Following on from my interest in the brain and perception and memory I have been reading Oliver Sack’s book The man who mistook his wife for a hat, which I discovered by accident in the library.
In the first chapter Sacks discusses the man who inspired the title of the book, (called only Dr. P) who had a very strange condition. He had stopped recognising ordinary objects, he could see them and describe them, but was baffled as to their use. He also frequently mistook inanimate objects for people, and people for objects. As a musician, Dr. P was connected to the world by sound, but vision had lost meaning for him, in fact daily tasks such as dressing or eating were possible only because Dr. P sang while he did them. If he were interrupted he became confused and seemed no longer to be able to distinguish what he was doing.
One test Sacks used on Dr. P was to ask him to imagine entering a local square, he was to picture himself walking through it from the north side and describe the buildings he passed. Dr. P did so, describing only those buildings that would be on the right hand side. When asked to imagine walking the square from the south side he once again only listed buildings on his right. Literally forgetting anything that was to the left even though he had mentioned them before (Sacks, 1986, p. 14).
It is fascinating how perception is formed so intricately in the brain, and that we take it so much for granted until some damage to the brain, physical or psychological, renders some part inactive and we can appreciate just how strange that makes the world.
Another patient suffered a stroke that took not only his sight but his visual memory too:
Questioning and testing showed, beyond doubt, that not only was he centrally or ‘cortically’ blind, but he had lost all visual memories, lost them totally – yet had no sense of any loss. Indeed, he had lost the very idea of seeing – and was not only unable to describe anything visually, but bewildered when I used words such as ‘seeing’ and ‘light.’ He had become in essence, a non-visual being. His entire lifetime of seeing, of visuality, had, in effect, been stolen. His whole visual life had, indeed, been erased – and erased permanently in the instant of his stroke. (Sacks, 1986, p. 39).
In Part Three Sacks talks about reminiscing, and that extreme reminiscence is thought to be caused by seizures (Sacks, 1986, p. 123). Sacks examines the studies of Wilder Penfield (1891 – 1976) who discovered that vivid recollections of past memories could be evoked if the cerebral cortex was electrically stimulated at ‘seizure prone’ points:
Such epileptic hallucinations or dreams, Penfield showed, are never phantasies: they are always memories, and memories of the most precise and vivid kind, accompanied by the emotions which accompanied the original experience. Their extraordinary and consistent detail, which was evoked each time the cortex was stimulated, and exceeded anything which could be recalled by ordinary memory, suggested to Penfield that the brain retained an almost perfect record of every lifetime’s experience, that the total stream of consciousness was preserved in the brain, and, as such, could always be evoked or called forth, whether by ordinary needs and circumstances of life, or the extraordinary circumstances of an epileptic or electrical stimulation. (Sacks, 1986, p. 130 – 131).
It seems to me that a lot of memories become less vivid over time, and that as they fade they are replaced by representations, such as a memory of the photograph rather than the event, or the memory of the story told about the memory rather than the direct connection to the recollection of the event itself. Perhaps most of our “memories” are actually only traces, representations of representations. It is interesting to note that they are still there somewhere, ready to be called up by a seizure for instance, but are perhaps otherwise difficult to bring into conscious thought. I think there must be three different kinds of memory: True memory (as brought back complete with sensations that occurred at the time, as described in the quote above), forgotten memory (that which is there somewhere in the subconscious, but is unable to be easily accessed), and then a kind of repetition memory in which is apparent through the multiplicity of retellings or recalling. And repetition memory, like any repetition, would be subject to slippage.