Memory consolidation has been described as the fitting of new information into categories already formed in the cerebral cortex. When information is transferred from short term memory to long term memory it does not become permanent immediately . The so-called memory trace is a synaptic pathway which can be increasingly strengthened after its first establishment. It is strengthened or consolidated by retracing of that synaptic pathway by rehearsals or repetitions of various kinds. This involves the process of long term potentiation, mediated by calcium ions and neurotransmitters. Consolidation enhances the permanency of a long term memory and increases the ease with which it can be retrieved. It also lessens the likelihood that it will be permanently lost.
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Memory encoded and transferred from short term memory to long term memory does not instantly become permanent. Over some time the cortex will fit each memory in categories already established, or into a certain positions in a scheme, to facilitate ease of retrieval. Physiologically, this involves the sensitizing of relevant neurons, the synchronizing of neuronal firing, and the deepening of synaptic pathways or memory traces. Long term potentiation(LTP) is a process that increases long term memory consolidation. In this process rehearsals cause the number and sizes of presynaptic terminals to increase; they also stimulate greater neurotransmitter release. An example of the way consolidation is facilitated is as follows: Sensory inputs to the association cortex may travel to the medial temporal lobe (+hippocampus) which communicates with the thalamus and the prefrontal cortex. Neurons in the basal forebrain release acetylcholine which facilitates the formation of memory pathways. In this process newly synthesized mRNA molecules are delivered to axons and dendrites; new proteins are synthesized and deposited at dendritic terminals; also axons and dendrites become modified in shape. The more often a memory is retrieved and rehearsed the more permanent or consolidated it becomes.