Synaptic plasticity: Understanding the neurobiological mechanisms of learning and memory. Part I

Plasticity of the nervous system has been related to learning and memory pr ocessing as early as the beginning of the century; although, remotely, brai n plasticity in relation to behavior has been connoted over the past two ce nturies. However, four decades ago, several evidences have shown that exper ience and training induce neural changes, showing that major neuroanatomica l, neurochemical as well as molecular changes are required for the establis hment of a long-term memory process. Early experimental procedures showed t hat differential experience, training and/or informal experience could prod uce altered quantified changes in the brain of mammals. Moreover, neuropsyc hologists have emphasized that different memories could be localized in sep arate cortical areas of the brain, but updated evidences assert that memory systems are specifically distributed in exclusive neural networks in the c ortex. For instance, the same cortical systems that lead us to perceive and move in our environment, are used as neural substrates for memory retrieva l. Such memories are the result of the repeated activity of millions of neu rons assembled into distinct neural networks, where plastic changes in syna ptic function leads to the strengthening of the same synaptic connections w ith the result of reconstructed permanent traces that lead to remembrance ( Hebb Postulate). Elementary forms of learning and memory have been studied in simple neural systems of invertebrates, and as such have led the way for understanding much of the electrophysiological and neurochemical events oc curring during LTP. Long-term potentiation (LTP) is the result of the incre ase in the strength of synaptic transmission, lasting as long as can be mea sured from hours to days. LTP has been detected in several areas of the bra in, particularly, in the hippocampus, amygdala, and cortex, including sever al related limbic structures in the mammalian brain. LTP represents up to d ate the best model available for understanding the cellular basis of learni ng and memory in the central nervous system of mammals including humans.