Littérature scientifique sur le sujet « Somatoparaphrenia »

The term somatoparaphrenia was firstly used by Gerstmann to describe a form of asomatognosia in which unawareness of ownership is accompanied by delusional misidentification and/or confabulation. This is a rare phenomenon and the few published case reports showed an association of this psychopathological entity with brain-damage. We present a patient with schizophrenia who believed his right arm and right foot were not his own. According to his delusion of foreign ownership, his foot didn’t belong to him because it was a “big foot only suited for work” and his right arm belonged to Maria, a woman from his neighbourhood. Remarkably, no organic causes were found to exist. To our knowledge, this is one of the rare cases of schizophrenia in which somatoparaphrenia can be identified. We further elaborate on the phenomenology of this particular patient.

Various psychopathologies of self-awareness, such as somatoparaphrenia and thought insertion in schizophrenia, might seem to threaten the viability of the higher-order thought (HOT) theory of consciousness since it requires a HOT about one’s own mental state to accompany every conscious state. The HOT theory of consciousness says that what makes a mental state a conscious mental state is that there is a HOT to the effect that “I am in mental state M.” I have argued in previous work that a HOT theorist can adequately respond to this concern with respect to somatoparaphrenia and thought insertion. There is also Cotard syndrome which is a rare neuropsychiatric disorder in which people hold the delusional belief that they are dead, do not exist, or have lost their blood or internal organs. In this paper, I argue that HOT theory has nothing to fear from it either and can consistently account for what happens in such unusual cases. I analyze Cotard syndrome in light of my previous discussion of somatoparaphrenia and thought insertion, and argue that HOT theory can provide a somewhat analogous account without the worry of inconsistency. It is crucial to recognize that there are multiple “self-concepts” and levels of HOTs which can help to provide a more nuanced explanation. With regard to the connection between consciousness and self-consciousness, it is proposed that Cotard patients are indeed capable of having some “I-thoughts” about their bodies and mental states.

This thesis describes behavioural observations and anatomical investigations concerning productive symptoms observable in right brain damaged patients with spatial neglect. A "productive" symptom is defined here as a behavioural manifestation that, contrary to what observed when performance is lacking or its failure is acknowledged by patients, is characterized by the active generation of acts or verbal reports reflecting a distorted mental representation of reality. A first classification of productive symptoms in neglect patients pertains the spatial frame of their manifestation, extrapersonal or personal. Following this classification, I examine these manifestations in separate sections of the thesis. Section 1 is dedicated to the peri/extrapersonal space, while, in Section 2, I focus on symptoms manifesting in the own bodily space. In chapter 2, I concentrate on graphic perseveration in cancellation tasks, the main productive symptom observable for the extrapersonal space in neglect patients. Together with omission of left-sided targets, a variety of irrelevant marks over already cancelled targets on the ipsilesional side can be observed. It is not clear whether these perseverative behaviours are functionally and anatomically connected, nor whether they correlate with the severity of spatial neglect. We retrospectively identified two well-distinct forms of perseveration on cancellation tasks ("additional marks" and "inkblot") in 33 neglect patients, and we investigated their relationship with neglect severity and their anatomical correlates. We show, on both a behavioural and anatomical level, that different kinds of perseverative behaviours are differently related with neglect. From chapter 3 onwards I concentrate on productive manifestations in personal space. One main such productive symptom is somatoparaphrenia, the delusional belief whereby a patient feels that a paralyzed limb does not belong to his body; the symptom is typically associated with unilateral neglect and most frequently with anosognosia for hemiplegia. In chapter 3, I describe the anatomical pattern associated with somatoparaphrenia in a wide sample of patients, and I propose that somatoparaphrenia occurs providing that a distributed cortical lesion pattern is present together with a subcortical lesion load that prevents most sensory input from being processed in neocortical structures. In chapter 4, I also show how somatoparaphrenia, that, so far, has been often considered simply the most severe and delusional manifestation along a continuum of body disorders also including anosognosia for hemiplegia, can be also observed in isolation from this symptom. I report anatomical observations on a small group of pure somatoparaphrenic patients and discuss the implications of this uncommon symptomatological dissociation. The experiments mentioned so far were based on classical anatomoclinical correlation inference. The study of productive/positive symptoms, however, would ideally need functional methods as well, in order to capture the neural correlates of the "active" component implied by the symptoms under investigation. I present an initial attempt along these lines. I considered the delusional behaviour of patients with anosognosia for hemiplegia (AHP): this has been often classified as a “negative” symptom as patients crucially “lack” the awareness of the motor deficit. However, beyond this defective aspect, AHP is usually characterized by an active delusional component that manifests in the patients’ firm assertion of having performed a movement with the paralyzed limb, in spite of any clear evidence that no movement has actually occurred. In this case, one has to postulate the presence of a residual, and maybe misinterpreted, motor brain activity to account for this delusional component. Here I illustrate, for the first time, the missing direct imaging evidence that the illusory movement of the left plegic hand is associated with brain activation of intact cortical motor regions implicated in motor control and intention (see chapter 5). It is suggested that motor delusions observed in AHP depend on a combination of well placed lesions and the presence of some motor intentionality represented by residual activity within the spared motor cortices. The diversity of the phenomena considered in this thesis makes it difficult to generalize anatomical considerations about productive manifestations associated with spatial neglect; yet, it is worth of notice the fact that all these disorders can be also conceptualized as self-monitoring disorders particularly related to motor/sensory control aspects in which the opercular part of the inferior frontal gyrus seems to play an important role. Indeed, we found it constantly involved in all the productive disorders considered, irrespective of whether defective monitoring was about the left plegic limb or the right intact one. In addition, we find it promising the adoption of functional methods to gather a more complete description of the neural underpinnings of symptoms of great complexity like the productive ones.

