Primary visual cortex shows laminar‐specific and balanced circuit organization of excitatory and inhibitory synaptic connectivity

Citations Over TimeTop 10% of 2016 papers

Abstract

In the mammalian neocortex, excitatory neurons provide excitation in both columnar and laminar dimensions, which is modulated further by inhibitory neurons. However, our understanding of intracortical excitatory and inhibitory synaptic inputs in relation to principal excitatory neurons remains incomplete, and it is unclear how local excitatory and inhibitory synaptic connections to excitatory neurons are spatially organized on a layer-by-layer basis. In the present study, we combined whole cell recordings with laser scanning photostimulation via glutamate uncaging to map excitatory and inhibitory synaptic inputs to single excitatory neurons throughout cortical layers 2/3-6 in the mouse primary visual cortex (V1). We find that synaptic input sources of excitatory neurons span the radial columns of laminar microcircuits, and excitatory neurons in different V1 laminae exhibit distinct patterns of layer-specific organization of excitatory inputs. Remarkably, the spatial extent of inhibitory inputs of excitatory neurons for a given layer closely mirrors that of their excitatory input sources, indicating that excitatory and inhibitory synaptic connectivity is spatially balanced across excitatory neuronal networks. Strong interlaminar inhibitory inputs are found, particularly for excitatory neurons in layers 2/3 and 5. This differs from earlier studies reporting that inhibitory cortical connections to excitatory neurons are generally localized within the same cortical layer. On the basis of the functional mapping assays, we conducted a quantitative assessment of both excitatory and inhibitory synaptic laminar connections to excitatory cells at single cell resolution, establishing precise layer-by-layer synaptic wiring diagrams of excitatory neurons in the visual cortex.

Related Papers

• → Synaptic dendritic activity modulates the single synaptic event(2020)9 cited
• → Relationships between Local Synaptic Connections and Orientation Domains in Primary Visual Cortex(1997)24 cited
• → The Neocortex-Inspired Locally Recurrent Neural Network (NILRNN) as a Model of the Primary Visual Cortex(2022)2 cited
• → Development of post‐tetanic potentiation at identified inhibitory and excitatory synapses in Aplysia(1982)16 cited
• → The Physiology of Synapses(1964)1 cited