Sensitivity of instrumental responses to an upshift in water deprivation

The uncertainty processing theory of motivation

Most theories describe motivation using basic terminology (drive, 'wanting', goal, pleasure, etc.) that fails to inform well about the psychological mechanisms controlling its expression. This leads to a conception of motivation as a mere psychological state 'emerging' from neurophysiological substrates. However, the involvement of motivation in a large number of behavioural parameters (triggering, intensity, duration, and directedness) and cognitive abilities (learning, memory, decision, etc.) suggest that it should be viewed as an information processing system. The uncertainty processing theory (UPT) presented here suggests that motivation is the set of cognitive processes allowing organisms to extract information from the environment by reducing uncertainty about the occurrence of psychologically significant events. This processing of information is shown to naturally result in the highlighting of specific stimuli. The UPT attempts to solve three major problems: (i) how motivations can affect behaviour and cognition so widely, (ii) how motivational specificity for objects and events can result from nonspecific neuropharmacological causal factors (such as mesolimbic dopamine), and (iii) how motivational interactions can be conceived in psychological terms, irrespective of their biological correlates. The UPT is in keeping with the conceptual tradition of the incentive salience hypothesis while trying to overcome the shortcomings inherent to this view.

Reward, motivation, and reinforcement learning

There is substantial evidence that dopamine is involved in reward learning and appetitive conditioning. However, the major reinforcement learning-based theoretical models of classical conditioning (crudely, prediction learning) are actually based on rules designed to explain instrumental conditioning (action learning). Extensive anatomical, pharmacological, and psychological data, particularly concerning the impact of motivational manipulations, show that these models are unreasonable. We review the data and consider the involvement of a rich collection of different neural systems in various aspects of these forms of conditioning. Dopamine plays a pivotal, but complicated, role.

Drinking while thirsty can lead to conditioned increases in consumption

A within-subject design was used to test whether repeatedly drinking a novel-flavoured and coloured drink while thirsty would influence subsequent liking for or consumption of that drink, compared to a different flavoured and coloured drink repeatedly consumed while less thirsty. Each participant was given 300 ml of one flavoured drink (H) after consuming a high salt meal (5.27 g of salt), and 300 ml of another flavoured drink (L) after consuming a low salt meal (1.27 g of salt). Participants had 4 sessions with each meal-type/drink combination, in an intermixed order. Pre- and post-training assessments of the drinks were conducted to determine the impact of the training regime on pleasantness and perceived thirst-quenching effect of the drinks. The final session included a choice test, and ad libitum access to the chosen drink, after either a high or low salt meal. In this final choice session, people drank almost twice as much H as L; however, there were no differential effects of past training on rated liking or choice. The increased consumption of H might reflect greater liking for H which was not detected by the rating scales; or it might reflect the learning of greater "conditioned thirst" in response to the flavour of H.

An assessment of factors contributing to instrumental performance for sexual reward in the rat

Male and female rats were gonadectomized, implanted in adulthood with capsules containing either testosterone propionate (TP) or cholesterol, and were trained to lever press for access to an oestrous female. When lever press performance was tested in extinction, only the male rats implanted with TP displayed significantly higher levels of responding than controls, demonstrating that lever pressing for oestrous females as a reward is sexually dimorphic. Ejaculation patterns from a separate assessment of these rats' copulatory ability were significantly correlated with their instrumental performance. In a second experiment, "masculinized" females exposed to TP postnatally and given TP implants responded in extinction at mean levels equivalent to those exhibited by adult males that were either intact or castrated with androgen replacement. These data suggest that organizational steroid exposure perinatally affects the actual reward value assigned to oestrous females in adulthood, in combination with consummatory sexual experience.

Dissociation of Pavlovian and instrumental incentive learning under dopamine antagonists

The administration of the dopamine antagonists, pimozide and alpha-flupenthixol, to rats reduced Pavlovian-instrumental transfer when a conditioned stimulus (CS) that had been paired with a noncontingent food reward was tested on instrumental performance. The administration of the antagonists during Pavlovian conditioning and/or testing abolished the enhancement of instrumental performance by the CS. The effect of both antagonists on instrumental incentive learning was then examined. After training in which the rats performed 2 responses for different food rewards, they consumed 1 type food under the antagonists and the other type under vehicle during reexposure. When instrumental responding was subsequently tested in extinction, performance was unaffected by whether the rats had been reexposed to the training reward under the antagonists. These results suggest that Pavlovian and instrumental incentive learning are not mediated by a common process.