Archive for the 'Neuroscience' Category

Jun 01 2018

Another Advancement in Prosthetic Limbs

I have been following the development of brain-machine interfaces and their application to artificial (prosthetic) limbs. A recent paper documents another incremental but significant advance – combining a new surgical technique for amputation with a prosthetic designed to take advantage of it.

The goal is to close the loop between voluntary muscle control and sensory feedback, which is critical to that control. The way our brains normally work is to constantly monitor various sensory streams in order to create the subconscious and conscious sensation that we occupy, own, and control the various parts of our body.

We may take these phenomena for granted, but they are an active construction of the brain that are critical to proper function. Without the sensation that we occupy our body, we would have “out-of-body” sensations, like we were floating in space, and this would make it difficult to interface with the physical world.

Without the sense of ownership, we don’t feel like a limb is part of us, and it is therefore not incorporated into our internal model of our own body. This is the current state-of-the art for normal prosthetics – they feel like they are attached to the user, but not part of them. It therefore takes more conscious effort to use them, and control is not as good as a normal limb.

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May 25 2018

ADHD Is Not a Fake Illness

Published by under Neuroscience

The headline on this dubious health website reads: “ADHD is a FAKE Disease Invented by Big Pharma to Drug Children for Profit.” Every bit of that headline is made up, ironically – it’s fake. I have written about ADHD previously, and also about mental illness denial itself. This is a common theme among proponents of alternative medicine or snake oil treatments, because it is a rhetorically convenient way to attack mainstream medicine and bolster medical conspiracy theories.

Let me dispense with the easy parts first – the diagnosis of attention deficit hyperactivity disorder (ADHD) was not “invented by Big Pharma.” Unsurprisingly, the article provides exactly zero evidence to support this conspiracy claim. Right there the author of this article, and the hosting site, have lost all credibility. This is a specific and dramatic factual claim. Any responsible journalist, or author on a site that takes it upon itself to dispense medical advice, would have invested the five minutes it would take to discover that it is not true.

It literally took me 30 seconds to find this reference, a published article detailing the history of the ADHD diagnosis (so someone less Google savvy might take 5-10 minutes, but I just searched on “history of ADHD diagnosis”). The medical profession does have a tendency to write things down and publish their observations and musings about medicine. This leaves a nice paper trail for any medical historian to follow. The first descriptions of something similar to ADHD go back to the 18th century. Sir Alexander Crichton published an entire book “On Attention and its Diseases” in 1798.

It is also interesting to note that, right from the beginning, it was recognized that disorders of attention are multifactorial:

“A distraction of attention does not necessarily have to be pathological, e.g. mental stimuli, volition, or education can have a great impact on healthy attention.”

What a concept – a behavior as complex as attention is the result of a combination of inherent ability and environment. In the subsequent 200 plus years our concept and knowledge of ADHD evolved, documented in the DSM, the standard manual of mental disorders. There is also a vast published literature on ADHD. Searching PubMed on ADHD results in over 2000 references. The second of which is a helpful review of the genetics of ADHD, in which they estimate that the heritability of ADHD is 30-40%. Roughly that means that the disorder is 30-40% genetic and 60-70% developmental or environmental.

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May 07 2018

The Waking Dead

Amid a continuous stream of terrible science news reporting, this one stands out from MSN: ‘Miracle’ Boy Wakes After Parents Sign Organ Donation Papers and Days of Being Brain-Dead. Actually the story is based on a local Fox news report. Everyone involved in these stories should be placed in the journalists penalty box.

This is a standard fluff narrative that comes up regularly – the person who wakes unexpectedly from a coma, or better yet, after being declared brain dead. There is a common pattern to the stories – you never get enough details to know what actually happened, but what details you do get do not hang together.

The basic facts of the case are this, 13-year-old Trenton McKinley of Mobile Alabama was injured in a dune buggy accident. He suffered severe head injury. Apparently his prognosis was so poor at one point that the doctors talked with his parents about organ donation, and they agreed that if his heart stopped they would go through the organ donation procedure. In other words, they would harvest his organs.

However, before that happened Trenton began to show signs of improvement. He started to move, and then to become conscious. He is now in rehab, able to talk, and to walk with assistance.

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May 04 2018

Be Wary of Dubious Brain Cancer Study

We have yet another example of a scientifically complex study being mangled by the mainstream media, who simply do not have the chops to provide an adequate analysis. The Telegraph reports:

Fresh fears have been raised over the role of mobile phones in brain cancer after new evidence revealed rates of a malignant type of tumour have doubled in the last two decades.

