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The Neural Correlates of Cake

A few years back my PhD department, the Helen Wills Neuroscience Institute at Berkeley, held a dessert competition at their annual holiday party. My wife and I came up with the above idea (which she then executed).

Basically I wanted to be a smartass and poke fun at "neural correlates of" fMRI studies. The transaxial brain slice is made of melted candy, and the nucleus accumbens are "lit up" using two LEDs embedded in the cake.

Needless to say, my wife won the competition.

However, as I try to do, embedded in my jackassery was a point of sorts. A point that escapes me right now...

Oh! I remember! Let's talk about "neural correlates".

So the phrase "neural correlates of" was most certainly popularized by Cristof Koch and Francis Crick's 1995 Nature paper, "Are we aware of neural activity in primary visual cortex?" wherein they discuss the topic of neural correlates of consciousness (NCC).

Look at how this phrase takes off after 1995:

Now, I'm not interested in NCC (well, actually, I am, but not in this post). What I'm interested in is the proliferation and misuse of this term.

As of this writing, there are 3571 papers in PubMed containing the phrase "neural correlates". Of those, 1892 contain that phrase and "fMRI". This means that just shy of 53% of all "neural correlates" papers aren't actually measuring anything neural. Or, at least, not directly.

At times, it seems to be an essentially meaningless phrase that says that your hypothesis consisted of "we'll find somewhere in the brain that correlates with the behavior we're measuring!"

I'm fascinated by these kinds of phrases in science, and how language and the metaphors we use as shortcuts affect the way we think about problems and conduct (restrict) research.

Like "pinpointing" brain regions. That phrase is used all the time, and belies a complete lack of understanding about how the brain works.

Some phrases seem to get adopted without much consideration. Is "neural correlates of" really the most rigorous, scientifically accurate way of saying what you want to say?

Note, I'm not actually trying to criticize anyone in particular. I'm appealing to my fellow neuroscientists (and myself!) to be more attentive to the questions we're asking, and to remember that the words we use when talking about brain and behavior may be limiting innovation and rigor.


Interesting personal aside: looking around on PubMed, I found that one of the earliest uses of the phrase "neural correlates" was by "AB Scheibel", or Arnold B. Scheibel. In fact, his is the third paper ever published containing this phrase, it would seem.

If his name doesn't jump out at you, he's the co-author, along with YouTube anatomy star and his wife Marian Diamond, of the Human Brain Coloring Book. He teaches neuroanatomy at UCLA, and Dr. Diamond teaches it at Berkeley.

I had the pleasure of teaching her neuroanatomy lab for two semesters during my PhD at Berkeley, but the first time I met her really epitomizes my perception of her.

We were at the neuroscience picnic during the first year of my PhD. I was pitching in the softball game and she came up to bat.

She was about 80 years old at the time.

I lobbed her a soft pitch and--I kid you not--she grabbed it out the air with one hand while still holding the bat with the other and says to me, "No. Throw me a real pitch," and throws the ball back to me.

She's an amazing woman.

Crick, F., & Koch, C. (1995). Are we aware of neural activity in primary visual cortex? Nature, 375 (6527), 121-123 DOI: 10.1038/375121a0
Scheibel AB (1961). Neural correlates of psychophysiological developments in the young organism. Recent Advances in Biological Psychiatry, 4, 313-28 PMID: 14498134

1 comment:

  1. Neat history lesson, but I can't help but laugh that you've decided any paper talking about neural correlates and not using fMRI isn't actually neural (since then my entire field isn't neuroscience).

    Seriously, a lot of animal researchers use neural correlates to mean things Q and Z (receptors, peptides, NT concentrations) in the brain that correlate with behavior or physiology. It's nice to know where the phrase comes from, but it's not clear there's a better more specific alternative when more than one thing is being referred to. I think the funny part really comes in not on the "neural correlates" end but the "of _______". Which is why that cake is so damn great! (And the Marion Diamond anecdote too).