How Reliable Is Our Memory?

How memories are formed, stored, and modified has been one of the key topics in neuroscience studies. It’s fascinating to realize that not only can we enhance our memory through constant practice and exercise, but also alter or eliminate existing memory in some trauma cases. Within the past few years, neuroscientists have even found ways to create fake memories or artificially manipulate memories. All of these lead to a huge question: how reliable is our memory?

Picture adapted from: https://pixabay.com/en/nerves-cells-dendrites-sepia-346928/

Picture adapted from: https://pixabay.com/en/nerves-cells-dendrites-sepia-346928/

Most of us have perhaps heard of the analogy that our brain functions like a computer. Information we perceive through our sensory organs is transduced and processed by various neurons and experiences are accumulated to create memories that are stored in different regions of the brain. As our existential evidence, memories constitute our identities and to certain extent determine who we are as human beings. Scientifically, the formation of memories is facilitated by the dynamic generation and deterioration of synapses that connect different neurons to spike different responses. Put it in a simple way, a new memory is created when neurons that didn’t connect before are wired together in the brain, forming new contacts and synapses. The memory will be strong if it is constantly revisited and the relevant synapses get strengthened by reactivating this particular group of neurons. On the other hand, the memory will gradually fade if these neurons stop firing and the synapses dissemble. This is similar to how we maintain friendships at the macro-level. Throughout our entire life, we have a lot of friends. We make new friends everyday and perhaps also lose some from time to time. Like some friends maintain close relationships because they spend time together more often, some memories stay lucid because of repetitive reminders. Understanding which neurons and synapses store which memory is thus like deciphering a codebook. By genetically labeling neurons and tracing their activities, scientists have made huge progress in decoding this mystery, revealing the possibility of Inception in real life.

A research group led by Dr. Steve Ramirez at Boston University have been the experts in memory studies for years. In 2013, they made a breakthrough of implanting fake memories into the brain of mouse. Published in Science, this study has demonstrated that when neurons in a particular region of the hippocampus get activated artificially through optogentics, a pain-related memory can be recalled without actual pain stimulus. By labeling different neurons in the brain, the researchers were able to identify neurons activated by a particular pain stimulus, a foot shock in this case. Mice exposed to foot shock once were separated into two groups: one would receive a real foot shock again to trigger this pain memory, and the other would be stimulated with light for artificial neuron activation. Using optogentics, the researchers activated the particular pain-responsive neurons with light and compared the response from mice that have received real foot shock. Interestingly, light activation of these neurons produced similar response as the normal pain stimulation, which means both groups of mice were “reminded” of the pain even though only one group actually received it.  Dr. Ramirez’s group smartly bypassed the sensory neurons for pain and created this fake memory in their mice. In other words, the researchers tricked the mice to memorize a pain that they weren’t exposed to simply by shining light on them.

Similarly in a followup study published in Nature in 2015, the same group managed to rescue behavioral disorders in mice due to stress by optogenetically activating the rewarding neurons to trigger good memory. Although human brain is a hundred times more complicated than a mouse brain, with the success in manipulating mouse memory, it’s promising that we will have the capacity of interfering with human memories soon. While advancements made in this field will help cure neurodegenerative disorders such as Alzheimer’s, memory altering technologies can also bring up ethical issues and concerns on how reliable our memories are. Without doubts, positive effects in response to rewarding memories can be extremely beneficial to the continuously growing population fighting with depression. On the other hand, if our life is composed of a mixture of fake and authentic memories for various reasons, how would we know what to trust and who we are? As fully conscious human beings, maybe it’s time to ponder on how reliable we want our memories to be.

Picture adapted from: https://pxhere.com/en/photo/654163

Picture adapted from: https://pxhere.com/en/photo/654163

Peer edited by Nicole Fleming.

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New Year, New Discoveries in Alzheimer’s Research

 Alzheimer’s disease is both debilitating and fatal. Its associated memory loss is more than a sign of normal aging, and Alzheimer’s is a leading cause of death in the United States. While the pace of Alzheimer’s treatment research is impressive, it is mirrored by a monumental projected increase in prevalence over the next 30 years.

https://www.nia.nih.gov/

Image shows a beta-amyloid protein (orange) and tau protein (blue). Image courtesy of the National Institute on Aging/National Institutes of Health.

