All posts filed under “papers

On effort and reward learning

We have recently published a new paper in PNAS, which investigates how the brains learns about different choice-relevant features, such as effort and reward. We found that learning about both, effort and reward arises from the dopamine-rich midbrain and propagates to different cortical and striatal brain regions.

Hauser TU, Eldar E & Dolan RJ (2017). Separate mesocortical and mesolimbic pathways encode effort and reward learning signals. Proc Natl Acad Sci USA. pdf

Noradrenaline blockade boosts metacognition

In a recent study published in eLife, we show that metacognition (the ability to consciously judge one’s performance) can be enhanced using a drug called propranolol. Propranolol blocks beta-adrenoceptors and thus impairs the effect of noradrenaline. Using a double-blind, placebo controlled drug study, we show that propranolol specifically enhances metacognition, but not perceptual decision making performance. A dopamine blockade (using amisulpride) did not affect either process.

Our paper also received some media coverage: The New Scientist just published a nice article about the study. Please note that the title of the article is misleading and was not approved by us. This study investigates the effect of drugs on metacognition and has nothing to do with OCD or OCD treatment.

Hauser TU*, Allen M*, Purg N, Moutoussis M, Rees G & Dolan R (2017). Noradrenaline blockade specifically enhances metacognitive performance. eLife 6: e24901

Information gathering in OCD

Can features of a psychiatric disorder actually have beneficial effects under certain conditions? This is the question that we asked in our new paper that just came out in PLOS Computational Biology. We were particularly interested in an indecisiveness that is often reported in patients with OCD.
Using an information gathering task, in which one is able to collect additional information before committing to a decision, we showed that juvenile OCD patients indeed won more points. Using computational modelling, we were then able to pin down the computational mechanism to a delayed emergence of a subjective feeling of urgency to respond. Our finding thus shows that under certain circumstance, an indecisiveness can actually have beneficial consequences.

Hauser TU, Moutoussis M, Iannaccone R, Brem S, Walitza S, Drechsler R*, Dayan P* & Dolan RJ* (2017). Increased decision thresholds enhance information gathering performance in juvenile obsessive-compulsive disorder (OCD). PLoS Comput Biol 13(4): e1005440

Metacognition in Compulsivity

I am really proud to announce that I have just preprinted my first ever paper on BioRxiv. In this paper, we investigate the link between metacognition and compulsivity.

Metacognition is the ability – or insight – to monitor your performance. So if you have good metacognitive abilities, you can reliably judge how well you perform on a given task. If not, you have difficulty to say how well you did. Obviously this is critical for our decision making, because you have to know how good you do in your tasks.

Interestingly, it has been suggested that many people with mental health problems have difficulties with such metacognitive decisions. Here we examined how healthy people with higher compulsivity scores perform on such a task. We find that high compulsive participants have a lower metacognitive ability. This difficulty extends a perceptual decision making weakness in our task.

Our findings support an idea of lower metacognitive abilities in a compulsivity spectrum, and thus suggest that metacognitive intervention may help people with higher obsessive-compulsive traits.

The link to our paper is here: http://biorxiv.org/content/early/2017/01/05/098277

Neural effects of tDCS in arithmetic

In our most recent paper, we investigate how brain stimulation (transcranial Direct Current Stimulation, tDCS) can alter neural activity, and how this is specific to a particular arithmetic operation. We used simultaneous tDCS-fMRI to probe the brain regions that are affected by tDCS. We find that activity in the inferior prefrontal cortex is altered during stimulation, but only so when subjects use arithmetic procedures (compared to fact retrieval). These findings are important because they adress two issues: first, it is largely unknown where tDCS really affects the brain – using simulations, we show that these models provide a useful approximation for where the effect really takes place. Second, we illustrate why there is not one single stimulation protocol that enhances all arithmetic/cognitive functions: the brain uses different networks for different functions. So it only works if we stimulate a network that is actually involved. This is also why we need stimulation protocols that are tailored to a specific function, rather than a general “cognition booster”.

