Where unconscious memories form

December 15, 2010

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 hippocampus, 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 amnesia, who had known damage to the perirhinal cortex or other brain areas. 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 control subjects.

The study helps us understand how memories are assembled in the brain and how different types of brain damage might impair memory, Wang said. For example, Alzheimer's disease often attacks the hippocampus and perirhinal cortex before other brain areas.
-end-
Co-authors on the study are Andy Yonelinas, professor of psychology and at the Center for Mind and Brain; Charan Ranganath, professor at the Center for Neuroscience; former UC Davis graduate student Michele Lazzara, now project coordinator at the University of Illinois at Chicago; and Robert Knight, professor of psychology at UC Berkeley.

The work was funded by the National Institutes of Health.

University of California - Davis

Related Hippocampus Articles from Brightsurf:

Brain remapping dysfunction causes spatial memory impairment in Alzheimer's disease
A research group elucidated the brain circuit mechanism that cause of spatial memory impairment in Alzheimer's disease.In the future, improving brain remapping function may reverse spatial memory impairment in patients with Alzheimer's disease.

Impact of family income on learning in children shaped by hippocampus in brain
A new study by a team of researchers at the University of Toronto identifies the region of the brain's hippocampus that links low income with decreased memory and language ability in children.

Inhibitory interneurons in hippocampus excite the developing brain
A new study from the George Washington University, however, reports that in some critical structures of the developing brain, the inhibitory neurons cause excitation rather than suppression of brain activity.

A good blood supply is good for memory
Memory performance and other cognitive abilities benefit from a good blood supply to the brain.

Scientists identify circuit responsible for building memories during sleep
Neuroscientists at the University of Alberta have identified a mechanism that may help build memories during deep sleep, according to a new study.

Lack of oxygen doesn't kill infant brain cells, as previously thought
Research, conducted at OHSU and published in the Journal of Neuroscience, raises new concerns about the vulnerability of the preterm brain to hypoxia.

Schizophrenia: Adolescence is the game-changer
Schizophrenia may be related to the deletion syndrome. However, not everyone who has the syndrome necessarily develops psychotic symptoms.

How the olfactory brain affects memory
How sensory perception in the brain affects learning and memory processes is far from fully understood.

Penn researchers discover the source of new neurons in brain hippocampus
Researchers have shown, in mice, that one type of stem cell that makes adult neurons is the source of this lifetime stock of new cells in the hippocampus.

Scientists find first evidence for necessary role of the human hippocampus in planning
A team of scientists reports finding the first evidence that the human hippocampus is necessary for future planning.

Read More: Hippocampus News and Hippocampus Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.