Monoamines, Acetylcholine and Contingency of Reward Delivery in Instrumental Behaviour
نویسندگان
چکیده
Introduction There is much empirical support for the notion that acetylcholine (ACh) and the monoamine neurotransmitters noradrenaline (NA), dopamine (DA) and serotonin (5-HT) modulate cognitive processes (including attention, learning and memory, executive control and decision-making) in specific and distinct ways. The application of in-vivo brain microdialysis in closely controlled behavioural settings has greatly facilitated research in this area, particularly in defining with greater precision the different task contingencies that produce robust and specific changes in ACh, NA, DA and 5-HT release. In recent experiments we have adapted this technique in rats within the context of a 5-choice serial reaction time task (5-CSRTT), which provides a sensitive behavioural assessment of visuospatial attention and impulsivity. The basic configuration of the task requires subjects to detect and respond to brief light stimuli presented randomly in one of five spatial locations over many trials in order to receive food reinforcement. The paradigm has a basic form that is analogous to the human continuous performance tests devised by Mirsky and Rosvold; and still much used in clinical settings to quantify attentional deficits in AD/HD and schizophrenia. It is known that discrete lesions of different sub-divisions of the prefrontal cortex (PFC) affect different aspects of performance on the 5-CSRTT, especially lesions of the medial PFC (including anterior cingulate, prelimbic and infralimbic cortices). In this presentation we present data from several recent studies that combine behavioural testing on the 5-CSRTT with in-vivo microdialysis. Probes were implanted in the medial PFC and animals were tested under different behavioural contingencies in order to tease apart the unique involvement of ACh, NA, DA and 5-HT in instrumental (response-dependent) visual attentional performance.
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