I finished listening to the audio-version of Oliver Sacks'
"Hallucinations". The book is what it is billed, an encyclopedia of
hallucinations. Sacks is a good writer and he creates a nice, easily
flowing narrative. The book is structured as a textbook, there is no
plot, climax and denouement; neither is there an agenda to debate a
point of view. Sacks just methodically and impartially describes the
aberrations in human perception. He specifically focuses on these
failures of perception, rather than more complicated delusions. Thus,
some of the more dramatic and disturbing diseases, such as
schizophrenia, are not covered.

The book even starts with some of the least exciting of them: charles
bonnet syndrome (CBS) - visual hallucinations in healthy people due to
vision loss. Sacks, btw, manages to repeat the same point multiple
times in that chapter.  Yet, it picks up from there as Sacks moves on
to sensory deprivation and then on to drug induced hallucinations. It
was amusing to read how Sacks himself, occasionally recklessly,
experimented with drugs and what kind of silliness he got himself into
due to his experiments.

The book then covers any and all possible hallucinations: olfactory,
migraines and ecstatic seizures, out of body experience, near death
experience, body doubles, demonic possession, epilepsy. This coverage
is exhaustive.

Among some of my impressions of the book is that brain is such a
complex organ that the science of psychiatry does not have a good
understanding as to how the brain works or what causes it to
malfunction. Inventing fancy Latin names for symptoms, they even have
a specific term for seeing little people, or writing research papers
describing them, does not advance such understanding
much. Occasionally, thankfully rarely, the book or the actor who reads
it, comes across as conceited in pretending to understand more than
they actually do. At other times, Sacks is actually humble in plainly
describing the limitations of modern-day psychiatry.

What was interesting to observe is how often Sacks -- I do not think
he did it on purpose, it just so happened -- points the neurological
sources for religious experiences. The temporal lobe diseases lead to
ecstatic seizures (epiphanies, seeing god, etc.) Out of body and end of
life experiences, caused by lack of blood flow to one part of the
brain or anther, seem like ascent to heaven. Auditory hallucinations,
rather common even in healthy people, but even more frequent under
stress or deprivation may cause, depending on interpretation, either
demonic possessions or speaking to god. Speaking of speaking to god,
such auditory experiences can be enhanced by regular training, also
known as prayer or meditation.

I listened to Sacks while on long runs, often in the dark. And some of
the colorful descriptions such as hallucinations of long-distance
athletes, visions of phantasmic dreamscapes of Chicago, inescapable
lights that triggered epileptic seizures, or nightmarish hypnogogic
hallucinations creeped me out, or depending on the interpretation,
added to the excitement of the night run.


Sacks makes the subject accessible. He is sparing with scientific
jargon. Learning some of the terms is even kind of fun.

micropsia - objects are perceived smaller than they are
senestesia - mixing of multiple senses (color hearing, etc.)
charles bonnet syndrome (CBS) - visual hallucinations due to lack 
	       of nervous stimulation
catatonia - motor immobility, stupor
parkinsonism is related to lack of dopamine 
lilliputian hallucinations - perception of little people 
narcolepsy - predisposition to fall asleep 
autoscopy - perceiving himself to be in another position in space 
out of body experience/near-death experience/sensed presence 
anton syndrome - a person is completely blind yet firmly believes that
      he can see
ecstatic seizure - a feeling of "spiritual" enlightenment
grand mal seizure - loss of consciousness and muscle convulsions in epilepsy
delirium tremens - acute withdrawal symptoms
hypnogogic/hypnopompic hallucinations - going into/coming out of sleep