William Anson McCulloch was an American psychologist and neuroscientist known for his contributions to the understanding of the brain's structure and function. He is particularly recognized for his work on the neuron and the development of the neuron doctrine, which posits that neurons are the fundamental units of the nervous system. McCulloch collaborated with Walter Pitts in the 1940s to create a mathematical model of neural networks, which laid the groundwork for future research in artificial intelligence and machine learning. Their work helped bridge the gap between biology and computer science, influencing various fields, including cognitive science and robotics.