Impaired working-memory after cerebellar infarcts paralleled by changes in BOLD signal of a cortico-cerebellar circuit

A considerable body of evidence supports the notion that cerebellar lesions lead to neuropsychological deficits, including impairments in working-memory, executive tasks and verbal fluency. Studies employing functional magnetic resonance imaging (fMRI) and anatomical tracing in primates provide evidence for a cortico-cerebellar circuitry as the functional substrate of working-memory. The present fMRI study explores the activation pattern during an n-back working-memory task in patients with an isolated cerebellar infarct. To determine each patient’s cognitive impairment, neuropsychological tests of working-memory and attention were carried out. We conducted fMRI in nine patients and nine healthy age-matched controls while they performed a 2-back task in a blocked-design. In both groups we found bilateral activations in a widespread cortico-cerebellar network, consisting of the ventrolateral prefrontal cortex (BA 44, 45), dorsolateral prefrontal cortex (BA 9, 46), parietal cortex (BA 7, 40), pre-supplementary motor area (BA 6) anterior cingulate (BA 32). Relative to healthy controls, patients with isolated cerebellar infarcts demonstrated significantly more pronounced BOLD-activations in the precuneus and the angular gyrus during the 2-back task. The significant increase in activation in the posterior parietal areas of the cerebellar patients could be attributed to a compensatory recruitment to maintain task performance. We conclude that cerebellar lesions affect remote cortical regions that are part of a putative cortico-cerebellar networ

Grey Matter Volume in the Cerebellum is Related to the Processing of Grammatical Rules in a Second Language: A Structural Voxel-based Morphometry Study

The experience of learning and using a second language (L2) has been shown to affect the grey matter (GM) structure of the brain. Importantly, GM density in several cortical and subcortical areas has been shown to be related to performance in L2 tasks. Here, we show that bilingualism can lead to increasedGMvolume in the cerebellum, a structure that has been related to the processing of grammatical rules. Additionally, the cerebellar GM volume of highly proficient L2 speakers is correlated to their performance in a task tapping on grammatical processing in an L2, demonstrating the importance of the cerebellum for the establishment and use of grammatical rules in an L2

Differences in cortical activation during smooth pursuit and saccadic eye movements following cerebellar lesions

Current evidence supports the proposal that the cerebellum mediates the activity of other brain areas involved in the control of eye movements. Most of the evidence so far has concentrated on the vermis and flocculi as the cerebellar agents of oculomotor control. But there is also evidence for an involvement of the cerebellar hemispheres in eye movement control. Straube et al. (Ann Neurol 42:891–898, 1997) showed that lateral hemispheric lesions affect initiation of smooth pursuit (SPEM) and saccadic eye movements. Ron and Robinson (J Neurophysiol 36:1004–1022, 1973) evoked smooth pursuit and saccadic eye movements by electrical stimulation of crus I and II, as well as in the dentate nuclei of the monkey. Functional MRI studies also provide evidence that the cerebellar hemispheres play a significant role in SPEM and saccadic eye movements. To clarify the role of the cerebral hemispheres in eye movement control we compared the eye movement related blood oxygen level dependent (BOLD) responses of 12 patients with cerebellar lesions due to stroke with those of an aged-matched healthy control group. Six patients showed oculomotor abnormalities such as dysmetric saccades or saccadic SPEM during the experiment. The paradigm consisted of alternating blocks of fixation, visually guided saccades and visually guided SPEM. A nonparametric random-effects group analysis showed a degraded pattern of activation in the patient group during the performance of SPEM and saccadic eye movements in posterior parietal areas putatively containing the parietal eye field