A key aspect of developing effective treatments for Alzheimer’s, and for any disease, is to understand how the disease progresses. One of the causes of Alzheimer’s is believed to correlated with malfunctioning tau proteins in our nerve cells, or neurons. Tau proteins, when under a normal function, stabilize neuron’s microtubules serving as information carriers. When tau proteins malfunction, the nerve cells reject the accumulated debris of tau and spit it out. Another small section of protein, beta-amyloid peptides, are involved in neuronal structure as well as in Alzheimer’s disease. Scientists believe the nasty feedback loop in which beta-amyloid’s failure would trigger tau protein malfunction and that tau tangles, in turn, enhance beta-amyloid toxicity. These extracellular proteins stick together in bundles, forming strands of tangles and clusters of plaques around the dying neurons. 

Research  out of the University of Cambridge, published in Brain this month, combined functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans to visualize the location and extent of tau proteins in the brains of 17 Alzheimer’s patients and 12 controls. They also included 17 patients with progressive supranucelar palsy (PSP), a brain disorder sometimes mistaken for Parkinson’s disease.

The Cambridge researchers wanted to test the theory of “transneuronal spread” – that tau tangles from one neuron pass to other neurons, rather than simultaneously occur at multiple locations. The imaging from their research study showed that abnormal tau proteins seemed to accumulate along heavily connected regions of the brain, where neurons are densely connected to one another. This theory supports the progressive nature of Alzheimer’s with an increasing loss of functional connectivity, and the researchers are planning additional studies to follow these patients over time and document the spread of these proteins. Animal research has previously shown tau propagation via synaptic connectivity in rodent models.

https://www.nia.nih.gov/

Image shows abnormal tau proteins in neuronal bodies (blue) and amyloid plaques (orange) in a diseased Alzheimer’s brain. Image courtesy of the National Institute on Aging/National Institutes of Health.

Interestingly, the Cambridge researchers found evidence of a different tau propagation in progressive supranucelar palsy (PSP) patients. The spread of tau tangles seemed to follow increased metabolic demand, not functional neuronal connectivity. This different mechanism may explain the different symptoms seen in Alzheimer’s, often presenting as memory loss, and PSP, often presenting as weakness.

Want to learn more about Alzheimer’s disease? Take an interactive tour of the brain and learn how the disease occurs and progresses at the physiological level.

 

Peer edited by Chiung-Wei Huang and Kate Newns.

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An Apple Logo a Day Means Your Memory’s Okay, But Not Perfect

Immediately close your eyes and draw the Apple logo from memory. How confident are you that your drawing is accurate? Keep reading to see how well you did!

Companies change logos frequently. Google, Uber, and Instagram all rebranded in the past year or so. But how well do we actually know what these logos look like? Consider this: which way is Lincoln facing on the penny? Don’t dig into your pocket. Think about it for a second.

In a now classic study, people could not accurately identify the details of pennies. Features were confused, misplaced, or left out altogether. We’ve seen pennies many times throughout our lives, yet we are remarkably poor at remembering their design.

The penny result may seem surprising. But when we are not specifically asked to learn something – and even when we are – our memory doesn’t always come through. Our memories are not perfect. They are a combination of the actual object or event that we experienced and our own expectations and knowledge.  “But okay,” you’re thinking, “I rarely use pennies. Surely I would remember something more meaningful.”

Since the penny study, researchers have continued to explore the connection between our exposure to objects and our memory for them. In one recent study researchers looked at the Apple logo, a symbol that is everywhere; it’s on TV, on billboards, and in the hands of the person sitting next to you. Logos are also made to be recognizable, so we must know what it looks like, right?

Once again, the answer is “Not really.” Participants were, justifiably, very confident in their ability to draw the logo from memory, but only one (out of 85!) did so perfectly. The drawings tended to include parts of apples that are not in the logo, such as stems, consistent with the idea that our memory is based on our expectations (in this case, expectations of what an apple should look like). Participants even struggled to pick out the logo from eight different variations: less than half chose the correct one.

Source: By Apple, Inc. [Public domain], via Wikimedia Commons

How well did you draw the Apple logo from memory?

A similar pattern is found for locating potentially life-saving objects. Here, researchers asked university faculty, staff, and students about the location of the nearest fire extinguisher in their building. These participants had worked in the building for about 5 years, yet most (about 75%) could not report the location.

