Pharmacological enhancement of dopamine neurotransmission does not affect illusory pattern perception

Abstract

Psychotic symptoms and delusional beliefs have been linked to dopamine transmission in both healthy and clinical samples and are assumed to result at least in part from perceiving illusory patterns in noise. However, the existing literature on the role of dopamine in detecting patterns in noise is inconclusive. To address this issue, we assessed the effect of manipulating dopaminergic neurotransmission on illusory pattern perception in healthy individuals (n = 48, n = 19 female) in a double-blind placebo-controlled within-subjects design (see preregistration at https://osf.io/a4k9j/). We predicted individuals on vs. off L-DOPA to be more likely to perceive illusory patterns, specifically objects in images containing only noise. Using a signal detection model, however, we found no credible evidence that L-DOPA compared to placebo increased false alarm rates. Further, L-DOPA did not reliably modulate measures of accuracy, discrimination sensitivity and response bias. In all cases, Bayesian statistics revealed strong evidence in favour of the null hypothesis. The task design followed previous work on illusory pattern perception, and comprised a limited number of items per condition. The results therefore need to be interpreted with caution, as power was limited. Future studies should address illusory pattern perception using more items, and take into account potential dose-dependent effects and differential effects in healthy vs. clinical samples.

Significance statement Psychosis and delusional belief have been linked to dopamine transmission in healthy and clinical samples and are assumed to partly result from perceiving illusory patterns in noise. However, the findings on the role of dopamine in detecting illusory patterns are inconclusive. To address this, we assessed the effect of enhancing dopamine transmission on illusory pattern perception in healthy individuals. Our hypothesis that enhancing dopamine transmission would increase participants’ tendency to perceive illusory patterns in noise was not confirmed. This null effect suggests that earlier findings may be less robust than previously thought and that the relationship between dopamine and illusory pattern perception may be subject to dose-dependent effects and that there may be differential effects in healthy vs. clinical samples.