Conscious awareness is a fascinating psychological function of the human mind. It describes a subjective first-person phenomenon (Damasio, 1998), that consists in both the cognitive processes of the self and its interactions with the external world. Therefore the construction of the self-awareness includes all the experiences re-lated to the body (James, 1980), in order to process and to represent the perceptual, motor, emotional and cognitive states as own bodily states. This function results to be impaired in several neuropsychological and neurologi-cal disorders (Flashman, 2002), causing interferences with the personal identity or the awareness about ourselves (Orfei, et al., 2007). These pathological conditions reveal insight to scientifically investigate the cognitive processes and the neuroanatomical networks involved in awareness of the bodily self (Fotopoulou, 2012). The self-awareness include both the 'sense of agency' as the feelings of the authorship and control of our actions and of the following changes on the external world and the 'sense of ownership' as the appreciation of the body as belonging to me (Gallagher, 2000) and they can be selectively or simultaneously impaired. The specific disorder of body agency is the Anosognosia for hemiplegia (Babinski, 1914), as the apparent unawareness of own sensorimotor deficits or the inability to acknowledge and appreciate the severity of the paralysis and other sensorimotor deficits following stroke (Cocchini, Beschin, Cameron, Fotopoulou, & Della Sala, 2009) Indeed the disturbances affecting the body ownership are the inability to recognize one's own body ('asomatognosia', Cutting, 1978) and the misattribution of ownership of own arm to another person ('somatoparaphrenia', Gerstmann, 1942). This thesis aims to investigate the possible influences of bodily aspects in self-awareness, by focusing on the specific role of actions. In Chapter 1 and 2, I introduced the disturbances of self-awareness of the Anosognosia for Hemipleia, and Somatoparaphrenia with neuropsychological and neuroanatomical accounts. Subsequently I wanted to highlight the importance of planning an action in these deficits in order to enhance the degree of motor awareness through both bottom-up and top-down mechanisms. My main projects focused on the investigation of the role of the Action in Anosognosia for Hemiplegia. In details in Chapter 3, 4 and 5 my experiments based on evaluating the fluctuations of motor awareness in patients with Anosognosia for Hemiplegia during the request to execute an action. I investigated this issue in some different tasks: in the attempts to act, in third-perspective view and in automatic bodily activation by measuring skin conductance responses. In addition I modulated the affective resonance of these tasks by using dangerous stimuli, so that I could evaluate the influences of both bottom-up sensorimotor and top-down emotional and cognitive components in awareness' fluctuations. I also integrated brain lesion-analyses to understand the neural networks underneath. In Chapter 6, I integrated the thesis with a single-case study of a patient with Crossed Somatoparaphrenia. This rare disorder gave me the possibility to investi-gate some aspects related to the body image and the body schema. I studied this patient in different situations assessing: multisensory integration and spatial components of proprioception and third-perspective view, in order to evaluate both sensorial and higher-order possible effects relating to the body representation. In addition, I also enclosed two single-case studies. The first was a young patient with Balint's syndrome, which was evaluated in a cross-modal task, the second a man affected by Tactile Agnosia, whit whom I applied a rehabilitation program with transcranical direct-current stimulation. These studies are included as extra experiemental studies not belonging to the main PhD topic.