Predictive mechanisms in the control of contour following

Abstract

In haptic exploration, when running a fingertip along a surface, the control system may attempt to anticipate upcoming changes in curvature in order to maintain a consistent level of contact force. Such predictive mechanisms are well known in the visual system, but have yet to be studied in the somatosensory system. Thus the present experiment was designed to reveal human capabilities for different types of haptic prediction. A robot arm with a large 3D workspace was attached to the index fingertip and was programmed to produce virtual surfaces with curvatures that varied within and across trials. With eyes closed, subjects moved the fingertip around elliptical hoops with flattened regions or Limaçon shapes, where the curvature varied continuously. Subjects anticipated the corner of the flattened region rather poorly, but for the Limaçon shapes they varied finger speed with upcoming curvature according to the two-thirds power law. Furthermore, although the Limaçon shapes were randomly presented in various 3D orientations, modulation of contact force also indicated good anticipation of upcoming changes in curvature. The results demonstrate that it is difficult to haptically anticipate the spatial location of an abrupt change in curvature, but smooth changes in curvature may be facilitated by anticipatory predictions.

Drawing ellipses in water: evidence for dynamic constraints in the relation between velocity and path curvature

“…Some characteristics of these velocity changes, such as the crossing of the average value before the radius change in the transition R 1 → R 2 (Fig. 5), may reflect an anticipatory control of path trajectory (Tramper and Flanders 2013). However, it is unclear why the reverse transition R 2 → R 1 did not involve a similar anticipation.…”

Whisking mechanics and active sensing

“…We therefore propose that — just as during human exploration with fingertips [70] — the rat exploits contact mechanics to determine object features such as contour. Although very few studies have examined whisker-object contact patterns, a few recent experiments provide clues as to how this computation is enabled by whisker motions.…”

Haptic Perception in Extreme Obesity: qEEG Study Focused on Predictive Coding and Body Schema

“…It is worth noting that haptic guidance of exploratory movement has been considered as the counterpart of visual guidance of eye movement, thus leading to the idea that this perceptual modality is strongly based on predictive coding [9]. This hypothesis has been recently confirmed by recording kinematic data collected from finger movement of healthy subjects manually exploring virtual surfaces [9].…”

“…Evidence of predictive coding in haptic exploration has been recently provided in a behavioral experiment on contour following [9]. As in other perceptual modalities, generative models are based on precision of sensory inputs.…”