Researchers decode how two layers of the brain communicate with each other during Reading
THOUGHT PROCESS: THE SPIRIT BEHIND THE LETTER
In a first, researchers have found how two
layers of the brain communicate with each other during reading, contributing to
the representation of language — an advance with implications for neuroimaging,
and expanding our knowledge of brain networks.
The study, published in the journal PNAS, noted that when
people read a word, two processes are combined in the brain: One is a
‘bottom-up’ relay of visual information to recognise the letters, another is a
‘top-down’ signalling of cognitive information to identify the word, and
retrieve its meaning from memory.
The researchers, including those
from the Max Planck Institute for Psycholinguistics in the Netherlands, said
that such top-down and bottom-up information streams were extremely difficult
to measure without having to open up the brain.
They used a device called the
laminar functional Magnetic Resonance Imaging (lfMRI) to measure neural
activation at different depths or ‘layers’ of the brain — which are generally
right next to each other, and thinner than a millimetre.
According to the researchers,
measuring at this level was important since the layers could be related to the
direction of the signals.
Deep layers, the study noted,
are associated with top-down information, while the middle layers are
associated with bottom-up flow of data.
Only laminar fMRI, the
researchers said, was sensitive enough to detect the deeper layers of the
brain.
Sifting through words
The researchers sought to know how the brain activity
varied when people listened to pseudowords such as ‘rorf’ and ‘bofgieneer’,
compared to the neural excitation pattern for real words such as ‘zalm’
(salmon) and ‘batterij’ (battery).
As part of the study, the
researchers asked 22 native Dutch speakers to silently read the words and
pseudowords while their brains were scanned.
The participants were also shown
some sequences of invented ‘false font’ characters that resembled existing
letters, and were asked to press a button when the items were real words.
The researchers could isolate
which area of the brain was involved in reading by comparing the neural
activation pattern for ‘readable’ items (words and pseudowords) and
‘unreadable’ items (false font).
This region of the brain, known
as the ‘visual word form area’, is situated in the temporal lobe.
The researchers also compared
the excitation pattern for words to that of pseudowords. They found that the
bottom-up sensory information was needed for both types of items, to recognise
the strings as letters.
Research Published at | https://www.pnas.org/content/early/2019/09/27/1907858116
Regards
Mr. Pralhad Jadhav
Research Scholar (IGNOU)
Senior Manager @ Knowledge Repository
Khaitan & Co
Mobile @ 9665911593
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