Elucidating the neurophysiological basis of time perception

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Our ability to accurately perceive time changes from one moment to the next. These variations contribute to moment-to-moment fluctuations in our experience of the world and other psychological functions such as coordinating our movements in response to environmental cues. Variations in our perception of time are thought to be caused in part by fluctuations in a specific brain chemical, dopamine. Dopamine is believed to activate brain regions involved in matching time intervals against other intervals we hold in memory and thereby affecting how we perceive the passage of time. When and how dopamine influences our experience of time is poorly understood because until very recently it was impossible to measure dopamine in the human brain over short timescales. A newly-developed method, fast-scan cyclic voltammetry (FSCV), allows us to accurately measure dopamine in humans and thus offers an excellent opportunity to study how dopamine contributes to variations in human time perception for the first time. Another method, electroencephalography (EEG), allows us to record a particular brain rhythm (beta oscillations) that is closely associated with dopamine and can thereby provide a complementary way to study the role dopamine plays in affecting different phases of time perception. The proposed research aims to use FSCV and EEG to investigate whether moment-to-moment variations in time perception can be predicted from participants' brain states. FSCV will be used to measure dopamine concentrations in striatum, a brain region previously implicated in time perception, in Parkinson's patients whilst they complete time perception tasks. This will allow us to determine whether dopamine concentrations can be used to predict how participants perceive time. Further analyses will investigate whether dopamine plays a similar role in time perception when we're storing an interval in memory as when we're trying to remember an interval and whether dopamine plays a similar role in both time perception and other cognitive functions such as attention and working memory. In a second, complementary set of studies, an advanced analysis technique, multivariate pattern analysis, will be applied to EEG data in healthy adults whilst they complete the same time perception tasks. This method will allow us to determine approximately when in time participants' experiences of time can be predicted and the role of specific brain rhythms. This approach will also help to clarify whether similar brain mechanisms support different phases of time perception and both time perception and other cognitive functions.This project has the potential to significantly advance current understanding of how fluctuations in brain states influence our subjective experience of time. This research will help to update contemporary theories of timing including when and how brain states shape our perception of time, how these states contribute to different phases of time perception, and how time perception relates to other basic psychological functions. Our perception of time influences how we perform a variety of actions such as coordinating our movements and predicting the trajectory of a ball so that we are able to catch it. Superior understanding of the brain mechanisms that contribute to variability in time perception may thus help to understand the sources of variability in human performance more generally. Individuals with different disorders such as Parkinson's disease and schizophrenia experience pronounced alterations in their perception. These time distortions are typically characterized by increased variability in the perception of time. By helping to strengthen current understanding of how variability in brain states contributes to fluctuations in our time perception, this project may also help to provide a methodological and theoretical framework for studying these distortions in a more refined manner including how they relate to other clinical symptoms.