Auditory Oddball fMRI in Schizophrenia: Association of Negative Symptoms with Regional Hypoactivation to Novel Distractors.

Schizophrenia is associated with abnormal processing of salient stimuli, which may contribute to clinical symptoms. We used fMRI and a standard auditory 3-stimulus task to examine attention processing. Target stimuli and novel distractors were presented to 17 patients and 21 healthy controls and activation was correlated with negative and positive symptoms. To targets, patients overactivated multiple regions including premotor cortex, anterior cingulate, temporal cortex, insula, and hippocampus, and also showed attenuated deactivation within occipital cortex. To distractors, patients overactivated left ventrolateral prefrontal cortex. This overactivation may reflect hypersensitivity to salient stimuli in schizophrenia. Patients also exhibited an inverse correlation between negative symptom severity and activation to novel distractors in the dorsolateral prefrontal cortex, premotor area, and ventral striatum. Novelty-induced activity within prefrontal cortex and ventral striatum may represent a useful intermediate phenotype for studies of negative symptoms.

Acute effect of methadone maintenance dose on brain FMRI response to heroin-related cues.

OBJECTIVE: Environmental drug-related cues have been implicated as a cause of illicit heroin use during methadone maintenance treatment of heroin dependence. The authors sought to identify the functional neuroanatomy of the brain response to visual heroin-related stimuli in methadone maintenance patients. METHOD: Event-related functional magnetic resonance imaging was used to compare brain responses to heroin-related stimuli and matched neutral stimuli in 25 patients in methadone maintenance treatment. Patients were studied before and after administration of their regular daily methadone dose. RESULTS: The heightened responses to heroin-related stimuli in the insula, amygdala, and hippocampal complex, but not the orbitofrontal and ventral anterior cingulate cortices, were acutely reduced after administration of the daily methadone dose. CONCLUSIONS: The medial prefrontal cortex and the extended limbic system in methadone maintenance patients with a history of heroin dependence remains responsive to salient drug cues, which suggests a continued vulnerability to relapse. Vulnerability may be highest at the end of the 24-hour interdose interval.

Visual attention circuitry in schizophrenia investigated with oddball event-related functional magnetic resonance imaging.

OBJECTIVE: Schizophrenia patients have problems directing attention. Sustained attention requires ensuring that brain resources are focused on a selected target (top-down task) while ignoring irrelevant distractors (bottom-up interference). Whether patients have too little ability to focus or too much interference from distraction has not been clarified. The oddball paradigm embeds infrequent targets and distractors into the stimulus train, and schizophrenia deficits have been linked to diminished responses to both. Cerebral activity underlying abnormal attention can be examined with event-related functional magnetic resonance imaging. METHOD: A visual oddball task was presented to 22 patients with schizophrenia and 28 comparison subjects. Statistical probability maps reflecting blood-oxygenation-level-dependent changes were generated for infrequent targets and novel distractors relative to frequent standard stimuli. Activation was related to performance and symptoms. RESULTS: Activation specific to targets and distractors was associated with faster performance. For targets, patients had diminished activation in superior temporal and frontal gyri, cingulate, thalamus, and basal ganglia. They had increased activation in right insula, mid-frontal gyrus, posterior cingulate, and left inferior parietal lobule. For distractors, patients showed less activation in occipital regions and left inferior parietal lobule but increased activation in parietal-occipital, right mid-frontal, and left inferior frontal gyri. Abnormal activation correlated with positive and negative symptoms. CONCLUSIONS: Abnormal activation in schizophrenia in response to attentional demands reflects both insufficient recruitment of brain systems required for target detection and overcommitment of resources for processing irrelevant distractors. Schizophrenia patients appear to have an inability both to focus on targets and ignore distraction.