Neuronal Recycling Hypothesis: 4. Letterbox

2010/01/18 at 5:59 pm | Posted in Cognition, Reading, Thought | Leave a comment

Below: The red region is the core of the neural recycle hypothesis - letter box.

At the 2009 X’mas Eve, Hsuan Chih Chen from Hong Kong Chinese University gave a talk to the fellows in the Dong Hwa University. During the dinner with Prof. Chen, I met Peter who is teaching at the department of life science of Dong Hwa University. He shared his astonished experience on learning Chinese which have made him suspect that Chinese ancestor created reading before writing contrary to that Indo-European created writing before reding. Coincidently I have learned Plato’s academy been the landmark that the western societies were beginning to accept the silent reading as a meaningful activity from Steven Fisher’s book “A History of Reading“. At that era, Chinese society have steped into “literatural” world. Until now we still have little clues to answer why did Chinese have the reading ability ealier than the western societies. Dehaene have suggested either Chinese or western readers depend on the same neural circuit for reading their own words.

That the left occipito-temporal region has been identified as “Letterbox” synthesizes the magnetic resonance imaging (MRI) data of the patitents suffered by the pure alexia. This reading deficit causes the readers percieve the string of letters as single visual feature rahter than a “complete” word. Letterbox exchange the information with the visual area, the region analyze the input visual information, and transfer to the meaning pathway and the phonological pathway. In the comparisons among the neuro imaging literatures, Dehaene and his colleagues concluded that the “letterbox” burden the responsibility to initiate the reading pathways across languages. More than the discoriveries on human readers’ brain, he figures out that the apes have the perception to detect the “proto-letters”, the visual stimuli have the shape as similar to strokes of the mordern letters. Many evidence have shown that the neugral circuits sponsering the apes’ perception are close to the letterbox in the human brain. In the summary of the functions and locations of this region across normal readers, reading deficit, and the apes, Dehaene propose his “bold” neural recylcing hypothesis. Our brain adapt the function of the neural circuits for percieving some specoific shapes to the function for reading words.

It is still a “hypothesis” because there are many mysteries amid the pathway between letterbox and visual area and more amid the connections among the other regions distrubited among the reading pathways. In addition, the modular scheme that Dehaene used to speculate his reading pathways is under debate till present and hard to see the end in a expectd future. The following comments will discuss these issues, and my introduction works temporarily stop here. It is joyful to finish this work just two days before Dahaene gave his talk about this book to Taiwan.