Subcortical brain structures such as the thalamus and nucleus accumbens play a critical role in controlling motor, emotional and associative activity. Dysfunction in communication between these structures and with the cortex can lead to serious diseases, including Tourette syndrome, obsessive-compulsive disorders (OCD) and Parkinson’s disease. However, it is extremely difficult to study these structures, which are located deep inside the brain, and it’s not precisely clear how they work.