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 Study relating to materials testing Detecting damages in non-magnetic steel through magnetism
23.07.2018 | Technische Universität Kaiserslautern

nachricht Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel

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: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

'Building up' stretchable electronics to be as multipurpose as your smartphone

14.08.2018 | Information Technology

During HIV infection, antibody can block B cells from fighting pathogens

14.08.2018 | Life Sciences

First study on physical properties of giant cancer cells may inform new treatments

14.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>