Neuroscientists unlocks the key to encoding and recalling memories. A coherent narrative may serve as the framework through which the hippocampus processes real-life memory.
Memory is a powerful agent. Remembering information helps us carry out simple tasks and progressively learn more complex concepts. Memories help us create mental models of the world, allowing us to navigate it safely and understand our role within it. The way we shape our narrative is influenced by past experiences, many of which are variegated and episodic in nature.
Functional fMRI studies conducted by neuroscientists at UC Davis in 2021 spotted activity in the hippocampus, suggesting that distant events are integrated to form a coherent narrative. Once a coherent narrative is established, recalling temporally separated and distinct events linked to the narrative triggers similar activity patterns in the hippocampal region. In other words, encoding memory is driven by a narrative that is coherent and such process of memory integration takes place in the hippocampus.
The hippocampus, shaped like a seahorse and located in the temporal lobe, is part of the limbic system. There are two hippocampi, and they play a crucial role in cognitive functions such as learning and memory. The hippocampus interacts with key brain structures, including the amygdala and prefrontal cortex, which collectively influence our learning and behavior.
Even though life’s events occur at disparate times, the hippocampus can form memories that integrate events into a larger, coherent narrative.
— Brendan I. Cohn-Sheehy, et. al., The hippocampus constructs narrative memories across distant events
Connecting events through time was further examined by Christopher Baldassano from the Dynamic Perception and Memory Lab at Columbia University. Baldassano employs functional fMRI to shed light into how the human brain interprets individual events, from which a coherent story can emerge. In 2023, Baldassano postulated that narrative stimuli in cognitive neuroscience research allow for meaningful predictions of future events.
Such predictive model reduces the uncertainty of an upcoming event based on how well connected the parts of the narrative are. The perception of uncertainty of a future event decreases as the coherence of the narrative supporting the prediction increases.
Narratives allow us to study the process by which people make and then continually update predictions, leveraging the complex real-world knowledge that we have developed over decades to enable sophisticated inferences about possible outcomes.
— Christopher Baldassano, Studying waves of prediction in the brain using narratives
Cognition happens by connecting events across time. A narrative may be reinforced by reactivating a memory relevant to the evoked stimulus, regardless of how distant the event is in time. Moreover, real-world cognition—an ongoing process beyond controlled experiments—entails memory retrieval of past experiences that ultimately shapes our course of actions.
Hippocampal event integration supported by narrative structure influences our decisions. In turn, real-world cognition constantly monitors the outcomes of these actions, adjusting our perceptions and updating our understanding of the world.
This raises the question: how do we select which memory to integrate into a coherent narrative from the multitude of equally viable candidates drawn from past experiences? How do we assign weights to memories of our past personal experiences? Do emotions figure in our selection? And do we also draw in memories acquired through stories we read and media we consume, including past experiences of others that we may have vicariously lived through?
Do we truly write our own neural scripts? How much of our narratives were based on external priming? How much freedom do we have in shaping our own narratives, given the concreteness of our past bringing, our environments and our past experiences? What other secrets do the hippocampus and the brain’s anatomical structures hold in shaping our personal story?
While neuroscientists have made significant strides in understanding how memories are encoded and retrieved within the framework of a coherent narrative, the stories we construct about our lives—and the extent to which we exercise self-determination in shaping these narratives—remain elusive.
A writing assignment for one of my courses, I decided to post it here after submission. I picked this topic out of a curious reaction to someone very close to me. In the process of protecting themselves at critical points of their lives, they decide to leave certain people out of their lives and when they do, they color the whole person, which consequently casts a shade on their memories of the person.
There's one of them, they color in black; and another in white. This person claimed that they have no good memories of the former while they only have good memories of the latter. I also reflected on the narratives I chose to keep, even those that I know are harmful. I stepped back and examined these stories, their weights, colors, texture and emotion. In the end, I focused on the questions of integration while challenging the concept of free will in writing our own neural scripts.