Cerebellar‐induced Locomotion: Reticulospinal Control of Spinal Rhythm Generating Mechanism in Cats^a

Abstract

In a decerebrate cat (locomotor preparation), stimulation of a restricted region along the midline cerebellar white matter has been found to evoke generalized augmentation of postural muscle tone on a stationary surface (Asanome et al. 1998. Neurosci. Res. 30: 257-269) and "controlled" locomotion on the surface of a moving treadmill. Characteristics of cerebellar-evoked locomotion were similar to those of mesencephalic locomotor region-evoked "controlled" locomotion on the same animal. Microinjection of a neural tracer (CTb-HRP) into the lesioned stimulus site of the cerebellar white matter resulted in both retrograde labelling of cells in the fastigial nuclei, bilaterally, and anterograde labeling of fibers descending to the brain stem. These results indicated that the effective cerebellar stimulus site (cerebellar locomotor region) corresponded to the midline region of the hook bundle of Russell (Rasmussen, A. T., 1933. J. Comp. Neurol. 57: 165-197), through which crossed fastigioreticular, fastigiovestibular, and fastigiospinal fibers pass. In this study, contribution of reticulospinal systems to the control of cerebellar-evoked locomotion was extensively studied. By stimulating the cerebellar locomotor region and the MLR in the same animal, a majority of antidromically identified pontomedullary reticulospinal cells were synaptically activated. The results of the present study demonstrated that fastigial cells with crossed fastigioreticular fibers and reticulospinal fibers play a crucial role in the control of posture and locomotion in the locomotor preparation.

Neuronal Basis of Crossed Actions from the Reticular Formation on Feline Hindlimb Motoneurons

“…Activation of commissural neurons by reticulospinal neurons will be expected under all of the conditions when the reticulospinal tract neurons are activated, e.g., during locomotion induced by stimuli applied in the hook bundle of Russel or the cuneiform nuclei (Orlovsky, 1970;Shefchyk and Jordan, 1985;Jankowska and Noga, 1990;Mori et al, 1998). During locomotion in intact animals, reticulospinal neurons show phasic bursts (Drew et al, 1986).…”

“…Lamina VIII interneurons constitute the main group of neurons forming synaptic contacts with contralateral motoneurons (Scheibel and Scheibel, 1966;Harrison et al, 1986;Alstermark and Kummel, 1990;Hoover and Durkovic, 1992). Recently, some commissural neurons (including lamina VIII neurons) were found to be excited by stimuli applied in the pontomedullary reticular formation (RF), the mesencephalic and cerebellar locomotor regions from which reticulospinal neurons are activated (Jankowska and Noga, 1990;Matsuyama and Mori, 1998;Mori et al, 1998), or both. Neurons located in lamina VIII at some level in the lumbosacral enlargement have thus been considered very strong candidates for mediating any crossed disynaptic reticulospinal actions on motoneurons but are not the only candidates.…”

Central Mechanisms Underlying Fish Swimming

“…Also, in the cat some medullary reticulospinal neurons fired tonically during fictive locomotion [Mori et al, 1998]. When a fish swims straightforward, we assumed that spinal CPGs are activated bilaterally by tonic drives resulting from spike trains from Nflm neurons, leading to symmetric tail beats.…”

A model of cerebrocerebello-spinomuscular interaction in the sagittal control of human walking

“…These locomotor regions both strongly recruit vestibulospinal, reticulospinal and other direct spinal efferent pathways (Shik and Orlovsky 1976). A parsimonious proposition is that the cerebellar and midbrain locomotor regions can each drive and potentially modulate a spinal locomotor control system consistent with previous suggestions (Grillner 1975;Mori et al 1998Mori et al , 1999Kandel et al 2000;Shik and Orlovsky 1976). (4) Tonic stimulation of frog spinal cord demonstrates synergistic patterns of muscle activities (Tresch et al 1999;Cheung et al 2005;d'Avella et al 2003;d'Avella and Bizzi 2005).…”

“…Several investigations (Ivanenko et al 2004, Davis and Vaughan 1993Olree and Vaughan 1995) have used factor and principal component analysis, and nonnegative matrix factorization to decompose to such activity into a combination of four or five principal waveforms, most of which have only modest, but not zero temporal overlap. (2) Experimental observations support a spinal locus for important rhythmic locomotor EMG pattern generation in humans (Dimitrijevic et al 1998;Grasso et al 2004;Calancie et al 1994;Dietz and Harkema 2004) often in response to tonic electrical stimulation (Dimitrijevic et al 1998). (3) Experimental stimulation of either the cerebellum or midbrain produces rhythmic locomotor movement in both intact and decerebrate cat with vigor and frequency that increase with stimulus intensity (Mori et al 1998(Mori et al , 1999. These locomotor regions both strongly recruit vestibulospinal, reticulospinal and other direct spinal efferent pathways (Shik and Orlovsky 1976).…”