Repeated BOLD-fMRI imaging of deep brain stimulation responses in rats.
Functional magnetic resonance imaging (fMRI) provides a picture of the global spatial activation pattern of the brain. Interest is growing regarding the application of fMRI to rodent models to investigate adult brain plasticity. To date, most rodent studies used an electrical forepaw stimulation model to acquire fMRI data, with α-chloralose as the anesthetic. However, α-chloralose is harmful to animals, and not suitable for longitudinal studies. Moreover, peripheral stimulation models enable only a limited number of brain regions to be studied. Processing between peripheral regions and the brain is multisynaptic, and renders interpretation difficult and uncertain. In the present study, we combined the medetomidine-based fMRI protocol (a noninvasive rodent fMRI protocol) with chronic implantation of an MRI-compatible stimulation electrode in the ventroposterior (VP) thalamus to repetitively sample thalamocortical responses in the rat brain. Using this model, we scanned the forebrain responses evoked by the VP stimulation repeatedly of individual rats over 1 week. Cortical BOLD responses were compared between the 2 profiles obtained at day1 and day8. We discovered reproducible frequency- and amplitude-dependent BOLD responses in the ipsilateral somatosensory cortex (S1). The S1 BOLD responses during the 2 sessions were conserved in maximal response amplitude, area size (size ratio from 0.88 to 0.91), and location (overlap ratio from 0.61 to 0.67). The present study provides a long-term chronic brain stimulation protocol for studying the plasticity of specific neural circuits in the rodent brain by BOLD-fMRI.
Department of Life Science, National Taiwan University, Taipei, Taiwan.
Tzu-Hao Harry
TH
Chao
Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan.
Jyh-Horng
JH
Chen
Department of Life Science, National Taiwan University, Taipei, Taiwan.
Chen-Tung
CT
Yen
D000818:Animals; D046690:Deep Brain Stimulation / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D004567:Electrodes, Implanted; D008279:Magnetic Resonance Imaging; D008297:Male; D020926:Medetomidine; D010100:Oxygen / Q000097:blood; D051381:Rats; D020318:Rats, Long-Evans; D018709:Statistics, Nonparametric; D013788:Thalamus / Q000502:physiology* / Q000601:surgery
D020926:Medetomidine; D010100:Oxygen