Archive for the 'Neuroscience' Category

Mar 31 2020

Decoding Speech from Brainwaves

Here is yet another incremental advance in brain-machine interface (BMI) technology – decoding what someone is saying from their brainwaves using a neural network and machine learning. We are still a distance away from using a system like this to allow someone who cannot speak to communicate, but the study nicely illustrates where the technology is. Here is the BBC’s reporting:

Scientists have taken a step forward in their ability to decode what a person is saying just by looking at their brainwaves when they speak.

They trained algorithms to transfer the brain patterns into sentences in real-time and with word error rates as low as 3%.

Previously, these so-called “brain-machine interfaces” have had limited success in decoding neural activity.

Now here are all the caveats from the paper. First, the technology used electrocorticography (ECoG), which is an EEG with brain surface electrodes. So this requires an invasive procedure, and persistent electrodes inside the skull and on top of brain tissue. Also, in order to get the best performance, they used a lot of electrodes – resulting in 256 channels (a channel is a comparison in the electrical activity between two electrodes). They simulated what would happen with fewer electrodes by eliminating many of the channels in the data, down to 64, and found that the error rates were about four times greater. The authors argue this is “still within the usable range” but they consider usable range up to a 20-25% error rate. What this shows is that – yes, more electrodes matter. You need the very fine discrimination of brain activity in order to get good (usable) results.

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Mar 24 2020

Body Ownership Illusion

Published by under Neuroscience

A new study offers a small advance in our understanding of the body ownership illusion, but it is a good opportunity to review this cool and important neurological phenomenon. It also has practical implications. The body ownership illusion is the subjective sense that you occupy or own your body and its parts. There is also a separate phenomenon that gives you the subjective sense that you control your body parts.

What I find extremely interesting about these phenomena is that we initially didn’t know they needed to exist. People don’t generally wonder what creates the sense that they own and control their own bodies. It’s not even a question people think to ask (unless they are somehow involved in neuroscience). At first it may seem obvious – we are our bodies, and we do control our bodies, so why shouldn’t we have that sense? But like everything you experience and feel, this is not a passive or automatic sensation. It is an active construction of your brain. There are dedicated circuits in the brain whose specific function is to create these sensations.

As with most neurological phenomena we first suspected their existence by encountering patients who have suffered brain damage (like from a stroke) and therefore have a lack of some subset of these functions. For example, there is alien-hand syndrome. This is the sense that a body part is acting “on it’s own” without your conscious control. There are also cases that demonstrate the separation of body parts from the sense that we own those body parts. Phantom limbs, for example, occur when a limb is removed but the brain circuitry that creates the sense of ownership of the limb is still there. There can even be supernumerary phantom limbs – an illusion of an extra limb that was never there. This can happen when a stroke paralyzes a limb but spares the circuitry that creates the sense of ownership. There are also cases of the apparent opposite – when a limb is present and functioning, but the person has the uncomfortable sense that it does not belong to them. We also have evidence from certain drug-induced and other states of feeling entirely separated from our bodies.

We have a partial understanding of how our brains create these sensations. They all involve circuits that compare two or more inputs. When they are synchronous we have the subjective sense of ownership or control. For the sense of control the circuits compare our intention to move and our actual movements. When they match, we feel we have control. For ownership the primary circuit involves “visual-motor synchronization” or visual-sensory synchronization. If what we see of ourselves matches what we feel, that synchronization produces the sense of ownership. Obviously, we don’t immediately have an out-of-body experience when we close our eyes. There are other sensory inputs that act redundantly – proprioception, vestibular function, tactile sensation, and muscle feedback. It’s a robust system, which is why the illusion rarely breaks in day-to-day life. You have to disrupt the main parts of the brain producing this sensation with drugs, oxygen deprivation, or something else.

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Mar 09 2020

Using Neural Networks for Image Sensing

A new study published in Nature details the use of a neural network on a 2-dimensional computer chip that by itself can be trained to recognize specific images within nanoseconds. This is more of a proof of concept than something with direct immediate applications, but let’s talk about that concept.

To back all the way out – evolution represents hundreds of millions of years of tinkering with multi-cellular structures, and even longer when talking about biochemistry. This is a natural laboratory that has developed some elegant designs, and at the very least can serve as a useful source of inspiration for modern technology. That is the concept of neural networks, designing computers to work more like a vertebrate brain. Specifically, the “neurons” in a neural network are not just binary, on or off, but rather can fire with various degrees of strength. Further, their firing affects the activity of those neurons they are connected to. Computer hardware with networks designed on these basic principles are called  artificial neural networks (ANN). They hold the promise of not only faster and more powerful computing, but are designed to learn (which is why they are so often associated with artificial intelligence).

Another principle at work here is top-down vs bottom-up processing, another concept that has increasingly been incorporated into AI. If we go all the way back to the early days of AI the basic idea was to create high level computer intelligence that could solve problems with the top down, with deep understanding. That goal, now referred to as general AI, is still a ways off. But meanwhile AI has advanced considerably through more of a bottom-up approach, using algorithms to sift data in increasingly sophisticated and adaptable ways. We now have deep learning AI and other specific processes that can produce impressive results without any general AI “understanding” what it is doing.

