We鈥檝e all found ourselves repeatedly making the same mistake, like playing the same wrong note in a piece of music, even though we know it鈥檚 wrong. It鈥檚 called perseveration 鈥� and it is particularly common among people with schizophrenia.
Now Dara Manoach and her team at Harvard Medical School in Boston think they know why. They monitored the brain activity of people with schizophrenia while they performed an antisaccade task, which involves looking at a screen on which a green ring is flashed up, either on the left side or the right. Before the ring appears, one of two cues is flashed which tells participants how to react to the ring. Depending on the cue, they have to either look towards the ring, or look away.
People instinctively look towards a new stimulus, so it is harder to look away. The subjects with schizophrenia were particularly prone to looking towards the ring when they were supposed not to (Brain, ). 鈥淭hey鈥檙e failing to learn from errors in the short term,鈥� Manoach says.
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When the team looked at the brain activity of the people with schizophrenia, they found that two circuits were firing less than in control subjects. Both originate in the anterior cingulate cortex 鈥� suggested to be the brain鈥檚 error-processing system.
The first affected circuit was the 鈥渞einforcement learning鈥� network. This circuit fires if our response to a stimulus turns out to be wrong, helping us learn from our mistakes. The other misbehaving circuit was the 鈥渁ffective appraisal鈥� network, which controls our emotional response to mistakes. The low activity suggests that the people with schizophrenia cared less about their errors.
鈥淟ower activity in specific brain circuits suggests that people with schizophrenia care less about their errors鈥�
The research is 鈥渁 very convincing demonstration鈥� of brain processes underlying perseveration in schizophrenia, says Philip Harvey of Emory University School of Medicine in Atlanta, Georgia. He adds that reduced activity in the two circuits identified by Manoach could help explain poor results in problem-solving tasks.
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