Phase-locking of hippocampal interneurons' membrane potential to neocortical up-down states


During quiet wakefulness and sleep, and under anesthesia, the membrane potentials of neocortical pyramidal neurons show synchronous, slow oscillations, so-called up-down states (UDS), that can be detected in the local field potential (LFP). The influence of this synchronized, spontaneous neocortical activity on the hippocampus is largely unknown. We performed the first in vivo whole-cell recordings from hippocampal dorsal CA1 interneurons and found that their membrane potentials were phase-locked to neocortical up-down states with a small delay. These results provide strong evidence for cortico-hippocampal interaction and suggest that neocortical activity drives hippocampal interneurons during UDS.

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Figure 1: Up-down states in neocortex and hippocampus.
Figure 2: CA1 interneurons' membrane potential is phase-locked to neocortical LFP with a short delay.


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We thank O. Ahmed, M. Blatow, R. Burwell, D. Haydon Wallace, J. Kauer and S. Schnall for reading the manuscript. M.R.M. was supported by the Rhode Island Foundation grant, the Salomon Foundation grant, US National Institutes of Health/Collaborative Research in Computational Neuroscience grant, a Young Investigator Award from the National Alliance for Research in Schizophrenia and Depression foundation and an early CAREER award from the National Science Foundation.

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Correspondence to Thomas T G Hahn or Mayank R Mehta.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Fig. 1

Cross-correlation coefficient between action potentials (AP) of hippocampal interneurons and neocortical LFP (AP-LFP correlation). (PDF 148 kb)

Supplementary Methods (PDF 43 kb)

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Hahn, T., Sakmann, B. & Mehta, M. Phase-locking of hippocampal interneurons' membrane potential to neocortical up-down states. Nat Neurosci 9, 1359–1361 (2006).

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