Somatosensory Stimulus Frequency-Dependent Neural, CBF, and BOLD FMRI Responses in Isoflurane-Anesthetized Rat

Tae Kim¹, Kazuto Masamoto², Alberto Vazquez¹, Mitsuhiro Fukuda¹, Seong-Gi Kim¹

Frequency-dependence of neural, CBF, and BOLD fMRI responses on stimulation duration were measured in the isoflurane-anesthetized rats. Higher frequency stimulation produced a larger neural activity per unit time during the early stimulation period, but dramatically decreased for later periods, while lower frequency stimulation induced smaller, but similar field potential amplitude responses maintained over the entire stimulation period. Similar frequency-dependent trends were observed in CBF and BOLD responses. Our findings suggest that the optimal stimulation frequency is dependent on stimulus duration, and it should be aware on the experiment design under isoflurane anesthesia.