Even frequent physical interaction with objects does not guarantee success: We can have poor memory for a well-traveled elevator, and self-identified Apple users were just as overconfident in their memory for the logo as were non-users.

Here’s what is happening. Passively encountering or interacting with something does not ensure we’ll remember it. We have little trouble remembering the gist of an event or object, but picking out particular features or locations is difficult.

Cognitive psychologist Alan Castel and colleagues differentiate between “seeing” and “noticing.” Being exposed to information frequently (or “seeing” it) does not guarantee we will notice and remember it. Actually, all that exposure may encourage us to stop paying attention to the details, particularly when they do not hold any real benefit, which is the case for specifics of a penny or the Apple logo. We know it’s a penny because of its size and color, not because of the direction Lincoln faces (it’s to the right).

But these memory lapses are not necessarily a bad thing. Not keeping track of every detail leaves us room to process other important things in the world around us. We can also rely on our expectations for where objects will be, such as that a fire extinguisher will be in an easily accessible place, or that the random piece of trivia knowledge can be found on Google.

Here’s a good place to start if you want to remember something: think about it. Cognitive scientist Daniel Willingham says that memory is the residue of thought. So when you want to remember the layout of that nickel in your pocket, spend some time mulling it over.


Peer edited by Amy Rydeen

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Is My Professor’s Lecture Style Affecting My Learning?

You’re sitting in class as your professor rambles on. The material is interesting, but the lecture is choppy. The professor stops-and-starts frequently, sounding uncertain, and you’re counting the number of times he says, “um.” Meanwhile, your friend is taking the same class with a different instructor known for his confident and clear style.

The content of the courses is the same, but the delivery of that content must be affecting your ability to learn the material, right?

Source: https://pixabay.com/en/birger-kollmeier-professor-910261/

Is the way your professor presents the material affecting your learning?

Maybe not. A recent study out of Iowa State University found that the lecture style of an instructor had no consistent effect on learning.

In the experiment, participants watched a 22-minute presentation of a scientific concept. Half of the participants heard the presentation narrated by an instructor who sounded hesitant, disengaged, and awkward. The other half heard the information from the same instructor but who now spoke in a calm and fluid manner. The actual material covered in the two presentations was identical.

Participants’ confidence in their learning did not differ between the two instructors either. In other words, those who learned from the awkward instructor thought they would perform just as well as those who learned from the confident instructor.

This result may sound surprising, but classrooms have a lot going on. Lectures are typically accompanied by a presentation, graphics, and demonstrations. If the material itself is generally considered hard, it might not matter how it is presented.

That’s what the researchers found: participants generally based their memory confidence on the material being learned and on their own learning abilities instead of on the instructor’s delivery.

But even if the clarity of presentation does not influence learning or confidence, it could affect other outcomes. Teaching evaluations hold a lot of weight in how instructors are perceived – by themselves, their students, and the institutions they work for. Therefore, instructors may look to improve these evaluations. One way to do this? Work on how you sound. Participants rated the clear and confident instructor as more organized, knowledgeable, prepared, and effective.

This study has takeaways for both teachers and students. First, instructors, if you value the perceptions of your students, try to present your lectures in an engaging and fluid manner. Students notice presentation style and judge their professors on how the material is given. But we all have rough days. There might be a time when you can’t prepare and rehearse as much as you’d like, and that’s okay. Your students’ comprehension may not be any worse off.

Now students, your understanding of the material may not be influenced by your instructor’s delivery. Actually, having an overly confident instructor could hurt your learning. A related study found that students learning from such an instructor thought that they understood the information much better than they actually did. So maybe you don’t have to be too envious the next time you hear about your friend’s awesome professor.

Peer edited by Salma Azam, Sara Duncan, and Lindsay Walton.

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Does Inside Out Accurately Portray Memory?

With the recent release of Pixar’s latest movie, The Good Dinosaur, I thought I would revisit their previous film, Inside Out. Inside Out follows the five main emotions (Joy, Sadness, Disgust, Anger, and Fear) of 11-year-old Riley as they guide her through her family’s move from Minnesota to San Francisco. Themes of the movie include how Riley experiences her world and how these experiences are translated into long-term memories, some of which define Riley’s personality. As a graduate student who studies memory, I was intrigued by the movie’s depiction of it. Fortunately, the movie does a nice (and entertaining) job. So what does it get right? Continue reading