Transneuronal degeneration results after a sudden massive loss of input from the olfactory bulb after it was removed .
Removing portions of an animal 's brain can be performed to induce transneuronal degeneration .
Transneuronal degeneration results after a sudden massive loss of input from the olfactory bulb after degeneration was removed .
Removing portions of an animal 's brain can be performed to induce transneuronal degeneration .