http://www.ghostofcharcot.net Musings on Neurological Education Fri, 04 Aug 2017 22:26:32 +0000 en-US hourly 1 https://wordpress.org/?v=4.8.1 41210217 Neuroimaging http://www.ghostofcharcot.net/neuroimaging/ http://www.ghostofcharcot.net/neuroimaging/#respond Fri, 04 Aug 2017 21:29:39 +0000 http://www.ghostofcharcot.net/?p=1600 Continue reading ]]> undefined

Von Hellerhoff – Eigenes Werk, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20045205

Question: An 8 year-old girl presents with cognitive delay and incoordination. What is the diagnosis? See below for the answer.


It goes without saying that neurologists must learn to interpret radiographic images; residents look at so many CTs and MRIs that it’s almost impossible not to develop some competence in this area. It’s important to develop, like our neuroradiology colleagues, a systematic approach to image interpretation–one can’t just scan the DWI or FLAIR images for areas of bright signal. Moreover, and as the senior residents are well aware, the RITE has a bunch of unusual imaging questions like the one above; indeed the exam includes a whole booklet of questions based on radiographic and pathological images.

Residents might find a recent Continuum issue on neuroimaging to be a helpful resource. It has an introductory chapter on MRI physics, and goes on to cover advances in stroke imaging, imaging patients with epilepsy, brain tumors, spinal cord disorders, etc.

There’s a particularly good chapter on imaging congenital malformations. This high-yield chapter covers a lot of topics pertinent to both pediatric neurologists and adult neurologists taking the RITE and boards (i.e. just about everybody). In addition to being a very good issue in general, that chapter would serve very well for test preparation.

Finally, here’s a link to an interesting podcast episode from The Guardian’s Science Weekly (episode 28). It covers the history of MRI and includes a digestible explanation of MR physics.


Answer: Dandy-Walker malformation. The cerebellum is hypoplastic. The fourth ventricle and posterior fossa are enlarged, and the cerebellar remnant is displaced superiorly.

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Exam Videos http://www.ghostofcharcot.net/exam-videos/ http://www.ghostofcharcot.net/exam-videos/#respond Thu, 03 Aug 2017 20:24:13 +0000 http://www.ghostofcharcot.net/?p=1589 Continue reading ]]> Dr. Hal Blumenfeld’s book, Neuroanatomy through Clinical Cases, is a great introductory text for neurology residents. It’s comprehensive, yet quite readable, with lots of superb drawings and illustrative cases. I think it occupies the space between Berkowitz’s Clinical Neurology and Neuroanatomy, (a new book that I recently reviewed here), and Brazis’s classic, Localization in Clinical Neurology. The former is particularly well-suited for beginners—students, interns, and junior residents who want a concise introduction to their future specialty; we give a copy to our PG1s. The latter is still my go-to for what I call “micro-localization”—when I need to refresh my memory on some precise neuroanatomical detail. It’s best digested in small chunks; we’re using it for book club this year.

Blumenfeld fits nicely between those two. It’s longer and more detailed than Berkowitz, but the layout and case discussions make it easier to digest than Brazis. Our residents are using it for their resident-led lecture series this year.

Recently, I discovered that Dr. Blumenfeld created an online companion to the book in which he demonstrates the neurological exam in a series of short videos. These are available on the web, for free, here. There’s also a longer video that includes an entire exam, but that one is gated; I assume you get access if you buy the book.

These exam videos are a great resource—there’s a big difference between reading about how to do the exam vs. seeing it done by an expert. For example, embedded below is the video on oculocephalic testing, and I added a link to the main webpage with all of the videos on the menu above, under Clinical Neurology Resources → General Neurology.


Two other video resources I’ve mentioned before (and that are also accessible via the menus above) are the Neuro-Ophthalmology Video Education Library (NOVEL) and the International Parkinson and Movement Disorder Society video library. The latter one requires a membership, but this is free for residents; the signup page is here.

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Pointing Towards Virtue http://www.ghostofcharcot.net/pointing-towards-virtue/ http://www.ghostofcharcot.net/pointing-towards-virtue/#respond Wed, 02 Aug 2017 17:59:21 +0000 http://www.ghostofcharcot.net/?p=1578 Continue reading ]]> Image result for finger pointing at the moon koanThe 2017-18 year is underway, and this is usually the time for orientations, “boot camps”, links to useful resources, etc. I have some some of the last queued up for soon-to-follow posts, but first wanted to address a deeper matter.

