Circuit simulation of working memory control by dopamine

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I did theoretical analysis and computer simulations of working memory control by dopamine. New models are constructed and a new theory is proposed. The study is devoted to the functions of D1 and D2 receptors. First, how dopamine changes the stability of working memory representation via D1 receptor activation has been explored. This study suggests that dopamine do not only change the robustness of working memory representation, as was suggested previously, but alter fundamental cognitive operations so that various kinds of operations can be performed. Second, by analyzing the dynamical characteristics of the dopaminergic modulatory system, this study elucidated the functions of the dopaminergic system regarding cognitive control. The dynamics is suggested to have different characteristics depending on the extracelullar dopamine concentration in the prefrontal cortex. Finally, I propose a new theory on schizophrenia, that is "the stability theory of schizophrenia". This theory states that the network for cognitive operations tends to be unstable under hypoglutamatergic conditions. This theory can account for not only the decrement of dopamine concentration in the prefrontal cortex but abnormal activation of the prefrontal cortex, which has often been observed by functional imaging studies while the patients with schizophrenia performed cognitive tasks. This theory should be applied to psychiatric research.