Disruptions in brain circuitry often underlie complex psychiatric symptoms, making it essential to examine neurobiological foundations of mental illness. Neuropsychiatric disorders and brain function are deeply interwoven, with conditions such as schizophrenia, Parkinson’s disease, bipolar disorder, and Tourette syndrome demonstrating intricate links between behavior and neural pathways. Innovations in neuroimaging, genomics, and electrophysiology allow deeper exploration into brain function and dysfunction. These insights inform not only diagnostics but also treatment, with options like neuromodulation and targeted pharmacotherapy gaining traction. Understanding how neurotransmitter imbalances and neural connectivity contribute to psychiatric symptoms opens the door to more personalized and effective interventions.