Investigation of the functional characteristics of reticulo-spinal fibers of the ventral funiculus

Abstract

Functional characteristics of single reticulo-spinal fibers of the ventral funiculi were studied at the level of the 10th thoracic segment of the spinal cord in anesthetized (with chloralose and pentobarbital) and decerebrate cats after removal of the cerebellum. The reticulospinal tract of the ventral funiculus consists of a broad spectrum of rhythmically active and "silent" fibers, divided into three groups: fibers with a high (65–110 m/sec), medium (45–60 m/sec), and low (20–40 m/sec) conduction velocity. Spontaneous rhythmic activity is more characteristic of the fibers of the last two groups. The quantitative ratio between rhythmically active and silent fibers was about twice as high in the decerebrate as in the anesthetized animals. Depending on the character of distribution of interspike intervals the spontaneous activity of the reticulo-spinal fibers of the animals of both groups could be classified in three types: I) with a uniform distribution of interval; II) with a tendency toward grouping of spikes into volleys; III) with marked grouping of the intervals. Fibers with low and medium conduction velocities more often had spontaneous activity of types I and II, while fibers with a high conduction velocity more often had activity of types II and III. The possible functional significance of the reticulo-spinal fibers of the ventral funiculi with different conduction velocities and types of spontaneous activity is discussed.