Impact of cerebellar lesions on reading and phonological processing

Abstract

The relationship between cerebellar function and reading abilities is unclear. One theory of developmental dyslexia implicates the cerebellum in this reading disorder. Neuroimaging studies in normal readers consistently show cerebellar activation in tasks that involve reading. However, neuropsychological evidence for a relationship between cerebellar function and skilled reading is sparse. To further examine the role of the cerebellum in reading, we assessed reading skills and phonological processing in a group of patients with focal damage to the cerebellum. The patients' accuracy in naming single words and nonwords and their reading fluency and comprehension did not differ from that of age- and education-matched healthy controls. The patients' performance on phonological awareness and phonological memory tasks was also within the range of the control group, although their performance was highly variable. In contrast, cerebellar damage did significantly compromise performance in two other tasks associated with phonological processing. In a visual rhyme judgment task, a subset of the patient group was impaired on items with a mismatch between orthographic and phonological information. On a verbal working memory task, the cerebellar compared to the control group recalled fewer items from a list of nonwords, but not from lists of familiar items. On the basis of the patients' pattern of behavioral impairments, we propose that cerebellar damage affects an articulatory monitoring process. Our findings indicate that intact cerebellar function is not necessary for skilled reading; however, we cannot exclude the potential contribution of the cerebellum to reading acquisition.