Dorsolateral prefrontal cortex circuitry at the intersection of cognition and disease.
Schizophrenia, major depressive disorder (MDD), and Alzheimer's disease (AD) involve dysfunction of distributed cortical-subcortical networks that support complex cognitive processes and emotion regulation. Convergent evidence identifies the dorsolateral prefrontal cortex (dlPFC) as a critical site of molecular, cellular, and circuitry alterations in these disorders. The primate dlPFC contains recurrent, excitatory microcircuits in layer III that sustain working memory and top-down control through specialized forms of neurotransmission and intracellular signaling. Specifically, NMDA receptor and cholinergic modulation, as well as tightly regulated calcium-cAMP signaling within dendritic spines, support task-specific firing of layer III pyramidal neurons, but may also increase vulnerability to genetic risk, stress, inflammation and aging. This review integrates findings from human postmortem studies, neuroimaging, and genetics to examine how dlPFC circuitry is altered in these disease states. In schizophrenia, layer III pyramidal neurons exhibit altered synaptic and cytoskeletal signaling, lower dendritic spine density, and compensatory shifts in inhibitory inputs that likely weaken recurrent excitation and network synchrony. In MDD, dysfunction of dlPFC pathways regulating subgenual cingulate cortex contributes to impaired top-down control of emotion and motivation. In AD and frontotemporal lobar degeneration, tau pathology and neurodegeneration target association cortices, including layer III dlPFC circuits, contributing to progressive cognitive decline and impaired executive function. The review also highlights how studies in rhesus macaques and genetically engineered marmosets have provided important insight into the organization, physiology, and disease vulnerability of primate dlPFC circuits. Together, these findings inform the development of emerging therapeutic strategies aimed at strengthening prefrontal network function.