Low Motivation in Schizophrenia Linked to Biochemical Rewards System
One of the most notable features of schizophrenia is lack of motivation. To date there has been little information available to determine why. In part, motivational problems are commonly viewed as secondary to long-term treatment effects, or the product of institutionalisation.
Recent research involving the use of a simple reaction time experiment, suggests that variations in the dopamine function of the brain holds the key to both an explanation for low motivation and a possible treatment.
Dopamine, a neurotransmitter, is thought to play an important role in incentive motivation and acts as part of our internal reward system. Any dysfunction in the reward system could explain low motivation and other symptoms such as stereotypical patterns of thought and behavior and delusional beliefs. If problems exist at the neurological level it could explain why people with schizophrenia sometimes attribute high significance to fairly innocuous events or, for example, amplify the importance of an internally generated voice, which leads to an abnormal perception. Finding the link between dopamine activity and lack of motivation could be a step towards new treatments.
In research conducted at the University of Cambridge Behavioural and Clinical Neuroscience Institute, Dr Graham Murray and colleagues compared the performance of 18 patients presenting with first-episode psychotic symptoms with 19 healthy volunteers. Participants took part in a computerised reaction time task where rewards, in the form of points and smiley faces, were given for correct/quick responses and low points and sad faces for incorrect/slow responses.
Eleven of the 18 patients were taking atypical antipsychotic medication but were stable before commencing the study. Medication is often thought to be responsible for de-motivating patients but the study controls ruled out any significant effects of medication.
In the control group of healthy volunteers, almost all participants reacted faster if rewards were higher. By contrast, less than a quarter of the first-episode psychosis group reacted in the same way, which points to an abnormal processing of incentives for their actions. "Patients with psychosis already have motivational deficits the first time they present to health services" said Dr Murray.
Murray suggests the next step is to investigate whether self-motivation can be stimulated in patients with psychosis using medications that can trigger the release of dopamine but do not worsen symptoms.
Murray, G.K., Clark, L., Corlett, P.R., Blackwell,A.D., Cools, R., Jones,P.B., Robbins,T.W., and Poustka, L (2008) Incentive motivation processing in first-episode psychosis: a behavioural study. BMC Psychiatry, 8:34. doi:10.1186/1471-244X-8-34