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The impact of 'bursting' thalamic impulses at a neocortical synapse

Abstract

Considerable effort has gone into understanding the mechanisms underlying high-frequency 'bursting' of thalamocortical impulses, their sensory information content and their involvement in perception. However, little is known about the influence of such impulses on their cortical targets. Here we follow bursting thalamic impulses to their terminus at the thalamocortical synapse of the awake rabbit, and examine their influence on a class of somatosensory cortical neurons. We show that thalamic bursts potently activate cortical circuits. Initial impulses of each burst have a greatly enhanced ability to elicit cortical action potentials, and later impulses in the burst further raise the probability of eliciting spikes. In some cases, multiple cortical spikes result from a single burst. Moreover, we show that the interval preceding each burst is crucial for generating the enhanced cortical response. The powerful activation of neocortex by thalamocortical bursts is fully consistent with an involvement of these impulses in perceptual/attentional processes.

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Figure 1: Relay mode and burst mode in VB thalamus
Figure 2: Methods and results from one experiment.
Figure 3: Thalamocortical efficacy of first and second impulses of bursts and pseudo-bursts.
Figure 4: The impact of later spikes in a burst.

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Acknowledgements

Supported by grants from NSF (IBN-0077694), NIMH (MH-59322) and the Russian Foundation of Basic Research (00-04-49163). We thank J.-M. Alonso and K. Lukatela for discussions and for comments on this manuscript.

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Correspondence to Harvey A. Swadlow.

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Swadlow, H., Gusev, A. The impact of 'bursting' thalamic impulses at a neocortical synapse. Nat Neurosci 4, 402–408 (2001). https://doi.org/10.1038/86054

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