FOS and essential tremor: Fos protein expression is widely used as a marker of neural activation to explore the brain regions linked to disease conditions (e.g., epilepsy, essential tremors) and drug responses (Morgan et al., 1987; Kovacs, 1998; Hoffman and Lyo, 2002; Ohno et al., 2008, 2009, 2011; Okuno, 2011; Tatara et al., 2015; Iha et al., 2016).