From a news report:

Now that they had evidence that the brain could generate both strategic and random behavior, Karpova and her colleagues wanted to know how it switched between modes. Since that switch determines whether or not an animal's internal model of the world influences its behavior, the scientists suspected it might involve a brain region called the anterior cingulate cortex, where that internal model is likely encoded.

Why is the indefinite article used here? The news report names the region, so it is quite a definite thing.

Would it be an error to use the definite article in its place? Would it change the meaning drastically?

  • 2
    As long as there is no more than one "anterior cingulate cortex" per brain, then, yes, either "a" or "the" could be used there. imo.
    – F.E.
    Commented Sep 26, 2014 at 7:04
  • 10
    Both choices are fine, but they have subtly different implications in terms of information structure. My intuition says a is appropriate in this case because it's being introduced as new information with no expectation that the reader is familiar with it.
    – user230
    Commented Sep 26, 2014 at 14:49
  • 1
    Another complication with talking about brain regions is that almost all regions, including this one, exist in both the left and right hemispheres. So there is a left ACC and a right ACC. Most neuroscientists use the terminology "the anterior cingulate cortex" to describe the entire structure, even though the left and right are physically separated. Old-fashioned neurobiologists sometimes use the plural "cortices" but I think this is falling out of favor.
    – cxrodgers
    Commented Sep 27, 2014 at 22:09

5 Answers 5


I think the reason to use 'a' here is to account for the knowledge of the reader, and is thus correct.

  • When using

The brain region called 'x' ...

the writer assumes that the name of the brain region explains what is specific about this brain region. However, the average reader of this article is none the wiser if he knows the name of the brain region. An alternative phrasing would prove this:

The 'x' brain region ...

This will leave the reader wondering "What 'x' region? I don't know such a thing!". So, if 'the' is used, the reader will expect some more information; e.g.

The brain region called 'x', located near your ears, ....

Compare with AllanaRose's answer, which explains that you can only use 'the' when the object is specified later; in this case, although 'x' does specify the object gramatically, it does not provide relatable information to the average reader.

  • When using

A brain region called 'x'

this could be read as

Some region called 'x'

This shows the writers intent not to explain anything about this brain region; he just puts the name of the region out there, and shows that, even though he could specify exactly what this region is all about, he chose not to.

Edit: since this is the language learning stack, I ought to add that 'the' is acceptable as well. This question may have been better fit at the English Language usage stack...

  • 7
    On the contrary, choosing the appropriate article (if any) is a problem learners face every day. It's a great question for this site! Native speakers rarely have to think about it, so I'm not sure they'd like this question over at ELU.
    – user230
    Commented Sep 26, 2014 at 17:13

I'm just an English speaker, not a teacher, but I think it has a little to do with grouping. If one uses "a", then the first part of the phrase stands on its own, "... it might involve a brain region," and then "called the anterior cingulate cortex" is a modifier on the brain region. If one uses "the," then the first part cannot stand on its own, "... it might involve the brain region." It is now dependent on the rest of the phrase.

... (it might involve a brain region) called the anterior cingulate cortex


... it might involve (the brain region called the anterior cingulate cortex)

I would consider this to be a kind gesture, because it lets a reader process the part of the sentence which is astounding (Scientists found a region of the brain which has all this raw power over us) from a very specific medical term that took three words to spell out!

Daring to look further into how scientists think about the brain, the regions of the brain are rather fuzzy. There's some physical structures separating them but behaviors often blur across the edges of those physical structures. "The brain region called the anterior cingulate cortex" is a very hard edged phrase demanding absolute agreement on how the regions of the brain are mapped. It gives me the feeling that a scalpel could excise the region, if a surgeon needed to.

"A brain region called the anterior cingulate cortex" feels softer to me, refering to just "a brain region" and qualifying it with something that I could paraphrase as "... which most scientists agree is generally in the anterior cingulate cortex." It leaves more room for disagreement.


I believe that given the sentence structure, "the" is more also correct.

When a specific item of a general type is first introduced, you typically use "a" unless the specific item is already known to the listener. In later references you would use "the". (See Use 10 of English Page).

Some examples:

  • I'm playing a game. The game is exciting.
  • There is a dog. The dog looks hungry.

In the article you mentioned, the general type would be "brain regions".

However, you should typically use "the" when you are about to give or have just given a specifier, as mentioned in Use 11 of English Page.

Some examples where "the" is correct:

  • I'm playing the best game, Solitaire. (Which game? The best game)
  • That is discussed in the book that I recommended yesterday. (Which book? The book I recommended).
  • The dog inside looks hungry. (Which dog? The one inside.)

In this article, since the specifier is included in the same sentence, "the" would make sense makes more sense .

However, in my personal experience, it is not uncommon to say things like "the show involves a technique called 'breaking the forth wall'" where "a" is used even though there is a specifier in the sentence. Edit: In both the article you mentioned and my example, the object may not be familiar to the listener. Use of "a" has a subtle connotation that fits the situation better.

Edit: Sanchises's answer hit on something that was bothering me about my own answer. It's not that you must use "the" if you are about to add a specifier, but that you can use it. I've edited my answer accordingly.

  • Agreed! It is talking about the proper noun further. My vote is also for the definite article! +1
    – Maulik V
    Commented Sep 26, 2014 at 7:41
  • +1 for "When a specific item of a general type is first introduced, you use typically use "a" unless the specific item is already known to the listener"
    – anotherDev
    Commented Sep 26, 2014 at 8:43
  • 6
    This is a good example of why rules for using articles fall short. This goes for many usage/grammar points. The article a is perfect here. I believe answers to other questions on this site have debunked both "Uses."
    – user6951
    Commented Sep 26, 2014 at 15:11

This is very simply a pedagogical register in which all information taught is presented as "new material" with the indefinite article (or no article in the case of plural nouns) in an expository style.


The sentence uses a variety of words to express uncertainty: "called", "suspect", "might" and "likely". Using an indirect article instead of a direct article supports this notion.

Furthermore the idea of a brain region is a fussy one. Different research might disagree about the exact borders of the anterior cingulate cortex.

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