Even when they are crystal clear, our memories are not as straightforward as we might think. In “Pieces of Light: How the New Science of Memory Illuminates the Stories We Tell About Our Pasts,” psychologist Charles Fernyhough goes on a personal journey to explore the science of autobiographical memory, finding that our recollections are created just as much in the present as in the past. We talked to him to find out more.

Brain World: This book is a personal take on memory. Why did you want to write it?

Charles Fernyhough: At a basic level, autobiographical memory is about narratives: the stories people tell about their pasts. When you are writing about the science of human experience, you have to try to tell about that experience from the inside. You have to deal with the neural, cognitive, and social processes, for sure, but you also have to say something about the subjective experience: what it is like to have a memory. My approach is to try to convey scientific information by wrapping it up in human stories, so that the reader feels like they’re reading a novel as much as a science book. Because it’s about our personal stories, memory is the perfect topic for this kind of approach.

BW: How can people remember the same event so differently?

CF: Episodic memory — memory for events, rather than for facts or information — works in three main stages. There’s the stage of encoding, storage, and retrieval. One reason why people can remember the same events so differently is that they vary in what they do at each stage. The reconstructive nature of autobiographical memory means that each person shapes the narrative in their own way, according to their current beliefs, motivations, biases, and so on.

BW: What role does imagination play in memory?

CF: The idea that imagination has special links to memory is a very old one. It’s there in Aristotle, and it was a big theme for medieval thinkers, too. What we are learning about the reconstructive nature of memory is making those links between imagination and memory even clearer. In the book, I describe some research that shows that merely imagining an event increases your likelihood of subsequently “remembering” it, even if the event never actually occurred.

BW: Why are some memories seared into our brains and others far less so?

CF: A basic fact of memory is that emotion makes events more memorable, and we now have a pretty good neuroscientific explanation of why this is the case. The powerhouse of episodic memory, the hippocampus, works closely with the neighboring amygdala, which processes the emotional significance of events.

The hormones and neurotransmitters that are released when the amygdala is activated seem to affect what’s going on in the hippocampus, specifically the synthesis of the proteins responsible for the consolidation of memories. If you take emotion out of the equation, though, memory can seem frustratingly random.

The Dutch novelist Cees Nooteboom likened it to “a dog that lies down where it pleases.” We don’t have good explanations for why some apparently trivial events can stick in our minds for a lifetime.

BW: What is our brain doing in both the act of recalling memories and the anticipation of the future that is similar?

CF: The scientific links between these processes has been one of the main breakthroughs of recent years. It seems that the hippocampus and medial temporal lobes form a basic core network that underlies our ability both to think about the past and to construct scenarios about the future. If this system is damaged, as in some amnesias, patients generally have deficits in both capacities.

The core network can be seen as a “scenario generator” — the neural powerhouse of imagination, in other words. Other brain regions, such as the precuneus and posterior cingulate, play roles in “tagging” the outputs of the core network according to whether they actually happened or were just imagined, whether they happened to the self or to someone else, and so on.

BW: What makes so-called flashbulb events so memorable?

CF: With a typical flashbulb memory, you can remember where you were when you heard the news, how you heard it, and who you were with. But it turns out that flashbulb memories are just as susceptible to distortion as ordinary memories. The researchers who have been studying flashbulb memories of 9/11 found that only just over half of the memories they recorded stayed the same over the first three years after the tragedies. It’s the extreme emotion of the events that makes the memories stick so powerfully, but the same processes of reconstructive memory are at work.

This article was first published in Brain World Magazine’s Spring 2013 issue.

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