Anosognosia for Hemiplegia: A Window into Self-Awareness

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Anosognosia for Hemiplegia: A Window into Self-Awareness

You wake up in a hospital bed, scared, confused, and attached to a network of tubes and beeping equipment. After doctors assault you with a barrage of questions and tests, your family emerges from the sea of unfamiliar faces surrounding you and explains what has happened; you have had a stroke in the right half of your brain, and you are at least temporarily paralyzed on your left side. You wiggle your left toes to test yourself; everything seems normal. You lift your left arm to show your family that you are obviously not paralyzed. However, this demonstration does not elicit the happy response you expect; it only causes your children to exchange worried glances with the doctors. No matter how many times you attempt to demonstrate movement in the left half of your body, the roomful of people insists that you are paralyzed. And you are, you just do not know it. How is this possible? You are suffering from anosognosia, a condition in which an ill patient is unaware of her own illness or the deficits resulting from her illness (1).

Anosognosia occurs at least temporarily in over 50% of stroke victims who suffer from paralysis on the side of the body opposite the stroke, a condition known as hemiplegia (1). Patients with anosognosia for hemiplegia insist they can do things like lift both legs, touch their doctor's nose with a finger on their paralyzed side, and walk normally (2). These patients are much less likely to regain independence after their stroke than patients without anosognosia, primarily because they overestimate their own abilities in unsafe situations (3). However, the implications of the illness go far beyond those for patients who suffer from it; anosognosia brings questions of the origin of self-awareness to the forefront. How can someone lose the ability to know when she is or is not moving? Is this some type of elaborate Freudian defense mechanism, or is this person entirely unaware of her illness? How is self-awareness represented in the brain, and is this representation isolated from or attached to awareness of others? Though none of these questions are fully answerable at this time, research into anosognosia has provided scientists and philosophers with insight into some of these ancient questions of human consciousness.

The question of "denial" versus "unawareness" is at the heart of debate between psychologists and neurologists about the origin of anosognosia (3).

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