Cuneate nucleus

1. Portion of the dorsal column system that senses fine touch, vibration, position, 2 point discrimination and pressure; carries signals that allow cortex to recognize form and texture of unseen familiar objects (stereognosis)
2. Large neurons synapse at the nucleus gracilis (lower limb) and nucleus cuneatus (upper limbs) (cuneatus is lateral to gracilis)
   1. fibers cross at medulla/spinal cord interface and form the medial lemniscus which joins with main sensory nucleus of CN 5 to end at the VPL (body) and VPM (face)
      1. medial lemniscus runs in the anterior portion of the brain stem right behind the corticospinal tracts
      2. where decussation of dorsal columns forms the medial lemniscus, the tracts are called the internal arcuate fibers
   2. somatotopic respresentation in the dorsal columns is for the legs to be medial in the spinal cord, lateral at the thalamus, and medial again at the cortex
3. proprioception from the muscle spindles, Pacinian corpuscles, Ruffini’s end organs, and Golgi tendon organs are carried from the lower extremities in the lateral column from Clarke’s column to the dorsal spinocerebellar tract to the cerebellum (NOTE: lower extremity proprioception is thus NOT in the posterior columns); upper extremity proprioception DOES travel in the posterior columns through the fasciculus cuneatus before synapsing on the accessory cuneate nucleus and then going to the cerebellum