A few weeks ago, I received a survey about character education in residency. It was comprised of questions like “Where in your residency program do trainees learn virtues such as honesty and integrity?” I found this line of questioning to be exasperating on a few counts. First, residents are adult learners—not schoolchildren. I presume that they will have developed their moral virtues well before entering residency training (at an average age of around 30). When and from whom do they learn moral virtue? Years prior, from their parents, school teachers, coaches, clergy, etc.

Moreover, to whatever extent people are lacking in certain virtues by the time they reach adulthood, they are not going to acquire them in a residency program—that ship has sailed, I thought.

Finally, I resented the implication that moral virtue could be codified as a set of behaviors or “competencies” to be checked off a list as part of yet another training milestone. If anything were to exemplify what I previously termed “competency theater“, this would serve splendidly.

And yet, as we roll into month #2 of this new year, I think that my initial reaction to this moral inquiry may have been too flippant. Consider that the Greek origin of  “character”, kharássō, means to scratch or engrave. It implies a process and not a fixed state—a process that, over time, imparts one with distinctive traits. Are residents not amenable to ongoing engraving of character? Aren’t we all?

Furthermore, it perhaps should not be taken for granted that virtues developed in the context of family life, grade school, etc., will always manifest in the context of residency training. This might be especially true when the virtue hasn’t really been tested before. Some young people might not yet have been in situations where they must choose whether or not to subordinate their own interests to those of another, or whether to be fully honest at the risk of great personal embarrassment or inconvenience. We all presumably learn about the moral virtues during our upbringing, but actually becoming virtuous in daily practice is the real challenge (and one that I don’t claim to have fully achieved).

There’s a Buddhist teaching, depicted above, that applies well to this crucial difference between the abstract knowledge of moral virtues versus their exercise: Imagine that someone is trying to show you the moon by pointing to it. One should not focus too much on the finger! With that caveat, following are some examples of how character is tested in the context of residency training; I hope that residents will find them to be useful pointers.


Humility. Neurology has become a very interdisciplinary field. Forget about the simplistic old saw that “The nurse can be your best friend or your worst enemy.” Today, we work with nurses, pharmacists, physical therapists, occupational therapists, speech/language pathologists, respiratory therapists, dietitians, social workers, case managers, etc., etc. Many of the above have graduate-level education, some doctorate-level. Most have years of experience—certainly more experience in their respective fields than a resident has in neurology. And regardless of age, each person is an expert in his or her area. I’m now PGY18 and have cared for thousands of stroke patients but I’m not as good at assessing the functional status of a stroke patient as my OT colleagues. And I’ll never be as good as they are, just like I’ll never read brain MRIs quite as well as our neuroradiology colleagues.

Therefore, when a nurse, therapist, pharmacist, or other member of the treatment team raises a concern or provides new information, it’s important to listen, consider the information on its merits, and integrate that into the case formulation. We must resist the urge to reject the information because it came from someone other than a physician (arrogance), because it doesn’t comport with our previous understanding of the patient’s condition (anchoring bias), or because acknowledging it would mean that we were wrong about something (denial).

That last point deserves emphasis: It’s OK to be wrong, as long as we remain open to correction! I know that doesn’t comport with our years of high school → college → medical school acculturation, where the point of the game, it often seemed, was to supply correct answers. But now we’re in a very different setting, where there are fewer right / wrong answers to be supplied and more assessments and plans to be made. EVERYBODY makes a sub-optimal judgment from time to time and it’s especially ridiculous to think that a PG2-4 neurology resident should be perfect in this regard. Our main mission is to take the best possible care of our patients. If there’s a piece of information or a perspective that might advance our patient’s care, we want to incorporate that as soon as is appropriate. And besides, resisting an opportunity to optimize a patient’s care or correct a mistake is much, much more injurious to a physician’s reputation than is the fact that he or she was once wrong about something. 

