Even with the more limited measures of impulsivity used across animal studies, there is evidence that these tasks may tap into different aspects of impulsivity. Research has shown that response inhibition and delay aversion are mediated by different neurobiological and neurochemical substrates, implicating dissociable cortico-limbic-striatal circuits and mechanisms. For example, different brain manipulations affect response inhibition and delay discounting (Evenden 1999; Dalley et al. 2007a). Additionally, the difference observed between HAD and LAD rats on a delay discounting task, described above (Wilhelm & Mitchell 2008), was not observed in short-term selected lines of mice, bred to voluntarily drink either high (STDRHI2) or low (STDRLO2) amounts of 10% ethanol. However, in a Go/No-go task, STDRHI2 mice showed significant impairments in ability to inhibit nose-poking in response to specific cues (Wilhelm et al. 2007). On this basis, the authors suggested that delay aversion and response inhibition are different forms of impulsivity (see also Evenden 1999; Winstanley et al. 2005; Dalley et al. 2007b; Winstanley 2007), and that future studies should examine ‘the link between genetics and specific subcomponents of impulsivity associated with
