Cerebellar size and cognition: correlations with IQ, verbal memory and motor dexterity

The objective of this study was to examine the structure/function relationship between in vivo cerebellar size and higher cognitive function in a sample of healthy young subjects. The design of the study involved correlation of in vivo cerebellar volume measurements with measures of general intelligence (WAIS-R V&P FSIQ, Vocabulary, Block Design, and Digit Span subtests), motor dexterity (Halstead-Reitan Finger Tapping), verbal (WMS Logical Memory), and visual (Rey-Osterrieth Figure) memory covaring for cerebrum size. A similar analysis was performed using left temporal lobe volumes as a control region. The sample consisted of 62 healthy subjects (30 females, 32 males) enrolled as controls at the MHCRC at the University of Iowa Hospitals and Clinics. This independent sample does not overlap with the groups studied in our previous report on the relationship between cerebellar and brain size and IQ. Cerebellar and total brain size were estimated through automatic, atlas-based volume measurements using MR images obtained with a T1-weighted three-dimensional SPGR sequence on a 1.5-T GE Signa scanner and locally developed software. Cerebellar volume significantly correlated with Finger Tapping (left hand: r = 0.218, p < 0.05; right hand: r = 0.211, p < 0.05) and with memory retention of complex narrative material (r = 0.27, p < 0.02). Cerebellar volume correlated with general intelligence in the expected direction (r = 0.19, p < 0.07). This study confirms previous work indicating that the cerebellum may make a contribution to several aspects of cognition. Cerebellar volume significantly correlated with the ability to retain already encoded information in the verbal domain and with fine motor dexterity. Cerebellar volume positively correlated with general but the relationship did not reach statistical significance. The structural/functional relationship between cerebellum and verbal memory abilities is consistent with evolutionary theory for the phylogenetical increase in the size of the cerebellum.