Setting the beat of an internal clock: Effects of dexamphetamine on different interval ranges of temporal processing in healthy volunteers

Abstract

Drug studies are powerful models to investigate the neuropharmacological mechanisms underlying temporal processing in humans. This study administered dexamphetamine to 24 healthy volunteers to investigate time perception at different time scales, along with contributions from working memory. Healthy volunteers were administered 0.45 mg/kg dexamphetamine or placebo in a doubleblind, crossover, placebo-controlled design. Time perception was assessed using three experimental tasks: a time-discrimination task, which asked participants to determine whether a comparison interval (1200 AE 0, 50, 100, 150, 200 ms) was shorter or longer than a standard interval (1200 ms); a retrospective time estimation task, which required participants to verbally estimate time intervals (10, 30, 60, 90 and 120 s) retrospectively; and a prospective time-production task, where participants were required to prospectively monitor the passing of time (10, 30, 60, 90 and 120 s). Working memory was assessed with the backwards digit span. On the discrimination task, there was a change in the proportion of long-to-short responses and reaction times in the dexamphetamine condition (but no association with working memory), consistent with an increase in the speed of an internal pacemaker, and an overestimation of durations in the timing of shorter intervals. There was an interaction between dexamphetamine, working memory, and performance on the estimation and production tasks, whereby increasing digit span scores were associated with decreasing interval estimates and increased produced intervals in the placebo condition, but were associated with increased interval estimates and decreased produced intervals after dexamphetamine administration. These findings indicate that the dexamphetamine-induced increase in the speed of the internal pacemaker was modulated by the basal working memory capacity of each participant. These findings in healthy humans have important implications for the role of dopamine, and its contributions to timing deficits, in models of psychiatric disorders.

Red visual stimulation in theGanzfeldleads to a relative overestimation of duration compared to green

“…In general, regardless of the induction method, ASC can be characterized by changes in the sense of self and time (Berkovich‐Ohana & Wittmann, 2017; Wittmann, 2015, 2018; Wittmann et al, 2019). Subjective changes in the passage of time and its perceived duration have been studied with different induction methods such as hypnosis (Lush & Dienes, 2019), meditation (Droit‐Volet & Dambrun, 2019; Singh & Srinivasan, 2019), and pharmaceutical agents (Graham‐Schmidt, Martin‐Iverson, & Waters, 2019), including psychedelics (Wittmann et al, 2007). In a recent study that used a special Ganzfeld technique where participants sit in an egg‐shaped, whole‐body perceptual deprivation chamber, the reported experience of time proved quite distorted (Glicksohn, Berkovich‐Ohana, Mauro, & Ben‐Soussan, 2017).…”

Systematic reviews of the acute effects of amphetamine on working memory and other cognitive performances in healthy individuals, with a focus on the potential influence of personality traits

“…( 2000 ) demonstrated that despite the lack of main effects, dexamphetamine (0.25 mg/kg) enhanced SWM performance on n ‐back tests in those subjects who had lower baseline capacity, while it impaired SWM performance in those subjects who had relatively higher baseline capacity. Likewise, dexamphetamine (0.45 mg/kg) enhanced VWM performance on digit span task in those subjects who had lower baseline capacity, but not in those subjects who had relatively higher baseline capacity (Graham‐Schmidt et al., 2019 ). Another fMRI study has shown that dexamphetamine‐induced dopamine release in older healthy individuals increased brain signal variability during the WM task, comparable to or exceeding the brain signal variability young adults had in the placebo condition (Garrett et al., 2015 ).…”

Dexamphetamine influences funneling illusion based on psychometric score

“…Similar sizes and numbers of capsules containing either placebo (glucose) or 0.45 mg/kg dexamphetamine were prepared using 1, 2.5, 5, and 10 mg dexamphetamine sulfate tablets. This dose of dexamphetamine was selected based on previous experiments in healthy subjects demonstrating significant effects on a range of illusory and psychophysiological measures (Albrecht et al, 2011(Albrecht et al, , 2012Graham-Schmidt et al, 2019;Woodward et al, 2011).…”