Pii: S0893-6080(97)00049-x

A combined neurophysiological and computational approach is reviewed that leads to a proposal for how neural networks in the temporal cortical visual areas of primates could function to produce invariant object representation and identification. A similar approach is then reviewed which leads to a theory of how the hippocampus could rapidly store memories, especially episodic memories including spatial context, and how later recall of the information to the neocortex could occur. Third, it is argued that the visual and memory mechanisms described could operate without consciousness, and that a different type of processing is related to consciousness. It is suggested that the type of processing related to consciousness involves higher-order thoughts ("thoughts about thoughts"), and evolved to allow plans, formulated in a language, with many steps, to be corrected. It is suggested that it would feel like something to be a system that can think linguistically (using syntax) about its own thoughts, and that the subjective or phenomenal aspects of consciousness arise in this way. It is further suggested that "raw sensory feels" arise in evolution because once some types of processing feel like something by virtue of a system capable of higher-order thoughts, it is then parsimonious to postulate that sensory and related processing, which has to be taken into account in that processing system, should feel like something. It is suggested that it is this type of processing, which must be implemented in neural networks, which is related to consciousness. q 1997 Elsevier Science Ltd. Keywords—Consciousness, Hippocampus, Memory, Invariance, Visual recognition, Higher-order thoughts, Visual