There is a stranger in my bed

The integrity of the physical body mental image seems to be ingrained in the self, as happens with amputees who continue "feeling" and sometimes trying to use their absent limb. In contrast to lesions of the body, damage of higher brain centers can produce a phenomenon that we conceptualize as the reverse of a phantom limb: the patients have an intact body, but the mental map of their bodies is altered. We believe that we perceive our body directly, as it is. However, our body is only known by constructing a mental image that actually consists of physical changes encoded in cellular brain networks. The fact that brain lesions, hallucinogenic drugs, or emotional states can alter our body image indicates that our image is different from the body itself. This implies that our corporeal awareness is not innate. We have unconsciously collected the impressions of our own body and stored them as our body image.

Macdonald Critchley distinguishes the conceptual from the perceptual aspects of the body image, which he calls corporeal awareness [6]. Tactile, visual, and positional awareness contribute to our body perception and to the development of our mental image. For example, Critchley indicates that congenitally blind children who have never seen their bodies tend to exaggerate the relative size of their hands, lips, and mouth when making clay models. This distortion is most likely related to the primary importance assigned to the parts of the body with which they mostly sense the external environment.

The conceptual and perceptual aspects of our corporeal awareness develop during childhood and adolescence and continue to change throughout life. Some aspects of our body image change not only with our emotional state, but also with the social circumstances and attires. The multitude of factors necessary to develop the body image indicate that the process is complex and could potentially be distorted in a variety of fashions by lesions of the corresponding brain areas. The disorders of the body image are determined in part by the location of the lesion and are affected by the alertness of the patient. We mostly know about disorders of the body image associated with lesions of the non-dominant side of the brain, because lesions of the dominant side (usually the left) are accompanied by serious language impairment.

One of the mildest disorders of the body image is called unilateral neglect, because the patients seem to "forget" to use spontaneously the limbs on one side of the body, even though the limbs can be moved on specific command. This neglect can also be referred to the tactile space, as commonly shown in patients who dress only one-half of their body, or shave only one half of their face. In the most pronounced cases, the patient may feel that one-half of his body has disappeared. Under the effects of LSD, one of my patients with a parietal lobe lesion said, "I feel like a chicken cut in half" [7].

Disorders of the body image are also complicated by the attitude of the patient toward the disease, by their alertness, and by the extent of the brain damage, which may impair the patient's collaboration with a complex examination. Thus, the symptoms may vary from a mild lack of concern to a complete denial of the illness, with elaborate stories (confabulations) to cover up the symptoms [8]. For example, when the patients walk, they may have the tendency to bump into objects located on one side. Neglect can be observed on either side, but right-side neglect is more difficult to study because it is produced by left-brain lesions that are frequently accompanied by speech disorders. Patients frequently say that the insensitive or paralyzed limb, which they can touch and feel with their healthy arm, belongs to a stranger. At other times the patient may insist: "There is a stranger in my bed." The "stranger" is sometimes given a name and can be considered friendly, but may also produce erotic feelings, bother, or sexually assault the patient.

Another disorder of the body image is the alien hand syndrome, in which the affected limb may move involuntarily, hitting or choking the patient who tries with varying degrees of success to hold and restrain the arm. Patients often personalize the arm, indicating that it belongs to a stranger or treating it as a misbehaving child [9, 10]. The arm also may perform simple involuntary activities, such as grasping objects, opening faucets, using tools, or making symmetrical movements. The alien hand syndrome is associated with a variety of brain lesions.3 However, the extreme cases of distorted body image are

3 The alien hand syndrome is associated with two main locations of the lesion. (1) The anterior or motor syndrome is produced by infarction or hemorrhage in the territory of the anterior cerebral arteries, which result in damage of the anterior corpus callosum and/or anteromedial frontal cortex. (2) The posterior or sensory form is due to corticobasal degeneration or posterior cerebral artery occlusion [9-11].

Fig. 4.5 Left visual sensory neglect. The visual neglect became evident when the patient was asked to draw a flower with a model in view (a) and from memory without a model (b)

mostly associated with large lesions that produce serious cognitive disorders and are also affected by patient alertness. Kurt Goldstein (1878-1965) remarked several times that the symptoms presented by a patient are quite complex, because they are not only the result of the disrupted function, but also of the reaction and accommodation to the catastrophic effects of the disease [12]. He also said: "Nobody will doubt that the observation and analysis of pathological phenomena often yield greater insight into the processes of the organism than that of the normal." ... "Since disease process is a modification—and indeed, a very significant modification—of a normal process, biological research cannot afford to neglect it" [12].

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