Archive for the 'Neuroscience' Category

Jan 06 2020

Zeroing In on Memories

Published by under Neuroscience

How do memories work? That has been a burning question for over a century, since Richard Semon introduced the term “Engram” in the early 20th century as the fundamental unit of memory in the brain. I should say, that is how long the question existed in its modern neuroscientific form. Thinking about the nature of memory goes back to the early Greek philosophers. In fact we have evidence that they figured out pretty quickly that the brain was central to cognitive function:

Yet an important development in Hellenistic medicine should not remain unmentioned: the discovery, by the Alexandrian anatomists Herophilus and Erasistratus (late fourth/early third century BCE), of the nervous system, of the central role of the brain in cognition and locomotion and the observation, by Herophilus, of the various ventricles within the brain.

Of course, the ancient philosophers also thought that we had souls and that memory and thinking were fundamentally a process of the soul. But the soul had to live somewhere in the body, and to interface with the physical body, and early observations suggested it lived in the brain. This debate carried forward to Medieval times. In the time of the great physician, Galen, the primary debate was whether or not the memories of the soul lived in the heart (cardiocentric view) or the brain (encephalocentric view). Galen himself took the encephalocentric view, that memories and reason are in the brain, but felt that other functions, such as emotion, were in the heart. This is a belief that still resonates with our culture today (amazing how persistent ideas can be).

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Oct 01 2019

Virtual Reality Therapy for PTSD

Published by under Neuroscience

Post-Traumatic Stress Disorder (PTSD) results from exposure to traumatic events. Soldiers in war, for example, are at high risk of PTSD because of repeated exposure over time. But even a single event, like experiencing the attacks on 9/11, can cause PTSD. The prevalence in the US is about 8.7%. Symptoms include:

“the development of characteristic symptoms, such as distressing memories or dreams about the traumatic event, flashbacks, psychological distress produced by internal or external cues that symbolize the traumatic event, physiological reactions, avoidance of associated stimuli, and negative alterations in cognitions and mood.”

The only real proven therapy for PTSD is exposure therapy. This has many variations, but at its core it involves exposure to stimuli that triggers PTSD symptoms or simulations of the initial trauma, while undergoing some type of cognitive therapy. The mechanism of exposure and the exact nature of the cognitive therapy vary, but the basic formula is the same. There are many treatments (such as eye movement or tapping therapy) that include additional features to the therapy, but the evidence shows that these extra features are superfluous and add nothing to the efficacy of the intervention. Every intervention that works seems to include some form of exposure therapy.

Much of the clinical research therefore focuses on optimizing this therapy. There are many variables, and it can be tricky to control for them well with such an intervention, but the research grinds forward. The working theory is that the traumatic event has become associated with the trauma itself, and so people avoid similar stimuli (locations, crowds, anything that might remind them of the traumatic event). But this avoidance locks in the negative association. Exposure therapy re-exposes patients to the conditions of the trauma, but in a safe space and without the associated trauma. This way the brain habituates to the stimuli and essentially forgets the association with trauma.

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Sep 27 2019

How Mandela Effected Are You?

Published by under Neuroscience

The Mandela Effect remains a fascinating phenomenon, although not for the reason that some people believe. I discussed the basic effect before – people often remember historical events as being different than current evidence reveals, and sometimes many people misremember the events in a similar way. This has led some to argue that it is not our memories that are flawed, but the universe has actually shifted reality of time.

I recently came across a site that tests how “Mandela Effected” you are with a list of ten questions. First, should it be “Mandela Affected?” Affect is the verb, effect is the noun. But it’s how affected are you by the Mandela Effect. We’ll call it poetic license.

Some of the questions on the test are interesting examples of the Mandela Effect. However, the test itself is needlessly horrible, rendering the results meaningless. First, they show pictures relating to the question. While they warn you that the picture may not be accurate, it’s obvious that they will have a biasing effect on the results. Second, the questions are a forced binary choice. There’s no, “I don’t know” option. A 5 point Likert scale would be better – definitely A, probably A, not sure, probably B, definitely B. I know this isn’t meant to be a scientific test, it’s just for fun, but why make it so blatantly terrible? It’s bad enough to spoil the fun.

