The free-energy self: a predictive coding account of self-recognition

Abstract

Recognising and representing one's self as distinct from others is a fundamental component of self-awareness. However, current theories of self-recognition are not embedded within global theories of cortical function and therefore fail to provide a compelling explanation of how the self is processed. We present a theoretical account of the neural and computational basis of self-recognition that is embedded within the free-energy account of cortical function. In this account one's body is processed in a Bayesian manner as the most likely to be "me". Such probabilistic representation arises through the integration of information from hierarchically organised unimodal systems in higher-level multimodal areas. This information takes the form of bottom-up "surprise" signals from unimodal sensory systems that are explained away by top-down processes that minimise the level of surprise across the brain. We present evidence that this theoretical perspective may account for the findings of psychological and neuroimaging investigations into self-recognition and particularly evidence that representations of the self are malleable, rather than fixed as previous accounts of self-recognition might suggest.

Keywords: Bayesian; Body ownership; Enfacement; Face recognition; Free energy; Prediction error; Predictive coding; Rubber hand illusion; Self-awareness; Self-recognition; Voice recognition.

Fig.1

Predictive coding of ‘surprise’ and ‘explaining away’ during the RHI. The green lines indicate top-down predictive information explaining away the bottom-up unexplained prediction errors or surprise indicated by the red lines. The solid black lines indicate a sensory input. In predictive coding this architecture dynamically reconciles predictive and unexpected information when a sensory event is unexpected. In all three panels the information is organised hierarchically within the sensory systems and this information converges on multimodal areas. In the left panel, before synchronous stimulation, the sensory input to the visual system has instantiated predictions in the visual system that one is seeing a rubber hand that has a low probability of being a real hand (but higher than a non-corporeal object) and has a low probability of being one’s own hand (but higher than if the hand was placed in a spatial location that is removed from the body). In the middle panel, the experience of touch evokes surprise in the somatosensory system and its temporal and specular congruency with touch on the rubber hand causes surprise in the visual system. This surprise is explained away by the top-down influence from multimodal areas and perceptual learning processes in the unimodal areas. As a result, the probability that the visually perceived rubber hand is part of ‘my’ body and is also a real hand increases. In parallel, the probability that this object is part of the body updates the probability that touch on the rubber hand will result in a somatosensory experience. As such, during the experience of the illusion (right panel) touch on the rubber hand is no longer surprising, as the object is perceived visually as part of one’s body and it is an object that touch upon evokes a somatosensory event.