Flexor rigidity

AbstractUpper limb flexor postures have frequently been described as part of the consequences of primate decortication, when such animals are placed in the vertical instead of horizontal position. Flexor postures have also been said by D. Denny Brown to occur following bilateral section of the eighth cranial nerve. In the present communication a pattern of alternating flexor postures (contralateral forelimb and ipsilateral hindlimb flexion with extension and magnet reaction in the ipsilateral forelimb and contralateral hindlimb) is described after postcollicular mesencephalic hemisection. In addition, quadriflexion (flexion of all four extremities) is described following midline section of the cerebrum and mesencephalon by a cut which, commencing with, and including, the supramammillary decussation extends back far enough to include the decussation of the brachium conjunctivum. In these experiments the optic chiasm, anterior commissure and rostral two thirds of the corpus callosum have not been cut, Severance of. the decussation of the brachium conjunctivum does not appear to be a determinative factor in the resultant flexor posture.