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.