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Localizing Language In the Brain
RogerRoast writes "A new study by MIT scientists pinpoints areas of the brain used exclusively for language (PDF), providing a partial answer to a longstanding debate in cognitive science. According to the study, there are parts of our brain dedicated to language and only language. After having their subjects perform the initial language task, which they call a 'functional localizer,' they had each one do a subset of seven other experiments: one on exact arithmetic, two on working memory, three on cognitive control, and one on music; since these are the functions 'most commonly argued to share neural machinery with language.' The authors say the results don't imply that every cognitive function has its own dedicated piece of cortex; after all, we're able to learn new skills, so there must be some parts of the brain that are both high-level and functionally flexible."
As someone who does neuroimaging research, what appears to be exciting about this approach to fMRI is that it is on an individual-by-individual basis, not at a group level (which is mentioned in the MITNews article). Almost all fMRI work is at a group level. While I perform some group analyses, most of my work is on an individual basis (but I do structural imaging, not functional). Group analyses can have severe limitations that are not always discussed by the researchers and are almost never understood by people outside the field of neuroimaging.
From the article: "It’s the same way for brains. 'Brains are different in their folding patterns, and where exactly the different functional areas fall relative to these patterns,' Fedorenko says. 'The general layout is similar, but there isn’t fine-grained matching.' So, she says, analyzing data by 'aligning brains in some common space is just never going to be quite right. Ideally, then, data would be analyzed for each subject individually; that is, patterns of activity in one brain would only ever be compared to patterns of activity from that same brain."
This process of aligning brains is called registration. Even if you are just working within one subject, there is registration involved (between the functional scan, in this case, and the structural - so you know what part of the brain is being activated). I spend about 25% of my imaging work dealing with checking registrations or trying to improve registrations. It's really a key step in neuroimaging work, one that not enough researchers consider seriously enough. So that's why this approach to fMRI is interesting - the researchers are trying to minimize the effects of poor registration, which can lead to completely invalid results.
I just watched this @Google talk yesterday, which finds wide variation in the way people think about various tasks. It doesn't contradict the findings of this MIT team, it just shows how variable and "plastic" these functions can be. One example that comes to mind is students from one country (France, IIRC) showed a lot of activation in the hearing areas of the brain when doing simple arithmetic tasks. They said this was because they learned arithmetic through rote repetition of tables, and thus used those aural regions when doing the tasks. (They also said they preferred doing math problems in a quiet environment to avoid distraction.)
IANA neuro-scientist, I just enjoy learning about this stuff. For any other armchair brain enthusiasts out there, you might also enjoy this lecture series on Human Behavioral Biology by Robert Sapolsky at Stanford.
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After having their subjects perform the initial language task, which they call a 'functional localizer,' they had each one do a subset of seven other experiments:
They could have just monitored a Geek trying to talk to a sexy girl and look for the part of the brain that shut down.
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I've got an undergraduate degree in linguistics - which, granted, isn't much, but i did spend some time learning about language acquisition. The general consensus within linguistics is that there exists both a language acquisition device (LAD) and a critical period for language learning. Language learning is a biological process on par with learning how to process visual data that (in neurotypical individuals) unfolds regularly given adequate input. After somewhere between 11-13 years the LAD switches off, and languages that are learned after this critical period are typically learned imperfectly.
I've seen side-by-side fMRI scans of people speaking two languages they learned before the critical period and of people speaking a language learned before and a language learned after. In the true bilingual speakers, both languages lit up the same area of the brain, and in the speakers who learned a new language after the critical period, the post-critical language lit up a different area of the brain from the native language.
As far as post-critical-period second language acquisition goes, there is some indication that the LAD is involved in the process - there is a specific order in which English speakers will learn grammatical features of German regardless of who taught them or what method they used to learn the language. There are actually some language acquisition theorists (Krashen in particular) who think that language processing and production (at a grammatical level) is all done at an automatic level, and that all our conscious brains do is monitor what comes out.
The environment you learn the language in and your degree of identification with the target language's culture do play a pretty big role in how accurately you'll be able to reproduce the target language, though.
Also, programming "languages" aren't capital-L languages and are (presumably) not handled by the part of the brain that handles language.