UC San Diego

The importance of memory to consciousness, evolution and self-awareness is unparalleled. Since early pivotal studies on hippocampal legions, the hippocampus has been recognized as an integral component of the memory formation. Decades of research has refined and improved our understanding of this small, yet complex, structure. The hippocampus has been implicated in not only in memory formation, but also recall of memory, navigation and time perception, among other things. Today we better understand how activity in this region and connections throughout the brain relate to the specific and parcellated functions it performs. The aim of this work is to understand the memory storage capacity of the brain; in other words, to quantify how much we can store, and in turn, how much we must forget.

Signal detection theory rose to popularity in] as a way to think about complex systems containing information. In application to the brain, a rich and dynamic information system, this elegant approach offers a metric to compare brain regions that are diverse and variable in gene expression, connectivity and activity. As such, information theory has been the basis for various predictions about the information storage capacity of the mammalian brain. Many such predictions, including our own, have relied on a singular, uniform storage capacity. Here we demonstrate that the dentate gyrus, which is older phylogenetically than the rest of hippocampus, stores less information than CA1.

Understanding how information storage capacity varies across species, brain region and age, can help further inform not only future research but also machine learning algorithms and other algorithms that aim to mimic and replicate the richness of the brain.