Devin Terhune
Senior Lecturer in psychology

For the Microdosing symposium:

The effects of microdose LSD on time perception and response to suggestion

As attention to microdosing increases, it is important to elucidate its impact on cognition and perception as well as top-down regulation of these functions. I will present two randomized, double-blind, placebo-controlled microdose LSD studies. In the first study, participants completed a temporal reproduction task. The LSD conditions were reliably characterized by over-reproduction of temporal intervals of 2000 ms and longer.

In the second study, participants were given associative suggestions prior to completing a colour-shape association task. In the LSD conditions, participants displayed greater performance for suggested than unsuggested associations. These results suggest that microdose LSD produces temporal over-reproduction and enhances response to suggestion. I will conclude by considering multiple interpretations of these results including those drawn from Bayesian and predictive coding models.

For the Adverse Reactions symposium:

Acquired synaesthesia following 2C-B use Synaesthesia is a neurodevelopmental condition in which inducer stimuli reliably and automatically elicit atypical concurrent experiences. The induction of transient episodes of synaesthesia with serotonin agonists has been widely reported and has potential implications for the neurophysiological bases of hallucinogen persisting perception disorder, multisensory processing, and cortical plasticity.

However, the induction of such experiences through the use of drugs remains controversial because drug-induced synaesthesias do not seem to meet standard behavioural adjudication criteria for this condition. We investigated whether a case of acquired synaesthesia (LW) following the ingestion of the recreational drug 2C-B meets standard diagnostic criteria for synaesthesia. LW has continuously reported a wide variety of different forms of synaesthesia, such as face-colour synaesthesia since taking an excessive dose of 2C-B over 7 years ago.

We contrasted LW against demographically-matched controls and evaluated the consistency of LW’s synaesthetic associations using a standardised battery and the behavioural automaticity of his associations using a face-colour priming task. Multiple forms of LW’s synaesthesia met behavioural criteria for inducer-concurrent consistency and he exhibited larger face-colour congruency effects in both error rates and response times in the priming task than controls. These results demonstrate a case of acquired synaesthesia through drug use that meets behavioural diagnostic criteria for synaesthesia (inducer-concurrent consistency and automaticity) and thereby implicates serotonin in the development of synaesthesia and challenges dominant neurophysiological models of this condition.

Devin is a Senior Lecturer in psychology at Goldsmiths, University of London where he co-directs the Goldsmiths Consciousness Research Unit and directs the timing, awareness, and suggestion lab. His lab uses methods from cognitive neuroscience and experimental psychology to study different features of awareness with a focus on the neural bases of time perception and the use of suggestion to regulate awareness. He completed his PhD at Lund University in Sweden and was previously a postdoctoral research fellow in the Department of Experimental Psychology at the University of Oxford.