Role of the dorsal stream in skilled reading
Reading is a complex cognitive process that draws on several regions throughout the brain. These brain regions are thought to be organized into at least two processing streams. The dorsal stream is thought to be particularly involved in integrating symbols (graphemes) and sounds (phonemes), or phonological decoding, whereas the ventral stream is related to visual word recognition. Neuroimaging research has shown that both streams are involved during reading in children and adults, though in adult readers, the ventral stream tends is relied on more for reading familiar words. As such, the development and role of the ventral stream in reading has been well characterized, while less is known about the dorsal stream. Specifically, it is unclear whether these two streams are part of a single mechanism for reading or represent two distinct processing routes. That is, does the ventral stream develop and function independent of the dorsal stream? Or does the development and function of the dorsal stream affect the ventral stream? In this dissertation, I explore the role of the dorsal stream in reading through a variety of methods. First, I examine how the changes in the dorsal and ventral streams relate to reading improvement in children. Then, I manipulate dorsal stream function using a neuromodulation technique to determine its effect on reading in adults. Finally, I use this same technique to examine the role of the dorsal stream in new learning. The results of my studies suggest that the development and of the dorsal and ventral streams are linked, and that the dorsal stream is critical for reading acquisition. Further, even in adulthood, the contribution of the dorsal stream is critical for continued reading improvement. This link between the dorsal and ventral streams has implications for teaching strategies for reading, as it suggests these two streams should be strengthened in tandem to better promote growth in reading skill.