Where unconscious memories form

A small area deep in the brain called the perirhinal cortex is critical for forming unconscious conceptual memories, researchers at the UC Davis Center for Mind and Brain have found.

The perirhinal cortex was thought to be involved, like the neighboring , in "declarative" or conscious memories, but the new results show that the picture is more complex, said lead author Wei-chun Wang, a graduate student at UC Davis.

The results were published Dec. 9 in the journal Neuron.

We're all familiar with memories that rise from the unconscious mind. Imagine looking at a beach scene, said Wang. A little later, someone mentions surfing, and the beach scene pops back into your head.

Declarative memories, in contrast, are those where we recall being on that beach and watching that surf competition: "I remember being there."

Damage to a structure called the hippocampus affects such declarative "I remember" memories, but not conceptual memories, Wang said. Neuroscientists had previously thought the same was true for the perirhinal cortex, which is located immediately next to the hippocampus.

Wang and colleagues carried out memory tests on people diagnosed with , who had known damage to the perirhinal cortex or other . They also carried out functional magnetic resonance imaging (fMRI) scans of healthy volunteers while they performed memory tests.

In a typical test, they gave the subjects a long list of words, such as chair, table or spoon, and asked them to think about how pleasant they were.

Later, they asked the subjects to think up words in different categories, such as "furniture."

Amnesiacs with damage to the perirhinal cortex performed poorly on the tests, while the same brain area lit up in fMRI scans of the healthy .

The study helps us understand how memories are assembled in the brain and how different types of brain damage might impair , Wang said. For example, Alzheimer's disease often attacks the hippocampus and perirhinal cortex before other brain areas.


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Dec 15, 2010
There is much more to our memories and brain than even this implies. I remember most of my dreams vividly, they are many times just as real as real life. Very often people in my dreams do things that seem illogical and without purpose at first that later turn out to have a logical reason. I am completely unaware of this until I find out why they did what they did. It is exactly as if they were real entities with their own agenda. This completely baffles me. The skeptics will attribute this to the subconscious. I am convinced that this can't be true. It would take a complete logical thought process that happens in my brain that I am completely unaware of until it's revealed by later actions of the people in my dreams. Yeah, you can try to explain it but you don't really understand what I am talking about. There are other things that happen in my dreams that defy any conventional explanation as well. You have to experience this stuff to understand. All I can say is that it is amazing.

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