Biology subjects

Kurtenbach, H.

Publications and source records attributed to Kurtenbach, H..

4 recordsLinked to original sources

bioRxiv2026

Role of GABA and NMDA receptors in shaping cortical timescales and large-scale network dynamics

Cortical brain regions integrate information across different timescales, ranging from fast sensory processing to longer integration windows, allowing cognitive functions like working memory. At the large-scale, brain regions organize into transient network states that rapidly switch over time and similarly contribute to cognition. Both cortical timescales and large-scale network dynamics are proposed to be determined by the balance between recurrent synaptic excitation and GABAergic inhibition. Here, we pharmacologically manipulated synaptic transmission at GABAA and NMDA receptors in 60 healthy male participants and acquired resting-state magnetoencephalography. Neuronal timescales followed a hierarchical gradient with shorter timescales in early sensory regions. Increasing GABAergic activity prolonged neuronal timescales across cortical regions. This effect was most prominent in the frontal default mode and in the dorsal attention network. Notably, dynamic network analyses revealed that the occurrence probability of the frontal default mode network increased, whereas the occurrence of the dorsal attention network was reduced. NMDA receptor modulation resulted in no significant changes. Together, these findings provide causal evidence that GABAergic inhibition is a key regulator of cortical temporal organization, linking microscale synaptic mechanisms to neuronal timescales and network dynamics that support diverse cognitive function.

neuroscience↗

bioRxiv2024

A role for acetylcholine in reinforcement learning and decision making under uncertainty

The neuromodulator acetylcholine has been suggested to govern learning under uncertainty. Here, we investigated the role of muscarinic acetylcholine receptors in reward-guided learning and decision making under different degrees of uncertainty. We administered the muscarinic antagonist biperiden (4 mg) to healthy male participants (n = 43) in a within-subjects, placebo-controlled design. Participants performed a gambling and a learning task involving different levels of uncertainty, while magnetoencephalography (MEG) was recorded. We show that biperiden did not affect decision making in the gambling task, where no learning was required. However, in the learning task, where option values were associated with uncertainty, biperiden reduced the sensitivity to probabilities, particularly when choice-outcome-contingencies switched frequently. Reinforcement learning models revealed that the change in behaviour was caused by noisier estimates of probabilities resulting from increased learning rates for rewarded choices under biperiden. These behavioural findings were paralleled by elimination of the lateral prefrontal representation of learnt reward probability in high-beta (20 - 30 Hz) power under biperiden. Together, these findings suggest that muscarinic acetylcholine transmission controls learning in highly uncertain contexts, when the demand for carefully calibrated adjustments is highest.

neuroscience↗

bioRxiv2024

Bidirectional modulation of reward-guided decision making by dopamine

RationaleThe neuromodulator dopamine is known to play a key role in reward-guided decision making, where choice options are often characterized by multiple attributes. Different decision strategies can be used to merge these choice attributes with personal preferences (e.g., risk preferences) and integrate them into a single subjective value. While the influence of dopamine on risk preferences has been investigated, it is unknown whether dopamine is also involved in arbitrating between decision strategies. ObjectiveIn the present study, we investigate the effects of pharmacological dopamine manipulations on arbitrating between different decision strategies in a healthy sample. Methods31 healthy male participants performed a reward-guided decision-making task under the influence of the dopamine D2/D3-receptor antagonist amisulpride (400 mg), the dopamine precursor L-DOPA (100 mg L-DOPA + 25 mg cardidopa), or placebo in a double-blind within-subject design. The effect of dopamine on reward-guided decisions and decision strategies was analyzed using hierarchical implementations of regressions and Bayesian models. ResultsNotably, we observed that the dopaminergic interventions shifted the (overall) weighting of option attributes without changing how option attributes are integrated into a subjective value (decision strategy). These effects were bidirectional: Amisulpride reduced whereas L-DOPA increased the degree to which choices were influenced by both reward magnitude and reward probability. These effects occurred in the absence of changes in statistically optimal behavior. ConclusionTogether, our data provide evidence for a role of dopamine in controlling the influence of value parameters on choice irrespective of decision strategies.

neuroscience↗

bioRxiv2022

Removal of reinforcement improves instrumental performance in humans by decreasing a general action bias rather than unmasking learnt associations

Performance during instrumental learning is commonly believed to reflect the knowledge that has been acquired up to that point. However, recent work in rodents found that instrumental performance was enhanced during periods when reinforcement was withheld, relative to periods when reinforcement was provided. This suggests that reinforcement may mask acquired knowledge and lead to impaired performance. In the present study, we investigated whether such a beneficial effect of removing reinforcement translates to humans. Specifically, we tested whether performance during learning was improved during non-reinforced relative to reinforced task periods using signal detection theory and a computational modelling approach. To this end, 60 healthy volunteers performed a novel visual go/no-go learning task with deterministic reinforcement. To probe acquired knowledge in the absence of reinforcement, we interspersed blocks without feedback. In these non-reinforced task blocks, we found an increased d, indicative of enhanced instrumental performance. However, computational modelling showed that this improvement in performance was not due to an increased sensitivity of decision making to learnt values, but to a more cautious mode of responding, as evidenced by a reduction of a general response bias. Together with an initial tendency to act, this is sufficient to drive differential changes in hit and false alarm rates that jointly lead to an increased d. To conclude, the improved instrumental performance in the absence of reinforcement observed in studies using asymmetrically reinforced go/no-go tasks may reflect a change in response bias rather than unmasking latent knowledge. Author SummaryIt appears plausible that we can only learn and improve if we are told what is right and wrong. But what if feedback overshadows our actual expertise? In many situations, people learn from immediate feedback on their choices, while the same choices are also used as a measure of their knowledge. This inevitably confounds learning and the read-out of learnt associations. Recently, it was suggested that rodents express their true knowledge of a task during periods when they are not rewarded or punished during learning. During these periods, animals displayed improved performance. We found a similar improvement of performance in the absence of feedback in human volunteers. Using a combination of computational modelling and a learning task in which humans performance was tested with and without feedback, we found that participants adjusted their response strategy. When feedback was not available, participants displayed a reduced propensity to act. Together with an asymmetric availability of information in the learning environment, this shift to a more cautious response mode was sufficient to yield improved performance. In contrast to the rodent study, our results do not suggest that feedback masks acquired knowledge. Instead, it supports a different mode of responding.

neuroscience↗