Honesty. Imagine a case1Perhaps this scenario seems too obvious or egregious to be true, but trust me—this kind of thing happens. where a patient presents to the ED one afternoon with a thunderclap headache and left-sided tingling. Exam is normal. CT shows no hemorrhage. CSF is colorless. Because of the focal symptoms and high-risk nature of the case, the patient stays in the ED’s observation area pending an MRI. The plan is to treat the pain, observe for some hours, and, if the clinical course and MRI/A/V are reassuring, discharge home with outpatient follow-up.

The next morning, the patient feels much better but the MRI still hasn’t been done. The ED resident informs you that the patient can only stay in the obs unit for a couple more hours—if more time is needed for the workup to be completed then he’ll need to be admitted. You make some phone calls and arrange for your patient’s MRI to be done next.

The ED resident calls again to report that the MRI is done and time is running out for an obs stay–a decision must be made now. You look at the MRI yourself (kudos!) and it looks OK. The prelim read is normal too. You call up your attending to explain that the patient is teed up for discharge, and he asks, “Do we have a final read on the MRI?”

Aaaargh! A final reading is going to take more time, and then you’ll be stuck admitting the patient only to discharge him a couple of hours later—a hassle for you both. And really, what’s the chance that the final read is going to be substantially different than the prelim? So, “Um, yeah, the MRI was read as normal,” you say. It’s sort of true, although not really. The patient goes home. And then the neuroradiology attending calls your attending a few hours later to report that they found a 2mm acomm aneurysm on the MRA. “Did that patient get discharged? We may need to bring him back . . .”

Always be honest—it’s best for the patient and, although it might not always seem that way in the moment, best for your reputation as well.

Kindness. It can be seemingly difficult to practice kindness while immersed in a challenging training program, or while running a busy clinical practice, or while managing a chaotic (e.g. child-rearing) household, or . . . you get the idea. But here’s a nice paradox: Being kind to your patient or colleague (or a family member, or perhaps especially to a stranger) is a reliable way to reduce both their suffering and yours.

And it can be really easy—I’m not talking about committing to 10 hours a week of volunteer work on top of everything else on your plate. Very simple things can go a long way: You took off the patient’s socks to check for Babinski’s sign? Put them back on. Carefully. Offer to cover her back up. Don’t forget to turn the TV back on if you turned it off. Did the nurse come in and silence the beeping IV while you assessed the patient? Thank him! Right then and there, in front of the patient. When the patient sees that you respect your colleagues, she’ll know that you respect her too. She will feel better about her care, and she will remember! She may not remember half the things you educated her about with respect to her stroke, but she *will* remember that you were kind. And once in a while, a patient will express to you, long after the fact and long after you’ve forgotten about it, her appreciation for that kindness. These are among the moments that sustain a medical career.


Obviously, this is a very limited list of virtues; please feel free to offer additional thoughts in the comments. I’d also be happy for interested residents to author guest posts. If nothing else, I hope this will get us thinking explicitly about the kind of physicians, and indeed the kind of people, we want to be.

Notes / References   [ + ]

1. Perhaps this scenario seems too obvious or egregious to be true, but trust me—this kind of thing happens.
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The Beautiful Brain: The drawings of Santiago Ramón y Cajal http://www.ghostofcharcot.net/the-beautiful-brain-the-drawings-of-santiago-ramon-y-cajal/ http://www.ghostofcharcot.net/the-beautiful-brain-the-drawings-of-santiago-ramon-y-cajal/#comments Fri, 03 Mar 2017 16:27:28 +0000 http://www.ghostofcharcot.net/?p=1568 Continue reading ]]> undefined

Public Domain, https://commons.wikimedia.org/w/index.php?curid=612581

Santiago Ramón y Cajal is one of the founding fathers of neuroscience. He was the foremost proponent of the neuron theory–that the nervous system is composed of interconnected but individual neurons as opposed to a continuous reticulum of nervous tissue. This conclusion stemmed from his use of the Golgi stain, which randomly stains only a fraction of the cells in a tissue sample, allowing for their individuation. He and Golgi shared a Nobel prize for this work.

Ramón y Cajal was a fantastic artist whose drawings elucidated the structure of the nervous system; the picture above shows two Purkinje cells and a few granule cells from a pigeon cerebellum. There’s now a traveling exhibit of his neuroanatomical work, with an accompanying book. It looks to be a terrific exhibition; here’s a New York Times review, which includes several more wonderful drawings. If you happen to live near one of the tour stops it might be well worth a visit.

