Rhythmic patterns of motor activity after lesions of the central nervous system in man

Summary

The behaviour of the motor activity was investigated in a selected group of neurosurgical patients with various cerebral and spinal lesions, as well in a group of healthy controls. Under predetermined standard conditions electromyograms were recorded simultaneously from six muscles, and the time-voltage-integrals of the muscle action potentials were continuously recorded. In this paper rhythmic patterns of the motor activity after lesions of the central nervous system are described.

I. Rhythm With a Frequency of 03–0.8/Minute

In decerebrate states paroxysmal increases in rhythmic sequences with a frequency of 0.3–0.8/minute can occur. The amplitude always predominated on the contralateral side of the body if there was a predominantly unilateral supratentorial lesion present. The shape was characterized in typical cases by a steep rise and an almost exponential fall. A synchronous rhythm of the respiration could appear simultaneously. Other motor rhythms could also appear at the same time. With the simultaneous appearance of different motor rhythms there was clear evidence of their interaction, which corresponded to what v. Holst (1939) designated “relative co-ordination”.

II. Rhythm With a Frequency of 12–18/Minute

In decerebrate states and the apallic syndromes following decerebration rhythmic fluctuations of motor activity with a frequency of 12–18/minute can appear. The amplitudes predominated unilaterally or were changing from side to side. The shapes of the ascending and descending phases were approximately the same. This rhythm has so far only been identified during paroxysmal increases of motor activity. It is possible that this involves a motor rhythm synchronous with respiration, which can appear as a pathological phenomenon after particular lesions of the central nervous system.

III. Rhythm with a frequency of 2–4/Minute

In lesions of the central nervous system at various levels rhythmic fluctuations of the motor activity with a frequency of 2–4/minute can occur. So far they have been detected (i) m large suprasellar tumours, (ii) in decerebrate states and the apallic syndroms following them, and also (iii) in spinal lesions. Although these lesions of the central nervous system are found at widely differing levels, the rhythmic fluctuations of motor activity with a frequency of 0.3/minute are probably identical processes in view of their common features. The predominant amplitudes changed from side to side. The shapes of the ascending and descending phases were approximately the same. The predominating intensity of the rhythm can change the location, in the sense of a “change of focus”, which was first described by Jung (1941) in human tremor. In the spinal lesions the relationship between the rhythm on the right and left sides of the body corresponded to a “relative co-ordination” (v. Holst 1939). In the spinal lesions section of the posterior nerve roots does not abolish the rhythmic fluctuations. The origin of the rhythm is therefore independent of peripheral afferents and of the gamma loop; from this it appears that it cannot be regarded as a reflex phenomenon. The rhythm disappears during sleep and reappears on waking. The rhythmic fluctuations were at times pure fluctuations of tone, but at other times were related to visible movements. A synchronous respiratory rhythm can exist simultaneously. Moreover in the decerebrate state, rhythmic paroxysmal increases of motor activity with a frequency of 0.3–0.8/minute can appear at the same time, which are themselves also related to the rhythm of respiration. In view of the relation of the two different motor rhythms to the synchronous respiratory rhythms which correspond with them it follows that in these cases the respiration can be influenced simultaneously by at least two different rhythms. The 3/minute rhythm seems to be a particular basic rhythm of the motor activity which is normally inhibited by a higher integration mechanism of the central nervous system and which can appear as a manifestation of disinhibition after particular lesions of the central nervous system.