Monday, February 8, 2010

Patching in awake animals gets you into Science!

Navigation activates the hippocampus. For each location we visit, specific place cells are activated. Conventionally, place cells are recorded by using chronic single- or multi unit recordings. The biggest drawback of these techniques is the lack of information about what is happening inside the cell. This part of information has been lacking for a long time. Whole cell, or sharp electrode recordings can provide this information, but are very challenging in awake behaving animals. The group of Michael Brecht (who else) have taken the challenge and recorded from a number of hippocampal neurons in awake navigating animals (Epsztein et al. Science, 2010).

The most interesting finding is the occurence of spikelets in these neurons. These spikelets are different from spikes and EPSPs, but still they are correlated with navigation. Of course this all sounds very interesting, but is it actually? What are we learning here? The spikelets probably do not transmit down the axon because they reflect subthreshold activity. They can, like EPSPs, be underlying spikes in these neurons. But, these spikes could have been detected by extracellular means as well.

Then there must be some exciting story at the input site! Of course there must be a cool story here, otherwise 'Science' would never consider it for publishing. Unfortunately, the authors have no clue what they are looking at. They propose axo-axonal coupling, dendritic spikes or extopic axonal spikes. But none of these explanations have been tested here. So, the input side of this story has not been investigated properly yet.

Now, what did we learn from this? 1. There are spikelets in hippocampal principal cells. 2. These spikelets can be underlying spike firing. 3. spikelets are correlated with navigation in a similar way as spikes.
So it seems that using a fancy technique is enough to get into science. Let's all go for patching in free-flying zebra finches. Not because we might actually learn something from it, but because we can and it gets us into 'Science'.

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