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A Zebra for Our Times: Transient Smartphone Blindness http://www.ghostofcharcot.net/a-zebra-for-our-times-transient-smartphone-blindness/ Sun, 26 Feb 2017 17:22:19 +0000 http://www.ghostofcharcot.net/?p=1564 Continue reading ]]>

By Japanexperterna.se from Japan – Person looking at smartphone in the dark, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=47395025

Here’s a neurological oddity to be aware of: Transient smartphone blindness. Per a case report in this week’s Green Journal:

When a patient lies on one side, the ipsilateral (lowermost) eye becomes functionally occluded (e.g., by a pillow) and its retina maintains adaptation to the ambient light level or may become relatively dark-adapted. Meanwhile, the contralateral (uppermost) eye becomes light-adapted while it is used to view the device, which illuminates the retina to a greater degree than ambient light (this differentiates the scenario from book reading). After the patient stops using the device and transitions to binocular vision with both retinae exposed to dim ambient light, she perceives normal vision with the dark-adapted eye but temporary blindness in the light-adapted eye.

It’s easy to see how this could be misdiagnosed as a retinal TIA, retinal migraine, functional disorder, or even MS as per the case report.

Update: Here’s an interesting and humorous commentary on the phenomenon, courtesy of Dr. Michel Accad.

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RITE Review http://www.ghostofcharcot.net/rite-review/ Fri, 03 Feb 2017 00:10:38 +0000 http://www.ghostofcharcot.net/?p=1561 In follow-up to the publication of the textbook reviewed below, Dr. Berkowitz created a Facebook page and is posting board-style review questions on it. I think the plan is to post one per day. Have fun!

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Neurology Book Report http://www.ghostofcharcot.net/neurology-book-report/ Mon, 02 Jan 2017 23:12:12 +0000 http://www.ghostofcharcot.net/?p=1539 Continue reading ]]> Image result for clinical neurology localization-based berkowitz“What should I read?”

It’s a common question from students, especially future neurology residents, as well as advanced practice providers and allied health professionals set to care for neurological patients. It’s a hard question to answer because neurologists often rely on a variety of texts for different purposes. Reference texts such as Adams and Victor’s or Bradley and Daroff are too encyclopedic to recommend for straight-through reading unless the intended use is as a sleep aid (the latest edition of Bradley’s weighs in at 2348 pages). Brazis’s Localization in Clinical Neurology is indispensable for refining one’s localization skills, but isn’t suitable for a beginner’s approach to the field. Closer to the mark is Patten’s Neurological Differential Diagnosis. It’s quite readable, full of anecdotes, and suitable for the beginning neurologist. The drawings are marvelous. As big a fan as I am, this text is rather dated, not having been updated since 1996.

Clinical Neurology and Neuroanatomy, by Harvard neurologist Aaron L. Berkowitz, threads the needle perfectly. This isn’t surprising; Dr. Berkowitz’s CV shows over a half dozen teaching awards. He’s authored several other textbooks and  he directs the Global Neurology Program at Brigham and Women’s. I suppose nothing develops one’s neurological skills quite like practicing and teaching neurology in resource-limited areas.

Like many neurology texts, this one is divided in two parts, the first on the approach to patients with the different types of symptoms and the second on the neurological diseases themselves (epileptic, vascular, etc.) The first chapter includes a very important discussion of the neurological method (my own take on that is here), including a helpful and under-appreciated mention of localizing neurological disease to specific structures (e.g. Broca’s area on the left) vs. tissue types (peripheral myelin vs. axons) vs. systems (pyramidal, extra-pyramidal, etc.) I also like how well Dr. Berkowitz marries the neuroanatomical descriptions, say of the visual pathways, to the approach to to the patient with, in this example, visual loss.

