Memory Storage Requires Neuronal Remodeling
In introducing the term synapse, a researcher by the name of Charles Sherrington speculated that synaptic alterations might be the basis of learning and memory storage, anticipating an area of research that to this day is one of the most intensive efforts in all of neuroscience (Alberini, 2011). Modern ideas about neural plasticity have their origins in the theories of Donald Hebb, who proposed that when a pre-synaptic and a post-synaptic neuron are repeatedly activated together, the synaptic connection between them will become stronger and more stable in order to form long term memories. Ensembles of neurons, or cell assemblies, linked via synchronized activity of these Hebbian synapses, could then act together to store long-term memory traces. It was this idea that would eventually be confirmed in various brain tissues, including the hippocampus. Most current theories of the cellular basis of learning and memory storage focus on plasticity of the structure and physiological functioning of synapses (Bays, Wu, & Husain, 2011).
Synaptic changes that may store information can be measured physiologically. The changes could be pre-synaptic, post-synaptic, or both. Such changes include greater release of neurotransmitter molecules and/or greater effects because the receptor molecules become more numerous or more sensitive. The result of such changes would be an increase in the size of the post-synaptic potential. Changes in the rate of the inactivation of the transmitter, through reuptake or enzymatic degradation, could produce a similar effect (Alberini, 2011).
Synaptic activity could also be modulated by inputs from other neurons causing extra depolarization or hyper polarization of the axon terminals and changes in the amount of neurotransmitter released. Long-term memory storage may require changes in the nervous system so substantial that they can be directly observed by the use of a microscope. Structural changes resulting from use are apparent in other parts of the body. For instance, exercise changes the mass and/or shape of muscles and bone. In a similar way, new synapses could form or synapses could be eliminated as a function of training (Alberini, 2011).
Simply put, memory storage is the more or less passive process of retaining information in the brain, whether in the sensory memory, the short-term memory, or the more permanent long-term memory. Each of these different stages of the human memory function as a sort of filter that helps to protect the individual from the flood of information that confronts them on a daily basis, avoiding an overload of information and helping to keep them sane. The more the information is repeated or used, the more likely it is to be retained in long-term memory. Due to the extensive research done in the 1950s and 1960s, it has since become clear that long-term memories are not stored in just one part of the brain, but are widely distributed...