Comparison of neuronal activities of external cuneate nucleus, spinocerebellar cortex and interpositus nucleus during passive movements of the rat's forelimb.

In this paper we examined the neuronal activities of external cuneate nucleus, spinocerebellar Purkinje cells and interpositus nucleus during passive forelimb movements in anesthetized rats with the aim of identifying common or different patterns of activation across structures. By means of principal components analysis, we identified two main patterns of discharge which explained most of the dataset variance. One component characterized the movement-related activity of external cuneate and spinocerebellar cortical neurons, while the other reflected neuronal activity of the interpositus nucleus. We also found that both principal components were related to global forelimb kinematics but, while most of the variance of the activity of external cuneate cells and spinocerebellar Purkinje cells was explained by the limb axis orientation and orientation velocity, interpositus neurons' firing was best related to length and length velocity. This difference in the forelimb kinematics representation observed in external cuneate nucleus and spinocerebellar cortex compared with the interpositus nucleus is discussed with respect to the specific role that these structures may play also during active control of limb movements.