EEG-ECeG coherence mapping of human cerebro-cerebellar projections: an exploratory study

The cerebellar and cerebral cortices are powerfully connected via reciprocal, crossed projections which mediate their coordination in motor, cognitive and affective processes. In the present paper we demonstrate non-invasive imaging of crossed cerebro-cerebellar connectivity by means of wavelet coherence. In a sample of six healthy adult subjects, we recorded EEG and the electro-cerebellogram (ECeG) with a 10% cerebellar extension montage during voluntary left and right index finger movements. EMG was also recorded from finger extensors and flexors and was used to generate triggers for movement related averaging (-2000 to + 2000 ms). Consistent with prior observations of movement related changes in delta/theta power, we observed significant movement related change in delta/theta-band EEG-ECeG coherence between cerebral and cerebellar leads. Of particular note, when lateralised seeds were selected (F1 vs. F2 and SO11 vs. SO12) the low-frequency coherence was distributed contralaterally and frontally for cerebellar seeds, likely reflecting the underlying crossed cerebro-cerebellar projections, as well as the cerebral contralateral somatosensory representation. For the F1/F2 seeds the movement related change in delta/theta-band EEG-ECeG coherence was more bilateral but with right-hemisphere dominance. The cerebral frontally seeded coherence further demonstrated strong cortico-cortical delta/theta coherence with bilateral posterior parietal and temporal cortex, as well as beta/gamma coherence with primary sensory-motor cortex for the hands. These preliminary findings further support the value of recording cerebellar ECeG and demonstrate its potential to contribute to the understanding of cerebro-cerebellar function and dysfunction.