The medical term for the surgical procedure involving the removal of the pineal gland is "pinealectomy" Its historical significance in neuroscience lies in its association with early attempts to treat psychiatric disorders and achieve spiritual enlightenment.
René Descartes famously referred to the pineal gland as the "seat of the soul" in the 17th century.
However, modern neuroscience has a much better understanding of its functions in regulating circadian rhythms and certain hormone secretion, rather than spiritual or metaphysical significance!