Figure 1.

In Vivo Monosynaptic Connectivity between L2 Primary Somatosensory Cortex Excitatory Pyramidal Neurons

(A) Cartoon schematic illustrating the experimental setup with the position of four recording pipettes.

(B) In vivo two-photon z stack after a simultaneous whole-cell recording from three L2 pyramidal neurons filled with Alexa Fluor 594.

(C) Anatomical reconstruction of the biocytin fill of the same three neurons as in (B), with barrels row labeled; color corresponds to cell numbers in (B). Lighter cell shading indicates the axon.

(D) Example averaged downstate synaptic connection from cell 3 to cell 2 in (B).

(E) A triple whole-cell recording showing the 0.5-Hz stimulation paradigm used to test for a synaptic connection.

(F) Averaging the postsynaptic responses to single APs in downstates from the recordings in (E) revealed a bidirectionally connected pair of neurons.

(G) Cartoon schematic and pie chart showing the proportion of tested connections that were unconnected (gray) or part of a unidirectionally connected (orange) or bidirectionally connected (green) pair. See also Experimental Procedures for n number description.

(H) Histogram of the numbers of unconnected, unidirectional, and bidirectional connections found as a function of the somatic distance; color coding in the inset is the same as in (G). Red line shows linear regression between connection probability and somatic distance with no significant relationship.

(I) Same as in (H) for depth of recording.

See also Figure S1.