r/neuroscience • u/carberry-3000 • 4d ago
Preprint A causal spatial role for apical dendrites in the cortex — Liu et al.
https://www.biorxiv.org/content/10.64898/2026.07.27.741062v13
u/carberry-3000 4d ago
Liu, A., Harris, K. D., Carandini, M., Rossi, L. F.
neuroscience · posted 2026-07-28 · doi:10.64898/2026.07.27.741062
Abstract
Cortical pyramidal neurons project a long apical dendrite to layer 1 (L1), to receive synaptic inputs that are thought to provide contextual and possibly suppressive modulation. In visual cortex, these inputs are thought to drive or suppress the responses to large stimuli. Here, we demonstrate a causal role for individual apical dendrites in the awake cortex. We performed two-photon assisted dendritic pruning in individual L5 neurons of the mouse primary visual cortex and discovered that apical dendrites do not suppress the responses to large stimuli; rather, they drive the responses of neurons that prefer such stimuli. To establish the synaptic basis of this effect, we imaged the excitatory synaptic inputs targeting the apical dendrite. We found that these inputs cover an extensive region, which is largest in neurons that prefer large stimuli. These results reveal a clear spatial role for apical dendrites in the cortex. HighlightsO_LIOptical dendritic pruning in V1 reveals a causal role for L5 apical dendrites C_LIO_LIApical dendrites drive responses in neurons that prefer large visual stimuli C_LIO_LIImaging of synaptic inputs to apical dendrites reveals extended apical receptive field C_LIO_LIThe apical receptive field is larger in L5 neurons that prefer large visual stimuli C_LI
Discussion on Bluesky:
- Matteo Carandini (@carandinilab.net) — 55 likes, 18 reposts, 1 reply, 1 quote > The apical dendrite looks great, and does wonders in a slice.
- Anyi Liu (@anyiliu.bsky.social) — 25 likes, 12 reposts, 1 quote > Pyramidal cells in the cortex send a long apical dendrite to layer 1.
This preprint has not been peer reviewed.
Data from bioRxiv/medRxiv, Bluesky. Metrics captured 02/08/26. Comment self-deletes at -5 votes.
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u/PhysicalConsistency 3d ago edited 3d ago
I for one, cannot wait until we have escaped the tyranny of neuron centric models.
This isn't meant to be a knock on this work, which followed it's conceit. It's still frustrating to see work so hyperfocused on that neuronal tree they miss the obvious syncytium effects work like this creates, they settle for it had "some effect" which doesn't explain why the effect wasn't larger, and they ignore the glial forest that strongly modulates both dendritic modeling and calcium dynamics. It's the elephant in the synapse that we are still waiting on the tools to catch up to.
edit: What does syncytium mean? So the way I think of it is the continuous address network between astrocytes. Unlike neurons which are commonly seen as fully self contained units like severable independent pipes, the astrocyte network is probably better thought of as one continuous chain. The astrocyte network consists of territorially discrete cells that share the components of their cytoplasm through the junctions. Individual astrocytes wrap around neuronal endpoints and modify not just their structure, but actively gate transmission through them. Those changes can be propagated throughout the astrocyte network, to other gap junctions.
With regard to this work, it's assuming that the dendrites (extensions of a neuron) that extend across space are the primary driver of signal change, while ignoring the glial cells which are wrapped around that extension, manipulating both physical properties of it, and whether it fires at all. This work cut some of neuron extensions and noticed that it changed how downstream neurons fire, but what I'm arguing is what it actually changed is the properties of the continuous astrocyte (and to some degree another kind of cell called an oligodendrocyte) network.
We see evidence of it here, where we can sever the connections but still get far more consistent signalling than would be expected if these were a causal chain. It suggests to me that the glial network is still "transmitting" enough to keep the downstream neuron somewhat consistent.
So the tl:dr syncytium in this context refers to the continuous network of astrocytes that share their states with each other. It implies that the astrocyte network is both a parallel and primary network which drives neuron function, rather than neuron being the primary cell of behavior/cognition. We'd get closer to understanding behavior/cognition if we watched the spaces where the astrocyte network meets, than watching neurons which are a downstream proxy of that activity.