Efficacy of thalamocortical and intracortical synaptic connections: Quanta, innervation, and reliability

Gil Ziv, Barry W. Connors, Yael Amitai

Research output: Contribution to journalArticlepeer-review

273 Scopus citations

Abstract

Thalamocortical (TC) synapses carry information into the neocortex, but they are far outnumbered by excitatory intracortical (IC) synapses. We measured the synaptic properties that determine the efficacy of TC and IC axons converging onto spiny neurons of layer 4 in the mouse somatosensory cortex. Quantal events from TC and IC synapses were indistinguishable. However, TC axons had, on average, about 3 times more release sites than IC axons, and the mean release probability at TC synapses was about 1.5 times higher than that at IC synapses. Differences of innervation ratio and release probability make the average TC connection several times more effective than the average IC connection, and may allow small numbers of TC axons to dominate the activity of cortical layer 4 cells during sensory inflow.

Original languageEnglish
Pages (from-to)385-397
Number of pages13
JournalNeuron
Volume23
Issue number2
DOIs
StatePublished - 1 Jan 1999

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