The Midbrain / Mesencephalon

Tectum - Tegmentum

Major components of Midbrain

• Tectum (dorsal region) — tic tac toc

• Tegmentum (ventral region)

Tectum

• “roof” of Midbrain & contains :

  • Superior Colliculus

  • Inferior Colliculus

Superior Colliculus

• Functions :

  — Process & integrate sensory info : visual

  → To coordinate hand movement

  → To coordinate eye movement (for gaze shifts) !main!

Inferior Colliculus

• Functions :

  — Process & integrate sensory info : auditory

  → To filter sounds & initiate wakefulness in response to certain sounds

  → To determine location of sounds !main!

Tegmentum

• Contains :

  • rostral region of Reticular Formation

  • nuclei for two Cranial Nerves

  • Cerebral Peduncle

  • Substantia Nigra

  • Ventral Tegmental Area (VTA)

Cerebral Peduncle

— fiber tracts output from cerebrum to pons, medulla, spinal cord

CP = connection ∴ connect Cerebellum → Spinal Cord & Cerebrum

Substantia Nigra

— produce Dopamine

— ouput to Basal Ganglia

— regulate initiation of voluntary movement

— spatial learning & reward processing

Ventral Tegmental Area (VTA)

— produce Dopamine

— reward processing & memory & motivation & learning

Brainstem

• includes Pons, Medulla, Midbrain