Philosophy : Logic, methods of reasoning, mind as physical system, foundations of learning, language, rationality.
Mathematics: Formal representation and proof, algorithms, computation, (un)decidability, (in)tractability
Probability/Statistics: Modeling uncertainty, learning from data
Economics: Utility, decision theory, rational economic agents
Neuroscience: Neurons as information processing units.
Psychology/ Cognitive Science: How do people behave, perceive, process cognitive information, represent knowledge.
Computer engineering: Building fast computers
Control theory: Design systems that maximize an objective function over time
Linguistics: Knowledge representation, grammars.