Spatiotemporal Dynamics of Word Processing in the Human Cortex (original) (raw)

Understanding language relies on concurrent activation of multiple areas within a distributed neural network. Hemodynamic measures (fMRI and PET) indicate their location and electromagnetic measures (MEG and EEG) reveal the timing of brain activity during language processing. Their combination can show the spatiotemporal characteristics (where and when) of the underlying neural network. Activity to written and spoken words starts in sensory-specific areas and progresses anteriorly via respective ventral ("what") processing streams towards the simultaneously active supramodal regions. The process of understanding a word in its current context peaks about 400 ms after word onset. It is carried out mainly through interactions of the temporal and inferior prefrontal areas on the left during word reading, and bilateral temporoprefrontal areas during speech processing. Neurophysiological evidence suggests that lexical access, semantic associations, and contextual integration may be simultaneous as the brain uses available information in a concurrent manner, with the final goal of rapidly comprehending verbal input. Because the same areas may participate in multiple stages of semantic or syntactic processing, it is crucial to consider both spatial and temporal aspects of their interactions to appreciate how the brain understands words. Keywords language; functional neuroimaging; N400; fMRI; ERP; MEG Language is essential to our communication with others and to our conceptualization of the world in general. It is largely through language that we share our uniqueness, our ideas, that we express ourselves as individuals while crafting social relationships and conforming to the intricate web of our social milieu. Through words we acquire a multitude of information, we articulate our thoughts, memories and feelings, we empathize with others, we play with words, and delight in mirth when sharing jokes. Because language is so fundamental yet so complex, because it interfaces with so many of our cognitive facilities, its underlying brain networks ought to be extensive and interconnected with neural systems supporting other capacities.