Clues:

The man awakes from the electroshock therapy the same way a baby is born: Does not know where he is, does not recall nor know his name, hears the sounds of a moaning woman in pain echoing in the back (which are nothing but machines), is wiped out of his identity, his job at the plant, and everything he used to be- the world as he knew it disappeared and now they (the men who performed the therapy) are like bringing him into the world again, only he is a "new person"

In *Invisible Man*, how does electroshock therapy symbolize the narrator's 'rebirth'?

That is Chapter 11 of Invisible Man and most of the elements in that chapter have symbolism. In this case, the doctor "with the new technology" suggested electroshock therapy as a radical way to deal with the man. When the treatment is given, I.M. says that he has changed into a new man "who does not even know his name". There is however, more symbolism involved which you can find out in this link.

http://www.fcps.edu/westspringfieldhs/projects/im98/im981/chap11.htm