The ‘credit assignment’ problem refers to when someone attributes an event to the wrong outcome. For example, passing an exam and instead of assigning your success to the many hours of studying put in, you put it down to the number of times you brushed your teeth that day. This psychological phenomenon is the root of many mental disorders, such as addiction and OCD, where the person believes engaging in their harmful or ritualistic behavior results in a beneficial outcome.
Specific regions regulate this behavior
A new paper, published in Science Advances, sheds light on the neuronal systems causing these pathways and the possibility of using ultrasound to regulate them. Studying macaque monkeys, the research group, led by the University of Plymouth, showed that credit assignment activity occurs in a specific area of the lateral prefrontal region. A big step forward for behavioral psychologists, as it is extremely difficult to find exact regions to pinpoint behavior.
“The brain is like a mosaic – there are multiple parts doing different things. Each part may be linked to a certain behavior. The challenge is first to know whether this behavior is causally linked to a certain brain region. Only brain stimulation allows you to answer this question,” said first author, Dr. Elsa Fouragnan.
Using ultrasound to alter decision making
The researchers displayed that by using low-intensity transcranial ultrasound stimulation (TUS), this behavior was able to be safely and effectively modulated. When stimulated, the monkeys became more exploratory in their behavior. Scientists were able to decipher that this modified their decision making built from previous experience due to the fact their choice was thrown off from their normal patterns.
This research is promising, but scientists need to make sure this modulation of decisions does not impact behavior in an unforeseen way. “If you disrupt or modulate one part, then it can affect several others, so we need to understand how brain areas work together, and how they affect each other if one is stimulated or disrupted,” Fouragnan stated.
She continued: “The really interesting finding in this study is not only discovering where certain decision making activities take place, but also how neuromodulation can change these and associated behaviors. We hope that this can pave the way to new studies in humans, particularly in patients experiencing mental health issues.”
Source study: Science Advances – Ultrasound modulation of macaque prefrontal cortex selectively alters credit assignment–related activity and behavior