Synapses Change with Experience

This is a very interesting fragment from the book In the Search of Memory: The Emergence of a New Science of Mind, from the honorable 2000 Nobel Prize in medicine or physiology, Mr. Eric Richard Kandel, an exponent in the field of Neuroscience. In the book, Mr. Kandel presents his rich biography together with also valuable findings in the scientific field, explaining in details how geniuses do their work, make decisions and change the world while living normal lives. Maybe not so normal, but living among us.

Eric Kandel in 1978

Eric Kandel in 1978

— …, we were begging to understand that the strength of a given chemical synapse can be modified in two ways, depending on which of two neural circuits is activated by learning–a mediating circuit or a modulatory circuit. In Aplysia, the mediating circuit is made up of the sensory neurons that innervate the siphon, the interneurons, and the motor neurons that control the gill-withdrawal reflex. aplysia The modulatory circuit is made up of sensory neurons that innervate the tail in a completely different part of the body. When the neurons in the mediating circuit are activated, homosynaptic  (activity-dependent) changes occur. This is the case in habituation: the sensory and motor neurons that control the gill-withdrawal reflex fire repeatedly and in a certain pattern in direct response to the repeat sensory stimulus. Heterosynaptic changes in strength occur when the neurons in a modulatory, rather than the mediating circuit are activated. This is the case with sensitization: the strong stimulus to the tail activates a modulatory circuit that controls the strength of synaptic transmission in the mediating neurons. We later found that classical conditioning recruits both homosynaptic and heterosynaptic changes. Indeed, our studies of the relationship of sensitization to classical conditioning indicate that learning may be a matter of combining various elementary forms of synaptic plastic into new and more complex forms, much as we use the alphabet to form word. I (Mr. Kandel, of course) now began to realize that the abundance of chemical over electrical synapses in the brains of animals may reflect a fundamental advantage of chemical over electrical transmission: the ability to mediate a variety of forms of learning and of memory storage. Viewed from this perspective, it became clear that the synapses between sensory neurons and motor neurons in the gill-withdrawal circuit–neurons that have evolved to participate in various types of learning–are much more easily changed than synapses that play no role in leaning. Our (Eric Kandel and his coleagues) studies showed dramatically that in circuits modified by learning, synapses can undergo large and enduring changes in strength after only a relatively small amount of training.” — In the Search of Memory: The Emergence of a New Science of Mind, Eric Kandel. First Edition 2007. Chapter 14 This gentleman and his crew, all renowned scientists, are trying to trap memory through the biological basis of human brain, at the cellular level (“one cell at a time”), bringing to light some obscure facts about the more powerful structure of our known universe–human brain. Such hard work should be praised by everyone. Project all the amount of technology this people used to reach their goals, and how dependent on innovation they were back in the 1950’s. They’re scientists, and since knowledge is power, are the real heroes for humanity. Kandel’s work help to explain some neurological pathologies as well as brain and mind structures, while help humanity to evolve. Certainly this man will be remembered as a genius in the future. EricxAplysia


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