transcript of episode 8: BRAIN GROOVOLUTION, 23rd April 2021

[🎶 INTRO: "Spring Swing" by Dee Yan-Kee 🎶]

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:

[🎶 BIG BEN BONGS 🎶]

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

[🎶 INTERLUDE 🎶]

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

conclusion

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

sources

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


[🎶 BIG BEN BONGS 🎶]

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

[🎶 INTERLUDE 🎶]

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

conclusion

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

sources

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...

[🎶 BIG BEN BONGS 🎶]

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

conclusion

no

sources

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


[🎶 BIG BEN BONGS 🎶]

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

conclusion

goodbye mr musk

sources

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


[🎶 BIG BEN BONGS 🎶]

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

conclusion

it's all in the brain

sources

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;


[🎶 OUTRO: "Cosmopolitan - Margarita - Bellini" by Dee Yan-Kee 🎶]

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