  The increasing prominence of neural explanations in cognitive, social, developmental, and clinical psychology raises important philosophical questions about explanation and reduction.  Anti-reductionism, according to which psychological explanations are completely independent of neurological ones, is becoming increasingly implausible, but it remains controversial to what extent psychology can be reduced to neuroscience and molecular biology.  Crucial to answering questions about the nature of reduction are answers to questions about the nature of explanation.  Explanations in psychology, neuroscience, and biology in general are plausibly viewed as descriptions of  mechanisms,  which are combinations of connected parts that interact to produce regular changes. In psychological explanations, the parts are mental representations that interact by computational procedures to produce new representations.  In neuroscientific explanations, the parts are neural populations that interact by electrochemical processes to produce new neural activity that leads to actions.  If progress in theoretical neuroscience continues, it should become possible to tie psychological to neurological explanations by showing how mental representations such as concepts are constituted by activities in neural populations, and how computational procedures such as spreading activation among concepts are carried out by neural processes.