper left, loop a). Due to the amount of time required to conduct signals from tactile (cutaneous) receptors and proprio (joint and muscle) receptors to the cortex and then back to the spinal cord, the update would influence a hand movement after about 100 ms (Johansson and Flanagan 2009).


Somatosensory comparison during haptic tracing.

Weiss EJ, Flanders M - Cereb. Cortex (2010)

Schematic model of reactions to somatosensory input at the spinal (right), subcortical (middle), and cortical (left) levels. Loop a) is a feedback-based updating of the motor command at the highest level (target state). Loop b) represents the comparison of somatosensory feedback with efference copy used to update the inverse model (square). The gray circle represents forward model operations used to facilitate this comparison and to update the current state. Loop c) is a hypothetical comparison of somatosensory input with efference copy at the level of the spinal cord. This could give rise to functionally appropriate modifications to motor output at spinal reflex latencies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3020584&req=5

fig8: Schematic model of reactions to somatosensory input at the spinal (right), subcortical (middle), and cortical (left) levels. Loop a) is a feedback-based updating of the motor command at the highest level (target state). Loop b) represents the comparison of somatosensory feedback with efference copy used to update the inverse model (square). The gray circle represents forward model operations used to facilitate this comparison and to update the current state. Loop c) is a hypothetical comparison of somatosensory input with efference copy at the level of the spinal cord. This could give rise to functionally appropriate modifications to motor output at spinal reflex latencies.
Mentions: According to the currently popular view, during this process, arm and hand muscles receive descending motor commands (gray arrows in Fig. 8) that are approximately accurate due to experience. Somatosensory input (Fig. 8, far right) can act as feedback to update the ongoing commands (upper left, loop a). Due to the amount of time required to conduct signals from tactile (cutaneous) receptors and proprio (joint and muscle) receptors to the cortex and then back to the spinal cord, the update would influence a hand movement after about 100 ms (Johansson and Flanagan 2009).

Bottom Line: Active sensing involves memory retrieval and updating as well as mechanisms that trigger corrections to the ongoing exploratory movement.This short latency indicates that spinally mediated corrections are engaged during this task.The results support the hypothesis that during haptic exploration, the neural comparison between expected and actual somatosensory feedback takes places at multiple levels, including the spinal cord.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.

ABSTRACT
Active sensing involves memory retrieval and updating as well as mechanisms that trigger corrections to the ongoing exploratory movement. The present study examined this process in a task where human subjects moved the index fingertip clockwise around the circumference of a virtual sphere created by a robotic device. The fingertip pressed into the sphere during the movement, and the subjects were to report slight differences in sphere size (or surface curvature), which occurred from trial to trial. During each 2- to 3-s trial, subjects gradually adjusted their speed and pressure according to the current surface curvature, achieving a consistent level of contact force in the last half of the exploration. The results demonstrate that subjects were gradually accumulating haptic information about curvature and, at the same time, gradually changing the motor commands for the movement. When subjects encountered an unexpected transition in curvature (from circular to flat), they reacted by abruptly decreasing contact force at a latency of about 50 ms. This short latency indicates that spinally mediated corrections are engaged during this task. The results support the hypothesis that during haptic exploration, the neural comparison between expected and actual somatosensory feedback takes places at multiple levels, including the spinal cord.

Show MeSH
Related in: MedlinePlus