Assessing sensory versus optogenetic network activation by combining (o)fMRI with optical Ca2+ recordings

Florian Schmid, Lydia Wachsmuth, Miriam Schwalm, Pierre Hugues Prouvot, Eduardo Rosales Jubal, Consuelo Fois, Gautam Pramanik, Claus Zimmer, Cornelius Faber*, Albrecht Stroh

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

51 Citations (Scopus)

Abstract

Encoding of sensory inputs in the cortex is characterized by sparse neuronal network activation. Optogenetic stimulation has previously been combined with fMRI (ofMRI) to probe functional networks. However, for a quantitative optogenetic probing of sensory-driven sparse network activation, the level of similarity between sensory and optogenetic network activation needs to be explored. Here, we complement ofMRI with optic fiber-based population Ca2+ recordings for a region-specific readout of neuronal spiking activity in rat brain. Comparing Ca2+ responses to the blood oxygenation level-dependent signal upon sensory stimulation with increasing frequencies showed adaptation of Ca2+ transients contrasted by an increase of blood oxygenation level-dependent responses, indicating that the optical recordings convey complementary information on neuronal network activity to the corresponding hemodynamic response. To study the similarity of optogenetic and sensory activation, we quantified the density of cells expressing channelrhodopsin-2 and modeled light propagation in the tissue. We estimated the effectively illuminated volume and numbers of optogenetically stimulated neurons, being indicative of sparse activation. At the functional level, upon either sensory or optogenetic stimulation we detected single-peak short-latency primary Ca2+ responses with similar amplitudes and found that blood oxygenation level-dependent responses showed similar time courses. These data suggest that ofMRI can serve as a representative model for functional brain mapping.

Original languageEnglish
Pages (from-to)1885-1900
Number of pages16
JournalJournal of Cerebral Blood Flow and Metabolism
Volume36
Issue number11
DOIs
Publication statusPublished - 1 Nov 2016
Externally publishedYes

Keywords

  • Optogenetic fMRI
  • calcium recordings
  • light propagation
  • optical neurophysiology
  • sparse network activation

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