Autoencoders

• A Hopfield net is an auto-associative memory, which is also called an undirected associative memory (from the deep belief net paper).
• Undirected associative memory, auto associative memory, or autoencoders all refer to the same thing. (Why so many names?)
• I've told you a lot about cell assemblies. They are also autoencoders.
• Hinton et al don't use CAs or Hopfield nets for their encoders; they use two layers of Boltzmann machines.
• In addition to auto-associative memory there is hetero-associative memory.
• Auto-associative associates a pattern with itself. Hetero-associative associates a pattern with another pattern.
• Hetero-associative memory is typically called just associative memory.
• It is an arc in a semantic net
• It is very important in human memory.