You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you will be given sentences in which your task is to recognize the name of the organ of the body. An organ is a collection of tissues that structurally form a functional unit specialized to perform a particular function. Although there might be several correct answers, you need to write one of them.

I have serious allergy in my left eye.
Solution: eye
Why? Eye is an organ which has been affected, hence should be tagged.

New input:  These differences make mature mice more susceptible to brain oxidative damage .
Solution:
brain