Neuron Review Neuromodulation of Thought: Flexibilities and Vulnerabilities in Prefrontal Cortical Network Synapses Amy F.T. Arnsten,1,* Min J. Wang,1 and Constantinos D. Paspalas1 1Department of Neurobiology, Yale Medical School, New Haven, CT 06510, USA *Correspondence:
[email protected] http://dx.doi.org/10.1016/j.neuron.2012.08.038 This review describes unique neuromodulatory influences on working memory prefrontal cortical (PFC) circuits that coordinate cognitive strength with arousal state. Working memory arises from recurrent excita- tion within layer III PFC pyramidal cell NMDA circuits, which are afflicted in aging and schizophrenia. Neuro- modulators rapidly and flexibly alter the efficacy of these synaptic connections, while leaving the synaptic architecture unchanged, a process called dynamic network connectivity (DNC). Increases in calcium- cAMP signaling open ion channels in long, thin spines, gating network connections. Inhibition of calcium- cAMP signaling by stimulating a2A-adrenoceptors on spines strengthens synaptic efficacy and increases network firing, whereas optimal stimulation of dopamine D1 receptors sculpts network inputs to refine mental representation. Generalized increases in calcium-cAMP signaling during fatigue or stress disengage dlPFC recurrent circuits, reduce firing and impair top-down cognition. Impaired DNC regulation contributes to age-related cognitive decline, while genetic insults to DNC proteins are commonly linked to schizophrenia. Introduction and can bring circuits ‘‘on-line’’ or ‘‘off-line’’ based on arousal The highly evolved neuronal networks of the dorsolateral state, thus coordinating the neural systems in control of prefrontal cortex (dlPFC) subserve working memory, our ‘‘mental behavior, thought, and emotion. However, this extraordinary sketch pad,’’ by representing information in the absence of flexibility also confers great vulnerability, and errors in this pro- sensory stimulation.