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 Do microplastics harbour additional risks by colonization with harmful bacteria?
05.04.2018 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University

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: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Joining metals without welding

23.04.2018 | Trade Fair News

Researchers illuminate the path to a new era of microelectronics

23.04.2018 | Information Technology

Rochester scientists discover gene controlling genetic recombination rates

23.04.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>