transcript of episode 8: BRAIN GROOVOLUTION, 23rd April 2021
welcome to the error bar: where grey matter gloss is peeled off
in this episode: explaining how the human brain evolved & develops, the sensitivity of our fingertip nerves, dementia, elon musk, horses, inflammation, shamanism & not much more
here is the brain news on the 23rd April 2021:
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BRAIN EVOLUTION EXPLAINED
two high-profile studies on human brain development & evolution have made the headlines
first, the Guardian & Daily Mail report a study of the development of human, gorilla & chimpanzee brain cells. human cells were artificially manipulated into growing more like gorilla cells, while their number, shape & biological properties were measured. these changes were related to the brain size differences between humans & the other great apes. both newspapers claimed that the puzzle of human brain size is solved
second, Science News, The Scientist & the Mail report a study of ape-like creatures living 1.7 million years ago. 5 skulls were scanned & compared with 33 more recent skulls. the oldest were shown to be more ape-like than human-like. in particular, the researchers focused on changes in the inferior frontal lobe of the brain - one of many important parts of the brain involved in language
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have we explained brain development & evolution?
these papers are beyond my expertise, so here is a superficial evaluation
in the first, the media stories are about why 'the human brain' is much bigger than chimps or gorillas. but the brain cells studied were only a few weeks old. we don't know what would happen over months of development, or whether the manipulated human cells would develop like gorillas'
the researchers claimed that their results show that we now understand the evolutionary basis of brain expansion. that's clearly not true. these do look like remarkable results, but more humility would be welcome - even in Science Magazine
the second paper's data are also powerful, beautiful & undoubtedly important contributions to understanding brain evolution
a minor gripe is that the paper could be written more clearly for non-specialist readers. why say "petalial asymmetry cannot be ascertained" when the authors mean: "we don't know if the brain was symmetrical"; why "gnathic morphology" when "jaw shape" is clearer?
the second gripe is bigger. the paper & media coverage focus on the frontal lobe & its possible role in language, tool use & complex thought. these are brain functions that are assumed - often incorrectly - to be specific to humans
but the gorilla in the room of this paper is the massive territory of human brain - probably 3 or 4 times as much - that has also expanded during evolution. why do these parts of the brain - the so-called temporal, parietal & occipital lobes - not get nearly as much attention as the sexy inferior frontal lobe?
this may be a new form of the brain disorder called parietal neglect
some impressive-looking methods & results - which i don't really understand - shed light on the development & evolution of the human brain. more clarity, humility & holism is needed
the science was by Benito-Kwiecinski et al. in Cell, & Ponce de León et al. in Science; reported in The Guardian by @iansample on 24/Mar/21, & The Daily Mail by Stacy Liberatore on 25/Mar/21, & The Daily Mail by @jwillchad on 8/Apr/21, & Science News by Charles Choi on 8/Apr/21, & The Scientist by @abbyolena on 19/Apr/21
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FEEL THE GROOVE OF TOUCH
the New Scientist & the Guardian report on a paper investigating the nervous system's processing of fine details by the human fingertip
12 adults sat in a dentists chair, their right arm Velcro'd down, a fingertip glued to a plastic frame, a robot probing their skin with raised dots & a wire needle plunged into their upper arm
this sophisticated form of torture is called microneurography. only a handful of scientists in the world can do it. experimenters sit for hours next to their subject's arm, prodding & poking & wiggling a wire in their skin until a single nerve fibre is found
when, or more likely, if they can do that, the experiment begins. from their 12 'volunteers' they recorded 34 single nerve cells, each one responding to touches on the fingertip
changing the speed & direction of the touches, mapping the skin's ridges & systematically testing the nerve responses produced beautiful fingertip maps & clear conclusions: the fingertip ridges give us sensitivity to tactile details as small as 0.4mm
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can we really feel the groove?