I found much else to like in this text:

    • There are great explanations of tricky material such as strabismus, cover testing, and the use of the Maddox rod and optokinetic drum. There’s a good introduction to peripheral neurology and EMG. The chapter on neuromuscular junction disorders has an excellent description of low- and high-frequency repetitive nerve stimulation in myasthenia gravis and Lambert-Eaton myasthenic syndrome.
    • The fact that it was written by a single author is not only impressive, but also lends excellent consistency to the text, with emphasis on clinical pearls and the avoidance of minutiae. For example, the stroke chapter describes the role of the ABCD2 score, contains discussion of the difficult issue of when anticoagulation might occasionally be used in the acute setting, and describes the uncommon but important phenomenon of amyloid spells.
    • It’s very contemporary, including descriptions of relatively new entities such as encephalitis associated with anti-LGI1 antibodies and their association with faciobrachial dystonic seizures and the use of the HINTS exam in differentiating central from peripheral vestibulopathy. I was also pleased to see some references to the role of cognitive bias in diagnosis, such as a warning to avoid premature closure when attributing a patient’s delirium to “toxic-metabolic” causes.
    • The drawings are excellent, and there is much integration of modern neuroimaging into the anatomical and clinical discussions.
    • The tables are very clinically-oriented, rather than just listing long differential diagnoses as some texts do. For example, there’s a very good table comparing and contrasting the various Parkinsonian syndromes and another describing the early, late, and treatment-related complications of HIV.
    • There is judicious use of mnemonics. I’ve seen these get out of hand in some texts, especially board review books, but here they are relatively few but easy to remember. Example: The vein of Trolard is on top; Labbé is lower and more lateral.

I’m hard-pressed to identify a weakness here. Probably the most difficult chapter for the beginner will be the one on the upper extremity roots, plexus, and nerves; I think that’s just the nature of the beast. As I’ve mentioned before, there’s a great course on the brachial plexus available on the AAN website (registration required). There’s a very brief introduction to EMG and nerve conduction studies; it would be nice to see a similarly brief introduction to the technical aspects of EEG.

Simply put, this is a great introduction to clinical neuroanatomy and neurology and I recommend it highly.

Disclosure: The editors at McGraw Hill provided me a copy of the text for the purpose of this review, but I received no compensation for it and retain full editorial control.

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On the Interpretation of Neuroscientific Findings http://www.ghostofcharcot.net/on-the-interpretation-of-neuroscientific-findings/ http://www.ghostofcharcot.net/on-the-interpretation-of-neuroscientific-findings/#comments Sun, 18 Dec 2016 06:41:07 +0000 http://www.ghostofcharcot.net/?p=1508 Continue reading ]]>

By now, many readers will know that I’m a devotee of Peter Hacker’s Wittgenstein-infused critique of neuroscientific research. I recently came across a podcast of a lecture that he gave on the topic and the corresponding YouTube video above. Here’s the iTunes podcast link (it’s episode #92). So, if you’re interested to learn more about this but don’t want to commit to reading the whole tome, the lecture will get you the gist of it in just under an hour.

Here, I’ll take a stab at applying this kind of analysis to newly-published work regarding the integration of brain activities while driving and listening to different kinds of audio. But first it’s necessary to review some foundational research on “split brain” patients. Once upon a time, severe generalized epilepsies were treated with commissurotomy (corpus callosotomy), the idea being that if the epileptic discharges could at least be confined to one brain hemisphere, this would be less disabling (and life-threatening) than if the patients kept having generalized seizures. Starting in the 1960s, Profs. Roger Sperry and Michael Gazzaniga published some extremely interesting studies on these patients. Here’s a diagram of one of their experimental setups:

Image result for split brain shovel claw

The subject fixes his vision on the center of the screen, while two different images are projected such that each is visible only in the left or the right visual field. He is asked to point with his right hand to the picture that corresponds to what he sees on the screen; he chooses the chicken. When asked why he so chose, he responds that the chicken claw goes with the chicken. When asked to point with his left hand to the picture that corresponds to what he sees, he chooses the shovel. And here’s the fascinating part: When asked why he chose the shovel, he doesn’t say anything about the snow but rather that the shovel is needed to clean out the chicken shed!

How should we interpret this? The researchers’ explanation is that the left hemisphere “sees” the chicken claw, and since language functions are lateralized to the left hemisphere, this hemisphere can state what it saw. The right hemisphere, however, “sees” the snow scene but can’t speak and is disconnected from the language-endowed left hemisphere. Therefore, the left hemisphere, which is unaware of what the right hemisphere “saw”, confabulates an explanation based on what it “saw”.

