The main paper of my PhD just got published: Rupprecht and Friedrich, Precise Synaptic Balance in the Zebrafish Homolog of Olfactory Cortex, Neuron (2018). (PDF)

You might like it if you are also interested in

• Classical balanced networks
• Things you can do with whole-cell voltage clamp
• Olfactory cortex
• More recent ideas about balanced networks
• Coordination of excitatory and inhibitory synaptic inputs in single neurons
• Adult zebrafish

To summarize this work in one sentence, this is a study of the coordination of excitatory and inhibitory synaptic inputs in single neurons. If you want to know the details, you should definitely read the paper.

The main part of the study is purely experimental, but one of its strengths is that it connects the experimental findings with computational concepts about balanced networks. The concept of a balanced state has been brought up in the mid-90s by Shadlen & Newsome and van Vreeswijk & Sompolinsky (among others). More recent theoretical work has, in my opinion, contributed a lot to identifying and correcting some weaknesses of the classical balanced network, and has come up with new concepts about circuit function of balanced networks that are of general interest to those who want to understand how the brain works. If you’re interested in a discussion of these concepts, I can recommend the following review articles as starting points (which are also discussed in our paper):

1. Denève S, Machens CK, Efficient Codes and Balanced Networks, Nature Neuroscience (2016).
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2. Hennequin G, Agnes EJ, Vogels TP, Inhibitory Plasticity: Balance, Control, and Codependence, Annual Review of Neuroscience (2017)..
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But let’s for one moment think beyond the scope of this work, which focused on synaptic inputs on the single-cell level – let’s think about the subcellular level. One thing I’d be interested in would be to have a closer look at the coordination of synaptic inputs on small dendritic segments instead of entire neurons. There is already a handful of studies that go into that direction, using mechanisms of synaptic plasticity (Chiu et al., Neuron, 2018) or the anatomical distribution of synapses (Iascone et al., bioRxiv) as entry points.

I’m really looking forward to seeing more research going into this subcellular level of neuronal processing. I can understand that people find population codes as observed by calcium imaging and extracellular recordings of interest, especially with respect to behavior. But I’m also convinced that mechanistic insights into how neurons work can be better obtained by investigating cellular and sub-cellular processes. Our published study investigates a variety of details on the cellular level; but this is only a small fraction of the many things that go unnoticed if you only look at the firing of neurons and not at underlying processes, for example the synaptic inputs.