A research team at the University Hospital Hamburg-Eppendorf (UKE) has investigated the underlying deficits in information processing and their neuronal foundations, the Nature Communications journal reported Thursday (January 3, 2019). Human beings ability to switch roles and goals is facilitated by the human frontal cortex, which is responsible for executive functions and cognitive control. Thus, it regulates the balance and conflicts between different goal requirements. A loss of this ability leads to so-called perseverative errors and indicates rigid adherence to past goals.
Diagnosis with neuropsychological tests
A working group led by Dr. Jan Gläscher from the Institute for Systemic Neurosciences at UKE in co-operation with U.S. researchers at the Californian Institute of Technology and the University of Iowa has investigated patients with brain lesions. The researchers used the Wisconsin Card Sorting Test, the world’s most widely used neuropsychological test, to diagnose deficits in cognitive control and behavioural flexibility. Patients had to sort cards with simple symbols into different stacks, but without knowledge of the sorting criterion i.e. colour, number or symbol. They were given feedback after each run. After a while, the criterion was changed unannounced. Patients with extensive frontal brain lesions did not manage to adjust or did so very slowly and made perseverative errors.
Negative feedback insufficiently perceived
Using detailed mathematical modelling, the researchers were able to describe exactly how information processing in the patients’ brains was disturbed. The negative feedback was perceived insufficiently and ignored. Patients did not notice the changed criterion and continued to sort the cards according to the previous criterion and made repetitive errors. The results showed that lesions in the right prefrontal cortex are associated with elevated perseverative errors and reductions in the sensitivity to punishment. The capacity to flexibly switch between tasks requires the detection of changes. These are enabled by sensitivity to punishment that reduces perseverative errors.