But in any case – the reason I like discussing the Mandela Effect is because of what it really reflects. It is not a glitch in the Matrix, nor a shifting of alternate universes. It is a combination of factors, mostly the fallibility of memory and the complexity of cultural influences and evolution. When there is a mismatch between our memory or perception and reality, however, we tend to first assume there is a problem with reality, rather than a problem with our brains. This is especially true in pathological conditions, when the brain is broken. We have a hard time perceiving the deficit, and rather assume the world is broken.

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Sep 10 2019

How the Brain Filters Sound

Published by under Neuroscience

Our brains are constantly assailed by sensory stimuli. Sound, in particular, may bombard us from every direction, depending on the environment. That is a lot of information for brains to process, and so mammalian brains evolved mechanisms to filter out stimuli that is less likely to be useful. As our understanding of these mechanisms has become more sophisticated it has become clear that the brain is operating at multiple levels simultaneously.

A recent study both highlights these insights and gives a surprising result about one mechanism for auditory processing. Neuroscientists have long known about auditory sensory gating (ASG) – if the brain is exposed to identical sounds close together, subsequent sounds are significantly reduced. This fits with the general observation that the brain responds more to new stimuli and changes in stimuli, and quickly become tolerant to repeated stimuli. This is just one way to filter out background noise and pay attention to the bits that are most likely to be important.

Further, for ASG specifically, it has been observed that schizophrenics lack this filter. You can even diagnoses schizophrenia partly by doing what is called a P50 test – you give two identical auditory stimuli 500ms apart, and then measure the response in the auditory part of the brain. In typical people (and mice and other mammals) there is a significant (60% or more) reduction in the response to the second sound. In some patients with schizophrenia, this reduction does not occur.

In fact researchers have identified a genetic mutation, the 22q11 deletion syndrome, that can be associated with a higher risk of schizophrenia and a failure of ASG. Reduced ASG may be the cause of some symptoms in these patients with schizophrenia, but is also clearly not the whole picture. It’s common for a single mutation is a gene that contributes to brain development or function to result in a host of changes to ultimate brain function.

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Sep 09 2019

Born That Way

Published by under Neuroscience

If someone is a bad person based on their behavior, are they more likely to have been born that way, or the result of environmental factors? Does it matter to how you would treat them, or how they should ethically be treated? If someone is a very good person, is their behavior the result of nature vs nurture? The actual answer to this age-old nature vs nurture debate is – it’s complicated. Both factors play a role in a complex interaction that differs for different people. It’s likely that true psychopaths were born that way, lacking an empathy circuit that most typical people possess in their brains. But of course there are also cultural norms that have a profound effect on our behavior.

Psychologists have been asking a slightly different question – not what the answer objectively is, but what do people assume that it is, and how does that affect their behavior toward other people. The assumption or belief that behavior is due primarily to instrinsic factors is called essentialism. A recent study looked at both children and adults and how they thought about characters with both morally good and morally bad behavior. Prior research suggests that in general we tend to attribute other people’s behavior to essential factors. People don’t just do good vs bad things, they are good vs bad.

This is part of what psychologists call the fundamental attribution error. We tend to attribute our own behavior to external factors and other people’s behavior to internal factors. I am the victim of circumstances beyond my control, but that other person (perhaps acting in an identical way) is just a bad person.

The new study adds some further nuance to this effect. They found that study participants (both children and adults) were more likely to attribute good moral behavior to essentialist causes than bad moral behavior. So if someone does good things, it’s because they are a good person. If they do bad things, it’s because of their bad environment. This is an interesting result, and suggest several questions to me. First, how universal is this? Is that result itself a product of learned behavior, a product of our time and culture? Would the result have been different in the 1950s in the US, and would it be different in other countries? I would also be interested in seeing how the results differ based on ideology.