One question is – will we be able to build a general AI out of these limited AI components? Is it just a matter of building in enough sophistication and complexity? We won’t know until we do it, but if living organisms are any guide, I think there is reason to be positive. Specifically – that is basically how our brains work.

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Mar 03 2020

The Brains of Newborns

Published by under Neuroscience

Most regular readers of this blog should know by now that the answer to nature vs nurture is – yes. Both are involved in neural development and function, and interact in a complex way. Further, while I still find myself reverting to it on occasion, the metaphors of hardware and software don’t quite work with the brain. Rather, the brain is wetware, which is a dynamic combination of both. A new study, looking at the visual cortex of young newborns, adds more information to this basic understanding.

Generally what people are trying to refer to with the term “hardwired” are patterns in the human brain determined largely by genetics, rather than any environmental input. But the fundamental misunderstanding that comes along as baggage with that metaphor is the notion that genes carry a blueprint of the brain – they don’t. They encode rules for how to develop a brain, and those rules include environmental input. So you cannot disentangle the two. Even newborns developed in an environment – the environment of the womb, with the brain also receiving feedback from the body of the fetus itself.

Newborns do come out of the womb with some behaviors, albeit a limited basic repertoire. They need to sleep, feed, and interact. They have limited movement, hearing, and vision, and a similarly limited range of emotions and mental states. But perhaps their biggest behavioral ability is learning – they are sponges that absorb information from their environment. The question is – how much of their trajectory from this infantile state to an adult state is determined by the pathways that are already laid out in their brains, and how much is determined by their environment? Both clearly have a dramatic effect, and interact with each other.

The purpose of the current study was to investigate what the visual cortex of newborns is like, and how they compare to adults. Vision is a pretty basic function, and we would expect the brain to be primed for it. We also know that deprived of visual stimulation, this part of the brain will fail to develop, or will be coopted for other uses. Using fMRI the researchers found that the basic adult structure of the visual cortex of infants was already present. We knew from prior research that there are two brain regions that talk to each other and are involved in facial recognition. Similarly, there are two brain regions that are wired together and function to visualize places. In infants (average age 27 days), the two face regions were active and synchronized together, while the two place regions were also active and synchronized together. This pattern was identical to that of adult brains – although not as robust.

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Feb 27 2020

Anti-Intellectualism and Rejecting Science

“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that ‘my ignorance is just as good as your knowledge.”
― Issac Asimov

As science-communicators and skeptics we are trying to understand the phenomenon of rejection of evidence, logic, and the consensus of expert scientific opinion. There is, of course, no one explanation – complex psychological phenomena are likely to be multifactorial. Decades ago the blame was placed mostly on scientific illiteracy, a knowledge deficit problem, and the prescription was science education. Many studies over the last 20 years or so have found a host of factors – including moral purity, religious identity, ideology, political identity, intuitive (as opposed to analytical) thinking style, and a tendency toward conspiratorial thinking. And yes, knowledge deficit also plays a role. These many factors contribute to varying degrees on different issues and with different groups. They are also not independent variables, as they interact with each other.  Religious and political identity, for example, may be partially linked, and may contribute to a desire for moral purity.

Also, all this is just one layer, mostly focused on explaining the motivation for rejecting science. The process of rejection involves motivated reasoning, the Dunning-Kruger effect, and a host of self-reinforcing cognitive biases, such as confirmation bias. Shameless plug – for a full discussion of cognitive biases and related topics, see my book.

So let’s add one more concept into the mix: anti-intellectualism – the generalized mistrust of intellectuals and experts. This leads people to a contrarian position. They may consider themselves skeptics, but they do not primarily hold positions on scientific issues because of the evidence, but mainly because it is contrary to the mainstream or consensus opinion. If those elite experts claim it, then it must be wrong, so I will believe the opposite. This is distinct from conspiracy thinking, although there is a relationship. As an aside, what the evidence here shows is that some people believe in most or all conspiracies because they are conspiracy theorists. Others believe only in some conspiracies opportunistically, because it’s necessary to maintain a position they hold for other reasons. There is therefore bound to be a lot of overlap between anti-intellectualism and holding one or more conspiracies, but they are not the same thing.

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Feb 21 2020

Binaural Beats, Mood and Memory

Published by under Neuroscience

Binaural beats are an auditory illusion created by listening to two tones of slightly different frequency. This produces a type of feedback effect in the brain that produces a third illusory sound that has a pulsating quality, hence binaural beats. All perceptual illusions are fascinating, at least to neuroscientists, because they are clues to how the brain processes sensory information. What we ultimately perceive is the result of a complex constructive process (not passive recording) and understanding the process offers insight into the strengths and weaknesses of human perception.

But there is another angle to binaural beats about which I have always been, appropriately, skeptical. There is popular belief that listening to the binaural beat illusion is a method for “hacking” into the brain and affecting mood and cognition, improving memory and alertness. Most “brain hack” claims turn out to be false, or at least massively overstated, so initial skepticism is warranted. Such claims are often based on, “Look, something is happening in the brain, therefore…” types of evidence.  But the brain is a machine, albeit a biological one, and it is not impossible that outside stimulation can make the machine work more or less efficiently. So I filed this away as – a small effect is not impossible, but I would need to see convincing evidence before I believe this “one simple trick” claim.

