Functional Organization of the Cuneocerebellar Tract in the Cat

H olmqvist , B., O. O scarsson and I. R osén . Functional organization of the cuneocerebellar tract in the cat. Acta physiol. scand. 1963. 58. 216–235. — The experiments were performed on unanesthetized, decerebrated, and decerebellated cats with the cord transected at C3 except for the dorsal funiculi. Mass discharges were recorded from the dissected restiform body and unit recording was made from axons. It is shown that the cuneocerebellar tract contains two subdivisions: one consists of neurones monosynaptically activated by group I muscle afferents from one or a few muscles, the other of neurones disynaptically activated from cutaneous afferents. The latter subdivision contains three subgroups: a) Units activated both on movement of hairs and pressure on skin. These units receive disynaptic excitation from high threshold muscle afferents in addition to the excitation from cutaneous afferents. b) Units activated exclusively from pressure receptors in pads. c) Units activated exclusively from hair receptors. It is concluded that the cuneocerebellar tract and the dorsal spinocerebellar tract have a similar organization and are largely equivalent as channels for information from forelimbs and hindlimbs respectively. A notable difference is that the synaptic linkage to the exteroceptive subdivision is disynaptic in the cuneocerebellar tract and monosynaptic in the dorsal spinocerebellar tract. — The demonstration of a gracilocerebellar tract by G ordon and S eed (1961) has been supported.