Background: Patients with schizophrenia and their first-degree relatives exhibit both abnormally diminished and increased neural activation during cognitive tasks. In particular, excessive task-related activity is often observed when tasks are easy, suggesting that inefficient cerebral recruitment may be a marker of vulnerability for schizophrenia. This hypothesis might best be tested using a very easy task, thus avoiding confounding by individual differences in task difficulty.
Method: Eighteen people with schizophrenia, 18 unaffected full siblings of patients with schizophrenia and 26 healthy controls performed an easy auditory target-detection task in a 3-T magnetic resonance imaging (MRI) scanner. Groups were matched for accuracy on the task. Blood oxygen level-dependent (BOLD) responses to non-target stimuli in participants with vulnerability for schizophrenia (siblings and patients) were compared with those of healthy controls, and those of patients with those of unaffected siblings. BOLD responses to targets were compared with baseline, across groups.
Results: Subjects with vulnerability for schizophrenia showed significant hyperactivation to non-targets in brain areas activated by targets in all groups, in addition to reduced deactivation to non-targets in areas suppressed by targets in all groups. Siblings showed greater activation than patients to non-targets in the medial frontal cortex. Patients exhibited significantly longer reaction times (RTs) than unaffected siblings and healthy controls.
Conclusions: Inefficient cerebral recruitment is a vulnerability marker for schizophrenia, marked by reduced suppression of brain areas normally deactivated in response to task stimuli, and increased activation of areas normally activated in response to task stimuli. Moreover, siblings show additional activation in the medial frontal cortex that may be protective.