Exploring the role of subcortical structures in developmental reading impairments: evidence for subgroups differentiated by caudate activity

Although the role of cortical structures in skilled and impaired reading has been the topic of considerable investigation, the contribution of subcortical structures to reading performance is less well understood. Here, we assess the role of the caudate, putamen, and thalamus in adults with and without reading impairment. Thirty-three individuals (19 skilled readers and 14 reading impaired individuals) participated in two functional MRI tasks: (a) silent reading of real words and (b) silent reading of nonwords. Percent signal change was calculated for each of the three structures by evaluating the signal change relative to the baseline (i.e. no task or fixation crosses), and response time was measured for each reading condition. We found that for skilled readers, activity in the putamen predicted behavioral performance for both real words and nonwords. In contrast, we found evidence for two subgroups of impaired readers: a positive caudate activity group and a negative caudate activity group. Interestingly, brain activity differentially predicted reading performance depending on whether individuals had positive or negative caudate activity. We discuss our findings in the context of developmental reading impairments, print-to-speech networks, and language processing in general. Correspondence to Jacqueline Cummine, PhD, Department of Rehabilitation Medicine, Faculty of Rehabilitation Medicine, University of Alberta, 3-58, 8205 114 St Corbett Hall, Edmonton, AB, Canada T6G 2G4 Tel: +1 780 492 3965; fax: +1 780 492 9333; e-mail: jcummine@ualberta.ca Received August 20, 2017 Accepted August 24, 2017 © 2017 Wolters Kluwer Health | Lippincott Williams & Wilkins

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