Dopamine: Go/No-Go motivation vs. switching

Abstract: Sensitivity to incentive motivation has a formative influence on extraversion. Mesoamygdaloid dopamine (DA) activity may, at one level, act as a micro-gate permitting an incentive to influence behavioral organization -'Go/No-Go' in this scheme. However data on function elsewhere in the mesocorticolimbic DA system is taken to support this particular function. At another level of analysis, the data in this review by D&C along with that on the rest of the VTA system may fit better with a "switching" function in information processing. This link is supported by correlations between measures of extraversion, learned inattention and overall DA activity. The point is extended to the novelty-seeking feature of the extraverted personality. Commentary: The neurotransmitter dopamine (DA), in areas innervated by the VTA, is undoubtedly an important part of the substrate for motor activation and responses to novelty, as expressed in the mesolimbic and modulated by the mesocortical system. Thus, via activation and impulsivity (D&C's terms), modulation by DA of limbic and neocortical activity in the expression of extraversion is not in contention. We support this in the animal model with psychostimulants (rearing, head-turning, and orientingmovements, Oades et al. 1985; What is in dispute is the exclusive role of the VTA-DA projection system in 'incentive motivation'. D&C section 3.3 specifically state that the approach of a rewarding goal is the essence of incentive motivation and this is facilitated by VTA-DA activity. They then qualify this (section 4.1) by saying that this facilitation does not consist of mediation (the strong version of the postulate) but instead should be seen as modulation. This 'weak' version flies in the face of the 'strong' version promulgated by Schultz and colleagues (e.g., 1995b) whom they so willingly cite in section 4.2, (the titles alone illustrate the point). Both versions are a kind of Go/No-Go theory to explain the extraversion/ introversion conflict over signals of reward and punishment described in section 2.4. A more widely applicable and more parsimonious alternative lies in selective information processing