Cellular and Molecular NeuroscienceReviewLearning and memory consolidation: linking molecular and behavioral data
Research highlights
▶Current research shows a complex image of mechanisms underlying memory formation. ▶ Molecular and behavioral data can be provisionally linked in an integrative approach. ▶Different families of proteins can promote memory consolidation and persistence.
Section snippets
Historical background
The Spanish Santiago Ramón y Cajal (1852–1934), whose intuition led him to infer the function of the nervous system from its morphology, was the first scientist suggesting plasticity in the number and strength of neural connections as the physical basis of learning and the support of memory (Ramón y Cajal, 1894). In 1949 the Canadian psychobiologist Donal O. Hebb (1904–1985) proposed associative plasticity as the mechanism from which coincidence in pre- and post-synaptic activity would be able
Hippocampal plasticity
Dendritic spines are branched protoplasmic extensions which are the major site of excitatory synaptic transmission in the vertebrate brain. Different authors and experimental research on the initiation and maintenance of synaptic plasticity, particularly in CA1 pyramidal neurons of the hippocampus, have shown that certain types of learning, as well as artificially induced LTP, can produce increases or morphological changes in dendritic spines giving rise to new or strengthen existing synapses
From short- to long-term memory
Short term memory (STM) is a brief retention (minutes, hours) of conscious information supported by transient or non-stabilized post-translational modification of preexisting molecules that alters the efficiency of synaptic transmission in plastic neural networks. When, as a consequence of saliency of information to be remembered, and/or repetition of experience, such changes persist, they can activate the above described machinery, producing the synthesis of new proteins and structural changes
System consolidation
Memory consolidation at synaptic level in places like the hippocampus can be followed by a more prolonged process that involves a gradual reorganization of the different brain regions that support memory. It has been suggested (Frankland and Bontempi, 2005) that the synaptic changes in the hippocampus can serve to integrate information from distributed cortical areas, each representing individual components of a memory. However, as the memory matures, connections between the different cortical
Memory allocation in neural circuits
Wherever memories are stored, it is important to know how learning selects the particular neurons and synapses where the information is allocated within a neural circuit avoiding interferences between the different memories stored throughout lifetime. This has been highlighted by recent experimental works from Silva and other researchers in UCLA. They have shown that several specific mechanisms could be involved in such selection. Thus, neurons activated by CREB during learning are more
Conclusion
Current experimental and clinical research shows a multiple and complex image of the synaptic and molecular mechanisms underlying learning and memory formation. Following different authors and laboratories, here we have tried to link some of these mechanisms together and with their related behavioral events in order to give an always partial and provisional, but somehow comprehensive, panorama of the different phases of these processes. This approach is obviously risky, but can prevent the
Acknowledgments
This research was supported by a Ministerio de Educación y Ciencia (MEC) grant (project PSI2009-07491), and a Generalitat de Catalunya grant (2009SGR).
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