EXTENSIVE (XTENSIVE bilateral ablation of extrapyramidal areas in pre- and post-Rolandic regions of cortex in the monkey, sparing the major site of origin of the pyramidal tract in area 4, leads to an intense fixity of posture that is bilaterally hemiplegic in distribution.1-7 This dystonic reaction results from release of labyrinthine and contactual reflexes, which determine the fixed attitudes.4 Bilateral section of eighth nerves in the dystonic animal removes labyrinthine influences and leaves contactual factors unopposed, converting the hemiplegic dystonia into a posture of intense flexion of all limbs.1,2 Ablation of the cortical pyramidal projection also results in a dystonic hemiplegic posture that differs from the effects of extrapyramidal cortical ablation in the presence of signs of spasticity.1
In each of these states, the released reactions could activate the alpha motoneuron either directly or indirectly by way of the gamma efferent and muscle spindle afferent