The Cerebral Linguistic Toolbox That Blows The Mind
“Depending on the type of grammar used in forming a given sentence, the brain will activate a certain set of regions to process it, like a carpenter digging through a toolbox to pick a group of tools to accomplish the various basic components that comprise a complex task” (1). This was the descriptive offered by one review on how it is that diverse regions of the human brain are recruited to tease out the meaning of sentences when we communicate with each other (1). Cutting edge research into brain function, using American Sign Language as a platform, has unpacked the detail of exactly how the brain achieves this split-second feat (1,2).
In sign language messages can be expressed in one of two ways. As with English, ‘signers’ can use ordered words to convey their message (eg: John gives his lunch to Mary). But they can also move their hands in a manner that specifically relays concepts and ideas- what linguists call inflection(2). In languages such as German and French inflections are easily identifiable as suffixes that can be tagged onto the ends of words to denote, amongst other things, the case or the gender of the word or the ‘role’ that a subject or object in a sentence plays in a given interaction (John giving lunch to Mary in the above example) (2). But sign language, notes Rochester University psychologist Aaron Newman offers “a unique opportunity to directly contrast these two means of marking grammatical roles within the same language” (2).
Newman employed functional Magnetic Resonance Imaging (fMRI) to zero in on the spatial-temporal brain activities that accompany both word order and inflection-based communication. What he uncovered was nothing short of remarkable. There exists a network of brain regions including the dorsolateral prefrontal cortex (DLPC), the superior and posterior temporal sulcus (STS), the caudate nucleus, the middle temporal gyrus (MTG), the angular gyrus (AG) and the left inferior frontal gyrus (IFG) that are operative during both the interpretation of word order and inflection processing (2). Importantly significant differences exist in the “relative weighting” of activation in these regions depending upon which of these two modes of message transmission is being called upon (2). The DLPC and the right hemisphere AG are more dominantly active when word order-critical sentences are put in front of us. In contrast the MTG and the posterior STS are more active during inflection processing (2). The overarching conclusion borne out by the results of this study is that “specific parts of the neurocognitive system recruited for grammatical processing are dependent on the type of information that must be processed” (2). Read More ›