Patients with focal cerebellar lesions show reduced auditory cortex activation during silent reading

Description: Functional neuroimaging studies consistently report language-related cerebellar activations, but evidence from the clinical literature is less conclusive. Here, we attempt to bridge this gap by testing the effect of focal cerebellar lesions on cerebral activations in a reading task previously shown to involve distinct cerebellar regions. In a previous fMRI-study of healthy young adults, we observed increased activation in the posterior cerebellum when the final word of a sentence was predictable, compared to when the final word was unpredictable; this effect was especially strong when the prediction was violated. In addition, an experimental contrast designed to function as a basic language localizer revealed activations in more medial cerebellar regions. All contrasts also yielded distributed cerebral activations. In the current study, patients (N=10) had lesions primarily affecting midline cerebellar structures, overlapping cerebellar activations previously seen for basic language processing, but distinct from prediction-related activations. In line with this pattern of cerebellar activation-lesion overlap, the patients did not differ from matched healthy controls (N=10) in cerebral activations related to prediction generation or prediction error processing. However, they exhibited a different cerebral activation pattern related to general language processing. Whereas controls showed increased activation in bilateral auditory cortex and parietal operculum when silently reading familiar words relative to viewing meaningless and unpronounceable letter strings, this effect was absent in the patients. Our results highlight the need for careful lesion mapping when investigating functional consequences of cerebellar pathology and suggest possible roles for the cerebellum in visual-to-auditory mapping and/or inner speech.

Related article: http://doi.org/10.1016/j.bandl.2015.08.004