Cortical instability and the mechanism of mania: a neural network simulation and perceptual test.

BACKGROUND: A previous neural network simulation suggested that manic states arise from excessive levels of noise that destabilize neural representations. The Necker cube stick figure provides a simple perceptual task that assesses stability of gestalt-type representations. METHODS: A neural network was developed that included a simulation of the Necker cube task. Noise was added to induce maniclike jumps from one representation to another. A parallel study of Necker cube perception was conducted with 16 patients diagnosed with manic-spectrum disorder, 18 patients with schizophrenia, and 19 normal control subjects. Cognitive speed and rate of indiscriminate responses were assessed using an auditory continuous performance task. RESULTS: During processing of the "Necker cube" stimulus, the reversal rate of the noise-destabilized "manic" network was increased by 30%. In the human subject study, the median score of Necker cube reversal rates for manic-spectrum patients was roughly twice that of normal control subjects and patients with schizophrenia. Accelerated reversal rates in the manic-spectrum group were not attributable to excessive cognitive speed or higher rates of indiscriminate responses. CONCLUSIONS: The two studies, considered together, support the hypothesis that excessive cortical noise destabilizes neural representations in manic-spectrum patients.

Gender differences in the associations between posttraumatic stress symptoms and problematic substance use in psychiatric inpatient adolescents.

This study examined gender differences in the associations between posttraumatic stress symptoms and problematic substance use in psychiatrically hospitalized adolescents. Ninety-five adolescent inpatients (38 boys, 57 girls) were systematically evaluated with a battery of psychometrically well-established self-report measures to assess trauma exposure, posttraumatic stress symptoms, problematic alcohol and drug use, and internalizing and externalizing psychopathology. Twenty-three percent (N = 22) of patients met DSM-IV-based symptom criteria for PTSD, and 37% (N = 35) and 34% (N = 32) of patients endorsed problematic levels of drug and alcohol use, respectively. Posttraumatic stress symptoms were significantly associated with problematic drug and alcohol use in girls but not in boys. There were no significant gender differences in posttraumatic stress symptoms and/or problematic substance use, to account for the gender differences in the association between PTSD and substance use. Our findings suggest that the link between substance abuse and PTSD may be especially salient for female adolescents.