Biology subjects

Knauth, K.

Publications and source records attributed to Knauth, K..

5 recordsLinked to original sources

bioRxiv2024

Dopamine and temporal discounting: revisiting pharmacology and individual differences

Disorders characterised by changes in dopamine (DA) neurotransmission are often linked to changes in the temporal discounting of future rewards. Likewise, pharmacological manipulations of DA neuro-transmission in healthy individuals modulate temporal discounting, but there is considerable variability in the directionality of reported pharmacological effects, as enhancements and reductions of DA signalling have been linked to both increases and reductions of temporal discounting. This may be due to meaningful individual differences in drug effects and/or false positive findings in small samples. To resolve these inconsistencies, we 1) revisited pharmacological effects of the DA precursor L-DOPA on temporal discounting in a large sample of N = 76 healthy participants (n = 44 male) and 2) examined several putative proxy measures for DA to revisit the role of individual differences in a randomised, double-blind placebo-controlled pre-registered study (https://osf.io/a4k9j/). Replicating previous findings, higher rewards were discounted less (magnitude effect). Computational modelling using hierarchical Bayesian parameter estimation confirmed that the data in both drug conditions were best accounted for by a non-linear temporal discounting drift diffusion model. In line with recent animal and human work, L-DOPA reliably reduced the discount rate with a small effect size, challenging earlier findings in substantially smaller samples. We found no credible evidence for linear or quadratic effects of putative DA proxy measures on model parameters, calling into question the role of these measures in accounting for individual differences in DA drug effects.

neuroscience↗

bioRxiv2024

Ambulatory physiological measures obtained under naturalistic urban mobility conditions have acceptable reliability

Ambulatory assessment methods in psychology and clinical neuroscience are powerful research tools for collecting data outside of the laboratory. These methods encompass physiological, behavioral, and self-report measures obtained while individuals navigate in real-world environments, thereby increasing the ecological validity of experimental approaches. Despite the recent increase in applications of ambulatory physiology, data on the reliability of these measures is still limited. To address this issue, twenty-six healthy participants (N = 15 female, 18-34 years) completed an urban walking route (2.1 km, 30 min walking duration, temperature M = 19.8{degrees} degree Celsius, Range = 12{degrees}-37{degrees} degrees Celsius) on two separate testing days, while GPS-location and ambulatory physiological measures (cardiovascular and electrodermal activity) were continuously recorded. Bootstrapped test-retest reliabilities of single measures and aggregate scores derived via principal component analysis (PCA) were computed. The first principal component (PC#1) accounted for 39% to 45% of variance across measures. PC#1 scores demonstrated an acceptable test-retest reliability (r = .60) across testing days, exceeding the reliabilities of most individual measures (heart rate: r = .53, heart rate variability: r = .50, skin conductance level: r = .53, no. of skin conductance responses: r = .28, skin conductance response amplitude: r = .60). Results confirm that ambulatory physiological measures recorded during naturalistic navigation in urban environments exhibit acceptable test-retest reliability, in particular when compound scores across physiological measures are analyzed, a prerequisite for applications in (clinical) psychology and digital health. Author summaryPsychophysiological assessments have been predominantly limited to controlled laboratory settings, leaving the reliability of field measurements unclear. In this study, we conducted a proof-of-concept investigation in N=26 healthy participants navigating the same urban route on two separate days. Cardiovascular and electrodermal activity were continuously recorded and combined with GPS-based location tracking. Psychophysiological measurements obtained under naturalistic urban mobility conditions showed acceptable test-retest reliability, in particular when multiple measures where combined into a compound score via principal component analysis. Shedding light on the reliability of ambulatory assessments in urban environments emphasizes the potential for psychophysiological measurements to contribute valuable insights beyond the constraints of traditional laboratory settings.

physiology↗

bioRxiv2023

Pharmacological enhancement of dopamine neurotransmission does not affect illusory pattern perception

Psychotic symptoms and delusional belief 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 modulate measures of accuracy, discrimination sensitivity and response bias. In all cases, Bayesian statistics revealed strong evidence in favour of the null hypothesis Future studies should address possible dose-dependent effects and differential effects in healthy vs. clinical samples.

neuroscience↗

bioRxiv2022

Appetitive cue exposure increases neural reward responses without modulating temporal discounting

When given a choice, humans and many animals prefer smaller but sooner over larger but later rewards, a tendency referred to as temporal discounting. Alterations in devaluation of future rewards have been reported in a range of maladaptive behaviors and clinical conditions. Although temporal discounting is highly stable over time and testing environments (e.g., laboratory vs. virtual reality), it is partly under contextual control. For example, highly appetitive cues such as erotic images might increase preferences for immediate rewards, although overall evidence remains mixed. Dopaminergic circuit activity and striatal dopamine concentrations are often assumed to drive increases in temporal discounting following appetitive cue-exposure, yet this was never explicitly tested. Here we examined cue-reactivity effects (erotic vs. neutral pictures) on subsequent temporal discounting in a pre-registered within-subjects study in healthy male participants (n=38). Functional magnetic resonance imaging (fMRI) assessed neural cue-reactivity, value-computations and choice-related effects. Preregistered analyses replicated previous findings of value coding in ventromedial prefrontal cortices, striatum and cingulate cortex. Likewise, as hypothesized, lateral prefrontal cortex activity increased during choices of delayed rewards, potentially reflecting cognitive control. As predicted, erotic vs. neutral cue exposure was associated with increased activity in attention and reward circuits. Contrary to our preregistered hypotheses, temporal discounting was largely unaffected by cue exposure. Likewise, cue-reactivity in key areas of the dopaminergic reward circuit (Nacc, VTA) was not significantly associated with changes in behavior. Our results indicate that behavioral effects of erotic cue exposure on temporal discounting might not be as unequivocal as previously thought and raise doubt on the hypothesis of an upregulated dopaminergic ramping mechanism, that might support myopic approach behavior towards immediate rewards.

neuroscience↗

bioRxiv2021

Trial-wise exposure to visual appetitive cues increases physiological arousal but not temporal discounting.

Humans and many animals devalue future rewards as a function of time (temporal discounting). Increased discounting has been linked to various psychiatric conditions, including substance-use-disorders, behavioral addictions and obesity. Despite its high intra-individual stability, temporal discounting is partly under contextual control. One prominent manipulation that has been linked to increases in discounting is the exposure to highly arousing appetitive cues. However, results from trial-wise cue exposure studies appear highly mixed, and changes in physiological arousal were not adequately controlled. Here we tested the effects of appetitive (erotic), aversive and neutral visual cues on temporal discounting in thirty-five healthy male participants. The contribution of single-trial physiological arousal was assessed using comprehensive monitoring of autonomic activity (pupil size, heart rate, electrodermal activity). Physiological arousal was elevated following aversive and in particular erotic cues. In contrast to our pre-registered hypothesis, if anything, we observed decreased temporal discounting following erotic cue exposure. Aversive cues tended to increase decision noise. Computational modeling revealed that trial-wise arousal only accounted for minor variance over and above aversive and erotic condition effects, arguing against a general effect of physiological arousal on temporal discounting.

neuroscience↗