Review
The mechanism of self-recognition in humans

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Abstract

Recognizing oneself as the owner of a body and the agent of actions requires specific mechanisms which have been elucidated only recently. One of these mechanisms is the monitoring of signals arising from bodily movements, i.e. the central signals which contribute to the generation of the movements and the sensory signals which arise from their execution. The congruence between these two sets of signals is a strong index for determining the experiences of ownership and agency, which are the main constituents of the experience of being an independent self. This mechanism, however, does not account from the frequent cases where an intention is generated but the corresponding action is not executed. In this paper, it is postulated that such covert actions are internally simulated by activating specific cortical networks or representations of the intended actions. This process of action simulation is also extended to the observation and the recognition of actions performed or intended by other agents. The problem of disentangling representations that pertain to self-intended actions from those that pertain to actions executed or intended by others, is a critical one for attributing actions to their respective agents. Failure to recognize one’s own actions and misattribution of actions may result from pathological conditions which alter the readability of these representations.

Introduction

How do we recognize ourselves and how do we distinguish ourselves from other people? In this paper, we examine theoretical and experimental evidence for a set of mechanisms by which we become aware of our body and our actions. These mechanisms are interesting to consider, for a number of reasons. First, the ability to recognize oneself as the agent of a behavior—the sense of agency—is the way by which the self builds as an entity independent from the external world. Second, by way of consequence, self-recognition is a prerequisite for attributing a behavior to its proper agent (be it oneself or another person) and ultimately for establishing social communication with our conspecifics. One of the main outcomes of the paper will be that our body is a behaving body, and that self-recognition is largely dependent on the recognition of one’s own actions. Thus, the distinction between self-generated actions and actions produced by other agents, and the corresponding ability to attribute an action to its agent will appear to be key functions for self-recognition.

The self/other distinction of the origin of an action may seem relatively simple when movements are overtly executed. In this condition, there is a possibility for monitoring sensory signals arising from the moving limbs and from the effects on the external world of the movements produced either by the self or the other, and comparing them with the signals resulting from the action generation mechanism. Which renders this distinction difficult is the existence of a number of situations where the action generation mechanism is activated, but where the action remains covert. In this paper, we will consider two such situations. One is that of imagined actions which has been extensively studied under the heading of “motor imagery”; another one is that of observation of actions performed by someone else, a situation which has been introduced more recently within the realm of covert action. Although the two situations are clearly dissimilar, they have in common to both rely on neural simulation of the imagined or the observed action.

The existence of covert action, which is an essential constituent of motor cognition, raises the problem for the self of disentangling from one another different modalities of motor representations which may be present more or less simultaneously within the same brain. Action recognition thus cannot be treated separately from the more general process extending to recognition of action-related mental states like intentions or desires. In this paper, we will develop the concept of “shared representations” as a potential difficulty for action recognition and self-recognition both in normal subjects and in subjects suffering pathological conditions.

Section snippets

Ownership and authorship in self-recognition

In the present section, we will focus on identifying the constituents of self-recognition in adult subjects. There are several potential sources of information which may contribute to self-recognition. First, the matching of visual, tactile and proprioceptive signals originating from the same body parts contributes to an intermodal sensory image of the body. Second, the matching of one’s intentions and the bodily effects of self-generated actions contributes to a sense of the self as an agent.

The nature of the mechanisms for self-recognition and attribution

There are several ways of conceiving the mechanisms involved in self-recognition. As we shall see in this section, however, most, if not all hypotheses about these mechanisms refer to one aspect of self-recognition, namely, action recognition. This predominance of action recognition over other possible cues for self-recognition, which was clearly highlighted by the above experiments, opens a number of empirical and theoretical questions.

In the following paragraphs, two empirically-based

Conclusion. A neural hypothesis for self-recognition and its failures: the ‘Who’ system

In this concluding section, a framework for integrating self-recognition to the neural substrate and for accounting for its failures is presented. Our present conception of action recognition [55], [58] is based on the existence of neural networks subserving the various forms of representation of an action. Accordingly, each representation entails a cortico-subcortical network including to a various extent activation of interconnected neural structures. Although these ensembles are clearly

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