Implicit and Explicit Body Representations

Abstract

Several forms of perception require that sensory information be referenced to representations of the size and shape of the body. This requirement is especially acute in somatosensation in which the main receptor surface (i.e., the skin) is itself coextensive with the body. In this paper I will review recent research investigating the body representations underlying somatosensory information processing, including abilities such as tactile localisation, tactile size perception, and position sense. These representations show remarkably large and stereotyped distortions of represented body size and shape. Intriguingly, these distortions appear to mirror distortions characteristic of somatosensory maps, though in attenuated form.In contrast, when asked to make overt judgments about perceived body form, participants are generally quite accurate. This pattern of results suggests that higher-level somatosensory processing relies on a class of implicit body representation, distinct from the conscious body image. I discuss the implications of these results for understanding the nature of body representation and the factors which influence it. Implicit Body Representations 3Our body is ubiquitous in perceptual experience, and is central to our sense of self and personal identity. As William James (1890) observed, our body is not ours, it is us. Thus, how we mentally represent our body has profound implications for our sense of identity, selfesteem, and overall mental health. Indeed, disordered body representation is central to several serious and debilitating diseases, including eating disorders (Treasure, Claudino, & Zucker, 2010), body dysmorphic disorder (Phillips, Didie, Feusner, & Wilhelm, 2008), and phantom limb pain (Flor, Nikolajsen, & Staehelin Jensen, 2006).The subjective, conscious experience of embodiment, however, is only one way in which the brain represents the body. Many forms of perception also require referencing to representations of the body, such as its size and shape. The use of binocular vision for depth perception, for example, requires that information about the spacing between the eyes be known (Banks, 1988). Similarly, the use of temporal differences in when sounds reach the two ears for auditory localisation requires that the distance between the ears be known (Aslin, Pisoni, & Jusczyk, 1983;Clifton et al., 1988). Other studies have shown that other types of body representations inform perception, such as eye-height which affects the perceived passability of doorways (Warren & Whang, 1987), hand size which affects the perceived size of seen objects (Linkenauger, Ramenzoni, & Proffitt, 2010), and arm length which affects the extent of the 'near space' immediately surrounding the body (Longo & Lourenco, 2007).While information about the body is used in perceptual modalities like vision and audition, it is for the most part secondary. In somatosensation, in contrast, representations of the body are central, since the primary receptor surface -the skin -is physically co-extensive with the bo...

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.…”

Multimodal Body Representation of Obese Children and Adolescents before and after Weight-Loss Treatment in Comparison to Normal-Weight Children

“…In this notion, body representation comprises not only attitudes about body weight and shape, but also a mental picture of one’s own body and implicit representations informed by proprioception, somatosensation and interoception. It is assumed that different body representations are organized along a continuum between implicit and explicit representations [12]. …”

Distorted Body Representations in Healthy Cognition

“…For example, altering somatosensory afferent signals through anesthesia alters the conscious body image (Gandevia & Phegan, 1999;Türker, Yeo, & Gandevia, 2005), while vision of the body modulates low-level aspects of somatosensory (e.g., Kennett et al, 2001;Longo, Pernigo, & Haggard, 2011) and even autonomic (e.g., Sadibolova & Longo, 2014) processing. Longo (2015a) proposed a hierarchical model of body representations, which suggests that implicit body representations (such as the body model) and explicit ones (such as the body image) lie at opposite ends of a continuum. This continuum can be thought of in terms of the spatial scale at which the body is represented.…”