The functional organization of cortical networks
Trenholm1, S., Wertz1, A., Roska1,2, B.

1Neural Circuit Laboratories, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; 2Department of Ophthalmology, University of Basel, Switzerland

stuart.trenholm@fmi.ch

Introduction: Many cortical neurons respond selectively to specific cues. For instance, in visual cortex, many neurons preferentially respond to specific orientations or directions of moving images. How this feature selectivity relates to that of the presynaptic network, which spans across cortical layers, remains unclear.

Methods: Using single-cell-initiated, monosynaptically-restricted, retrograde transsynaptic tracing with rabies viruses expressing a calcium indicator, we imaged, in vivo, visual motion evoked activity of individual postsynaptic neurons and their presynaptic neuronal networks across cortical layers in primary visual cortex in mouse.

Results: This technique labelled hundreds of presynaptic cells connected to single postsynaptic pyramidal cells in primary visual cortex. Most presynaptic neurons were located locally in primary visual cortex, and were situated across all cortical layers. Long range connections, from outside primary visual cortex, were also consistently found. Next, using 2-photon in-vivo calcium imaging we characterized the response properties of the electroporated cell (i.e. the postsynaptic cell) to moving visual stimuli, as well as the response properties of the local presynaptic network in primary visual cortex. We found that presynaptic networks connected to individual cortical pyramidal cells could be classified into different groups based on functional organization. Furthermore, we found layer-specific functional presynaptic modules.

Conclusion: These results reveal the existence of different presynaptic network configurations belonging to individual pyramidal neurons in visual cortex.

HFSP Long-Term Fellow (Award year 2013)
Fellow: TRENHOLM, Stuart
Host supervisor: ROSKA, Botond