Pink elephants
serenading the world's tallest woman might be an improbable situation, but our
brain is able to comprehend this thought. Humans can generate an infinite set
of ideas from a finite set of words, but how the brain accomplishes this feat remains
unclear. Now, a new study by US scientists suggests the human mind flexibly
combines the meanings of individual words to compose structured thoughts.
Researchers in the Department of Psychology at Harvard University, devised two
experiments to identify regions in the brain that encode for meaning where the
structure of the sentence is critical; and then how the brain represents this
meaning. In the first experiment, 18 participants undergoing a functional MRI
scan read simple sentences that could be conveyed in either the active or
passive voice. These sentences could also be arranged to have mirror meanings: ‘the
dog bit the man’ or ‘the man bit the dog’.
Through this
they were able to identify that the left mid-superior temporal cortex in the
brain plays a key role in decoding of sentence meaning and predicting the
required response based on this information. In the second experiment, four
nouns -- man, girl, dog, cat -- and five verbs (chased, blocked, approached,
bumped and scratched) were used in various combinations to create sentences. For
example the 34 participants would read sentences while undergoing fMRI such as
‘the dog chased the man’ and ‘the girl was scratched by the cat’. An analysis
of the scans from this experiment show one distinct area of the left
mid-superior temporal cortex is responsible for processing "Who did
it?" (the agent) while a neighbouring separate region encoded for "To
whom it was done?" (the patient). The researchers say the findings support
long-held theories that the brain acts like a computer processing data.
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