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Sep 06 2019

Information Gerrymandering

Democracy, in a very real sense, is math. The point is to aggregate decision-making in order to arrive at the fairest outcome for the greatest number of people. Andrea Jones-Rooy, who spoke at NECSS this year, gave a great lecture about this. Here is an article she wrote about Arrow’s Theorem that goes over the basic concept, but she went into more detail during the talk. Essentially there is no system of voting that has perfect fairness (ranked choice vs least objectionable option, for example), so we just have to pick one and live with the trade-offs.

Jones-Rooy, however, was talking about different systems that work as intended, no cheating. If, however, one group puts their thumb on the scale, the democratic process can be massively distorted. Beyond a certain point you no longer even have a true democracy. Voting becomes a sham used to give a patina of legitimacy to a dictator or minority rule.

Perhaps the best known form of voting distortion in the US is gerrymandering. The best description I have heard of this is that it is a way for politicians to choose their voters, rather than voters to choose their politicians. The idea is to carve up voting districts deliberately to favor one party, so that even if they have 40% of the voters in one state, they can secure 60% or more of the representatives. (This doesn’t work for senators or presidents where voting is state-wide.)

Researchers, however, have published an article in Nature in which they describe a more insidious form of distortion – information gerrymandering. This amounts to a rigorous mathematical description of a phenomenon we have been discussing, the effect of social media networks on public opinion. They found:

Players are assigned to competing groups (parties) and placed on an ‘influence network’ that determines whose voting intentions each player can observe. Players are incentivized to vote according to partisan interest, but also to coordinate their vote with the entire group. Our mathematical analysis uncovers a phenomenon that we call information gerrymandering: the structure of the influence network can sway the vote outcome towards one party, even when both parties have equal sizes and each player has the same influence.

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Aug 26 2019

False Memories and Fake News

Here’s yet another reminder that our memories are reconstructed fabrications our brains use to reinforce existing narratives. A new study of 3,140 participants finds that exposing people to fake news created false memories of the depicted events in about half of subjects.

What the researchers did specifically was show people in Ireland prior to the 2018 referendum on abortion, six news stories, two of which were fake. One of the fake stories was about campaign posters being destroyed after it was discovered that they were illegally funded by an American. Later, about half of the subjects reported false memories regarding at least one of the two fake stories. About one third of the subjects included details in their fake memories that were not included in the original stories.

Further, subjects were more likely to form false memories if the fake news dealt with a scandal for the other side (so “yes” voters were more likely to form false memories regarding a scandal involving the “no” vote). And perhaps most concerning, when the subjects were told which news stories were fake, this only decreased the false memories slightly. It did not correct the effect.

None of this is entirely new, but it is the first study like it involving a real-time political event. This research reinforces what psychologists have been demonstrating for years – that memories are constructed, and then reconstructed in remembering, that memories are partly thematic and the details will morph to fit the theme, and that fake memories are relatively easy to create. Once formed a fake memory feels just like a real memory. They are just as vivid and compelling as a genuine or more accurate memory. Vividness does not predict accuracy, despite the fact that this is what most people assume.

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Aug 22 2019

AI and Scaffolding Networks

A recent commentary in Nature Communications echoes, I think, a key understanding of animal intelligence, and therefore provides an important lesson for artificial intelligence (AI). The author, Anthony Zador, extends what has been an important paradigm shift in our approach to AI.

Early concepts of AI, as reflected in science fiction at least (which I know does not necessarily track with actual developments in the industry) was that the ultimate goal was to develop a general AI that could master tasks from the top down through abstract understanding – like humans. Actual developers of AI, however, quickly learned that this might not be the best approach, and in any case is decades away at least. I remember reading in the 1980s about approaching AI more from the ground up.

