Mechanisms for the generation of synapse specificity in long-term memory: the implications of a requirement for transcription.

Since long-term memory (LTM) depends on transcription, signals required for LTM must emanate from the cell body. In some cases, signals from the cell body are not only required, but are also sufficient for LTM. However, It is difficult to reconcile this finding with the need to modify synapses independently. To retain synapse specificity during LTM, a form of memory is required that is independent of transcription, and that produces a synaptic 'mark' which interacts with molecules synthesized in the cell body. To reconcile the sufficiency of transcriptional signals for LTM with the need for synapse specificity, I propose that not all LTM is synapse-specific; activation of transcription presynaptically results in cell-wide LTM, whereas postsynaptic transcriptional activation leads to synapse-specific LTM.