The Behavioral Tagging Hypothesis and Its Implications for Long-Term Memory Formation

Abstract

Memories are experience-dependent internal representations of the world that can last from short periods of time to a whole life. The formation of long term memories relies on several biochemical changes, which inducing modifications in the synaptic efficiency change the way the neurons communicate each other. Interestingly, the formation of a lasting memory does not entirely depend on learning itself; different events occurring before or after a particular experience can affect its processing, impairing, improving, or even inducing lasting memories. The overlapping of neuronal networks involved in the processing of different types of learning might explain why different experiences interact at neuronal level. However, how and where this does really happen is an issue of study. In 1997, the Synaptic Tagging and Capture (STC) hypothesis provided a strong framework to explain how synaptic specificity can be achieved when inducing long lasting changes in electrophysiological models of functional plasticity. Ten years later, an analogous argument was used in learning and memory models to postulate the Behavioral Tagging hypothesis. This framework provided solid explanation of how weak events, only capable of inducing transient forms of memories, can result in lasting memories when occurring in the context of other behaviorally relevant experiences. The hypothesis postulates that the formation of lasting memories rely on at least two parallel processes: the setting of a learning tag that determines which memory could be stored and were; and the synthesis of plasticity-related proteins,which once captured at tagged sites will allow the consolidation of a memory for long periods of time. Therefore a weak learning, only able to induce transient forms of memories but also capable of setting a learning tag, could be benefited from the proteins synthesized by a different strong event, processed in the same areas, by using them to consolidate its own lasting memory. In this chapter we will detail the postulates and predictions of the Behavioral Tagging hypothesis, deepen the mechanisms involved in the setting of the tag and the synthesis of proteins, and revise the universe of experiments performed from rodents to humans in order to discuss its implications on learning and memory processing.