Hauser TU, Rütsche B, Wurmitzer K, Brem S, Ruff CC, Grabner RH. (2016). Neurocognitive effects of transcranial Direct Current Stimulation in arithmetic learning and performance: A simultaneous tDCS-fMRI study. Brain Stim

Computational Psychiatry of ADHD

Our new paper in Trends in Neurosciences, we explain how computational psychiatry tries to understand the mechanisms in psychiatric disorders like attention deficit hyperactivity disorder (ADHD). We demonstrate how important it is to have an understanding of several levels of description (Marr’s levels of analysis), and to combine these levels to develop biologically driven, mechanistic new hypotheses about pathomechanisms. In this paper we further suggest that ADHD is mainly a disorder of aberrant neural gain modulation and we show how converging evidence on different levels of description support our notion.

Hauser TU, Fiore V, Moutoussis M & Dolan RJ (2016). Computational Psychiatry of ADHD: Neural Gain Impairments across Marrian Levels of Analysis. Trends Neurosci.

Timing of medial prefrontal regions to reward

Our recent paper with the awesome Laurence Hunt investigates the timing of different brain responses to speciffic stimuli. Particularly, we were interested whether the ventromedial prefrontal cortex (vmPFC) and the dorsomedial prefrontal cortex (dmPFC) process reward information at different times. To this end, we developed a novel way of analysing simultaneous EEG-fMRI data. We used single-trial fMRI responses from these regions to inform our EEG data to search for temporal relations. We found that vmPFC consistently preceded dmPFC activation.

Hauser TU*, Hunt LT*, Iannaccone R, Walitza S, Brandeis D, Brem S* & Dolan RJ* (2015). Temporally Dissociable Contributions of Human Medial Prefrontal Subregions to Reward-Guided Learning. J Neurosci 35(32):11209-11220.

Arithmetic learning modulated by tDCS

We and others have previously shown that one can modulate arithmetic performance using transcranial direct current stimulation (tDCS; cf. Hauser et al., 2013; Rütsche et al., 2015). In this study, we investigated the effect of tDCS on arithmetic learning. Arithmetic learning is characterized by the transfer from effortful calculation of arithmetic problems to fast memory-based fact retrievals. This is known to be one of the crucial processes that are learnt in school. Here, we investigated whether 30 minutes of tDCS can change the learning curve of healthy subjects. We found that anodal stimulation over parietal areas improved learning whereas cathodal tDCS impaired the learning. Moreover, the cathodal effect lasted for at least 24 hours after the stimulation. This study thus shows that even short-term stimulation can induce lasting stimulation effects.

Grabner RH, Rütsche B, Ruff CC & Hauser TU (2015). Transcranial direct current stimulation of the posterior parietal cortex modulates arithmetic learning. Eur J Neurosci.

Modulating arithmetic using tDCS

In this paper, we used transcranial Direct Current Stimulation (tDCS) to evaluate it’s effect on arithmetic performance as well as on the neural correltates in the EEG. Bruno Rütsche replicated our previous finding that tDCS improved performance in complex subtractions (Hauser et al.,  2013). However, the same stimulation impaired performance in simple arithmetic fact retrieval. The stimulation effects were also accompagnied by changes in alpha / theta de- / synchronizations.

Rütsche B, Hauser TU, Jäncke L & Grabner RH (2015). When problem size matters: Differential effects of brain stimulation on arithmetic problem solving and neural oscillations. PLOS One.

Classifying ADHD using fMRI

Psychiatric disorers are difficult to diagnose and the field is thus working towards finding new and more quantitative biomarkers. In this study, my colleague Reto Iannaccone used fMRI to classify juvenile ADHD patients with quite promising classification accuracies. He also showed that it is crucial which cognitive process is used for classifying the ADHD subjects.

Iannaccone R, Hauser TU, Ball J, Brandeis D, Walitza S & Brem S (2015).Classifying adolescent attention-deficit/hyperactivity disorder (ADHD) based on functional and structural imaging. Eur Child Adolesc Psychiatry