Activation of cerebellar lobules VI-VII during motor imagery but not during motor activation in unilateral cerebellar hypoplasia

We report the case of a 25 year-old patient who underwent morphological and functional brain magnetic resonance imaging (fMRI) to investigate a left neocerebellar hypoplasia discovered incidentally. We compared brain activation during overt and covert finger movements, and haptic discrimination. The contralateral cerebellar hemisphere compensated for mental imagery of hand movements and haptic discrimination, but not for motor execution. Moreover, the resting-state functional connectivity did not show compensatory functional coherence between the right cerebellum and cerebral areas connected with the hypoplastic cerebellum. Our case illustrates for the first time that cerebellar compensatory recruitment is an active, specific process related to task complexity and under the control of executive networks.