I love this book.
The medical condition of a stroke on the other side of the brain. Most strokes happen on the left side of the brain, so you're likely to see motor dysfunction, like a droopy face, or a limp arm or leg . . . on the right side (left side of the brain affects right side of the body).
But a stroke on the right side of the brain, which is not as common, affects more nebulous aspects of thinking that are quite different.
In the case of the man who mistook his wife for a hat, he had trouble identifying objects unless they were in motion . . . his wife was sitting in the foyer, on a large seated hat rack. He KNEW it was a hat rack, not because he saw a hat rack, but because the location is where the hat rack is located - THAT he remembered. He grabbed his wife, because she was seated where his hat should have been. In spite of his problem identifying things, he simply compensated in other ways, such as asking questions of others: "That is my shoe, yes?".
A fascinating read, with many stroke patients with many unusual symptoms and coping mechanisms.