The cerebellum is a crucial brain structure for the control of movement. Recent data from lesion studies, neuroimaging, and neuroanatomy also implicate its lateral portion in non-motor functions, including cognitive processes. The lateral cerebellum may participate in such functions through its closed-loop connections with prefrontal and parietal cerebral cortex. A critical segment of these loops involves circuitry within the laterl cerebellum itself, extending through its cortical mantle to the dentate nucleus. Essentially nothing is known about non-motor signals in these intracerebellar circuits. We will record the signals directly in macaque monkeys that perform tasks involving cognitive demands such as self-timing of behavior. The studies are challenging because the cerebellar cortex, even just its lateral portion, is vast. Moreover it is highly foliated and deep in the brain, making it difficultto survey neurophysiologically. Efficient and systematic neurophysiology can now be achieved, however, based on recently available neuroanatomical maps that detail the motor and non- motor domains of cerebellar cortex.
Our first aim i s to record from neurons in two restricted zones of lateral cerebellar cortex known to be functionally connected with prefrontal and parietal cerebral cortex. The recording zones will be targeted using structural MRIs of each monkey's cerebellum referenced to published connectivity maps. During recordings, we will use physiological criteria to identify signals conveyed at three functional levels: cerebellar cortical output (Purkinje cells), input (mossy and climbing fibers), and local processing (Golgi cells).
Our second aim provides for a definitive follow-up by comparing our recording sites with histologically documented cerebellar circuits in the same animals. This anatomical conclusion is crucial for interpreting the results of the first aim and for informing the strategies of future studies. The end result of this project will be a systematic description of both the non-motor and motor information conveyed within physiologically identified, and anatomically confirmed, circuits of the lateral cerebellum. The broader outcomes will be to improve our understanding of how the cerebellum helps to mediate cognition and to provide a novel functional perspective on the relation between cerebellar dysfunction and neuropsychiatric disorders.
It is textbook knowledge that the cerebellum contributes to motor learning and coordination, but recent evidence from imaging, anatomy, and lesion studies implicate it, as well, in non-motor functions such as cognition. Our work will analyze the information conveyed within microcircuits of the cerebellum in monkeys that perform both motor and non-motor tasks. The results will provide a circuit-level description of cerebellar participatin in non-motor functions and new insights into the association between cerebellar dysfunction and neuropsychiatric disorders.