The magnetothermal activation of neurons in the CeA was examined using immunoanalysis of c-fos expression, which is widely used as a measure of neuronal activation. The proportion of cells expressing c-fos in the CeA was 57.78 ± 3.50% after low-dose (0.05 μg) FVIO stimulation, as shown in Fig. 4 (f and g). However, a significantly lower percentage of c-fos-positive cells (37.16 ± 0.77%) was detected in the high-dose (0.80 μg) SPIO-stimulated mice. The results suggested that FVIO-mediated magnetothermal neurostimulation can efficiently activate many more neurons in the CeA than can SPIO-mediated neurostimulation under the same conditions.