Neural-Based Forgetting

Equally as important as the neural process of building memories is the neural process of forgetting or not forging a memory. This neural dynamic is particularly important to address when seeking to understand something about the mnemonist and infinite memory. For many years it was assumed by neuroscientists (and most of us) that forgetting is a passive process. Our memories simply fade away – like the flavor of last evening’s soup or the colors in a photograph or painting left out in the sun. We now know that forgetting involves active suppression of retained memories and that this suppression serves an important adaptive function (as the dysfunction of our mnemonists has demonstrated).

While the forgetting process is complex and not yet fully understood, it seems to involve dopamine and GABA (an inhibitory neurotransmitter) as they function in the hippocampus and prefrontal cortex. It is worth noting that these studies of forgetting may have major implications for the treatment of many mental illnesses which often involve forgetting – and remembering (especially of traumatic events). Furthermore, our understanding of the active forgetting process illuminates the importance of a good night of sleep. While forgetting occurs throughout the day, it does its final (and probably most important) work at night through the process of selection and consolidation that I mentioned earlier.

Neural-Based Memory Retention

Finally, as we gain an appreciation of the adaptive function served by forgetting, we also come to appreciate the adaptive function served by those few memories that are not forgotten. As I have already mentioned, these are memories related to traumatic and fearful events in our life. We DON’T want to forget what happened (as a child) when we touched the front burner on the stove or when as a teenager we drove into a tree after drinking too many beers. As already noted, we assign some of our trauma-related memories to our amygdala (which is located next to the hippocampus). Apparently, none of our forgetting neurochemicals and processes are to be found in the amygdala. Hence, nothing is forgotten.

Our immediate experience of retained memories in our amygdala is found in the “flashbulb” memories we have of specific past experiences in our life that were filled with trauma (either personally or collectively). Like most people of my age, I have very clear, detailed memories of the day when John Kennedy was assassinated (Brown and Kulik, 1982). We do need to remember what has threatened us individually and collectively so that we can prepare for this happening again in the future. Important evolutionary (survival) functions are being served by an amygdala that never forgets traumatizing experiences.