There is a recent study of the effects of binaural beats which prompted this review, but this is just the latest in a couple of decades of research. Let’s first look at the most recent study – Binaural beats through the auditory pathway: from brainstem to connectivity patterns. The study looked at two things, the effect of binaural beats on the overall pattern of brain activity, and the effect on mood. What they found is discouraging for those who think binaural beats have some special effect on the brain. They found: Continue Reading »

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Feb 11 2020

Hyperexcitability in Migraines

Published by under Neuroscience

Migraines are a complex neurological phenomenon that offer a window into some general principles of brain function. A new study confirms previous findings and adds more details to the observation that the visual cortex in those who suffer from migraines is hyperexcitable – it has increased activity in response to stimuli. But this is also clearly only part of the picture.

Let’s start with some background on what migraines are. They are a clinical syndrome, which means they are defined entirely by how people present, not by any diagnostic tests. There is no imaging study, blood test, biopsy, or anything else helpful or used to make the diagnosis. Here are the specific criteria doctors use to make the diagnosis:

(1) At least five attacks fulfilling criteria (2)–(4)
(2) Headache attacks lasting 4–72 h (untreated or unsuccessfully treated)
(3) Headache has at least two of the following four characteristics:
(a) unilateral location
(b) pulsating quality
(c) moderate or severe pain intensity
(d) aggravation by or causing avoidance of routine physical activity (e.g. walking or climbing stairs)
(4) During headache at least one of the following:
(a) nausea and/or vomiting
(b) photophobia and phonophobia
(5) Not better accounted for by another ICHD-3 diagnosis.

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Feb 07 2020

Neurodiversity and Inner Voice

Published by under Neuroscience

When you think all to yourself (not engaging with others) do you hear an inner voice, do you conjure images, or do you just have abstract feelings? For most people the answer is, yes. Recently a Twitter post has triggered people to consider their inner voice, and whether or not they have one. The post was intriguing to many people mostly because they had not considered that other people may be different in this respect than they are. It was not a variable they thought could differ among people.

The episode brings up a few interesting points, the first of which is the core question – how do people think? If you have never considered the question, consider it now. Do you actually “hear” a virtual voice in your head? Do you think mostly in pictures, or in the abstract? Or is the mode of your thought very context dependent – depending on what you are thinking about or what task you are trying to complete.

For me, I think I do everything. If anything I may be biased toward verbal inner monologue, but that may be an artifact of the fact that I write every day and give lots of lectures. I definitely practice lectures and conversations entirely in my head.  People who know me well even “catch” me doing this, because I may talk with my hands or throw in the occasional gesture or facial expression while doing so. But I can also be very visual when the task calls for it, bringing to mind detailed images, schematics, or spatial relationships. When I think about abstract concepts, I tend to give them some verbal or visual representation. So I would say, rough estimate, I am 60-40 verbal-visual, but again that may be because of my writing and lecturing.

I have known for a long time that other people (at least those close to me) do not do this nearly as much as I do, and I have also learned over the years of my neurological study and science communication that, generally speaking, there is far more neurodiversity than we naively assume. There are those who essentially have no verbal inner monologue. They are far to the visual end of the spectrum.

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Jan 17 2020

Personality Test Pseudoscience – Swedish Edition

Published by under Neuroscience

Our skeptical colleagues over in Sweden have been tackling one of the most popular pseudosciences there (thanks to Swedish Skeptics president Pontus Böckman for the heads up) – their “Fraudster of the year in 2018 was author Thomas Erikson for his book Surrounded by Idiots. The book popularized a dubious personality test known as DiSC, which uses four colors to characterize personality types, red, green blue, and yellow. The book is a best seller in Sweden and is now being exported to many languages. It is also incredibly popular in corporate culture.

Dan Katz, licensed psychologist and psychotherapist, does a great job of breaking down why Erikson’s claims are not based on science. I’m not going to repeat his article, just read the original. The short version is that Erikson has no qualifications, and the DiSC model is not based on any scientific evidence. The entire thing is a giant scam. What I do want to do is extend the discussion about personality tests in general.

The core scientific question behind any personality test is this – is there even such a thing as a personality type? The current best short scientific answer is – mostly no. But let’s get a bit deeper and more nuanced. First we need to distinguish personality traits from personality types. A personality trait is simply a behaviorial tendency that someone has that transcends any particular context and is consistent over long periods of time. Introversion/extroversion is probably the best established personality trait. The big five personality trait spectra that are the best established and are generally accepted by psychologists are OCEAN – openness, conscientiousness, extroversion, agreeableness, and neuroticism.

But we have to acknowledge that these are just cultural and scientific constructs. They are our best attempt at understanding some of the building blocks of personality, but we don’t know if they are bedrock, meaning that they are real neurological phenomena. My sense is that introversion/extroversion probably is a fundamental neurological phenomenon – one reason for this is that there are known genetic disorders that have extremely consistent extroversion personality traits.

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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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