The paper reviews the empirical and theoretical development of the P300 event-related brain potential (ERP), focusing on its amplitude, latency, and general characteristics. It details the neuropsychological origins of the P3a and P3b subcomponents, discusses how target/standard discrimination difficulty modulates scalp topography, and outlines the neural loci of P3a and P3b generation. A cognitive model is proposed, suggesting that P3a originates from stimulus-driven frontal attention mechanisms during task processing, while P3b originates from temporal-parietal activity associated with attention and is related to subsequent memory processing. The paper highlights the role of neurotransmitters, particularly dopamine and norepinephrine, in associating P3a with frontal/dopaminergic and P3b with parietal/norepinephrine pathways. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations. The review also covers the historical context, methodological approaches, and the relationship between P300 and attention, memory, and individual differences.The paper reviews the empirical and theoretical development of the P300 event-related brain potential (ERP), focusing on its amplitude, latency, and general characteristics. It details the neuropsychological origins of the P3a and P3b subcomponents, discusses how target/standard discrimination difficulty modulates scalp topography, and outlines the neural loci of P3a and P3b generation. A cognitive model is proposed, suggesting that P3a originates from stimulus-driven frontal attention mechanisms during task processing, while P3b originates from temporal-parietal activity associated with attention and is related to subsequent memory processing. The paper highlights the role of neurotransmitters, particularly dopamine and norepinephrine, in associating P3a with frontal/dopaminergic and P3b with parietal/norepinephrine pathways. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations. The review also covers the historical context, methodological approaches, and the relationship between P300 and attention, memory, and individual differences.