Figure 1.

Neuronal basis of RP. Because premovement building of the RP both at the EEG (a) (Libet et al., 1983) and single-unit (b) (Fried et al., 2011) levels precedes the emergence of the intention to act, it was originally considered to reflect causal and subconscious neuronal preparation of the action. Emmons et al. (2017) suggested that such ramping activity encodes time intervals. Recent studies have revealed dopamine as a potential neuromodulatory system mediating the encoding of time intervals as well as action-related cognitive processes through similar ramping patterns of activity (c) (Soares et al., 2016; Howard et al., 2017; Kim et al., 2017).