Introduction to the special issue on functional brain imaging of language (2003)

Language is one of the most significant and immense aspects of human evolution. Not surprisingly, it has been a research topic of scientists working in many disciplines. Numerous questions have been raised from this important research: Why is language so quickly acquired by children living in very different cultures with very different languages? How does the human brain produce and comprehend language? How is second-language learning influenced by the native language? Is the neural network that mediates language processing universal across languages? For years, scientists have attempted to answer these questions. With the advent of new technology, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), the past decade has seen an extremely rapid expansion of research on the aforementioned issues. Such technical advances have given researchers great power to visualize the activity of the intact human brain that is associated with language processing and language learning, and have consequently made significant contributions to the vast amount of discoveries in brain research. Whilst imaging technologies are improving every year, because language processing demands higher-order cognition, its neuro-cognitive mechanisms are very complex and much research remains to be done. Cross-linguistic studies provide a powerful contrast to elucidate the universality and specificity of the neural basis of language. Although the direct subtraction of the processing of the native language in one population (Language A) from the processing in another population (Language B) might seem like an interesting comparison, cognitive and psycholinguistic research has established that even at the lexical level, cognitive processing involves dozens of variables, such as visual and auditory complexity, spelling–sound regularity, word frequency, word familiarity, and age of acquisition. Thus, in brain mapping research, direct subtraction of two different populations may include a confounding of linguistic variables in two different languages, and these variables are often un-confoundable. For example, it might be possible to find seemingly identical words in two different languages (“banana” is banana in English and banana in Italian). However, the processing might be quite different due to many factors such as syllable structure (banana has a much more typical structure in Italian than in English), how common the spelling–sound relationships are (because far fewer spelling–sound relationships exist in Italian than in English, they are much more frequent), how consistent the spelling–sound relationships are (graphemes in English often map onto many different sounds but in Italian they typically do not), and so on. A better understanding of the generality and specificity of neural mechanisms associated with language should build on knowledge and conclusions from research on individual languages, rather than from a direct subtraction approach. A number of studies in this special issue show how cross-language research can lead to important insights. This special issue emerged from a research symposium in April 2002 at the University of Hong Kong, in which we as co-organizers invited researchers who were very active in the fields of cognitive neuroscience, cognitive psychology, and linguistics to present their functional brain imaging findings. These pages feature contrastive studies of Chinese and English, two languages that differ markedly in almost every aspect: phonology, orthography, semantics, and syntax. We hope that our readers will learn from these new findings, and will be inspired to further such research with their own particular knowledge and skills.