Posted by IsoM on February 21, 2003, at 17:08:41
For any interested:
"Remember: Fire Like This"
(Hippocampal interneuron firing patterns may help coordinate memory storage and retrieval.)
By Richard RobinsonUnderstanding how the brain stores and retrieves memories is one of the most complex problems to remain unsolved in neuroscience. Oscillatory firing patterns in the hippocampus are thought to be central to both processes. In the 20 February Nature, Thomas Klausberger and colleagues at the University of Oxford , UK, demonstrate that different classes of hippocampal interneurons display characteristic firing patterns which may contribute to the activities of neural networks (Nature, 421:844-848, February 20, 2003).
Klausberger et al. measured firing rates in anesthetized rats of three types of inhibitory interneurons -- axo-axonic cells, basket cells, and O-LM (oriens-lacunosum-moleculare) cells distinguished by their morphology, immunohistochemistry, and connectivity to pyramidal cells of the hippocampus. They recorded firing patterns during two types of hippocampal neural activity: theta oscillations, which are regular and rhythmic that characterize movement, exploration, and REM sleep; and ripple oscillations, which are short bursts of activity that characterize slow-wave sleep and rest. During theta oscillations, maximum activity of axo-axonic cells occurred at the peak of the theta wave, while basket cells fired just after the wave peak, and O-LM cells at the trough. During ripple oscillations, axo-axonic cells fired in phase with the ripples, basket cells only at the start of the burst, and O-LM cells were silent.
The individual firing patterns observed may facilitate different aspects of hippocampal activity -- spikes from axo-axonic cells during ripple oscillations "could time-lock the activity of thousands of pyramidal cells," suggest the authors.
In an accompanying News and Views article, Edvard Moser at the Norwegian University of Science and Technology , Trondheim, notes that these studies need to be extended to active behaviors in awake animals, and that combining such physiological studies with genetic manipulations of cells involved in hippocampal neural networks may allow discoveries of "the most fundamental principles of memory formation in the neuronal assemblies of the hippocampus."
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Links for this article:J Csicsvari et al., "Oscillatory coupling of pyramidal hippocampal pyramidal cells and interneurons in the behaving rat," Journal of Neuroscience, 19:274-287, 1999.
[PubMed Abstract]T. Klausberger et al., "Brain-state- and cell-type-specific firing of hippocampal interneurons in vivo," Nature, 421:844-848, February 20, 2003.
http://www.nature.com/nature/University of Oxford
http://www.ox.ac.ukE. Moser, "Interneurons take charge," Nature, 421:797-799, February 20, 2003.
http://www.nature.com/nature/Norwegian University of Science and Technology
http://www.ntnu.no
poster:IsoM
thread:202578
URL: http://www.dr-bob.org/babble/20030219/msgs/202578.html