Question

Which of the following is true about decorticate rigidity?

• A. Removal of cerebral cortex and basal ganglia
• B. Flexion of lower limbs and extension of upper limbs
• C. Rigidity is less pronounced than decerebrate rigidity
• D. None of the above

Hint:

Intact basal ganglia mean milder tone than in the decerebrate state.

Answer 1

The Correct Option is C

Step 1: Decorticate rigidity is produced by removing the whole cerebral cortex but leaving the basal ganglia intact. So option (a), which says basal ganglia are also removed, is wrong.
Step 2: The posture is characterized by flexion of the upper extremities at the elbow and extension of the lower extremities. Option (b) reverses this and is therefore wrong.
Step 3: The flexion results from rubrospinal tract excitation of flexors in the upper limbs, with hyperextension of the lower limbs.
Step 4: Because the basal ganglia remain intact, the decorticate animal does not develop the intense hypertonia seen in decerebrate rigidity. Hence the rigidity is less pronounced than decerebrate rigidity, making option (c) correct.