Cortical-cerebellar loops during attention to visual motion
For a long time the role of the human cerebellum was thought to be limited to motor functions such as coordination of well-learned motor sequences (e.g., an experienced golf player swinging the golf club). It is, however, being increasingly recognized in the neuroscience community that specific parts of the cerebellum play a much wider role in human cognitive functions than what has been previously assumed.
In a recent study by Kellermann et al. (2012), the involvement of cerebellar-cortical loops in a visual attention-to-motion task was investigated using functional magnetic resonance imaging. Healthy volunteers were shown stationary vs. moving grating stimuli; in the test condition the subjects were instructed to attend slight changes in the speed that the bars were moving. In reality there were no changes in movement velocity and thus the only factor that was experimentally manipulated in the test vs. control conditions was the level of attention to visual motion.
The authors observed increased effective connectivity between the cerebellum and neocortical dorsal visual stream structures with increasing level of attention to visual motion. Further, it was observed that, under attention, functional connectivity from cerebellum to visual area V5 (that processes visual motion) was enhanced, whereas connectivity from V5 to posterior parietal cortex (that is a higher-order attention-directing structure in the brain) was attenuated.
The authors interpret these findings as indicating that, under conditions where visual motion is highly predictable (i.e., when internal models can strongly guide perception), the posterior parietal cortex feeds top-down predictions to the hierarchically lower motion processing area V5 via crus I of cerebellum (thus potentially enhancing the precision of input-predictions of V5 neurons), while at the same time influence of bottom-up inputs from V5 to posterior parietal cortex are suppressed; the authors further note that the task-specific input-output patterns of the cerebellum likely determine the functional role that the cerebellum plays in various cognitive processes. Overall, these findings highlight the importance of cerebellar-cortical loops in perceptual-cognitive functions, something that has been regrettably often neglected in the human functional neuroimaging literature.
Reference: Kellermann T, Regenbogen C, De Vos M, Mößnang C, Finkelmeyer A, Habel U. Effective connectivity of the human cerebellum during visual attention. Journal of Neuroscience (2012) 32: 11453–11460. http://dx.doi.org/ 10.1523/JNEUROSCI.0678-12.2012