The first analogy I recall is that of walking – how do we program a robot to walk? We don’t need a human cortex to do this. Insects can walk. Also, much of the processing required to walk is in the deeper more primitive parts of our brain, not the more complex cortex. So maybe we should create the technology for a robot to walk by starting with the most basic algorithms similar to those used by the simplest creatures, and then build up from there.

My memory, at least, is that this completely flipped my concept of how we were approaching AI. Don’t build a robot with general intelligence who can do anything and then teach it to walk. You don’t even build algorithms that can walk. You break walking down into its component parts, and then build algorithms that can master and combine each of those parts. This was reinforced by my later study of neuroscience. Yeah – that is exactly how our brains work. We have modules and networks that do very specific things, and they combine together to produce more and more sophisticated behavior.

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Aug 19 2019

Facts vs Stories

There is a common style of journalism, that you are almost certainly very familiar with, in which the report starts with a personal story, then delves into the facts at hand often with reference to the framing story and others like it, and returns at the end to the original personal connection. This format is so common it’s a cliche, and often the desire to connect the actual new information to an emotional story takes over the reporting and undermines the facts.

This format reflects a more general phenomenon – that people are generally more interested in and influenced by a good narrative than by dry facts. Or are we? New research suggests that while the answer is still generally yes, there is some more nuance here (isn’t there always?). The researchers did three studies in which they compared the effects of strong vs weak facts presented either alone or embedded in a story. In the first two studies the information was about a fictitious new phone. The weak fact was that the phone could withstand a fall of 3 feet. The strong fact was that the phone could withstand a fall of 30 feet. What they found in both studies is that the weak fact was more persuasive when presented embedded in a story than along, while the strong fact was less persuasive.

They then did a third study about a fictitious flu medicine, and asked subjects if they would give their e-mail address for further information. People are generally reluctant to give away their e-mail address unless it’s worth it, so this was a good test of how persuasive the information was. When a strong fact about the medicine was given alone, 34% of the participants were willing to provide their e-mail. When embedded in a story, only 18% provided their e-mail.

So, what is responsible for this reversal of the normal effect that stories are generally more persuasive than dry facts? The authors suggest that stories may impair our ability to evaluate factual information. This is not unreasonable, and is suggested by other research as well. To a much greater extent than you might think, cognition is a zero-sum game. When you allocate resources to one task, those resources are taken away from other mental tasks (this basic process is called “interference” by psychologists). Further, adding complexity to brain processing, even if this leads to more sophisticated analysis of information, tends to slow down the whole process. And also, parts of the brain can directly suppress the functioning of other parts of the brain. This inhibitory function is actually a critical part of how the brain works together.

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Aug 13 2019

Weber’s Law

Published by under Neuroscience

I confess I have never heard (or at least don’t remember ever hearing) about Weber’s Law (pronouned vayber) until reading about it with this news item. It is the Law of Just Noticeable Differences. It deals with the minimum difference in a stimulus necessary to notice. While clearly established, and there are many hypotheses to explain the phenomenon, there has never been a way to test which hypothesis is correct. The news items relates to new evidence which may provide a mechanism.

Weber’s law applies to all sensory modalities – sight, sound, taste, smell, and tactile sense. For any sensory stimulus there is a minimum difference that a person can notice. For example, if you are visually comparing the length of two lines trying to determine which one is longer, or if you are holding two weights and trying to determine which one is heavier. There is a minimum difference that is necessary to be able to notice. Experimentally this means there is a relationship between the ratio of the difference and the probability of determining the correct answer.

So if you are trying to determine which light is brighter, an experiment may determine that for lights of 100 and 110 lumens there is a 75% chance of correctly detecting which light is brighter. What Weber’s law states is that one this relationship is determined, it holds true no matter what the absolute value of the stimulus is, as long as the ratio is the same. So for lumens of 200 and 220, or 1000 and 1100, there would still be a 75% probability of being correct. The only thing that matters is the ratio.

As you might expect, there is a lot of nuance to the law, such as subtle variations in the math and differences between vertebrates and insects, etc., which I won’t get into. They are not important for the current discussion, but know that they exist.

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