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LeDoux starts his first chapter with a quote from Bart Simpson: "Dad, what is the mind? Is it just a system of impulses or something tangible?" My kind of humor.
LeDoux's Synaptic Self is a wonderful book loaded with clear understandable explanations and insights (his wife, a "fantastic writer," assisted) on how the brain works based on the most current neuroscience (e.g., how neurons/synapses/neurotransmitters/neuro modulators work/don't work, implicit/explicit learning/memory mechanism explanations, nature/nurture considerations, the "mental trilogy" of cognition/emotion/motivation, and much more). The book's bottom-line, he writes, is "you are your synapses." With this book, "know thyself," and even fix thyself, seem more attainable. It's a book I'll reread/study for a while.
The following are quotes from the last chapter:
Life requires many brain functions, functions require systems, and systems are made of synaptically connected neurons. We all have the same brain systems, and the number of neurons in each brain system is more or less the same in each of us as well. However, the particular way those neurons are connected is distinct, and that uniqueness, in short, is what makes us who we are.
What is remarkable is that synapses in all of these systems are capable of being modified by experience... Emotion systems [as an example]... are programmed by evolution to respond to some stimuli, so-called innate or unconditioned stimuli, like predators or pain. However, many of the things that elicit emotions in us or motivate us to act in certain ways are not preprogrammed into our brains as part of our species heritage but have to be learned by each of us. Emotion systems learn by association - when an emotionally arousing stimulus is present, other stimuli that are also present acquire emotion-arousing qualities (classical conditioning), and actions that bring you in contact with emotionally desirable stimuli or protect you from harmful or unpleasant ones are learned (instrumental conditioning.) As in all other types of learning, emotional associations are formed by synaptic changes in the brain system involved in processing the stimuli. Some of the brain's plastic emotional processors include systems involved in detecting and responding to danger, finding and consuming food, identifying potential mates and having sex.
Because synaptic plasticity occurs in most if not all brain systems, one might be tempted to conclude that the majority of brain systems are memory systems. But [as LeDoux argues in chapter 5], a better way of thinking about this is that the ability to be modified by experience is a characteristic of many brain systems, regardless of their specific function. Brain systems, in other words, were for the most part not designed as storage devices - plasticity is not their main job assignment. They were instead designed to perform particular tasks like processing sounds or sights, detecting food or danger or mates, controlling actions, and so on. Plasticity is simply a feature that helps them do their job better.
Functions depend on connections: break the connections and you lose the functions...
From LeDoux's Synaptic Self
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This book is as good as a popular science book can be, and explains in easy terms some of the most important concepts in neuroscience. For this it should be widely read. However, Ledoux wants to explain the self, and not only to write a popular book on cognitive neuroscience. Now, given that it is very difficult not to accept that the self at some level is nothing but synapses, Ledoux does seem to base the self on neurobiological mechanisms. But this is no more enlightening than sayying that vision, attention, language, or even qualia are nothing but synapses, claims that at some level must also be correct. So one would expect the bulk of the book to develop principles that tie or at least correlate the self with brain mechanisms. Do we get this in Synaptic Self? well, yes and no.
Ledoux concentrates on memory, having in his last book focused on emotion. He explains memory systems from molecules to circuits, with the classical and most recent findings, including some from his own lab. He also gives a quick overview of the emotional systems of the brain, the working memory complex of the prefrontal cortex, and motivational systems of neuromodulator and brainstem and thalamocortical systems. He calls that the mental trilogy, namely cognition, emotion and motivation. Ledoux also wrote a nice chapter on some brain diseases that seem to alter these functions selectively. And thats it. Ledoux has explained the self. Or has he? Well, memory, emotion, cognition and motivation surely contribute to the making of the self, especially memory. How much of a self is left in a retrograde and anterograde severe amnesic? But this is not saying that putting them together is all the self is about. Its like saying vision, attention and waking are what consicousness is. Vision provides content, attention access, and waking a necesary condition for consicousness, but together they are not the phenomenon in question. I bring out consicousness because Ledoux says the really hard and important question in neuroscience is the self, and not consciousness. To me it seems almost silly to try to understand the former without the latter.
Ledoux then forgets about the feeling of the self itself, the possible bases of it on body schemas and body signals, the primacy of movement. He does touch on volition and free will, and is as naturalistic about these issues as one can be, which I think is a good thing. The final chapter presents 7 principles he can extract from his discussions, and meybe here we can find his theory of the self. Unfortunately, he seems just to add another thing, binding, to the picture. So binding, convergence zones, emotion and motivation, memory, placticity, hebbbian mechanisms of memory, together are the self. Again, I would say they are an important part of the self, but not the self itself. I may be wrong or maybe dogmatic about what would count as an explanation for the self. Maybe there is nothing more to the self than those mechanisms Ledoux lists. But work in theorethical neuroscience like by Damasio, or Patricia Churchland and philosophers like Bermudez show that the self is more complex than Ledoux seems to think.
At the end this book is of value, and I never said it did not make progress on the problem of the neurobiology of the self. However, it does not by any means solve it. It presents a nice theory of the integration of cognitive and affective mechanisms, and manages to cover a great deal of issues in simple terms, and that is always an achievement.