img: Knights et al. 2021

the part of the brain dealing with images of hands also processes how to grab cutlery & the differences between grabbing cutlery & rods. hands & tools inter-digitate in the visual brain  

original article: Knights et al., 2021 (Journal of Neuroscience), reported in: Twitter by James Rosen-Birch on 13th May 2021 image source

this story was in episode 11 #hand #tool #FMRI #visual #grasp #decode

the error bar says

the life of a volunteer inside a brain scanner is not easy

strapped into a dark, noisy tube, a plastic spoon is lit up for a quarter of a second. it's grabbed between finger & thumb. this happens four more times. after 10 seconds' reprieve it happens again. now a strange rod. next grabbing a plastic knife blade, then a pizza cutter, then another rod. again & again & again for an hour

20 volunteers' brains were scanned each for about 2 hours while they viewed then grasped different items of cutlery & unfamiliar rods & while they just looked at similar images

the researchers in Cambridge & Norwich, UK, found that brain areas thought to be for processing visual images of hands also contain information on the orientation of spoons, knives & pizza-cutters, but not about unfamiliar rods

reports on social media suggested that we finally understand how the brain interprets tools as if they were literally a part of the body

does the brain bit for hands also do tools?


this is a good news story. it is a technical achievement just to adapt the brain scanner to do this work successfully & the researchers clearly spent a lot of time with each of their volunteers to get really good data over multiple sessions inside the torture tube, err, the brain scanner

figure 2 in the paper is a masterpiece in efficiency & clarity of data reporting - everything you need to know is right there

and like all good studies, it raises more questions

first, two overlapping parts of brain - for hands and tools respectively - showed quite different responses. the separate areas were defined independently - which is the right way to do it - so it raises the possibility that these brain areas can be defined in a different way and that could even give better results

second, like most studies of this kind, the statistical effects were really very small - signals in the brain areas distinguished typical from atypical grasps, or cutlery from rods, only about 55 to 60 percent of the time, with chance being just 50%. this study was powerful enough to find these tiny signals in the brain, but these are needles-in-haystacks

while the excitement on social media is justified by this study's quality, we still have a lot to learn about how the brain deals with tools


how we grasp familiar cutlery is processed by brain areas that normally deal with images of hands. another tile in the mosaic of the brain has been put firmly into place