Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A fork in memory lane: UCSD research indicates hippocampus supports two aspects of recognition

02.02.2006


Anyone who has recognized a person but then struggled with the particulars – "I know I know her, but how…?" – can also appreciate the distinction between "familiarity" and "recollection."

Recollection, as defined by memory specialists, is the ability to call up specific details about an encounter, while familiarity is simply knowing that someone or something has been encountered before. Both are elements of recognition memory and both, new research suggests, are functions of the brain’s hippocampus.

Published in the Feb. 2 issue of the journal Neuron, the University of California, San Diego study contradicts a recent body of work which maintains that the hippocampus is involved only in recollection.



Led by senior researchers John Wixted, chair of the UCSD psychology department, and Larry Squire, a professor of psychiatry and neurosciences at the UCSD School of Medicine and the San Diego Veterans Affairs Health System, the study addresses one of the central debates in the neuroanatomy of memory.

A seahorse-shaped structure in the left and right medial temporal lobes of the brain, the hippocampus has long been known as a critical area for processing memory. Memory is impaired, often severely, in people whose hippocampi have been damaged by trauma or disease – by Alzheimer’s, for example, or oxygen deprivation following a heart attack.

The details of hippocampal function, however, are hotly contested in scientific circles.

"It is important to be able to assign a process to a specific region of the brain, but it is also intoxicating…," Wixted said. "Psychologists and neuroscientists have jumped at the notion that the hippocampus is critical only for the recollection component of recognition and that the adjacent cortical areas take care of familiarity only. But our findings suggest that conclusion might have been premature."

The study compared six memory-impaired patients with discrete hippocampal damage – that is, patients whose brain damage was localized to the hippocampus, as determined by magnetic resonance imaging (MRI) and other techniques – to an age-matched control group.

Subjects were tested with standard verbal tests of recognition memory. They were given lists of common words to study and after a short interval (three minutes filled with chit-chat) were then given test lists composed of both new and old words. For each word on the recognition test, the subjects were asked to rate their confidence that the word was old or new.

Results were analyzed with the receiver operating characteristic (ROC) curve, a statistical tool widely used to evaluate the accuracy of a classifier. In this case, the ROC curves are confidence plots where the points are derived from rates of true-positive versus false-positive answers (saying "yes" correctly to a word that was on the previous list v. saying "yes" incorrectly to a word that wasn’t).

Some theories of recognition, said Wixted, an expert on signal-detection models of memory, hold that the shape of the ROC is significant: A symmetric curve indicates that only the process of familiarity is involved, while an asymmetric curve indicates that both familiarity and recollection are at work. Also, the greater the asymmetry, the more significant the role of recollection.

After controlling for memory strength – by testing the brain-damaged patients, who have diminished abilities, with shorter (and therefore easier) word lists than those given to controls – the recognition accuracy of both groups was almost identical. Critically, once accuracy was equated, the asymmetry of the ROC curves was identical as well.

This is the first ROC study, Wixted noted, to age-match the subjects and to "strengthen" the memories of the hippocampal patients so that their ROCs could be meaningfully compared to that of the controls. The similarity of the ROCs suggests that recollection is operative even in patients with extensive hippocampal damage.

"The simple idea that these processes can be dichotomized and assigned to separate brain structures is challenged by our results. Both processes appear to be supported by the hippocampus and by the structures in the adjacent parahippocampal gyrus," the researchers write.

"This work is helping us piece together how the brain accomplishes learning and memory," Squire said, "and this is important in efforts to develop treatments for memory disorders."

The paper is titled "The Hippocampus Supports Both the Recollection and the Familiarity Components of Recognition Memory."

Inga Kiderra | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Studies and Analyses:

nachricht Multi-year study finds 'hotspots' of ammonia over world's major agricultural areas
17.03.2017 | University of Maryland

nachricht Diabetes Drug May Improve Bone Fat-induced Defects of Fracture Healing
17.03.2017 | Deutsches Institut für Ernährungsforschung Potsdam-Rehbrücke

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Chlamydia: How bacteria take over control

28.03.2017 | Life Sciences

A Challenging European Research Project to Develop New Tiny Microscopes

28.03.2017 | Medical Engineering

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>