yes. this is a rare win-win for brain science & brain science communication - this gorgeous paper is well-reported by both media sources
the expertise, equipment, skill & patience required to do this kind of work is Herculean. it rightly deters weaker mortals from attempting it. the data obtained & the maps of the hand's nervous system that it provides are almost mythological treasures
on the stats side, i should add that phrases like 'cross-correlation', 'data shuffling' & 'Fisher's transformation' all suggest that this is proper science done properly by proper scientists
a painstaking investigation of the spatial response properties of the nerves in the human fingertip reveals beautiful maps of the exquisite sensitivity of our skin
the science was by Jarocka et al. in Journal of Neuroscience; reported in The New Scientist by @christalestelas on 15/Mar/21, & The Guardian by @NicolaKSDavis on 15/Apr/21, & Twitter by @andpru on 16/Mar/21
and the brain in brief...
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IS EVERYTHING LINKED TO DEMENTIA?
in a trio of articles on dementia, the Daily Mail claims that household chores & brushing teeth prevents dementia, while hydrogen sulphide - a gas that smells like bad eggs - causes it
the first claim - that doing housework prevents dementia - refers to a study of older adults in which the researchers specifically excluded people with even mild dementia
the second claim - that tooth brushing prevents dementia - refers to another study of healthy older adults in which the frequency of brushing was found not to be associated with biomarkers of dementia found in spinal fluid
and the third claim - that a toxic gas in your brain causes dementia - this refers to the electrical & chemical properties of rat brain cells studied in a dish. in a dish!
that's 0 out of 3. no doubt there's more from the Dementia Mail next episode
the science was by Koblinsky et al. in BMC Geriatrics, Kamer et al. in Alzheimer's and Dementia, & Dallas et al. in Scientific Reports; reported in The Daily Mail by @jwillchad on 16/Apr/21, & The Daily Mail by @JoePinkstone on 12/Apr/21, & The Daily Mail by @jwillchad on 14/Apr/21
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WELCOME TO THE MUSK SHOW
in another trio, the Daily Musk provides three articles linked to distinguished scientist & philanthropist Elon Mail
the stories are perfectly plausible - that wireless computer systems allow humans to type & monkeys to play games without moving their body & that we can create dinosaurs if we wanted to
the first two stories are correct - brain-computer interfaces have been around for many years, allowing people to control computers without moving. the developments here are in the wirelessness & aesthetics of these systems
on the third story, the error bar does not comment on dinosaurs
goodbye mr musk
the science was by Simeral et al. in IEEE Transactions in Biomedical Engineering; reported in The Daily Mail by @RyanMorrisonJer on 9/Apr/21, & The Daily Mail by @jwillchad on 8/Apr/21, & The Daily Mail by Stacy Liberatore on 2/Apr/21
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THIS EPISODE'S NEURAL CORRELATES ARE...
horse-assisted psychotherapy reduces grey matter in your thalamus & caudate nucleus - important parts of the brain involved in movement, reward, thought & sensation
inflammation in your nose & sinuses decreases the connectivity between the frontal & parietal regions of your brain
entering a shamanic state of consciousness & listening to drumming increases electrical brain activity in the so-called gamma frequency band & decreases the beta-band. these are exactly the changes you would expect if the shamans moved around more than the control group. luckily enough, movement wasn't measured, so this paper can be published
and finally, in episode 2, the brain's orbitofrontal cortex was associated with obsessive-compulsive disorder. forget that. a new study of 2551 children shows that OCD is, in fact, associated with a larger thalamus - an important part of the brain involved in horse-assisted therapy
it's all in the brain
the science was by Zhu et al. in Human Brain Mapping, Jafari et al. in JAMA Otolaryngology-- Head & Neck Surgery, Huels et al. in Frontiers in Human Neuroscience, & Weeland et al. in Journal of the American Academy of Child and Adolescent Psychiatry;
it's closing time at the error bar, but do drop in next time for more brain news, fact-checking & neuro-opinions. take care.
the error bar was devised & produced by Dr Nick Holmes from the University of Nottingham. the music by Dee Yan-Kee is available from the free music archive. find us at the error bar dot com, on twitter at bar error, or email talk at the error bar dot com.ε