The human visual system has tremendous capabilities for processing a complex world. For literate people, such expertise includes extremely efficient processing of written script. How does the visual system achieve this goal? One hypothesis is that an area in the mid-fusiform cortex, often called the Visual Word Form Area (VWFA), plays an important role in processing visual words. However, the level of functional selectivity of VWFA remains controversial, as well as its learning capacity (plasticity). With the support from the National Science Foundation, Dr. Sheng He and colleagues at the University of Minnesota, in collaboration with colleagues in China (Chinese Academy of Sciences, Chinese University of Hong Kong, and Huaxi hospital in Chengdu), will investigate the specific functional selectivity of VWFA, especially in terms of its role in processing Chinese characters. The project will be able to obtain information at very fine spatial scales using high field functional magnetic resonance imaging (fMRI) scanners. Fast dynamical information will be obtained using magnetoencephalography (MEG) and electroencephalography (EEG). Advanced data analysis methods will be used to extract more information from the brain imaging data than has previously been possible. The completion of this research project will result in a comprehensive understanding of the properties of the mid-fusiform region. Through close collaboration with colleagues in China, this project will also have the unique opportunity to track the potential change of functional properties of the mid-fusiform region in native Chinese illiterate participants as they are taught to read. Results from illiterate adults learning to read Chinese will be compared to results from native English speakers learning Chinese. This comparison will help determine whether extensive visual experience in adulthood is sufficient for the development of a functional specialization in the brain, or if early exposure is critical.
Detailed understanding of the specific functional selectivity and plasticity of this early brain area related to reading will contribute to the formulation of scientifically sound educational strategies. Because the project will explore the extent of plasticity in the adult reading brain, it will provide guidance to the strategies and policies regarding the alleviation of adult illiteracy. It could also contribute to better rehabilitation procedures and processes for people who suffer from reading disabilities due to brain damage. The use of multiple advanced brain imaging techniques will provide excellent training opportunities to both graduate students and undergraduate students. The collaboration between scientists in the US and China will facilitate long-term communication on many fronts and promote an exchange of ideas between the scientists of these two countries.
This research project investigated a particular part of the human brain believed to be important for reading – the so-called Visual Word Form Area (VWFA) at the bottom of the left temporal lobe. Finding from multiple experiments in this project show that in this part of the brain, written words were selectively and preferentially processed by sub-regions that are very close to (only a few mm apart) sub-regions devoted to processing of the face information. Often the word-sensitive region is on the outside relative to the position of the face-selective region. The spatial position as well as the detailed activation pattern of the word sensitive region is robust and invariant to changes in subjects’ tasks. For people who could read different languages, essentially the same area is engaged for processing written words of different languages. These results support the idea that the VWFA is intrinsically and invariantly sensitive to the written words. Not surprisingly, such a region could not be identified in the brain of illiterate adults. However, following a relatively short period of intensive reading training, a brain area consistent with the location of VWFA became strongly engaged in processing words. This occurs despite the fact that in this group of illiterate subjects, this VWFA has been missing for 40 to 50 years. That this relatively specialized brain area for processing written words could be induced in adult illiterates and the consistency in its location compared with the VWFA identified in normal readers tell us that there must be some special properties that make this area uniquely positioned and qualified for processing reading related visual inputs.
