Learning by neurones: role of attention, reinforcement and behaviour.

The importance of the behavioural situation, attentional demands of the task, and stimulus-reinforcement contingencies in promoting or permitting experience-dependent neuronal plasticity is argued. Evidence is provided for the specific activation of the locus coeruleus noradrenergic system of the rat by novel stimuli encountered while investigating the environment, as well as during a formal learning situation. Noradrenergic neurons are particularly concerned with changes in the predictive value of the stimulus, when new learning should occur. Noradrenaline, released at LC terminals in target sensory systems, could facilitate shifts in attention, information processing and memory through its well-documented gating and tuning effects and its permissive role in long-term potentiation. Dopamine neurons, which fire persistently to reward during learning, could be involved in maintaining the behavioural response.