The neural basis for reading can be improved by studying early brain activity, reseachers concue after a new study on the topic.
Led by Piers Cornelissen, Morten Kringelbach, Ian Holliday and Peter Hansen from the Universities of York, Oxford, Aston, and Birmingham UK, the study showed very early interactions between the vision and language domains during reading.
Using brain imaging, researchers showed that the speech motor areas of the brain (inferior frontal gyrus) were active at the same time (after a seventh of a second) as the orthographic word-form was being resolved within a brain region called the fusiform gyrus.
The finding challenges the conventional view of a temporally serial processing sequence for reading in which letter forms are initially decoded, interact with their phonological and semantic representations, and only then gain access to a speech code.
Also, the finding has a potentially important clinical application in relation to developmental dyslexia (affecting between 15-30 million people in the US alone) and those with acquired reading disabilities through injury or disease.
The researchers have claimed that a better understanding of normal reading processes could potentially help these individuals.
Using a neuroimaging method called magnetoencephalography (MEG) at Aston University, UK, the researchers tried to decode the highly automatized processing of words.
Thus, they used an implicit task that required participants to monitor the colour of a small red cross and to press a button as soon as the colour changed.
This was interspersed with words, consonant strings and faces that were shown for 300 ms, but which were not important to solve the task.
After the experiment, the researchers found key differences in the early brain activity of normal adults when they were reading words compared to reading consonant strings and seeing faces.
Time-frequency analyses showed a left-lateralized inferior frontal gyrus (pars opercularis) response to words between 100-250 ms in the beta frequency band that was significantly stronger than the response to consonant strings or faces.
The left inferior frontal gyrus response to words peaked at approximately 130 ms.
The response was significantly later in time than the left middle occipital gyrus, which peaked at approximately 115 ms, but not significantly different from the peak response in the left mid fusiform gyrus, which peaked at approximately 140 ms, at a location coincident with the fMRI-defined visual word form area (VWFA).
Also, they detected significant responses to words in other parts of the reading network, including the anterior middle temporal gyrus, the left posterior middle temporal gyrus, the angular and supramarginal gyri, and the left superior temporal gyrus.
The left inferior frontal gyrus is located in the front of the brain, which is a key region of the language brain and lesions can lead to the inability to articulate words.
As far as the experiment is concerned, the inferior frontal gyrus apparently plays a key role integrating the visual and language aspects of reading.
The study is published in the open-access, peer-reviewed journal PLoS ONE.