Abstract
Dopamine is central to a number of cognitive functions and brain disorders. Given the cost of neurochemical imaging in humans, behavioural proxy measures of dopamine have gained in popularity in the past decade, such as spontaneous eye blink rate (sEBR). Increased sEBR is commonly associated with increased dopamine function based on pharmacological evidence and patient studies. Yet, this hypothesis has not been validated using in vivo measures of dopamine function in humans. To fill this gap, we measured sEBR and striatal dopamine synthesis capacity using [18F]DOPA PET in 20 participants (nine healthy individuals and 11 pathological gamblers). Our results, based on frequentist and Bayesian statistics, as well as region‐of‐interest and voxel‐wise analyses, argue against a positive relationship between sEBR and striatal dopamine synthesis capacity. They show that, if anything, the evidence is in favour of a negative relationship. These results, which complement findings from a recent study that failed to observe a relationship between sEBR and dopamine D2 receptor availability, suggest that caution and nuance are warranted when interpreting sEBR in terms of a proxy measure of striatal dopamine.
Highlights
Dopamine is a key ascending neuromodulator subserving a range of cognitive functions, including motivation, learning and attention
Using [18F]fallypride positron emission tomography (PET) and the dopamine D2 receptor agonist bromocriptine, they found that dopamine D2 receptor availability was neither related to baseline spontaneous eye blink rate (sEBR) or bromocriptine-induced changes in sEBR. We focused on another aspect of dopamine function, namely striatal dopamine synthesis capacity, as measured by [18F]DOPA PET
We tested the hypothesis of a positive relationship between sEBR and striatal dopamine synthesis capacity, based on the proposal that sEBR is positively related to striatal dopamine function
Summary
Dopamine is a key ascending neuromodulator subserving a range of cognitive functions, including motivation, learning and attention. Striatal dopamine dysregulation is a common feature across many psychiatric disorders in which those functions are impaired, including addiction, schizophrenia, attention deficit hyperactivity disorder and depression (Russo & Nestler, 2013; Nutt et al, 2015; Grace, 2016). Direct assessment of dopamine function in humans is only possible with expensive and invasive techniques such as positron emission tomography (PET), which require complex infrastructure and in-depth methodological expertise. *G.S., R.L. and R.J.H. shared first authorship. Received 25 November 2017, revised 17 February 2018, accepted 27 February 2018. Reviewed by Linh Dang, Vanderbilt University, USA; and Filip Van Opstal, University of Amsterdam, Netherlands
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