ABSTRACT
The developing and mature nervous system must solve two major problems. The brain must be able to function properly, or at least well, and it must be able to change. We will see that these two problems are aspects of the same task. I am reminded of a 1931 painting by Salvador Dali called “The Persistence of Memory.” In the painting, the faces of clocks had become rather fluid, and they hung loosely and folded over tree branches. The plastic clocks reminded me that we do retain our 368memories over long periods of time, but the memories change and gradually become distorted. While we clearly do have brain mechanisms for storing information, or for maintaining functions, there is a struggle for stability that is only partially achieved. Better stability may be possible, but perhaps not in systems that are also designed to change and to acquire new memories, and new functions. Our brains must be capable of processing information, retrieving information, and controlling behavior in a predictable and reliable manner, and this would seem to depend on morphologically and functionally stable machinery, the circuits of the brain. And yet, the circuits cannot be completely stable if we are going to acquire new skills and abilities, and adjust to sensory loss and other impairments. We also realize, as memories fade and distort, that brain circuits change even when you do not try to change them or want them to change. It may be true that once you learn to ride a bike, you can always ride a bike; however, it is not true that skills and abilities can be maintained at a high level without practice. The professional athlete or musician fully realizes how much effort is needed just to maintain abilities. These talented individuals practice to fine-tune the neural circuits used in their professions. Experience both changes and maintains.
