Director, Cognitive Neuroscience Laboratory
At Northwestern’s Cognitive Neuroscience Laboratory, electroencephalograms (EEGs) and functional magnetic resonance imaging are used to link acts of memory–remembering, forgetting, and falsely remembering–with specific activity in the human brain. Recently lab director and professor of psychology Ken Paller and his colleagues were among the first researchers to locate where certain false memories are formed.
Harold Henderson: Is memory like a photograph or videotape of the past that’s always there if we just knew how to access it?
Ken Paller: That’s a myth we haven’t fully disproved, but our current understanding does suggest that some memories are indeed lost forever. Others change over time. We store little fragments of experiences in our brains. When we remember something, we successfully retrieve these fragments and put them together again. Remembering is an inference or reconstruction.
HH: Sounds like the brain isn’t much like a computer either.
KP: That analogy only goes so far. The brain’s cortex is specialized so that different kinds of information are processed and stored in different places–people, places, emotions, words, ideas, and so on. There’s no single “memory bank” where all memories sit frozen, waiting to be retrieved.
HH: What’s your overall goal in this research?
KP: I want to understand how mental functions–the whole amazing range of human abilities–can arise on the basis of events in the brain. Memory research gets at one piece of that puzzle. We look at the connection between neural signals of memory and the awareness of remembering. This might eventually help us understand awareness in general.
HH: Is it easier to study memory when it doesn’t work quite right?
KP: Memory failures do provide some unique perspectives. People with amnesia, for instance, lose the ability to consciously remember, but they retain forms of memory that don’t require conscious remembering, such as responding more quickly to a familiar face even when it doesn’t seem familiar. False memories can also be informative, so we set up a laboratory situation in which false memories were created–people remembered an imagined event but misconstrued it by thinking that the event really happened. This way we could relate brain activity to true and false remembering.
HH: This is the experiment you and your collaborators described in “Neural Evidence That Vivid Imagining Can Lead to False Remembering,” published recently in Psychological Science?
KP: Yes. People saw 350 nouns, one at a time, half with corresponding object photos and half without. A short time later they were asked which objects they had seen. You can take a brief version of the test by clicking on the link at www.northwestern.edu/people/kap.
HH: And they gave at least some wrong answers–otherwise you wouldn’t have had anything to study.
KP: A false memory occurred whenever a person claimed to have seen an object they hadn’t. We also analyzed correct memories. And we used the procedure twice, once using EEGs to monitor when critical electrical signals in the brain occurred and again using functional MRI scanning to monitor where. On average, due to the action of certain brain areas that process visual imagery, electrical activity was greater when a false memory was being formed. When you imagine in detail what an apple looks like, you activate these imagery areas. The stronger the activation, as you generate a vivid image of that apple in your mind, the more likely you’ll mistakenly remember seeing an apple.
HH: So are we about to have some sort of superdetector here, one that could determine whether a memory is true or false?
KP: No–although I wouldn’t rule out the possibility of eventually doing something like that. I do know some entrepreneurs interested in it.
HH: How about a less drastic version? If my brain shows this kind of extra activity when a memory is formed, what percentage of the time will my memory actually be false? What’s your batting average on predicting that?
KP: We haven’t worked on the challenge of obtaining high-fidelity measures of brain activity to adjudicate on the accuracy of any one specific memory in real life. We do want to understand memory, and we think knowledge about the relevant brain functions will lead to useful applications in the long term. That’s why federal funding for science is so important. We don’t know which findings will lead to advances and cures in the future, so we need to continue a wide range of investigations into the basics of how the brain works.
HH: Do you see any limits to this long-term process of associating specific mental events with the electric firing of specific areas in the brain?
KP: That’s a great question. I think we’ll never be eliminating or replacing mental phenomena. But we would like to understand them better. These personal experiences have a special status. No one can peer into your brain and say, “You’re not experiencing pain,” when you know that you are.
Art accompanying story in printed newspaper (not available in this archive): photo/Lloyd DeGrane.