부산대학교 도서관

Pavlovian influences notoriously interfere with operant behaviour. Evidence suggests this interference sometimes coincides with the release of the neuromodulator dopamine in the nucleus accumbens. Suppressing such interference is one of the targets of cognitive control. Here, using the examples of active avoidance and omission behaviour, we examine the possibility that direct manipulation of the dopamine signal is an instrument of control itself. In particular, when instrumental and Pavlovian influences come into conflict, dopamine levels might be affected by the controlled deployment of a reframing mechanism that recasts the prospect of possible punishment as an opportunity to approach safety, and the prospect of future reward in terms of a possible loss of that reward. We operationalize this reframing mechanism and fit the resulting model to rodent behaviour from two paradigmatic experiments in which accumbens dopamine release was also measured. We show that in addition to matching animals' behaviour, the model predicts dopamine transients that capture some key features of observed dopamine release at the time of discriminative cues, supporting the idea that modulation of this neuromodulator is amongst the repertoire of cognitive control strategies. Author summary: Evolution provides us with behavioural tendencies that are usually adaptive, but sometimes interfere with our goals. The glimpse of a cream bun in the bakery window may lure us to actions defeating our dieting aims; the sound of a loud car horn as we cross a street may cause us to freeze reflexively when it would be better to hasten out of the way of oncoming traffic. Such 'Pavlovian' influences over behaviour, in these examples respectively promoting active approach and behavioural inhibition, involve the action of neuromodulators, such as dopamine, in subcortical brain areas. Here, we consider the possibility that one strategy the brain employs to attempt to control such occasionally errant processes is to manipulate the neuromodulatory signal itself. We examine experimental results from two rodent studies that measured subcortical dopamine release while rats made active responses to evade punishment, or inhibited their responses to gain reward. We build a model of the rats' behaviour that includes the possibility of controlling dopamine release, and show that the model can capture key patterns in the data. This lends support to the idea that the brain may sometimes exert control by manipulating neuromodulation itself. [ABSTRACT FROM AUTHOR]