Synaptic background activity controls spike transfer from thalamus to cortex

Jakob Wolfart, Damien Debay, Gwen Le Masson, Alain Destexhe and Thierry Bal

Nature Neuroscience 8: 1760-1767, 2005.

PDF copy of the full paper

Abstract

Characterizing the responsiveness of thalamic neurons is crucial to understanding the flow of sensory information. Typically, thalamocortical neurons possess two distinct firing modes. At depolarized membrane potentials, thalamic cells fire single action potentials and faithfully relay synaptic inputs to the cortex. At hyperpolarized potentials, the activation of T-type calcium channels promotes burst firing, and the transfer is less accurate. Our results suggest that this duality no longer holds if synaptic background activity is taken into account. By injecting stochastic conductances into guinea-pig thalamocortical neurons in slices, we show that the transfer function of these neurons is strongly influenced by conductance noise. The combination of synaptic noise with intrinsic properties gives a global responsiveness that is more linear, mixing single-spike and burst responses at all membrane potentials. Because in thalamic neurons, background synaptic input originates mainly from cortex, these results support a determinant role of corticothalamic feedback during sensory information processing.

Supplementary Material

The supplementary material to this paper includes:

Supplementary information on methods, giving more details on the stochastic model used in the paper, as well as on data analysis;
Supplementary Fig. 1 shows the subthreshold response variability of TC cells;
Supplementary Fig. 2 shows spike-triggered averages of Vm and conductances preceding single spikes and bursts;
Supplementary Fig. 3 tests the dynamic-clamp by comparing real and model Vm fluctuations.

PDF copies of these supplementary files are available, together with a PDF copy of the paper, in a ZIP archive.

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