Letter

Nature 457, 1133-1136 (26 February 2009) | doi:10.1038/nature07658; Received 2 September 2008; Accepted 17 November 2008; Published online 18 January 2009

Intracortical circuits of pyramidal neurons reflect their long-range axonal targets

Solange P. Brown1 & Shaul Hestrin1

  1. Department of Comparative Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Edwards Building, R314, Stanford, California 94305-5342, USA

Correspondence to: Shaul Hestrin1 Correspondence and requests for materials should be addressed to S.H. (Email: shaul.hestrin@stanford.edu).

Cortical columns generate separate streams of information that are distributed to numerous cortical and subcortical brain regions1. We asked whether local intracortical circuits reflect these different processing streams by testing whether the intracortical connectivity among pyramidal neurons reflects their long-range axonal targets. We recorded simultaneously from up to four retrogradely labelled pyramidal neurons that projected to the superior colliculus, the contralateral striatum or the contralateral cortex to assess their synaptic connectivity. Here we show that the probability of synaptic connection depends on the functional identities of both the presynaptic and postsynaptic neurons. We first found that the frequency of monosynaptic connections among corticostriatal pyramidal neurons is significantly higher than among corticocortical or corticotectal pyramidal neurons. We then show that the probability of feed-forward connections from corticocortical neurons to corticotectal neurons is approximately three- to fourfold higher than the probability of monosynaptic connections among corticocortical or corticotectal cells. Moreover, we found that the average axodendritic overlap of the presynaptic and postsynaptic pyramidal neurons could not fully explain the differences in connection probability that we observed. The selective synaptic interactions we describe demonstrate that the organization of local networks of pyramidal cells reflects the long-range targets of both the presynaptic and postsynaptic neurons.

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