lum by Ramon y Cajal.As another clinical example, one with rather bizarre symptoms,
consider the case of someone who has a stroke resulting in damage to
both the posterior frontal and anterior parietal lobes. Posterior frontal
lobe damage results in paralysis. Anterior parietal lobe damage results
in loss of body sensation and other somatosensory weirdness, such as
somatosensory neglect. These effects are experienced on the side of
the body contralateral to the side of the brain affected by the stroke.
If the stroke lesion is to the right hemisphere, one suffers paralysis
of the left side of the body coupled with somatosensory weirdness
on the left side of the body, and if the stroke lesion is to the left hemi-
sphere, we see paralysis and somatosensory weirdness on the right
side of the body—contralateral effects. However, it turns out that with
a right-hemisphere lesion, something else very odd often happens: in
addition to sensory and motor effects on the left side of the body, the
patient may deny that there is anything wrong at all!
Clearly, this is a very weird condition. Someone suffers a stroke and
is in the hospital as a result. Half of her body is paralyzed, and she is
confined to bed or in a wheelchair. One half of her body has lost sensa-
tion and sometimes may seem to not even be there. And yet she is say-
ing that nothing is wrong with her and wondering why she is even in
the hospital: “Why can’t I go home? There is nothing wrong with me.”
This condition is called anosognosia (Greek nosos = disease, gnosis =
knowledge, a = not) and is characterized by a lack of knowledge about
one’s own disease.
There is a wonderful illustration of anosognosia in a book titled
The Man Who Mistook His Wife for a Hat, by the neurologist Oliver
Sacks. One particular clinical vignette—“the man who fell out of