On the relation of rat's external cuneate activity to global parameters offorelimb posture

USING anesthetized adult rats, we studied the relationships between the act ivity of cells belonging to the external: cuneate nucleus (ECN) and passive forelimb positions. In essence, we sought to distinguish between a represe ntation of limb position based on local limb parameters (individual joint a ngles, for example) or a representation based on more global parameters suc h as the length and the orientation of the limb axis. Using multivariate re gression analyses we found that most neurons showed strong linear relations hips with the length and the orientation of the limb axis. Relationships to individual joint angles were, instead, rather weak and in most cases not s ignificant. This result implies an extensive integration of sensory informa tion at the level of second order sensory neurons. (C) 1999 Lippincott Will iams & Wilkins.