Prof. Hacker argues that this is a nonsensical explanation. Neither brains nor their individual hemispheres can see, think, be aware of anything, transfer information, or talk–people do those things. Certainly, people must have properly functioning brains in order to exercise their perceptual, attentional, cognitive, and linguistic abilities, but it doesn’t make sense to attribute to some portion of a person’s anatomy what is conceptually only properly attributable to the person. The conceptual nature of the argument is critical: It is not the case that these “split brain” experiments have been contravened by new empirical research or invalidated by the discovery of a design flaw. Rather, this perfectly valid empirical research has been interpreted in a way that transgresses the bounds of sense. Questions of sense and nonsense precede questions of truth and falsity.

How should the remarkable behavior of these subjects be explained? Prof. Hacker describes it as a dissociation of normally coordinated capacities. Normally, our visuoperceptual and language capacities are fully coordinated. In post-commissurotomy subjects however, these capacities are partially dissociated and result in confabulation under this experimental condition. The point may become clearer if one considers it from a linguistic perspective: Does the subject see the snow scene or does he not see it? As ascertained by the subject’s motor response, he saw it; as ascertained by his verbal response, he did not. The very meaning of the concept “to see” has been strained by the dissociation of neurological functions resulting from commissurotomy.

As fascinating as these particular experiments are, such dissociation of functions should not seem esoteric to us as clinical neurologists; we traffic in them! Consider the relatively mundane case of supranuclear gaze palsy: We ask the patient to look down, but he can’t. Then we ask him to tilt his head down a bit and then rapidly tilt it upwards. We see that the eyes move downward. The voluntary control of vertical gaze is thus dissociated from the reflex; can he “look down” or not? Or consider a patient with vascular dementia: We give him a few words to remember and then ask for them later in the evaluation. He can’t restate the words spontaneously, but he can select them from multiple choice lists; did he “remember” them or not? Examples like this abound–localization and differential diagnosis in clinical neurology depend heavily on an understanding of such structure-function relationships.

This brings us to the present research, which sought to demonstrate a functional split in brain functions, as opposed to the structural split resulting from commissurotomy. Subjects were scanned with fMRI while performing a driving simulation under two different auditory conditions. In one, they were listening to GPS driving instructions–an “integrated” task in that the subject had to integrate the auditory instructions with her visual perceptions and motor responses. In the other, they listened to a radio show–a “split” task in that the subject would presumably not integrate what she heard on the radio with the visuoperceptual and motor aspects of driving. And indeed, the fMRI results showed much higher neural system integration during the GPS condition than during the radio show condition. The paper describes how such integration was measured, but I’m not knowledgeable enough to critique the experimental methods in such detail. I want to stipulate that the fMRI methods are valid and instead focus on what I think is a conceptual problem with one of the study’s interpretations (emphasis added):

An intriguing question is what happens to consciousness when driving while listening in the split condition. Is there a single conscious stream, with attention deployed primarily to a dominant task, typically listening, and much less to driving? Alternatively, does driving become unconscious, as on autopilot? Or, does a normally integrated conscious stream split into two separate conscious streams that coexist within the same brain, as indicated by studies of patients with an anatomically split brain? 

What does it mean to have “two conscious streams” and do post-commissurotomy patients have such? As with the case of “seeing”, “looking down”, and “remembering”, a lot turns on the definition of “conscious”. There are at least three types of consciousness: One can speak of being conscious as opposed to unconscious–sleeping, post-ictal, or comatose for whatever reason. One can be conscious of something, such as the distance between my vehicle and the one in front of me, the fact that I’m late for a meeting, or the pleasant aroma of the coffee I’m drinking. One can also be self-conscious, which itself has several different aspects. When considering structural or functional segregations of brain function, it seems that the second sense of “consciousness” is the most relevant one.

Most of us have had the experience of driving from point A to point B but being so lost in thought that we don’t recall any of the details of the journey. Or we may come to the sudden realization that we’ve overshot our highway exit. But does it make sense to say that, in addition to the stream of consciousness that we can recall–our cogitations along the way, the songs we heard on the radio, etc.–there was a second stream of consciousness that we can’t recall? That this stream of consciousness was responsible for the operation of the vehicle? No, I think that the term “conscious” means that if we weren’t aware of it along the way, and can’t recall anything about it later, then we simply weren’t conscious of it. People are able to carry out many activities without being conscious of them.

