A Conceptual Model of Tactile Processing across Body Features of Size, Shape, Side, and Spatial Location

Abstract

The processing of touch depends of multiple factors, such as the properties of the skin and type of receptors stimulated, as well as features related to the actual configuration and shape of the body itself. A large body of research has focused on the effect that the nature of the stimuli has on tactile processing. Less research, however, has focused on features beyond the nature of the touch. In this review, we focus on some features related to the body that have been investigated for less time and in a more fragmented way. These include the symmetrical quality of the two sides of the body, the postural configuration of the body, as well as the size and shape of different body parts. We will describe what we consider three key aspects: (1) how and at which stages tactile information is integrated between different parts and sides of the body; (2) how tactile signals are integrated with online and stored postural configurations of the body, regarded as priors; (3) and how tactile signals are integrated with representations of body size and shape. Here, we describe how these different body dimensions affect integration of tactile information as well as guide motor behavior by integrating them in a single model of tactile processing. We review a wide range of neuropsychological, neuroimaging, and neurophysiological data and suggest a revised model of tactile integration on the basis of the one proposed previously by Longo et al.

Spatially modulated alpha-band activity does not mediate tactile remapping and fast overt orienting behavior

“…Contrary to this hypothesis, during crossedhand informative trials, connectivity manifested intrahemispherically, contralateral to the external stimulus location and, thus, ipsilateral to the stimulated hand's body side. Viewed together with the modulation of alpha-band activity in ipsilateral central electrodes by hand posture, and previous evidence indicating that primary and secondary somatosensory areas process both contra-an ipsilateral stimuli (Tamè et al, 2019), this result suggests that the somatosensory cortex ipsilateral to the anatomical side is involved in the transfer of information during postures that change regular, relative limb position.…”

Bodily awareness and novel multisensory features

“…de Vignemont argues that joint angle information provided by our muscle spindles, joint receptors, and Golgi tendon organs is normally supplemented and structured by a previously constructed representation of the configuration and metrics of the body's parts-a representation variously referred to in the philosophical and scientific literature as the "long-term body image" (O'Shaughnessy 1980), the "implicit body model" Tsakiris 2010;Longo 2015;Wong 2017;Tamè et al 2019), and the "body map" (de Vignemont 2014(de Vignemont , 2018. This stored, relatively stable representation of the subject's anatomy enriches and imposes spatial order on information provided by proprioceptive receptor systems (see O'Shaughnessy 1980, chapters 7-8).…”

“…When combined with sources of proprioceptive information, visual, auditory, and tactile signals can thus all be used to represent locations in external space using common, body-relative reference frames (Bermúdez 1998, chap. 6;Spence and Driver 2004;Grush 2007;Briscoe 2009;Clark 2011;Wu 2014;Briscoe and Schwenkler 2015;Tamè et al 2019). And coordinate transformation thus makes it possible to assess whether the sources of signals arriving different modalities are spatially congruent as is often required for purposes of non-generative, optimizing integration (Briscoe 2016).…”

An Investigation of Lower Limb Representations Underlying Vision, Touch, and Proprioception in Body Integrity Identity Disorder

“…Specifically, it has been proposed that perceiving the distance between two (tactile) points applied to a body part or localizing an unseen landmark on the body requires reference to a higherorder representation, i.e. the body model (34,35). That is, the raw tactile and proprioceptive afferent information (e.g.…”

“…That is, the raw tactile and proprioceptive afferent information (e.g. about joint angle or skin stretch) is not informative about the size of the body part per se, so in order to estimate these tactile distances or localize one's position in space, the brain needs to refer to and integrate with a higher-order representation of the size and shape of the body (34)(35)(36). We suspect that these higher-order representations (or the connections to them) could be underdeveloped in BIID.…”