More than skin deep: Body representation beyond primary somatosensory cortex

Abstract

The neural circuits underlying initial sensory processing of somatic information are relatively well understood. In contrast, the processes that go beyond primary somatosensation to create more abstract representations related to the body are less clear. In this review, we focus on two classes of higher-order processing beyond somatosensation. Somatoperception refers to the process of perceiving the body itself, and particularly of ensuring somatic perceptual constancy.We review three key elements of somatoperception: (a) remapping information from the body surface into an egocentric reference frame (b) exteroceptive perception of objects in the external world through their contact with the body and (c) interoceptive percepts about the nature and state of the body itself. Somatorepresentation, in contrast, refers to the essentially cognitive process of constructing semantic knowledge and attitudes about the body, including: (d) lexicalsemantic knowledge about bodies generally and one's own body specifically, (e) configural knowledge about the structure of bodies, (f) emotions and attitudes directed towards one's own body, and (g) the link between physical body and psychological self. We review a wide range of neuropsychological, neuroimaging and neurophysiological data to explore the dissociation between these different aspects of higher somatosensory function.Body Beyond SI 3

Mapping the internal geometry of tactile space.

“…Touch, however, can clearly also be used to perceive the extrinsic physical properties of objects. Longo, Azañón, and Haggard (2010) argued that perceiving the metric properties of objects touching the skin requires that immediate sensory signals be combined with (Berryman, Yau, & Hsiao, 2006), sounds produced by action (Tajadura-Jiménez et al, 2012, 2015, the rubber hand illusion (Bruno & Bertamini, 2010), and tool use (Canzoneri et al, 2013;Miller, Longo, & Saygin, 2014, 2017. Thus, in analogy with the modulation of perceived passability of apertures when apparent eyeheight was altered shown by Warren and Whang (1987), these results show that experimental manipulations of represented body size alter perceived tactile distance.…”

Implicit body representations and tactile spatial remapping

“…We used a two-point registration procedure (Bookstein coordinates) to assess localisation biases (as in Azañón et al, 2010;Mancini et al, 2011;Margolis & Longo, 2015). In this procedure, two landmarks are designated as points (0,0) and (1,0), thus defining a twodimensional coordinate system centred on and scaled to the two landmarks (Bookstein, 1991).…”

Integration of anatomical and external response mappings explains crossing effects in tactile localization: A probabilistic modeling approach

“…Furthermore alternative explanations of crossing effects that refer to the unfamiliarity of the crossed posture (Azañón et al, 2010b;Longo et al, 2010) or the need for interhemispheric transmission in the crossed posture (Buchholz et al, 2012) seem improbable, given the lack of an influence of hand crossing on touch detection. Further, these alternative explanations do not receive support from our modeling results; our results suggest that crossing effects are not due to posture per se, but, instead, to the anatomical and external response codes being incongruent in crossed, but not in uncrossed postures.…”

“…However, it is unclear whether this conflict bears on the remapping process, impairing the establishment of the external response mapping (Yamamoto & Kitazawa, 2001a;Röder et al, 2004;Kóbor et al, 2006;Azañón & Soto-Faraco, 2007;Kitazawa et al, 2008), or whether it unfolds its effect at the stage of information integration once remapping is complete (Shore et al, 2002;Badde et al, 2013;Badde et al, 2015). Additionally, it has been suggested that crossing effects might simply be caused by the additional demands of the unusual, presumably uncomfortable crossed posture (Azañón et al, 2010b;Longo et al, 2010;Haggard et al, 2003) or by additional hemispheric transmission costs, which are specific to the crossed posture (Buchholz et al, 2012;Canzoneri et al, 2014). Furthermore, it has been debated whether crossing effects critically depend on the application of more than one stimulus in the TOJ task (Yamamoto & Kitazawa, 2001a;Kitazawa, 2002;Shore et al, 2002).…”