Again, let’s consider a mundane example: Think about the last time you walked from your car to your house. You may recall what you were carrying, what you were thinking about, etc. However, you probably don’t recall much, if anything, about the mechanics of the walking–the height of your step, the length of your stride, how it felt when your right heel struck the floor upon your first step into the house, how it felt in the knee and hip. Undoubtedly, there was neural activity underlying all of this, and specifically neural activity in the brain and spinal cord. I hypothesize that if it were possible to conduct an fMRI study of this behavior, one would find results similar to the “functional split” condition in the driving experiment above. That is, there would be no integration between the neural activity underlying your cogitations while walking and that underlying the walking itself. But it doesn’t follow from this that there was a second “conscious stream” that was responsible for the walking, any more than it implies the existence of a “spinal soul“.

I’ve never had the opportunity to examine a post-commissurotomy patient. My understanding is that they function quite normally in most situations, and strikingly abnormally under certain specific conditions. Undoubtedly, the study of the relationships between the behavior of such patients and their structural and functional neuroanatomy is very interesting and leads to insights about the neural conditions that must obtain in order for a person to exercise capacities such as perception and speech. But I don’t think it makes sense to say that such patients have two streams of consciousness. I assume that, like all people, they are conscious of some things and not conscious of others. Uniquely, they exhibit under certain conditions a dissociation between normally coordinated functions.

Likewise, the present research provides insights into the functional neuroanatomy underlying driving, listening, driving while concentrating on what’s being said and listening while not concentrating on driving. This is all very interesting, and I think the best interpretation vis a vis consciousness is, as the authors offer in the first two (related) hypotheses quoted above, that the subjects simply weren’t attending to the driving task while listening to the radio program–they were conscious of the latter but not the former. The study doesn’t show that there are two conscious streams because that concept just doesn’t make sense.

ResearchBlogging.org

Sasai, S., Boly, M., Mensen, A., & Tononi, G. (2016). Functional split brain in a driving/listening paradigm Proceedings of the National Academy of Sciences, 113 (50), 14444-14449 DOI: 10.1073/pnas.1613200113

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Assessing Consciousness http://www.ghostofcharcot.net/assessing-consciousness/ Sun, 11 Dec 2016 23:32:28 +0000 http://www.ghostofcharcot.net/?p=1506 Continue reading ]]> This week’s Green Journal has an interesting fMRI study in which the authors identify specific lesional areas in the pontine tegmentum that are associated with coma. The study raises the possibility that such imaging could be useful in the diagnosis and prognosis of disorders of consciousness. This is important because, as the accompanying editorial points out, the risk of misdiagnosis is quite high in such disorders.

The assessment of consciousness offers yet another example of where adherence to protocols can improve clinical performance. There’s a tool called the Coma Recovery Scale – Revised that has been shown to be superior to clinical consensus in differentiating the vegetative state from the minimally conscious state. I added a “Rehab” entry to the clinical neurology resources in the menu above, with a link to this scale. It appears to be somewhat cumbersome, but worthwhile. After all, the stakes can be high in such cases, as decisions about the intensity of care may hinge on the neurologist’s assessment. Moreover, to the extent that such cases sometimes engender disputes among family members and between families and the clinical teams, employing a validated tool could be helpful in achieving consensus.

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Quick Followup on Torture http://www.ghostofcharcot.net/quick-followup-on-torture/ Mon, 28 Nov 2016 03:20:57 +0000 http://www.ghostofcharcot.net/?p=1495 Continue reading ]]> File:Rod of Asclepius2.svgA few years ago, I posted an essay about the medical and psychological, professions’ involvement in torture, particularly of detainees in the war on terror, and my own possible light brush with that world. Last week the New York Times ran a piece describing in more detail the role of physicians in not only carrying out the torture program, but in designing it. Again, this isn’t something that most of us will ever confront, but I think it’s worth noting the recent history and reminding ourselves every once in a while of our ethical obligations . . .

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