The new article by Oliver Sacks is one of the most riveting things I've ever read. It concerns Clive Wearing, a distinguished musicologist and musician who has been left by an illness with near-total amnesia -- his brain cannot form new, conscious memories, and his past memories, up to the immediate moment, have been erased.

He lives in a kind of eternal "now", forgetting what he experiences within seconds of experiencing it. It is, apparently, like waking up from a coma every seven to thirty seconds, not realizing that you had woken up from a coma before that, and before that, and before that...

What we refer to using the general term "memory" comprises a group of functions, located in different regions of the brain. Wearing has no episodic memory function, and his semantic memory is also severely impaired. However, his procedural memory is intact. As a result, he can still play the piano with skill and feeling and conduct a choir -- although afterwards he will have no recollection of having done so. He remains a witty and charming conversationalist, can speak several languages, is able to shave, make coffee, play cards and dance, but cannot explain how he knows these things. He retains deep emotional connections, especially with his wife -- whom he greets passionately at each meeting, as though she had been gone for years.

Just as interesting as the Sacks piece is a BBC documentary about Wearing, which someone has uploaded to YouTube.