CONVERSION OF PHASIC INTO TONIC MOVEMENTS BY PYRAMID LESIONS

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Abstract
The conversion of a cortically induced phasic movement into a tonic movement by dorsal root section is a true neural effect and is not related to acute conditions, the route by which the dorsal roots are approached nor vascular damage. The conversion of a cortically induced phasic movement into a tonic movement by lesions placed in the position of the ventral spinocerebellar tract as previously reported is the result of partial damage to the pyramidal system and phasic activity is not converted into that of a tonic type by damage done to the spinocerebellar tract alone nor by rubrospinal tract elimination. Cortically induced phasic movements furthermore cannot be converted into tonic movements by removal of all nor any part of the cerebellum, nor destruction of the cerebellar nuclei. Cortically induced phasic movements may be obtained even though only the pyramids remain in connection between the medulla and cortex (though the medulla be entirely transected excepting for the pyramids). Epileptiform seizures cannot be evoked from the cortex if only the pyramids are intact but can be evoked if they alone are severed. Further, the cortex of one hemisphere still retains its capacity for spinal inhibition after its corresponding pyramid has been severed.

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