They further report about the study:

They analysed 79,241 malignant brain tumours over 21 years, finding that cases of GBM in England have increased from around 1,250 a year in 1995 to just under 3,000.

This sounds alarming. The mainstream reporting was not horrible (unlike some of the fearmongering by advocacy groups) but was completely inadequate to really put this study into context. The Science Media Center put together analysis from various experts, and the entire page is worth a read. It is a good demonstration of how to really analyze a scientific paper.

The Telegraph article does point out that this new study is looking at brain cancer incidence only, and did not present any data that correlates the risk of brain cancer with any specific risk factor. The paper only speculates about possible causes, including the rise in cell phone use. But that is just scratching the surface.

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Apr 30 2018

Keeping Brains Alive Outside the Body

Published by under Neuroscience

Researchers at Yale report (at a meeting – not yet published) that they were able to keep pig brains alive for up to 36 hours after the pigs were decapitated. They acquired the pig head from a slaughterhouse, and experimented on them about 4 hours after death. This research is a long way from an alive “brain in a jar” but it does raise some early ethical questions.

First the technical stuff, with the caveat that the study is not yet published in the peer-reviewed literature so some details are sparse. We know the researchers experimented on pig heads. The report does not say explicitly whether the brains were completely removed from the skulls or not, but they did have access to the brain itself so it was at least exposed if not removed. They attached a series of pumps to the blood vessels and pumped oxygenated blood through them. They also used drugs to prevent the brains from swelling, and the researchers say these drugs would also prevent some brain cell activity (they are channel blockers).

They used brain-surface EEG to record electrical brain activity and – there was none. The pig brains were flat-line. But when they later dissected the brain tissue there was cellular activity for up to 36 hours.

This is clearly a baby step in the direction of maintaining a living brain outside of a body. Four hours after death is a long time, and there would certainly already be a lot of cellular death by that point. If the goal (and this wasn’t their goal) is to maintain a fully functional extracorporeal brain, then it would need to be hooked up to external blood flow within minutes of death, not hours. You can’t just get pig heads from the slaughterhouse.

But there is no theoretical reason why this would not work. If the brains were kept oxygenated throughout the process, and they were hooked up to an external system that fed oxygenated blood with managed CO2 levels and a supply of glucose (basically normal arterial blood), there is no reason why the cells could not survive for a long time. There are likely to be many technical hurdles here, but as a thought experiment it seems plausible.

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Apr 23 2018

What Were You Expecting?

Published by under Neuroscience

The art of magical illusion is partly exploiting people’s expectations. Our brains encode a model of how we expect the world to work. When we let go of something, it should fall to the ground. If it doesn’t, we are surprised. This also means that our behavior is predictable – we will tend to look for the object to fall to the ground, meaning the magician will know where we are going to look and can take advantage of that to do things out of our sight.

In our effort to better understand how the brain works, neuroscientists are looking at how the brain reacts to unexpected stimuli. This type of research can have a dual function – looking at the anatomical correlates of a mental phenomenon, and also validating the mental phenomenon itself (because it has an anatomical correlate). This also makes the research tricky, because the questions we ask (how we conceptualize mental phenomena) will dramatically affect the outcome.

For this reason no one study is ever going to tell a complete story. It can, at best, be one piece to a very large and complex puzzle.

The recent study, however, is looking at a fairly straightforward phenomenon – what happens in the brain when it is confronted with unexpected events? The researchers exposed subjects to visual and olfactory stimuli, pictures paired with specific odors. The odors were of food, and either sweet or savory. After being exposed to the pairs sufficiently to form a memory of the correlations, the researchers then showed the subjects a picture with the “wrong” odor. They did this while looking at their brain activity with fMRI scans. (Functional MRI scans look at blood flow in the brain, which is a good way to infer brain activity.)

What they found is that the midbrain became more active when the subject was confronted with a surprising stimuli. The midbrain is part of the brain stem, which is a very primitive part of the brain, shared with all vertebrates. For this reason it is sometimes referred to as our “lizard brain.” The brain stem is a relay center, and controls many basic functions, like breathing. The midbrain in particular is involved in relaying sensory information.

What neuroscientists have found over the years is that even the most primitive parts of the brain are highly involved in processing sensory information. Much of the basic processing of vision and sound occurs before the signals even get to the cortex. The midbrain specifically appears to be involved in filtering sensory input, and determining what we should pay attention to.

