A New Insight on the Role of the Cerebellum for Executive Functions and Emotion Processing in Adults

Abstract

Objective: We investigated whether the cerebellum plays a critical or supportive role in in executive and emotion processes in adults. Many investigators now espouse the hypothesis that participants with cerebellar lesions experience executive functions and emotions (EE) disorders. But we hypothesized that these disorders would be milder if the damage is relatively limited to the cerebellum compared to damage involving the cerebellum plus additional cortical areas. Methods: We studied veterans with penetrating Traumatic Brain Injury (pTBI) participating in the Vietnam Head Injury Study (VHIS). We selected veterans with a cerebellar lesion (n = 24), a prefrontal cortex lesion (n = 20), along with healthy controls (HC) (n = 55). Tests of executive functions and emotions were analyzed as well as caregiver burden. We performed between-group null hypothesis significance testing, Bayesian hypothesis tests and correlational analyses. Results: Performance of participants with cerebellar lesions which extended to the cerebral cortex was similar to the HC on the Executive Function tests but they were significantly impaired on the Working Memory Index. No differences were found on the emotional processing tasks with one exception-the Facial Expression of Emotion-Test (FEEST). We then examined a sub-group of participants with large cerebellar lesions (>15%) but minimal lesions in the cerebral cortex (<15%). This sub-group of participants performed similarly to the HC on the Working Memory Index and on the FEEST. Conclusions: We suggest that the cerebellar cortex may not be critical for executive functions or processing emotional stimuli in adults as suggested. Instead, we find that the cerebellum has a supportive role characterized by its computing of the motor requirements when EE processing is required.

Keywords: brain network; cerebellum; emotion; executive functions; traumatic brain injury.

Figure 1

Representative axial slices depicting the lesion overlay density maps of TBI participants in the cerebellar group (n = 24). Z-values shown at the bottom of each slice indicate the z coordinates (MNI) of each axial slice represented in the 3D view of the brain by white line. The color indicates the number of veterans in the group with damage to a given voxel. Images are in radiological space (i.e., right is left).

Figure 2

Representative axial slices depicting the lesion overlay density maps of TBI participants in the prefrontal group (n = 20). Z-values shown at the bottom of each slice indicate the z coordinates (MNI) of each axial slice represented in the 3D view of the brain by white line. The color indicates the number of veterans in the group with damage to a given voxel. Images are in radiological space (i.e., right is left).

Figure 3

Representative axial slices depicting the lesion overlay density maps of TBI participants in the sub-group of cerebellar participants with a large cerebellar lesion (>15%) but a small lesion (<15%) in other part of the brain (n = 9). Z-values shown at the bottom of each slice indicate the z coordinates (MNI) of each axial slice represented in the 3D view of the brain by white line. The color indicates the number of veterans in the group with damage to a given voxel. Images are in radiological space (i.e., right is left).

Figure 4

Violin plots, sample size and individual data points of the three groups (cerebellar group; prefrontal group; HC group) of the Weschler Adult Intelligence Scale IV (WAIS-IV) working memory index score. **Significantly different p < 0.05.

Figure 5

Scatter plots of the significant correlation analysis between the WAIS Working Memory Index Score and the percentage of brain volume loss of cerebellar left Crus I (A), left lobule IV-V (B), and left lobule VIIb (C).

Figure 6

Representative axial slices depicting the anatomical overlap between the participants used in the Koenigs et al. study and in the current study who were members of the cerebellar group with large cortical lesions. Anatomical overlap is represented in pink. Z-values shown at the bottom of each slice indicate the z coordinates (MNI) of each axial slice represented in the 3D view of the brain by white line. Images are in radiological space (i.e., right is left).