How might Ishi's actions following Mother's death be described as a type of symbolic death?

Even though Ishi does not physically die after Mother dies, he does experience in many ways a symbolic death. He loses his desire to remain in the living world, and so he sleeps for long periods. This sleep is much like the sleep of death because he has no concept of time passing or any memory of the time. During his waking periods, he spends most of his time following the voices of spirits rather than taking care of his own physical needs. Interestingly, his long periods of sleep also coincide with Earth's time of sleep, winter.