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Mar 30 2018

Social Jet Lag

Published by under Neuroscience

Sleep is critical for optimum health and performance, but is often underappreciated by the general public. For example, I see many patients with chronic symptoms that are either caused by or greatly exacerbated by poor sleep, but didn’t make the connection to their chronic insomnia.

Not only is adequate quality sleep necessary, people have different daily (“circadian”) rhythms – some people are most alert in the morning, others mid-day, and still others in the evening. Further, this does not seem to be due entirely to habits, and therefore we cannot just tell night owls to go to bed earlier. They are not in control of their biological rhythm.

The sleep rhythm is affected by light levels and seasonal differences, so there is some room for tweaking the environment to improve sleep overall and adjust the daily cycle. Bright lights and close-up electronic devices are terrible for sleep in the late evening. If someone is having trouble getting to sleep, having 2 hours or so without electronic devices prior to bed time is a good idea.  But there are limits here as well – night owls will still be night owls.

A recent study looks at the effect of circadian rhythm on school performance. The hypothesis was that a mismatch between a student’s internal schedule and their forced school schedule would affect performance.

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Mar 27 2018

Wearable Magnetoencephalography

There are scientific advances, and then there are advances that help us make more scientific advances. The latter are often trickier to communicate to the public, because their connection to any tangible benefit is indirect. But improvements in research technology itself can have incredible potential to transform our future.

One category of scientific instruments that I am particularly interested in, as a neuroscientist, are ways to scan the brain, both anatomically and functionally. A functional scan is one that looks at how the brain is functioning in real time, it looks at the pattern of activity of brain cells. If we can correlate this brain activity with specific tasks, then that will teach us something about how the brain works.

Using this type of technology scientists are trying to reverse-engineer the brain, to map all of its connections (the connectome) and learn what the brain’s networks actually do. The ultimate goal is to be able to simulate those networks in a computer, or to build a computer that works like the brain. That would be the ultimate brain research tool – then you could run countless simulations and tests and see how the various networks in the brain behave.

As an aside, it’s likely that even a simulated brain, if it were functioning, would be self-aware. That raises a lot of ethical question in terms of further research.

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Mar 12 2018

The Brain and Predictive Coding

Published by under Neuroscience

One way to learn about how a system functions is to examine how it fails. Historically much of our knowledge of the most complex system we know, the nervous system, derived from examining patients with neurological deficits and then examining their brain (prior to imaging, this meant at autopsy).

This process is particularly fascinating with the human brain because we don’t yet know all of the things that the brain does. Some brain functions are obvious, like vision or motor control, because they are conscious. But most of what the brain does is subconscious, and we have had to specifically learn that the brain even needs to do certain things, mostly by examining what happens when the brain fails to do those things.

For example, we take for granted that we move as much as we desire to more, no more or less. But this balance between desire to move and the resulting movement is not automatic. There is an entire system within the brain, the extrapyramidal system, that is a series of feedback loops that carefully modulate moment to moment the gain of voluntary movement (the relationship between input – desire to move, and output – movement). Parkinson’s disease results from a disruption in this circuit which causes the gain to be turned down, so people move less and can even freeze. Chorea (as in Huntington’s chorea) involves the gain being turned up, so people with this disease are constantly writhing.

There are many other amazing examples of things most people are not aware that their brains do, or even that they have to do them. There are circuits in the brain necessary for feeling that you occupy your body, that you own and control your various body parts, and that you are separate from the universe. Disrupt these circuits, and your reality changes.

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Mar 02 2018

Déjà vu and Familiarity

Published by under Neuroscience

Most people have had the common experience of feeling as if we have been someplace before, or that events that are occurring in real time have happened before. Sometimes we feel as if we know what is going to happen next – and then it happens. Unsurprisingly some have interpreted these phenomena as evidence for some type of extrasensory perception. Something weird certainly seems to be going on.

Neuroscientists have been extremely successful in at least partially explaining many such weird experiences. What is uncanny is that our experience of reality is a constructed illusion, and occasionally we experience the glitches in this construction. The most obvious examples of this are optical illusions. We marvel at how our visual construction can be deceived, or can flip between different states.

But everything, not just vision, is a similarly artificial neurological construction subject to illusory effects. That includes memory.

That déjà vu is a memory glitch is old news. But neuroscientists have been teasing apart the phenomenon in more detail, revealing some aspects of how our memories work. A recent study adds another bit of information to our understanding, which we can use as a jumping off point to review what we know.

Anne Cleary, a cognitive psychologist at Colorado State University, has been researching déjà vu and related phenomena. She believes that déjà vu is a manifestation of a memory phenomenon known as familiarity.

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