The second intensive study program (ISP) in neuroscience, in 1969, surveyed the field at each level from the molecular and cellular through the neural to the behavioral. This book contains the lectures and symposia from that program. As a result of formal and informal discussions and of subsequent reconsideration by the authors, the majority of the chapters go beyond the manuscripts originally prepared and given at the ISP. The arrangement of this book follows the four thematic strands, and plenary and symposium lectures are clustered in accordance with the subject matter.