“…Several lines of evidence suggest that the DA system not only affects top-down attentional control processes (Noudoost & Moore, 2011b;Sarter, Albin, Kucinski, & Lustig, 2014;Sarter, Gehring, & Kozak, 2006) (Colzato, Pratt, & Hommel, 2010;Colzato, Slagter, de Rover, & Hommel, 2011), but also modulates bottom-up perceptual processes (Bao, Chan, & Merzenich, 2001;Noudoost & Moore, 2011a;Ziegler, Pedersen, Mowinckel, & Biele, 2016), possibly by improving the signal-to-noise ratio (SNR) of sensory input (Kroener, Chandler, Phillips, & Seamans, 2009;Yousif et al, 2016). This modulation of the SNR is considered to reflect neuronal gain control mechanisms (Li, Lindenberger, & Sikström, 2001;Servan-Schreiber, Printz, & Cohen, 1990;Yousif et al, 2016;Ziegler et al, 2016). Increasing gain control can be conceptualized as amplifying an information processing system's responsivity to input signals from multiple levels, for example, from the sensory level (Salinas & Thier, 2000).…”