Schizophrenia dulls brain's reward centre
Muted response The part of our brain that recognises and learns from reward is relatively inactive in people with schizophrenia, Australian research shows.
The finding, published in Molecular Psychiatry, suggests new drug therapies that target this reward centre could help improve the daily lives of people with schizophrenia.
Study co-author Dr Thomas Weickert, of the University of New South Wales's School of Psychiatry, says previous studies show the ventrial striatum, a small area deep inside the brain, is critically involved in reward learning. It is also connected to other parts of the brain that are linked to decision making, planning and cognition.
Using functional magnetic resonance imaging (fMRI), Weickert and his colleagues found in healthy adults the ventral striatum lights up with activity in response to rewards. However in people with schizophrenia the area was largely unresponsive.
The study involved 16 healthy adults and 16 people with schizophrenia who were receiving second-generation medication.
Participants were trained to play a card game in which certain cards led to a reward (expected reward), in this case an image of nine $50 bills.
They were then placed in a fMRI scanner and asked to play the same game. However after a period of time the cards that led to a reward were changed (unexpected reward).
Weickert says the healthy adults in the trial had no problem dealing with the increased unpredictability.
But the fMRI scans showed people with schizophrenia were not able to tell the difference between expected and unexpected rewards.
"We could see this region of the brain wasn't firing correctly," says Weickert.
"It is hard for people with schizophrenia to differentiate to a change in environment and hard for them then to benefit from those types of changes."
Reward responses are important to human learning, says Weickert, because they help us to redirect attention and behaviour towards things that are beneficial.
"People with schizophrenia often have difficulty determining what is beneficial for them and what is not, so they have trouble taking cues from their environment and, consequently, can make some bad decisions."
Although the people with schizophrenia were taking medication, Weickert does not believe this confounded the results.
Rather it indicated the current drug treatments were not helping this part of the brain function better.
"Ultimately we would like to see some new medications that improve the ventral striatum function," Weickert says.
"These results should help direct further studies on the ventral striatum in which we can look at the effect of therapies and potentially genetic influences on this particular region of the brain."