Midbrain
The midbrain was a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, alertness, and temperature regulation.

In the 22nd century, mind melds were frowned upon partly because they caused a disruption of neuroelectric impulses in the Vulcan midbrain, which could lead to the early stages of Pa'nar Syndrome. ()

In 2371, Dr. Julian Bashir implanted Bareil Antos with a positronic matrix which interfaced with his midbrain. ()

Soon after, Ptera was placed in a Vhnori cenotaph to end her life as she was dying of a tumorous lesion to her midbrain. ()

In 2373, in an imaginary scenario in which the Sacajawea had crashed causing the death of Kathryn Janeway, Kes informed The Doctor there was minimal electrical activity in Janeway's midbrain. ()

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Brain anatomy