Properties of convergent thalamocortical and intracortical synaptic potentials in single neurons of neocortex

Ziv Gil, Yael Amitai

Research output: Contribution to journalArticlepeer-review

100 Scopus citations

Abstract

We explored differences in the properties of convergent afferent inputs to single neurons in the barrel area of the neocortex. Thalamocortical slices were prepared from mature mice. Recordings were made from neurons in layer V, and either thalamocortical afferents or horizontal intracortical axons were stimulated. Monosynaptic EPSPs from both sources had latencies shorter than 1.8 msec and low shape variance. Disynaptic thalamocortical IPSPs had latencies longer than 1.8 msec. All neuronal types, as defined by intrinsic firing patterns, received both thalamocortical and intracortical monosynaptic input. The shape parameters (rate of rise and half-width) of monosynaptic EPSPs from the two inputs did not differ significantly. The rate of rise of EPSPs varied considerably across cells, but the rates of rise of thalamocortical and intracortical EPSPs onto single cells were strongly correlated. The relative thresholds for activation of synaptic excitation and inhibition were strikingly different between the two tracts: thalamocortical stimulation induced GABA(A)-dependent IPSPs at stimulus intensities equal to or less than those required for evoking EPSPs in 35% (24 of 68) of the cells. In contrast, the threshold response to intracortical stimulation was always an EPSP, and only stronger stimuli could generate di- or polysynaptic (PSPs. We suggest that postsynaptic factors may tend to equalize the waveforms of EPSPs from thalamocortical and intracortical synapses onto single neurons. A major difference between the two convergent tracts is that the thalamocortical pathway much more effectively activates feedforward inhibitory circuits than does the horizontal intracortical pathway.

Original languageEnglish
Pages (from-to)6567-6578
Number of pages12
JournalJournal of Neuroscience
Volume16
Issue number20
DOIs
StatePublished - 15 Oct 1996

Keywords

  • EPSPs
  • barrel cortex
  • feedforward inhibition
  • intracortical synapses
  • local cortical circuit
  • slices
  • thalamocortical synapses

ASJC Scopus subject areas

  • General Neuroscience

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