This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.

Contribute Thoughts | Search Serendip for Other Papers | Serendip Home Page

Biology 202
2003 Second Web Paper
On Serendip

Anosognosia for Hemiplegia: A Window into Self-Awareness

Cordelia Stearns

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). Proponents of a psychological explanation for the disorder insist that patients are aware on some level of their paralysis, but deny this information, as it would be traumatizing to the image of the self to admit to a lack of ability to control one's own body (4). However, this theory is countered by the fact that anosognosia in stroke patients almost always occurs after a stroke in the right hemisphere of the brain; though a stroke in the left hemisphere is no less devastating to the body, patients with left hemisphere strokes nearly always fully recognize the impact of their strokes on their bodies (5).

Another explanation of anosognosia draws on the fact that this disorder and hemiplegia are nearly always accompanied by hemispatial neglect, in which the patient does not recognize or attend to visual information on the side of the visual field contralateral to the brain damage (6). Some researchers believe that since right-brain stroke patients can be inattentive to visual information on the left side, they may simply be displaying the same inattention to the left half of their bodies when they have anosognosia (4). In other words, if one pays no attention to the left arm, one would not notice if the left arm is doing something odd, like not moving.

However, one of the premier experts on anosognosia, Dr. Vilayanur Ramachandran, has pointed out a key flaw in this theory: though hemispatial neglect patients with right brain damage acknowledge seeing stimuli presented to the left visual field if it is brought to their attention, for example by being moved or set on fire, no amount of attention drawn to an anosognosiac's immobile limbs will make her acknowledge that her limb is paralyzed (4). Usually the anosognosiac will insist that her limb is moving. If pressed, she will cite her arthritis or a lack of motivation as a reason for her immobility. When forced, the patient may even venture completely out of the realm of reality in defending her ability to move, stating that the immobile limb belongs to someone else, or is not a limb at all. Dr. Edoardo Bisiach, another expert in the field, once saw a patient who claimed that his paralyzed hand belonged to Bisiach himself. When Bisiach held his own two hands together with the patient's immobile hand, and asked how it was possible that he had three hands, the patient calmly replied, "A hand is the extremity of an arm. Since you have three arms, it follows that you must have three hands" (4). Ramachandran insists that this type of unrealistic rationalization is particular to patients with anosognosia; a patient suffering only from hemispatial neglect will not justify her beliefs with peculiar stories, but will accept a doctor's diagnosis(4).

Ramachandran favors an explanation of anosognosia dependent on both psychology and neurology. He maintains that due to the vast amount of sensory information the brain regularly receives, it must have a filter of some sort that lets it process only necessary information (4). Ramachandran's idea is that the left hemisphere of the brain contains a schema of the body in its entirety, which is updated as needed by a section of the right hemisphere. This right hemisphere function compares incoming sensory information to the left-brain schema, and decides which discrepancies are worth informing the left-brain about (4). For example, while a few sneezes can be brushed off, a fever will bring the right brain to inform the left-brain that one is sick. Not all discrepancies in information change the left-brain's schematic representation of the body, but the most important or startling ones do. Ramachandran believes that the right brain's ability to detect these discrepancies is damaged in patients with anosognosia (1). Thus, the left-brain receives no information about a change in the body's ability to move, and the current representation of the body as fully mobile is maintained (7).

Recent experiments have shown that if any information of a change in the body's abilities is present in anosognosiacs, it is extraordinarily inaccessible to the I-function. Ramachandran asked three hemiplegic anosognosiacs and two stroke victims with hemiplegia and no anosognosia to choose between winning a small prize for completing a task involving one hand (i.e., stacking blocks) and winning a large prize for completing a task involving two hands (i.e., tying a bow) (4). The hemiplegics with no anosognosia consistently opted for the smaller prize. However, the hemiplegic anosognosiacs chose repeatedly to attempt the two handed task, never learning from their failures, and never recognizing their limitations (4).

Amazingly, many anosognosiacs also seem unable to recognize their own limitations in other people (7). In a recent experiment, Ramachandran found that two thirds of tested hemiplegic anosognosiacs were not able to recognize paralysis in another person (4). He suggests that this is because we have a schema for the bodies of others as well as ourselves, and that they are represented in close proximity in our brains (7). This idea was supported by recent research with monkeys, which showed that the same areas that were active when a monkey completed a certain task were also active when he watched another monkey complete the same task (7). This information suggests that self-awareness is crucial in awareness of others. However, this research is in its early stages, and has not yet been used in the treatment of anosognosiacs.

Two methods of treatment, one primitive and one modern, are used currently to help bring a sense of awareness of failure to anosognosiacs. The first method, invented by Bisiach, involves pouring cold water in the ear of the patient on the side of the paralysis (4). Since nerves in the ear contribute information about the body's balance to the brain, Bisiach figured by shocking these nerves he might startle the part of the body responsible for updating the body schema with new information (4). This appears to work astonishingly well; patients undergoing this treatment often fully realize their paralysis for several hours. The second method of treatment uses virtual reality programming to give patients repeated feedback about their failures in a safe setting (3). This type of program helped I.S., a man with anosognosia for hemispatial neglect, without hemiplegia. I.S. was determined to drive, and saw no reason why he should not, until he was treated with a virtual reality program simulating street crossing. Since I.S. did not pay attention to cars coming on his left side, he consistently had "accidents", which caused the program to make crashing noises and flash warnings. This type of confrontation with his limitations seemed to cause I.S. to begin trusting his doctors over his own sense of self (3). Presumably, the shock of knowing that if he followed the information given to his I-function by the rest of his brain, he would die, caused him to realize that he needed to learn new ways to perceive himself and the world around him, perhaps even by trusting others over himself.

The issue of trust stands out as key in anosognosia, a disorder in which the patient can no longer trust her own information about herself. This seems almost unthinkable, hence the reason I chose to open this essay by addressing you, the reader. Could you possibly believe someone else's information about your body over your own? And, if you ever learned to survive as someone who could no longer trust your brain (and, thus, yourself), could you ever again have any type of free will? Could you be creative or original without fully believing in your own mind? The fact that free will is so hard to imagine without an intact sense of self makes me appreciate the seemingly ridiculous lengths to which anosognosiacs will go to defend their perceptions. For if there were an element of choice involved, I might rather believe that a man could have three hands than believe I had lost the ability to perceive myself. Perhaps, in anosognosia, ignorance about one's own ignorance is bliss.


1)Some Selected Aspects of Motor Cortex Damage in Man, Lecture notes explaining hemiplegia, hemineglect, and anosognosia

2)Neuropsychology and Neuropathology, Brief summaries of discussions on several neuropsychological disorders, including anosognosia and prosopagnosia

3)Unawareness and/or Denial of Disability: Implications for Occupational Therapy Intervention, Article discussing unawareness as obstacle in treatment, gives several case studies (download as pdf file)

4)The Brain that Misplaced its Body, Article discussing Ramachandran's research and several specific case examples (search in archive for article)

5) Unilateral Hemineglect and Anosognosia of Hemiparesis and Hemiplegia , Extremely comprehensive graduate student project on said topics

6) Memory: A Neurosurgeon's Perspective, Only briefly touches on anosognosia, but interesting regardless

7)Mind Over Body, Update on research and speculation on impact of anosognosia on general self-awareness

| Course Home Page | Course Forum | Brain and Behavior | Serendip Home |

Send us your comments at Serendip

© by Serendip 1994- - Last Modified: Wednesday, 02-May-2018 10:53:04 CDT