Understanding the neurobiological machanisms of learning and memory: cellular, molecular and gene regulation inplicated in synaptic plasticity and login-term potentiation. Part IV C (original) (raw)
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Synaptic plasticity: understanding the neurobiological mechanisms of learning and memory: Part I
Salud …, 2001
Plasticity of the nervous system has been related to learning and memory processing as early as the beginning of the century; although, remotely, brain plasticity in relation to behavior has been connoted over the past two centuries. However, four decades ago, several evidences have shown that experience and training induce neural changes, showing that major neuroanatomical, neurochemical as well as molecular changes are required for the establishment of a long-term memory process. Early experimental procedures showed that differential experience, training and/or informal experience could produce altered quantified changes in the brain of mammals. Moreover, neuropsychologists have emphasized that different memories could be localized in separate cortical areas of the brain, but updated evidences assert that memory systems are specifically distributed in exclusive neural networks in the cortex. For instance, the same cortical systems that lead us to perceive and move in our environment, are used as neural substrates for memory retrieval. Such memories are the result of the repeated activity of millions of neurons assembled into distinct neural networks, where plastic changes in synaptic function leads to the strengthening of the same synaptic connections with 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 occurring during LTP. Long-term potentiation (LTP) is the result of the increase in the strength of synaptic transmission, lasting as long as can be measured from hours to days. LTP has been detected in several areas of the brain, particularly, in the hippocampus, amygdala, and cortex, including several related limbic structures in the mammalian brain. LTP represents up to date the best model available for understanding the cellular basis of learning and memory in the central nervous system of mammals including humans.
2002
SUMMARY One of the central issues in neuroscience is concerned with the activity-dependent synaptic plasticity in learning and memory. In such context, changing the strength of synaptic activity between neurons has been widely accepted as the mechanism responsible by which memory traces are encoded and stored in the brain. Thus, the synaptic plasticity and memory hypothesis (SPM hypothesis) shows that activity-dependent synaptic plasticity is induced at appropiate synapses during memory formation, which is essential for information storage for the type of memory involved in the brain area where plasticity is detected or observed. Several criteria and experimental strategies are outlined, and used to investigate this hypothesis. Long-term potentiation (LTP) as an experimental model to study the cellular basis of learning and memory, is one of the most fascinating phenomena that have raised a great interest in neuroscience. LTP is a form of synaptic plasticity that is accepted as a ce...
Long-Term Potentiation (LTP): A Simple yet Powerful Cellular Process in Learning and Memory
Clinical Schizophrenia & Related Psychoses, 2021
Learning and memory are natural responses of the body to assist us in living. Neurodegenerative diseases wreak havoc on the neuronal processes that control memory development and consolidation, causing mental, social, and financial hardship for millions of people around the world. In the mammalian brain, many neurotransmitters are involved in memory formation and consolidation. The cellular mechanisms and signaling pathway involved in this, however, are not fully understood. Donald Hebb suggested the synaptic reorganization hypothesis in support of memory development decades ago. Two types of synaptic plasticity, Long-Term Potentiation (LTP) and Depression (LTD), have been implicated in the formation and consolidation of memory in mammalian brains as a result of the advancement of modern electrophysiology and molecular biology techniques. The synapses are also thought to be the source of information storage, according to Hebbs' theory of neuronal connectivity and firing properties. As a consequence, information can be altered by altering synaptic intensity through LTP or LTD. The physiology of synaptic organization in the brain is altered in certain memory-related cognitive impairments. Although there is literature on the non-synaptic memory system in the mammalian brain, this review will concentrate on a few key findings from in vitro and in vivo synaptic plasticity studies to link the role of LTP and LTD-a signature model in memory formation and consolidation. This will help us better understand neurological disorders involving neural processes and get us closer to discovering a cure.
Synaptic Plasticity and Memory: An Evaluation of the Hypothesis
Annual Review of Neuroscience, 2000
Changing the strength of connections between neurons is widely assumed to be the mechanism by which memory traces are encoded and stored in the central nervous system. In its most general form, the synaptic plasticity and memory hypothesis states that "activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the information storage underlying the type of memory mediated by the brain area in which that plasticity is observed." We outline a set of criteria by which this hypothesis can be judged and describe a range of experimental strategies used to investigate it. We review both classical and newly discovered properties of synaptic plasticity and stress the importance of the neural architecture and synaptic learning rules of the network in which it is embedded. The greater part of the article focuses on types of memory mediated by the hippocampus, amygdala, and cortex. We conclude that a wealth of data supports the notion that synaptic plasticity is necessary for learning and memory, but that little data currently supports the notion of sufficiency. Annu. Rev. Neurosci. 2000.23:649-711. Downloaded from arjournals.annualreviews.org by Iowa State University on 02/10/05. For personal use only. Annu. Rev. Neurosci. 2000.23:649-711. Downloaded from arjournals.annualreviews.org by Iowa State University on 02/10/05. For personal use only.
G ENETIC A PPROACHES TO M OLECULAR AND C ELLULAR C OGNITION : A Focus on LTP and Learning and Memory
Annual Review of Genetics, 2002
▪ Long-term potentiation (LTP) is the predominant experimental model for the synaptic plasticity mechanisms thought to underlie learning and memory. This review is focused on the contributions of genetics to the understanding of the role of LTP in learning and memory. These studies have used a combination of genetics, molecular biology, neurophysiology, and psychology to demonstrate that molecular mechanisms of synaptic plasticity are critical for learning and memory. Because of the large scope of this literature, we focus primarily on genetic studies of hippocampal-dependent learning. Altogether, these findings not only demonstrate a role for plasticity in learning, they also lay down the foundations for the new field of molecular and cellular cognition.
Synaptic Plasticity. Stairway to Memory
The Japanese Journal of Pharmacology, 1995
Since the idea that memory is associated with alterations in synaptic strength was accepted, studies on the cellular and molecular mechanisms responsible for the plastic changes in neurons have attracted wide interest in the scientific community. Recent studies on memory processes have also pointed out some unifying themes emerging from a wide range of nervous systems, suggesting that regardless of the species or brain regions, a common denominator for memory may exist. Thus, the present review attempted to create a hypothetical and universal synaptic model valid for a variety of nervous systems, ranging from molluscs to mammals. The cellular and molecular events leading to short-and long-term modifications of memory have been described in a sequential order, from the triggering signals to the gene expression, synthesis of new proteins and neuronal growth. These events are thought to represent the late phases of memory consolidation leading to persistent modifications in synaptic plasticity, thereby facilitating the permanent storage of acquired information throughout the individual's life.