It's not at all a language model in the way that LLMs are. At this point we might as well just say that both process information, that's about the level of similarity they have except for the implementation detail of neurons.

Language came after conceptual modeling of the world around us. We're surrounded by social species with theory of mind and even the ability to recognise themselves and communicate with each other, but none of them have language. Even the communications faculties they have operate in completely different parts of their brains than ours with completely different structure. Actually we still have those parts of the brain too.

Conceptual representation and modeling came first, then language came along to communicate those concepts. LLMs are the other way around, linguistic tokens come first and they just stream out more of them.

This is why Noam Chomsky was adamant that what LLMs are actually doing in terms of architecture and function has nothing to do with language. At first I thought he must be wrong, he mustn't know how these things work, but the more I dug into it the more I realised he was right. He did know, and he was analysing this as a linguist with a deep understanding of the cognitive processes of language.

To say that brains are language models you have to ditch completely what the term language model actually means in AI research.