The initial negative activity appearing at 15-18msec from stimulation of the upper extremity is thought to be generated by the thalamus.
The upper extremity or arm is a practical unit of the higher body. It consists of 3 sections, the higher arm, forearm, and hand. It extends from the enarthrosis to the fingers and contains thirty bones. It additionally consists of the many nerves, blood vessels (arteries and veins), and muscles.
Thalamus is an oval structure within the middle of your brain. It's called a relay station of all incoming motor (movement) and sensory data — hearing, taste, sight and bit (but not smell) — from your body to your brain
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