Binary and analog variation of synapses between cortical pyramidal neurons
Abstract
Learning from experience depends at least in part on changes in neuronal connections. We present the largest map of connectivity to date between cortical neurons of a defined type (layer 2/3 [L2/3] pyramidal cells in mouse primary visual cortex), which was enabled by automated analysis of serial section electron microscopy images with improved handling of image defects (250 × 140 × 90 μm3 volume). We used the map to identify constraints on the learning algorithms employed by the cortex. Previous cortical studies modeled a continuum of synapse sizes by a log-normal distribution. A continuum is consistent with most neural network models of learning, in which synaptic strength is a continuously graded analog variable. Here, we show that synapse size, when restricted to synapses between L2/3 pyramidal cells, is well modeled by the sum of a binary variable and an analog variable drawn from a log-normal distribution. Two synapses sharing the same presynaptic and postsynaptic cells are known to be correlated in size. We show that the binary variables of the two synapses are highly correlated, while the analog variables are not. Binary variation could be the outcome of a Hebbian or other synaptic plasticity rule depending on activity signals that are relatively uniform across neuronal arbors, while analog variation may be dominated by other influences such as spontaneous dynamical fluctuations. We discuss the implications for the longstanding hypothesis that activity-dependent plasticity switches synapses between bistable states.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 16, 2022
- Source ID
- 10.7554/elife.76120
Entities
People
- Adam A. Bleckert
- Agnes L. Bodor
- Aleksandar Zlateski
- Alyssa M. Wilson
- Andreas S Tolias
- Casey M Schneider-Mizell
- Chris S. Jordan
- Daniel J. Bumbarger
- Derrick Brittain
- Dodam Ih
- Emmanouil Froudarakis
- Forrest Collman
- Gayathri Mahalingam
- H. Sebastian Seung
- Ignacio Tartavull
- Jacob Reimer
- Jingpeng Wu
- JoAnn Buchanan
- Jonathan Zung
- Kisuk Lee
- Lynne Becker
- Manuel Castro
- Marc Takeno
- Nicholas L. Turner
- Nico Kemnitz
- Nuno Macarico da Costa
- R Clay Reid
- Ran Lu
- Russel M Torres
- Sergiy Popovych
- Shelby Suckow
- Sven Dorkenwald
- Szi-chieh Yu
- Thomas Macrina
- William Silversmith
- William Wong
- Yang Li
Organizations
- Allen Institute for Brain Science
- Army Research Office
- Baylor College of Medicine
- G. Harold & Leila Y. Mathers Foundation
- Intelligence Advanced Research Projects Activity
- Massachusetts Institute of Technology
- National Eye Institute
- National Institute of Mental Health
- National Institute of Neurological Disorders and Stroke
- Princeton University
- Rice University