Research on the brain, one of the few genuine frontiers remaining in science, continues to fascinate us, as it offers a glimpse into the deepest foundations of humanity. But in spite of great progress in understanding specific mental functions, like perception, memory, and emotion, little has been learned about how the self - the essence of who a person is, both in his or her own mind and in the eyes of others - relates to the brain.

In 1996 Joseph LeDoux's The Emotional Brain presented a revelatory examination of the biological bases of our emotions and memories. Now, in Synaptic Self, LeDoux follows that pathbreaking work with a new book that tells a larger and more profound story: how the brain, and particularly its synapses, creates and maintains personality.

Synapses, the spaces between neurons, are the channels through which we think, act, imagine, feel, and remember, and also the means by which our most fundamental traits, preferences, and beliefs are encoded. In short, they enable each of us to function as a single, integrated individual - a synaptic self - from moment to moment, from year to year.

Challenging the common view that regards the self in terms of self-awareness, LeDoux emphasizes the importance of both conscious and unconscious processes in its construction. Rather than taking sides in the age-old debate of whether nature or nurture is the determining factor in human development, LeDoux also shows how both contribute to synaptic connectivity and personality. Nevertheless, because memory plays such an important role in maintaining our personality over time, much of Synaptic Self concerns the mechanisms by which synapses store information, and how learning is coordinated across the many systems involved in encoding a given experience. Ultimately, it is at the level of the synapse that psychology, culture, and even spirituality meet, where memory joins with genes to create the ineffable essence of personality.

Provocative and mind-expanding, Synaptic Self promises to become a major work on our understanding of what it means to be human.