Role of Motor Cortex in Control of Locomotion
The activity of 252 motor cortex (MC) neurons (including 70 pyramidal tract neurons) was recorded extracellularly in the cat by means of a mobile electrode during free locomotion in a box.
The activity of 89% MC neurons was modulated during locomotion. The modulation was related to the stepping movements, since it increased in one stepping phase and decreased in the next.
MC neurons were also studied while the animal moved up a flat inclined surface, walking at different speeds, with a load of 85g attached to each forelimb, when the cat had to perform snakelike movements (turns) or walk on the flat surface placed in a horizontal plane. The pattern of MC neuron activity changed little under these conditions in comparison with uncomplicated locomotion.
The activity of 68 neurons was recorded in experiments with barriers and involving locomotion on a horizontal ladder which restricted the possible paw positions along the direction of locomotion. These tasks greatly affected the MC activity.
Neither bilateral MC lesion nor tetrodotoxin inactivation hampered uphill locomotion, walking along a moving floor, or locomotion involving turns and loaded forelimbs. On the contrary, it proved to be necessary for the MC to be intact for locomotion with space linked stepping limb movements (i.e. with barriers, on a ladder) to be possible.
Bilateral destruction of the ventrolateral nucleus of the thalamus (VL) resulted in a decrease in the rhythmical modulation of MC neurons during locomotion. After VL lesion the cat could walk quite well on the horizontal surface and uphill, at various speeds, with the forelimbs loaded; it could perform turns and could walk on the moving floor. The cat proved to be incapable, however, of walking with barriers and on the ladder.
KeywordsSwing Phase Step Movement Narrow Corridor Locomotor Task Spinal Mechanism
- Armstrong, D.M., and Drew, T., 1984a, Discharges of pyramidal tract and other motor cortical neurons during locomotion in the cat, J. Physiol., 346: 461–470.Google Scholar
- Burlachkova, N.I. and Ioffe, M.E., 1978, About motor cortex nuclear specificity in organization of precision motor reaction, J. visch. nerv. deiit., 28: 475–481 (in russ.).Google Scholar
- Denny-Brown, D., 1966, The cerebral control of movement. Thomas, Springfield.Google Scholar
- Hancock, J., 1985, Motor cortical discharges and locomotion in the cat, J. Physiol. 364, 28P.Google Scholar
- Orlovsky, G.N., Severin, F.V., and Shik, M.L., 1966, The influence of speed and load on the coordinated movements during dogs locomotion, Biophisika, 11: 364–366 (in russ.).Google Scholar
- Orlovsky, G.N., and Shik, M.L., 1976, Control of locomotion: a neurological analysis of the cat locomotor system, Intern. Rev. Physiol., 10: 281–317.Google Scholar
- Palmer, C., Marks, W.B., Bak, M.J. and Pedersen, G., 1980, The activity of closely spaced motor cortical pyramidal tract projecting neurons during locomotion, Neurosci. Abstr., 6:158.Google Scholar
- Snider, R.S. and Niemer, W.T., 1961, A stereotaxic atlas of the cat brain. The University of Chicago Press. Chicago, 110 p.Google Scholar
- Stepien, I., Stepien, L. and Konorski, J., 1961, The effects of unilateral and bilateral ablations of sensorimotor cortex on the instrumental (type II) alimentary conditioned reflexes in dogs, Acta biol. exptl., 21:121–140.Google Scholar