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True and apparent optogenetic BOLD fMRI signals
Author(s) -
Schmid Florian,
Wachsmuth Lydia,
Albers Franziska,
Schwalm Miriam,
Stroh Albrecht,
Faber Cornelius
Publication year - 2017
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26593
Subject(s) - optogenetics , neuroscience , thalamus , somatosensory system , stimulation , opsin , visual cortex , neuroimaging , functional magnetic resonance imaging , photic stimulation , psychology , visual perception , chemistry , rhodopsin , retinal , biochemistry , perception
Purpose Optogenetic fMRI (ofMRI) is a novel tool in neurophysiology and neuroimaging. The method is prone to light‐induced artifacts, two of which were investigated in this study. Methods ofMRI was performed in rats using two excitatory opsins (ChR2 and C1V1 TT ) virally transduced in somatosensory cortex or thalamus. Heat‐induced apparent BOLD activation at the site of the optical fiber and stimulation light–induced activation of the visual pathways were investigated, and control experiments for these two artifacts were established. Results Specific optogenetic BOLD activation was observed with both opsins, accompanied by BOLD in the visual pathways. Unspecific heat‐induced BOLD was ruled out by a control experiment employing low‐level constant illumination in addition to pulsed optogenetic stimulation. Activation of the visual pathways was confirmed to be physiological by direct visual stimulation of the eyes and was suppressed by additional low‐level constant light to the eyes. Light inside the brain was identified as one source of the BOLD signal observed in the visual pathways. Conclusion ofMRI is a method of tremendous potential, but unspecific activations in fMRI not caused by the activation of opsins must be avoided or recognized as such. The control experiments presented here allow for validating the specificity of optogenetic stimulation. Magn Reson Med 77:126–136, 2017. © 2016 Wiley Periodicals, Inc.