Normally I wouldn't say anything, but stuff like New Technique Offers Faster, More Accurate Way to Count Brain Cells compels me to respond (Wall Street Journal, October 10, 2014).
Such stories seduce me. I am weak.
Counting brain cells helps scientists explain how humans differ from other animals, but until recently, enumerating billions of cells by species was too onerous a task to tackle. That changed with the work of a Brazilian researcher who pioneered a technique that is both fast and accurate.
We’re looking at the most basic properties of brain tissue,” said Suzana Herculano-Houzel, who developed the approach. “What is it made of, what are the rules of putting a brain together and how does the human brain compare to other brains?”
Ms. Herculano-Houzel, who heads the Laboratory of Comparative Neuroanatomy in Rio de Janeiro, has counted the cells of 190 brains in 101 different species. Human brains, she has learned, have about 86 billion neurons, the basic unit that processes information. Mice have 71 million. And elephants have a whopping 257 billion—although relatively few are in the region of the brain associated with intelligence.
"A technique for rapidly counting cells allows researchers to compare the brains of different species in an effort to explain why humans are cognitively superior."
So far, Ms. Herculano-Houzel has examined four human brains, including three from men in their 50s and one from a man in his 70s.
Additional brains could alter the average, but because the human brain contains so many more neurons than nearly any other species, normal variations wouldn’t affect conclusions about the differences between humans and other species.
Hang on! Wait a minute! Has she examined this brain?
Despite the obvious similarity here, I mean the human brain on the left, not the deer-in-the-headlights brain on the right.
No, Ms. Herculano-Houzel has not figured out the cortex/cerebellum ratio of the brain above because the person in question is still "using" it (loosely speaking). If such brains were included in her study, it might significantly alter her results.
But I digress.
For example, by Ms. Herculano-Houzel’s count, humans have 16 billion neurons in the cerebral cortex, where conscious thought occurs—more than any other animal. The elephant has only 5.6 billion. Nearly all of its other neurons are concentrated in the cerebellum, where fine motor skills are controlled, perhaps for the purpose of operating the animal’s massive trunk.
Here it comes. Get ready.
Such differences, Ms. Herculano-Houzel said, help explain the cognitive superiority of humans. “If you look at the sheer number of neurons,” she said, “it’s got to be one of the most remarkable reasons for us not acting [like] great apes.”
It is impossible to add anything to these statements which is not already implicit in them, so I will leave it at that.
Crucially, and making some generous assumptions about how the neocortex actually functions, it is now possible to calculate the "Flatland" ratio (in billions of neurons).
16/86 = 0.186
Remember that number. That's the most important number you will ever see.
The study smacks of phrenology and anthropocentrism by itself, and I know the humor here is that greater cognitive ability doesn't normally equal greater understanding in humans, but I'll take the subject seriously (and boringly) for a bit.
I can tell you why Dr. Herculano-Houzel hasn't measured a female human brain yet. It's because others have done that, and the general findings are that males have more neurons in their cortex than human females:
http://www.ncbi.nlm.nih.gov/pubmed/10073431
That would be a highly inconvenient result as it would apply to her theory. Here's Dr. HH on TED:
https://www.youtube.com/watch?v=_7_XH1CBzGw
It's a hard watch. She's not alone in her posit that humans developed a larger and denser neuronic cortex because of cooking, though:
http://io9.com/5895119/how-cooking-turned-humans-into-an-invasive-species
Personally, I think we'd be better off understanding our similarities to our animal brethren than our differences, and what makes us "special", but I suppose both have their place.
And now, I'll take the remaining .814 of my brain and eat nachos. Nom nom.
Posted by: Jim | 10/20/2014 at 03:38 PM