For most people having a good memory means being able to remember more information clearly for long periods of time. For neuroscientists too, the inability to remember was long believed to represent a failure of the brain’s mechanisms for storing and retrieving information.
Paul Frankland, a senior fellow in CIFAR’s Child & Brain Development program, and Blake Richards, an associate fellow in the Learning in Machines & Brains program, say that our brains are actively working to forget. These researchers from University of Toronto propose that the goal of memory is not to transmit the most accurate information over time, but to guide and optimize intelligent decision making by only holding on to valuable information.
The review paper, published in the journal Neuron, review literature on remembering, known as persistence, and the newer body of research on forgetting, or transience. The recent increase in research into the brain mechanisms that promote forgetting revealed that forgetting is just as important a component of our memory system as remembering.
One of these mechanisms is the weakening or elimination of synaptic connections between neurons in which memories are encoded. Another mechanism is the generation of new neurons from stem cells. As new neurons integrate into the hippocampus, the new connections remodel hippocampal circuits and overwrite memories stored in those circuits, making them harder to access. This may explain why children, whose hippocampi are producing more new neurons, forget so much information.
It may seem counterintuitive that the brain would expend so much energy creating new neurons at the detriment of memory. Richards, whose research applies artificial intelligence (AI) theories to understanding the brain, looked to principles of learning from AI for answers. Using these principles, the authors frame an argument that the interaction between remembering and forgetting in the human brain allows us to make more intelligent memory-based decisions.
Forgetting allows us to adapt to new situations by letting go of outdated and potentially misleading information that can no longer help us maneuver changing environments. And forgetting facilitates decision making by allowing us to generalize past events to new ones.