The cerebrocerebellar system: anatomic substrates of the cerebellar contribution to cognition and emotion

The contribution of the cerebellum to the modulation of cognition and emotion is facilitated by the connections between the cerebellum and brain structures known to be associated with a wide array of non-motor behaviors. The cerebellum has interconnections with brainstem and thalamic reticular systems that subserve arousal. Autonomic activity is supported by the reciprocal interconnections with the hypothalamus. Limbic and paralimbic connections include the hypothalamus, septal region, hippocampus, and cingulate gyrus. Associative connections consist of both feedforward and feedback limbs. The basilar pons receives inputs from the prefrontal, posterior parietal, superior temporal, parahippocampal, and cingulate cortices, as well as from the sensorimotor cortices. This information is conveyed from the pons to cerebellum, before it is relayed back via thalamus to the associative and paralimbic regions of the cerebral cortex. The anatomical arrangement of segregated loops of cerebral cortical connections stands in contrast to the cerebellar cortical architecture that is essentially uniform. This has theoretical and clinical ramifications. It is the anatomical basis for the dysmetria of thought hypothesis that postulates a universal cerebellar transform, in which the cerebellum performs its unique computation in a topographically precise manner on diverse streams of information relating to almost all aspects of behavior including cognition and emotion. It provides an anatomic basis for the observations of cerebellar activation by cognitive and affective paradigms in functional neuroimaging experiments. It helps explain the clinical phenomena that characterize the cerebellar cognitive affective syndrome, and it provides an anatomic basis for a causal relationship between cerebellar pathology and psychiatric and neurobehavioral conditions. Knowledge of these anatomical pathways is critical to the further development of hypotheses, experimental approaches, and clinical questions that can advance the understanding of the contribution of the cerebellum to cognition and to disorders of intellect and emotion.