Scientists know that memory is fragile.

Simply by recollecting or imagining what could have been, we rewrite memories. Now, research with amnesiacs suggests a deeper relationship between the landscapes of memory and imagination.

Men with amnesia were asked to imagine themselves in familiar scenes such as a museum, a bar, and a beach, and to describe the scenes in as much detail as possible. Compared to men without brain injuries, their imagined scenes were bare bones. They contained concrete details and facts, but lacked the richer sense of atmosphere that characterizes the imagined scenes of people without brain damage. It seems that amnesia involves a severing of imagination as much as a severing of the past.

Scientists know that the hippocampus, a small area deep inside the brain, is fundamental to the formation of memories. The precise nature of the role of the hippocampus in memory making and retrieval, however, is the subject of debate.

One group of scientists thinks that once memories are wired in other areas of the brain, the job of the hippocampus is finished. They explain amnesiacs' bare imaginations as a result of a lack of memories to feed those scenes. If childhood memories are all that remains for amnesiacs, then imagining a scene at a bar would understandably be difficult.

Another group, including the authors of this research, thinks that the hippocampus may provide a spatial setting for our mental dramas. Without that setting, we may have a hodge podge of characters and other details that our brains don't know how to assemble into a coherent narrative.

Whatever the verdict, the connection between memory and imagination is new territory and of much interest to neuroscientists studying memory.