Causal Evidence for Task Regulation by Anterior Cingulate Cortex

Overview

The exact function of the anterior cingulate cortex (ACC) is one of the largest riddles in cognitive neuroscience and a major challenge in mental health research. ACC dysfunction contributes to a broad spectrum of neurological and psychiatric disorders, such as depression, ADHD, Parkinson's disease, OCD and many others, but nobody knows what it actually does. Recently a new theory has been developed about ACC function; the HRL-ACC (Hierarchical Reinforcement Learning Theory of ACC). This theory proposes that the ACC selects and motivates high-level tasks based on the principles of hierarchical reinforcement learning. The ACC associates values with tasks (these values are based on the reward positivity produced by the midbrain dopamine system), selects the correct tasks and applies control over other neural networks (such as the dorsolateral prefrontal cortex and basal ganglia), which execute the tasks. The goal of this study is to investigate the consequences of ACC damage (and other areas of the frontal lobe) on task regulation within a group of patients who have suffered a stroke in the frontal lobe. Furthermore, the correlation between ACC damage and mood disorders such as depression and apathy is going to be investigated.

This is a monocentric prospective interventional clinical trial that will include patients with a stroke in the frontal lobe. Depending on the recruitment manner, participants will undergo one or two sessions of cognitive experiments. The patients will be recruited in two ways, through the Stroke unit and through the outpatient clinic: 1. If a patient with an acute stroke in the frontal lobe is admitted to the Stroke unit and is eligible for this study, the patient will be asked if he is willing to participate. After giving informed consent, the first session will take place once the patient has been transferred to a regular neurological ward. After discharge, a second session will take place 6 to 12 months later at the outpatient clinic, preferably combined with a consultation (as part of the standard of care of stroke patients). 2. Patients who have had a stroke are followed at the outpatient clinic. Patients who are eligible for this study, will be contacted by the treating stroke supervisor during their consultation (either Prof. Veerle De Herdt or Dr. Dimitri Hemelsoet). If they are willing to participate, the first session will take place either right after the consultation at the outpatient clinic, or - if the patient is not available at that time - a new appointment will be made. One experimental session consists of the following steps: * Clinical neurological examination with determining of NIHSS score. * First cognitive task: the coffee-tea task. During this task, a sequence of 7 images is shown and each image contains three objects. The patient has to choose the right objects to make either coffee or tea. At the end of each sequence they get feedback if they have prepared the beverage correctly or not. * Short break with positioning of 21 EEG electrodes. * Second task: the virtual T-maze task with video-EEG recording. During this task, a virtual T-maze is shown and the patient has to choose at each junction whether they go left or right. Depending on which direction they choose, they either get positive or negative feedback. This task is known to elicit the reward positivity. During this task, video-EEG will be recorded and this EEG-data will later on be analysed using ERP analysis. * If second session, administering of questionnaires: Oxford Cognitive Screen, Becker Depression Inventory, DEX apathy questionnaire. Furthermore, the investigators are going to use voxel-based lesion symptom mapping to analyze the relationship between tissue damage and behavioural problems and reward positivity amplitude. It is expected that the coffee-tea task will be more difficult for patients with ACC damage compared to patients with lesions in other areas of the frontal lobe. Also, the amplitude of the ERP signals during the virtual T-maze task will be smaller in patients with ACC damage. Furthermore, the investigators expect to find a connection between ACC damage and mood disorders.