ganglion

noun4

1. •
   An encapsulated collection of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber.

   • [T]he wonderfully diversified instincts, mental powers, and affections of ants are generally known, yet their cerebral ganglia are not so large as the quarter of a small pin's head. — 1871
2. •
   Any of certain masses of gray matter in the central nervous system, as the basal ganglia.
3. •
   A benign cystic tumour on a tendon sheath or joint capsule.
4. •
   A centre of intellectual or industrial force, activity, etc.