Mizuseki K, K Diba, E Pastalkova, G Buzsáki. Hippocampal CA1 pyramidal cells form functionally distinct sublayers. Nat Neurosci. 2011 Aug 7;14(9):1174-81. PDF
Publications
Temporally compressed replay in mPFC
Today, I want to introduce a relatively short, but interesting and suggestive paper.
Fast-Forward Playback of Recent Memory Sequences in Prefrontal Cortex During Sleep
Euston DR, Tatsuno M, McNaughton BL.
This paper shows that mPFC neuronal activity was replayed during sleep following task period, and this replay was task dependent. In addition, it is temporally compressed. The authors confirmed these results using two different methods; cross-correlation and template matching. Both analysis shows the pattern is compressed by a factor about 6. It is convincing that similar values are acquired with two distinct ways.
But they don’t mention to correlation between the replay and sleep stages (slow-wave sleep / REM sleep). I wonder whether frequency of mPFC replay were depend on sleep stage. Regarding to this, I’m also interested in whether it is correlated with EEG patterns, especially sharp-waves.
The authors suggest that processing speed of brain is faster than physical limitation. This is unique and interesting view points. But what does the replay do? The replay seems in hundred millisecond order, so it may be too slow to induce synaptic plasticity.
Sullivan, Csicsvari, Mizuseki, Montgomery, Diba, Buzsáki, J. Neurosci. 2011
Sullivan D, J Csicsvari, K Mizuseki, S Montgomery, K Diba, G Buzsáki. Relationships between Hippocampal Sharp Waves, Ripples, and Fast Gamma Oscillation: Influence of Dentate and Entorhinal Cortical Activity. J. Neurosci. 2011 Jun 8;31(23):8605-16. PDF
Preplay of firing sequence
Today, I pick up the following paper (because of my personal reflection).
Preplay of future place cell sequences by hippocampal cellular assemblies.
Dragoi G, Tonegawa S.
Temporal sequences of place cell firing are observed during awake quiescence and slow-wave sleep following exploring behaviors. This is called “replay”. This paper shows that such temporal sequences are also observed before exploring (figure 1). They call this “preplay”. Preplay is also observed in animals which haven’t explored linear tracks (figure 4). This phenomenon may reflect network dynamics.
This paper may indicate that many (but less than number of all combination of firing order) activity patterns exist as a candidate sequence for information coding. If a candidate pattern matches the sequence during exploration, it will be strengthen during replay. In this view, preplay is a preparation for future learning, and learning is selecting suitable pattern from prepared patterns. Preparing many candidates may require much energy, but it may enable animals to learn quickly, so such mechanism may have advantage in evolutions.
Replay during waking and sleeping
This is my first post to this blog. I’ll post brief reviews about papers which interest me. The first paper is
Awake replay of remote experiences in the hippocampus.
Karlsson MP, Frank LM. 2009, Nat Neurosci.
Replay events of place cells firing sequences are separated in two categories; one occurs during experience, and the other occurs following experience. An awake replay was thought to be depend on sensory inputs, thus it didn’t contain a later type of a replay event. However, this paper shows that both types of replay occur during waking state (figure 2 and 4). In addition, the paper shows firing rate during SWRs are lower in awake state than in quiescent state (figure 3) but replay pattern is more robust in awake state than in quiescent state (figure 3 and 4). I think the paper indicate awake replay has a role for memory consolidation, and the role might be different from that of replay during sleep.
First, I thought the difference of robustness of replay sequence might correlate with that dream is obscurer and more fragmentized than recalling during waking. But now I don’t think it is such simple because human dreams during REM sleep during which sharp-wave ripple isn’t observed. There are many discussions about correlation between memory consolidation and dream. They may be complicated, but interesting.
Buzsáki and Diba, In: Dynamic Coordination in the Brain. 2010
Buzsáki G, K Diba (2010) Oscillation-supported information processing and transfer in the hippocampus-entorhinal-neocortical interface. In: Dynamic Coordination in the Brain: From Neurons to Mind, ed. C. von der Malsburg, W. A. Phillips, and W. Singer. Strüngmann Forum Reports, vol. 5. Cambridge, MA: MIT Press. PDF
Geisler, Diba, Mizuseki, Pastalkova, Royer, Buzsáki, P.N.A.S. 2010
Geisler C, K Diba, K Mizuseki, E Pastalkova, S Royer, G Buzsáki (2010) Temporal delays among place cells determine the frequency of population theta oscillations in the hippocampus. Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7957-62. Epub 2010 Apr 7. PDF
Schmidt, Diba, Leibold, Schmitz, Buzsáki, Kempter, J. Neurosci. 2009
Schmidt R†, K Diba†, C Leibold, D Schmitz, G Buzsáki, R Kempter. Single-trial phase precession in the hippocampus. J Neurosci. 2009 Oct 21;29(42):13232-41. †These authors contributed equally. PDF
Diba and Buzsáki, J. Neurosci. 2008
Diba K, G Buzsáki (2008) Hippocampal network dynamics constrain the time lag between pyramidal cells across modified environments. J Neurosci. 28: 13448-13456. PDF
Diba and Buzsáki, Nat. Neurosci. 2007
Diba K, G Buzsáki (2007) Forward and reverse hippocampal place cell sequences during ripples. Nat Neurosci. 10, 1241-1242. PDF