How Do Pre- and Post-Encoding Processes Affect Episodic Memory?:
A major line of research in my lab regards post-retrieval processes that cause forgetting. For decades there had been controversy as to whether forgetting is caused by decay over time or by interference from irrelevant information, and a coherent account for forgetting was lacking. My colleagues and I have proposed the Representation Theory of Forgetting, according to which forgetting can occur either due to decay or due to interference, depending on the nature of the memory-representation and the brain-structure supporting it. The hippocampus—a structure playing a crucial role in recollection—has a unique neurobiological property, termed pattern-separation, which enables it to represent similar memories in orthogonal patterns. In contrast, familiarity-based memories, supported by extrahippocampal structures are not represented in orthogonal patterns. Therefore, hippocampal-memories will be relatively resistant to interference from one another, but susceptible to decay over time; the reverse would be true for extrahippocampal-memories. In my talk, I will present behavioural evidence in support of our theory.
In addition, I will present a related research program, in which I ask whether memory is affected not only by post-retrieval processes (like decay and interference), but also by processes occurring prior to encoding. I hypothesize that the scaffold of a memory engram is spontaneously laid even before the experience occurs. In support of this hypothesis, we have shown— using multivoxel-pattern-analysis of fMRI data—that the mnemonic fate of information depends on whether spontaneous neural representations prior to perceiving the information are reinstated during encoding.