1. Both tactile and non-tactile force-related inputs contribute to the estimation of fingertip distance, and these signals appear to be linearly integrated. 2. Tactile signals alone or non-tactile signals alone elicited a smaller bias than when presented together. 3. The observation of bias in perceived relative finger position based on tactile and non-tactile signals suggests this estimation involves the cerebellum and parietal lobule.

1. Contact Info: diceshibata@unm.edu, simone.toma@asu.edu, marco.santello@asu.edu
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Tactile and non-tactile signals are linearly integrated for the estimation of fingertip distance
Neural Control of
Movement Laboratory
Daisuke Shibata¹⁺, Simone Toma²⁺, Francesco Chinello³, Domenico Pratichizzo⁴, Marco Santello²
¹Department of Health Exercise and Sports Sciences, University of New Mexico, New Mexico, USA
²School of Biological and Health Systems Engineering, Arizona State University, Arizona, USA
³Department of Business Development and Technology, Aarhus University, Midtjylland, Denmark
⁴Department of Information Engineering, University of Siena, Italy
⁺ Co-first author
Tactile and non-tactile inputs of force bias
perception digit relative position
Discussion
Our findings suggest that:
1. Both tactile and non-tactile force-related inputs contribute to the estimation of fingertip distance
2. Tactile and non-tactile signals presented in isolation elicited a smaller magnitude of bias than when presented in combination
3. Tactile and non-tactile signals might be integrated in a linear fashion during digit distance estimation
4. Tactile signals appear to have a greater contribution on the estimation of digit vertical distance
5. The observation of bias in relative fingers position as a function of both tactile and non-tactile signals suggests a cortical
network involving the cerebellum11 and the parietal lobule10 as a basis for the estimation of digit distance
Tactile and non-tactile inputs are linearly
integrated for the estimation of fingertip distance
Sensitivity to directional bias is influenced
by sensory modality and force direction
1
1
0
0.5
0.5
Residualp(bias)
negative dy error
Tactile only
Non-tactile only
positive dy error
TUP-IUP TDW-IDW TUP-IDW TDW-IUPFn-only
The CNS relies on feedback of digit position to accurately modulate force distribution1-4. We have recently found that,
when digit forces were exerted in opposite directions, participants consistently perceived digits as vertically apart
although the vertical distance between the center of pressure of thumb and index finger (dy) was always zero (i.e.,
collinear positions)5. The observed perceptual bias , measured as matching errors was interpreted as evidence for a
contribution of the expected sensory consequences of force-related motor commands (i.e., efference copy) to the
estimation of vertical digit distance during manipulation.
It is still not clear whether one or more force-related signals contributed to the observed perceptual bias. Thus, our
previous findings raised important questions regarding the CNS’ limited ability to integrate feedback from tactile and
proprioceptive inputs with efference copy, and their relative contribution to the estimation of fingertip distance. Here
we addressed these questions by investigating the relative role of tactile and non-tactile inputs (proprioception and
efference copy) on force-related bias of fingertip distance estimation.
Background
Primary & Secondary
Somatosensory cortex9
Premotor &
motor areas8 Inferior Parietal
Lobule10
Tactile
Afferents6
Proprioceptive
Afferents7
Anterior
cerebellum11
Matchingerror(mm)
TDW-IUPTUP-IDW
0
-10
10
-5
5
Tactile
Non-tactile
Combined (Exp.1)
Tactile + Non-tactile
Experiment 1: Tactile + Non-tactile inputs
-10
Matchingerror(mm)
10
0
5
-5
-10
Matchingerror(mm)
10
0
5
-5
TUP-IUPTDN-IDN TUP-IDNTDN-IUP Null Fn-only
-10
Matchingerror(mm)
10
0
5
-5
*
*
*
*
*
*
Experiment 2: Tactile input only
Experiment 3: Non-tactile input only
Thumb
Index finger
FORCE COMBINATION
Control
Fn only Null
Opposite
TDN - IUPTUP-IDN
Finger pad stretch
(±2.5 to ±3.5N)
Finger pad compression
(4 to 5 N)
Fn: Normal Force
(4 to 5 N)
Tangential force
(±2.5 to ±3.5N)
Digit center of
pressure/ force
application point
Exp.1: T + Non-T
dy ≈ ±10 mm
dy ≈ ? mm
dy ≈ ? mm
Exp.3: Non-T only
Exp.2: T onlyExp.2: T only
Exp.1: T + Non-T
Exp.3: Non-T only
SENSING & MEMORIZATION MATCHING
Same
TUP-IUP TDN-IDN
Methods Results
7. Proske, U, Gandevia, SC. (2012). Physiol Rev. 92, 4 1651–1697
8. Gandevia, SC, Smith, JL, Crawford, M, Proske, U, Taylor, J. (2006). J. Physiol. 571, 703-710.
9. Kim SS, Gomez-Ramirez M, Thakur PH, Hsiao SS. (2015). Neuron. 86: 555-566.
10. Clower, D.M., West, R.A., Lynch, J.C., Strick, P.L. (2001). J. Neurosci. 21, 6283-6291
11. Blakemore, S.J., Wolpert, D.M., Frith, C.D. (1999). Neuroimage. 10, 448-459.
This work was partially supported by a National Science Foundation BCS-1455866 grant.