The findings have "fascinating implications," said principal investigator Jonathon Crystal, both in evolutionary terms and for future research into the biological underpinnings of memory, as well as the treatment of diseases marked by memory failure such as Alzheimer's, Parkinson's and Huntington's, or disorders such as schizophrenia, PTSD and depression.
The study further opens up the possibility of creating animal models of memory disorders.
"Researchers can now study in animals what was once thought an exclusively human domain," said Crystal, professor in the Department of Psychological and Brain Sciences in the College of Arts and Sciences. "If you can export types of behaviors such as source memory failures to transgenic animal models, you have the ability to produce preclinical models for the treatment of diseases such as Alzheimer's."
Of the various forms of memory identified by scientists, some have long been considered distinctively human. Among these is source memory. When someone retells a joke to the person who told it to him, it is an everyday example of source memory failure. The person telling the joke forgot the source of the information -- how he acquired it -- though not the information he was told. People combine source information to construct memories of discrete events and to distinguish one event or episode from another.
Nonhuman animals, by contrast, have been thought to have limited forms of memory, acquired through conditioning and repetition, habits rather than conscious memories. The kind of memory failures most devastating to those directly affected by Alzheimer's have typically been considered beyond the scope of nonhuman minds.
The study owes much to another quality these rodents share with humans: They love chocolate. "There's no amount of chocolate you can give to a rat which will stop it from eating more chocolate," Crystal said.
Using chocolate as bait in an eight-arm radial maze, the study was made up of a series of five experiments that together provide converging evidence. In the first two, in order to obtain the chocolate, the rats needed to remember the source by which they acquired it, whether they were placed near the trough containing the chocolate or had to run on their own to get there. Using different mazes helped rule out the possibility that overlearned cues from a particular maze led to the positive results.
A third experiment showed that the rats' source memory, the means by which it retrieved the chocolate, lasted for a week rather than the one day that other, more ordinary forms of memory last. This provided converging evidence, said Crystal, that the rats were relying on source memory insofar as source memories decay more slowly than other memory systems.
In the fourth experiment, the rats could obtain the chocolate when the researcher placed them at the trough. The rats remembered this rule, too. Finally, in the fifth experiment, researchers temporarily disabled the rats' hippocampus, the brain region thought to be crucial for accurate source memory. If the task requires source memory, inactivating that area would impair the ability to remember source information, which it did.
"What we're trying to do is to develop behavioral approaches with rodents that tap into those types of memory systems," Crystal said. "This study is the demonstration, the proof of the concept that source memory exists in animals. But the mechanism that supports it is open. We're now interested in working out the sub-areas of the hippocampus that are involved in episodic memory, testing hypotheses about different regions being involved in short-term and long-term episodic memory, working out the neuroanatomical pathways."
This study is the latest breakthrough in Crystal's Comparative Cognition Laboratory, which seeks to develop animal models of memory types that are impaired in human diseases. Past experiments have similarly uncovered evidence of other presumably human forms of memory and cognition in rats.
Other researchers include Visiting Scholar Wesley T. Alford; graduate student Wenyi Zhou; and Andrea G. Hohmann, Linda and Jack Gill Chair of Neuroscience and Professor in the IU Department of Psychological and Brain Sciences.
The study "Source Memory in the Rat" was published in Current Biology and is online at http://dx.doi.org/10.1016/j.cub.2013.01.023.
For a copy of the study, or to speak with Crystal, contact Liz Rosdeitcher at 812-855-4507 or email@example.com, or Tracy James at 812-855-0084 or firstname.lastname@example.org.
The research was supported with a grant from the National Institute of Mental Health.
Liz Rosdeitcher | EurekAlert!
Making fuel out of thick air
08.12.2017 | DOE/Argonne National Laboratory
‘Spying’ on the hidden geometry of complex networks through machine intelligence
08.12.2017 | Technische Universität Dresden
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years' time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of the trade journal "Nature Communications."
Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the...
08.12.2017 | Event News
07.12.2017 | Event News
05.12.2017 | Event News
08.12.2017 | Life Sciences
08.12.2017 | Information Technology
08.12.2017 | Information Technology