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Implicit and explicit representations of hand position in tool use.

Rand MK, Heuer H - PLoS ONE (2013)

Bottom Line: Furthermore, we found a number of differences between explicit and implicit judgments of hand directions.Moreover, age-related changes were also different between these judgments.These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

View Article: PubMed Central - PubMed

Affiliation: IfADo-Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany. rand@ifado.de

ABSTRACT
Understanding the interactions of visual and proprioceptive information in tool use is important as it is the basis for learning of the tool's kinematic transformation and thus skilled performance. This study investigated how the CNS combines seen cursor positions and felt hand positions under a visuo-motor rotation paradigm. Young and older adult participants performed aiming movements on a digitizer while looking at rotated visual feedback on a monitor. After each movement, they judged either the proprioceptively sensed hand direction or the visually sensed cursor direction. We identified asymmetric mutual biases with a strong visual dominance. Furthermore, we found a number of differences between explicit and implicit judgments of hand directions. The explicit judgments had considerably larger variability than the implicit judgments. The bias toward the cursor direction for the explicit judgments was about twice as strong as for the implicit judgments. The individual biases of explicit and implicit judgments were uncorrelated. Biases of these judgments exhibited opposite sequential effects. Moreover, age-related changes were also different between these judgments. The judgment variability was decreased and the bias toward the cursor direction was increased with increasing age only for the explicit judgments. These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

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Variance reduction through sensory coupling.Relative variances of biased proprioceptively (a: var(P')/var(P)) and visually (b: var(V')/var(V)) sensed spatial characteristics, such as directions, are plotted against the proportional bias toward the other modality, vision and proprioception, respectively. Var(P') and var(V') are the variances of the biased directions, whereas var(P) and var(V) are the variances of the unbiased directions based only on proprioception and vision, respectively. The relative variances are plotted as a function of bias for different ratios of var(V)/var(P) (0.2 to 0.7). Equations are given in Appendix (Text S1). Note that sensory coupling serves to reduce variability (a, b) to a minimum at an intermediate bias, and a weak coupling (small bias) does so even for the more precise visually sensed spatial characteristic (b).
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pone-0068471-g001: Variance reduction through sensory coupling.Relative variances of biased proprioceptively (a: var(P')/var(P)) and visually (b: var(V')/var(V)) sensed spatial characteristics, such as directions, are plotted against the proportional bias toward the other modality, vision and proprioception, respectively. Var(P') and var(V') are the variances of the biased directions, whereas var(P) and var(V) are the variances of the unbiased directions based only on proprioception and vision, respectively. The relative variances are plotted as a function of bias for different ratios of var(V)/var(P) (0.2 to 0.7). Equations are given in Appendix (Text S1). Note that sensory coupling serves to reduce variability (a, b) to a minimum at an intermediate bias, and a weak coupling (small bias) does so even for the more precise visually sensed spatial characteristic (b).

Mentions: In tool-use actions, such as controlling a cursor on a monitor through a computer mouse, however, visual information specifies the position of the effective part of the tool (i.e., cursor), while proprioceptive information specifies the position of the hand. These two positions of different objects have a clear spatial separation. They are related to each other only through the tool's kinematic transformation. Even though the positions of the hand and the cursor remain distinct perceptually, they might be biased toward each other. This kind of interaction between sensory signals, which does not result in a fused percept but in distinct perceptions with mutual biases, has been referred to as coupling [4]. Coupling can also be conceived in terms of weighted averages of the different sensory signals (see Appendix – Text S1). It can serve to reduce the variances of the biased estimates, and thus, to enhance the precision even when visual and proprioceptive information refer to different objects. This is illustrated in Figure 1. Note that even the smaller variance of the visually based perceptions can be reduced by sensory coupling.


Implicit and explicit representations of hand position in tool use.

Rand MK, Heuer H - PLoS ONE (2013)

Variance reduction through sensory coupling.Relative variances of biased proprioceptively (a: var(P')/var(P)) and visually (b: var(V')/var(V)) sensed spatial characteristics, such as directions, are plotted against the proportional bias toward the other modality, vision and proprioception, respectively. Var(P') and var(V') are the variances of the biased directions, whereas var(P) and var(V) are the variances of the unbiased directions based only on proprioception and vision, respectively. The relative variances are plotted as a function of bias for different ratios of var(V)/var(P) (0.2 to 0.7). Equations are given in Appendix (Text S1). Note that sensory coupling serves to reduce variability (a, b) to a minimum at an intermediate bias, and a weak coupling (small bias) does so even for the more precise visually sensed spatial characteristic (b).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3716878&req=5

pone-0068471-g001: Variance reduction through sensory coupling.Relative variances of biased proprioceptively (a: var(P')/var(P)) and visually (b: var(V')/var(V)) sensed spatial characteristics, such as directions, are plotted against the proportional bias toward the other modality, vision and proprioception, respectively. Var(P') and var(V') are the variances of the biased directions, whereas var(P) and var(V) are the variances of the unbiased directions based only on proprioception and vision, respectively. The relative variances are plotted as a function of bias for different ratios of var(V)/var(P) (0.2 to 0.7). Equations are given in Appendix (Text S1). Note that sensory coupling serves to reduce variability (a, b) to a minimum at an intermediate bias, and a weak coupling (small bias) does so even for the more precise visually sensed spatial characteristic (b).
Mentions: In tool-use actions, such as controlling a cursor on a monitor through a computer mouse, however, visual information specifies the position of the effective part of the tool (i.e., cursor), while proprioceptive information specifies the position of the hand. These two positions of different objects have a clear spatial separation. They are related to each other only through the tool's kinematic transformation. Even though the positions of the hand and the cursor remain distinct perceptually, they might be biased toward each other. This kind of interaction between sensory signals, which does not result in a fused percept but in distinct perceptions with mutual biases, has been referred to as coupling [4]. Coupling can also be conceived in terms of weighted averages of the different sensory signals (see Appendix – Text S1). It can serve to reduce the variances of the biased estimates, and thus, to enhance the precision even when visual and proprioceptive information refer to different objects. This is illustrated in Figure 1. Note that even the smaller variance of the visually based perceptions can be reduced by sensory coupling.

Bottom Line: Furthermore, we found a number of differences between explicit and implicit judgments of hand directions.Moreover, age-related changes were also different between these judgments.These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

View Article: PubMed Central - PubMed

Affiliation: IfADo-Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany. rand@ifado.de

ABSTRACT
Understanding the interactions of visual and proprioceptive information in tool use is important as it is the basis for learning of the tool's kinematic transformation and thus skilled performance. This study investigated how the CNS combines seen cursor positions and felt hand positions under a visuo-motor rotation paradigm. Young and older adult participants performed aiming movements on a digitizer while looking at rotated visual feedback on a monitor. After each movement, they judged either the proprioceptively sensed hand direction or the visually sensed cursor direction. We identified asymmetric mutual biases with a strong visual dominance. Furthermore, we found a number of differences between explicit and implicit judgments of hand directions. The explicit judgments had considerably larger variability than the implicit judgments. The bias toward the cursor direction for the explicit judgments was about twice as strong as for the implicit judgments. The individual biases of explicit and implicit judgments were uncorrelated. Biases of these judgments exhibited opposite sequential effects. Moreover, age-related changes were also different between these judgments. The judgment variability was decreased and the bias toward the cursor direction was increased with increasing age only for the explicit judgments. These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

Show MeSH
Related in: MedlinePlus