Moving forward: age effects on the cerebellum underlie cognitive and motor declines

Abstract

Though the cortical contributions to age-related declines in motor and cognitive performance are well-known, the potential contributions of the cerebellum are less clear. The diverse functions of the cerebellum make it an important structure to investigate in aging. Here, we review the extant literature on this topic. To date, there is evidence to indicate that there are morphological age differences in the cerebellum that are linked to motor and cognitive behavior. Cerebellar morphology is often as good as - or even better - at predicting performance than the prefrontal cortex. We also touch on the few studies using functional neuroimaging and connectivity analyses that further implicate the cerebellum in age-related performance declines. Importantly, we provide a conceptual framework for the cerebellum influencing age differences in performance, centered on the notion of degraded internal models. The evidence indicating that cerebellar age differences associate with performance highlights the need for additional work in this domain to further elucidate the role of the cerebellum in age differences in movement control and cognitive function.

Keywords: Aging; Cerebellum; Cognition; Motor performance; Neuroimaging.

Figure 1

Cerebellar-prefrontal interactions (via the thalamus) are illustrated as an example circuit that is disrupted in advanced age. In young adults (solid lines), we see strong functional connectivity between these regions. In older adults (dashed lines), connectivity is decreased. We suggest that age effects on these cerebellar-prefrontal interactions may play a critical role in motor and cognitive performance declines in advanced age. Disruption of additional cerebello-cortical circuits, including those with the motor cortex and basal ganglia, contribute to the wide variety of motor and cognitive performance declines seen in age. The bottom schematic illustrates the hypothesized framework linking the cerebellum to age-related declines in motor and cognitive performance. With advanced age, there is a loss of cerebellar volume, and there are also degraded connections, both structural and functional, between the cerebellum and cerebral cortex. Together, we suggest that this results in degraded internal models that have a negative impact across task domains, given the closed-loop circuitry of the cerebellum. Ultimately, this contributes to the motor and cognitive performance declines seen in older adulthood. Non-invasive brain stimulation and behavioral interventions targeting the cerebellum may help mitigate some of these declines.