Online sensory feedback during active search improves tactile localization

Abstract

<jats:title>Abstract</jats:title><jats:p>Many natural behaviors involve closed feedback loops in which ongoing sensory input refines motor behavior. Previous research on tactile localization, however, has implemented localization as open-loop behavior. For instance, participants indicate a touched position on a silhouette shape of the body or on an occluding board mounted above the hand. Such studies have suggested that humans often make large errors when localizing touch on the skin, or that “perceptual body representations” are distorted. However, by artificially preventing tactile feedback from the target body area, the natural action-perception loop is interrupted. Therefore, these localization approaches may underestimate individuals’ localization ability and draw erroneous conclusions about the role and precision of body representations. Here, we tested tactile localization in a natural setting, in which participants first received brief touches on their left forearm and then searched for the target location by moving the right index finger across the skin. Tactile search reduced localization error when the searching finger was far from, but not when it was near the target, resulting in a remaining error of 1-2 cm. Error reduction was absent when participants searched on an acrylic barrier mounted above the arm, suggesting that availability of tactile feedback on the target arm but not proprioceptive and motor signals of the searching arm determined precision, thus confirming the pivotal role of closed-loop sensory feedback for tactile localization. We suggest that actively produced online tactile feedback routinely refines coarse spatial body representations, similar to the refinement of sparse spatial representations in visual memory through consecutive saccades.</jats:p>

A neural surveyor to map touch on the body

“…Instead, we found that touch localization was slightly biased towards the wrist in Experiments 1-2 and towards the knuckle in Experiment 3. These findings are consistent with studies that have observed joint-ward biases (13,18). Curves based upon the expected errors due to truncation could not fit the data of any participant in any our experiments (all R 2 <0;…”

“…This computation is likely implemented, at least partially, in the somatosensory cortex. Future work should address how multilateration can be extended to cases of localization in two (see Supplementary Information) or three dimensions (15), as well as when touch occurs under more dynamic contexts (17,18).…”

“…Equally crucial to localizing objects in the environment is localizing objects on the personal space of the body. In the 180 years since Weber's seminal investigations on the sense of touch (6), researchers have extensively characterized tactile localization at both the behavioral (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and neural (19)(20)(21)(22)(23)(24)(25) level. However, despite this progress, the computations underlying tactile localization remain largely unknown.…”

Movement tracking of psychological processes: A tutorial using mousetrap

“…Much of movement tracking theory and analysis have been developed with this paradigm in mind, however, this does not imply that the promise of movement tracking would be limited to this paradigm. Movement tracking has also been successfully applied to other paradigms involving more than two options (e.g., Koop & Johnson, 2011;Moher & Song, 2014), responses in surveys (Fernández-Fontelo et al, 2021;Horwitz et al, 2017;McKinstry et al, 2008), or even sensi-motor localization experiments (Fuchs et al, 2020).…”

Alpha oscillations are involved in localizing touch on hand-held tools

“…Since it is essential to identify the position of a tactile object in order to interact with it, more than a century of research has characterized the perceptual processes underlying tactile localization at a behavioral level ((Badde et al, 2015;Cholewiak and Collins, 2003;Fuchs et al, 2019;Harrar and Harris, 2009;Ho and Spence, 2007;Liu and Medina, 2021;Mancini et al, 2011;Miller et al, 2020;Parrish, 1897;Sadibolova et al, 2018;Stevens, 1992;Weber, 1846); for a review see (Heed et al, 2015)). These studies have identified different spatial codes that are utilized to localize tactile stimuli.…”