Learning to like : behavioural expression and neural bases of conditioned preferences in humans

Novel stimuli in the environment can acquire affective and motivational significance through their association with rewarding events. This process of Pavlovian associative conditioning has consequences for behaviour, as these conditioned stimuli can act as rewards in their own right, eliciting behaviour and affecting mood. Although reward conditioning has been extensively studied in animals, both on a behavioural and neuroanatomical level, relatively little is known about it in humans. Various issues concerning how and under what conditions human Pavlovian conditioning can be observed, and the extent to which research in animals can be extrapolated to humans, have been topics of debate. Unlike animals, humans can be explicitly aware of the conditioning manipulation, which may contaminate the behavioural expression of learning. In this thesis I develop a novel paradigm in which previously neutral stimuli acquire emotional significance in the absence of awareness of the conditioning manipulation. I then use this paradigm to explore reward conditioning and other factors that influence preferences, such as ageing, familiarity, and novelty, in humans. These mechanisms of preference conditioning are subsequently linked to neural substrates through neuropsychological work in patients with brain damage and through functional magnetic resonance imaging (fMRI). fMRI, however, is subject to signal dropout in the inferior part of frontal cortex. These areas are part of the regions of interest in reward processing. Here I demonstrate that fMRI sensitivity in reward-related areas can be improved using a novel methodological tool.EThOS - Electronic Theses Online ServiceGBUnited Kingdo