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Abstract

Dopamine is vital in forming mental models of 'what' and 'when' sensory events occur that essentially guide goal-directed behaviour. However, it remains largely unknown how variations in temporal predictability are incorporated into such mental models. A better understanding of the underlying mechanisms is important, considering dopaminergic depletion in diseases such as Parkinson's Disease and Schizophrenia, where abnormal temporal processing is observed. Some electroencephalographic (EEG) studies indicate that noradrenergic mechanisms, as reflected in the P3b event-related potential, are modulated by temporal predictability, whereas others indicate that dopaminergic mechanisms as reflected in the P3a, underlie surprise. In this study, resting-state and task-dependent EEG was recorded from 24 healthy participants who were administered a selective D2 agonist or antagonist before they performed a pure tone auditory 'oddball' task. Two oddball sequences included either partially predictable, with inter-stimulus intervals (ISIs) of 400ms/1200ms; or fully temporally predictable tones, with a consistent ISI of 600ms. Tones following 400ms ISIs were perceived as surprising, or 'early', as shown in an enhanced P3a response; tones following a 1200ms ISIs showed a much reduced P3a response ('late'). The agonist accentuated the 'late' effect, demonstrating that drugs targeting D2 receptors modulate temporal prediction. These findings differentiate the role of the dopaminergic system in temporal processing and model-based auditory predictions.