By examining how sounds are registered during the process oflearning, UC Irvine neurobiologists have discovered a neural codingmechanism that the brain relies upon to register the intensity ofmemories based on the importance of the experience.
Whileneurobiologists have long hypothesized this type of neural coding, thestudy presents the first evidence that a "memory code" of any kind mayexist. The UCI researchers believe that this code, as well as similarcodes that may be discovered, will not only broaden our understandingof normal learning and memory but also may shed light on learningdisorders. It may also one day be possible to manipulate these codes tocontrol what and how we remember – not only basic sounds, butcomplicated information and events.
"This memory code may helpexplain both good and poor memory," said Norman Weinberger, a professorof neurobiology and behavior in UCI’s Center for the Neurobiology ofLearning and Memory. "People tend to remember important experiencesbetter than routine ones."
Weinberger and his colleagues foundthat when the brain uses this coding method, information is stored in agreater number of brain cells, which should result in a strongermemory. However, the researchers believe that if the brain fails to usethe code, the resulting memory – even if it is an important one – wouldbe weaker because fewer neurons would be involved.
Weinberger andpostdoctoral researcher Richard Rutkowski discovered this coding systemthrough studying how the primary auditory cortex responds to varioussounds.
In the study, the researchers trained rats to press a barto receive water when they heard a certain tone. The tone was varied inits importance to different rats as shown by their different levels ofcorrect performance.
After brain mapping these test rats, theresearchers found that the greater the importance of the tone, thegreater the area of the auditory cortex that became tuned to it. Theresults in rats that received the same tones but were trained to avisual stimulus did not differ from those in untrained rats, showingthat the behavioral importance of the tone, not its mere presence, wasthe critical factor.
Study results appear on the Online EarlyEdition of the Proceedings of the National Academy of Sciences. TheNational Institute on Deafness and Other Communication Disorderssupported the effort.
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