Identifying the neural correlates of fluent reading

Fluent reading is an integral gateway to understanding text. Skilled readers focus on comprehension, not on decoding words or reading rate. Readers with dyslexia struggle to read with efficiency, which can compromise text understanding. Reading fluency is an important skill for readers of all ages and abilities, but has yet to be explored using functional magnetic resonance imaging fMRI) using a hypothesis-driven approach. In this dissertation, I present findings from two fMRI studies investigating the neural correlates of fluent reading in 18 skilled adult readers, The first study identifies the neural correlates of fluent sentence reading. To measure reading fluency, the rate of presentation for a word-by-word sentence reading paradigm was manipulated. Three rate conditions corresponded to minimal, moderate, and challenging reading speeds. Participants showed similar sentence reading performance in and out of the scanner. Findings from fMRI revealed that as the rate of presentation increased, bilateral inferior frontal gyri, left parietal, left superior temporal, left occipito-temporal, bilateral occipital, and cerebellar regions showed more activation. Readers with higher scores on a standardized reading fluency measure showed greater activation in the left occipito-temporal region, which is associated with fast and efficient word recognition. In the second study, the neural correlates of rapid naming, considered to be an index of reading fluency, were identified in the same group. Stimuli included matrices of letters, numbers, and alternating letters and numbers (2-set). Brain regions preferentially recruited for rapid naming compared to fixation included left frontal, left superior parietal, right inferior parietal, bilateral occipital, and cerebellar regions. Findings indicate a distributed network, similar to that recruited for reading text, is required for rapid naming. These studies elucidate brain networks that are associated with two aspects of fluent reading in skilled adult readers. The studies of sentence reading and rapid naming identified brain regions consistent with previous research relying on single word reading, and provide insight into how the brain accomplishes efficient and fluent reading. The current research sets the platform for further study of fluent reading in developmental dyslexia and in younger participant groups.