Alkon (chief of the neural systems laboratory at the National Institutes of Health and a senior scientist at the Woods Hole Marine Biological Laboratory) tells a personal as well as a professional story in this first-rate exposition of current research on memory. Haunting the narrative is the memory of the beautiful and talented Michelle, a childhood friend subject to the constant torment, abuse, and criticism of a demanding, never-satisfied father. Alkon traces Michelle's passage from obsessive perfectionism to outrage to repression, fantasy, alcoholism, psychosis, and suicide--a journey in which memory is distorted and denied and patterns of behavior so ingrained that Alkon now believes no treatment would have availed. Indeed, there is an abiding theme here that catastrophes (isolation, abuse) during the developing years may be next-to-impossible to overcome. Underlying these thoughts are Alkon's experiments in conditioning and associative memory using the snail Hermissenda. The snail learns to associate light with a rotation that causes it to cling tightly to the surface it is on. The neural substrate for this conditioning is a network, connecting visual and motion-sensitive cells, in which, according to Alkon's research, certain synapses are strengthened, accompanied by biochemical changes in the cell membrane. Alkon believes that memories that become hard-wired during critical periods of development are well-nigh permanent and interact with genetic, temperamental, and personality factors to determine behavioral limits. New memories become linked to old and may be able to alter them through inhibitory mechanisms. In addition to meticulously describing his own research, Alkon provides an excellent summary of 19th- and 20th-century psychology and neurology. He discusses the limits and potential for artificial neural networks, compares his work with others' in the field, and provides wonderful insights into the life and style of doing and mentoring science today.