Abstract #3913
Local EPI Distortion Induced by Blue Light Delivery in the Nave Brain: Implications for Optogenetic fMRI Studies
Russell W. Chan 1,2 , Alex T.L. Leong 1,2 , Joe S. Cheng 1,2 , Victor B. Xie 1,2 , Partick P. Gao 1,2 , Aaron Mok 2 , Kevin K. Tsia 2 , and Ed X. Wu 1,2
1
Laboratory of Biomedical Imaging and Signal
Processing, The University of Hong Kong, Hong Kong,
China,
2
Department
of Electrical and Electronic Engineering, The University
of Hong Kong, Hong Kong, China
Previously, it has been reported that blue light
delivery in the nave brain resulted in pseudo positive
and negative fMRI responses, which were attributed to
NMR frequency shifts, and T1 and T2* changes. EPI is
known to be susceptible to NMR frequency shifting, field
inhomogeneity and T2* changes. However, the effects of
blue light delivery in the nave brain and EPI
distortion have not been examined. The aim of this study
was to investigate the local EPI distortion induced by
laser stimulation in the nave posterior thalamus. Our
results showed that the pseudo negative fMRI response
was at the fiber tip, while the pseudo positive fMRI
response was adjacent to the pseudo negative fMRI
response along the phase encoding direction. This study
brings attention to EPI distortion as a possible
confounder which must be taken into account when
optogenetic fMRI experiments are designed.
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