Magnet Reaction

 

 

 

 

 

Sherrington’s classic decerebrate rigidity experiments

Author: Charles Scott Sherrington
Paper:

• On the spinal animal (1897)
• Decerebrate rigidity, and reflex coordination of movements 

 

 

 

 

Decerebrate Rigidity

 

Sherrington showed that:

·         Transection of the brainstem below the red nucleus → extensor rigidity

·         Reflexes become exaggerated

·         Limbs show strong tonic extension to stimuli (basis of magnet reaction)

 

 

 

 

 

Magnet Reaction 

 

Magnet reaction (in decerebrate rigidity)

Definition:
When a stimulus is applied to the sole of the foot, the limb shows strong extension and seems to stick to the stimulus, as if attracted by a magnet.

How it is tested

• Examiner presses or strokes the sole
• The leg extends forcefully
• The limb may follow the stimulus → appears "magnet-like"

This happens because of:

• Hyperactive extensor reflexes
• Loss of cortical inhibition
• Overactivity of vestibulospinal pathways

 

 

 

 

 

Snapshot