Memory is not exact. It can often be distorted by prior knowledge or experiences. Researchers, led by Alexa Tompary, PhD, an assistant professor in Drexel University’s College of Arts and Sciences, are examining the parts of the brain they believe are responsible for the distortions in memory and if these distortions can be reduced. The study was recently published in the Journal of Cognitive Neuroscience.
According to Tompary, the new research highlights how the brain pieces together memories and explains why our memories are unreliable, which will help us recognize the fallibility of memory – and potential consequences – in everyday life.
Tompary explains how memory works, how the study was conducted and what the findings mean for future memory research.
Can you describe memory?
When you remember something, you’re not just replaying an experience as if your brain is a video camera. Instead, you’re piecing together fragments of information stored in different parts of your brain to create a cohesive picture. For example, let’s say you’re trying to remember a birthday party you attended last year. You might remember the cake, the balloons and the friends you were with. But your brain might also fill in some details that aren’t entirely accurate, like the color of the balloons or the exact conversation you had with your friend. This process of ‘filling in’ details is what gives rise to distortions in memory.
What is the study about?
We suspected that the anterior temporal lobe was responsible for the ‘filling in’ of incorrect details that could create a distorted memory. The anterior temporal lobe is one of the language and memory centers in the brain. It helps us to understand words and their meanings, like being able to recognize that an apple is a fruit that is, crunchy, sweet and often red but sometimes green. It makes sense that when we try to remember something, we may rely on this region to help us.
We designed a study where people learned new facts about things that belong in categories, like birds and musical instruments. Then we tested their memory for this new information. We wanted to see if their memory was influenced by the category each item belonged to. We found that if participants completed this task after receiving transcranial magnetic stimulation (TMS) to the anterior temporal lobe, their memories were less distorted by category details. To be clear, their memory didn’t get better – they still forgot things – but the information that they remembered was less distorted by category details.
Can you expand on the use of transcranial magnetic stimulation (TMS) – what it is? And why it’s used?
Scientists use TMS to temporarily change activity in specific parts of the brain. A special device is placed on the scalp, which generates small magnetic pulses. These pulses pass through the skull and into the brain, and the magnetic pulses can ‘switch’ a specific part of the brain on and off temporarily. We can use this technique to ask how different brain areas are involved in certain behaviors or cognitive processes. In this case, we asked whether ‘switching off’ the anterior temporal lobe would reduce distortions in memory, because we think that distortions in memory can be caused by ‘filling in’ details based on our knowledge and expectations about the world.
Memory was tested in a lab setting; how does this translate outside of the lab?
The nice thing about testing memory in a lab setting is that we can control and standardize the tasks that we ask people to do, which lets us isolate and investigate different aspects of memory in order to understand the bigger picture. Of course, memory outside of the lab is influenced by many other factors that we can’t easily recreate in the lab environment, like personal experiences or distractions. However, even in a more complex and unpredictable setting, we would expect that memories for new experiences would be subject to the same types of distortions.
What comes next?
This is the first time that we have shown that we can reduce distortions in memory using TMS, and it opens up a lot of new questions that we can ask next. For example, at what point can distortions become inserted into a memory – does your prior knowledge immediately change a new experience as you’re experiencing it, or does it only happen later, once you are trying to piece the memory together?
Outside of our lab, this research tells us something about how the way that the brain pieces together memories and gives us an explanation for our unreliable memories. A clearer understanding of this process will go a long way towards recognizing the fallibility of memory and its consequences for us in the real world. For instance, in eyewitness testimony when people are called on to piece together memory for a complicated and often stressful event, they may unintentionally include false information or details from other sources, like news reports or conversations with other witnesses, in their memories.
Is it bad that we rely on what we know to remember things?
It’s not all doom and gloom! It’s not necessarily a bad thing to rely on what we know to remember things. Our past experiences can actually guide us to remember specific events more accurately. For example, if I asked you what you had for breakfast last Tuesday, you’d likely skip over unlikely choices like roast turkey or apple pie and think about the more common breakfast foods you usually have, like cereal, eggs or toast.
Media interested in speaking with Tompary should contact Annie Korp, assistant director, News & Media Relations, at 215-571-4244 or amk522@drexel.edu.
