"I wondered what terrible thing it was that I had done"
Italian poster for film 'One Flew Over the Cuckoo's Nest'
Creative Commons AttributionItalian poster for film 'One Flew Over the Cuckoo's Nest' - Credit: lerble, Flickr

Esther Greenwood sees the horrific experience of the ECT as a punishment, which reminds us of the opening chapter of The Bell Jar where the Rosenbergs' punishment by electrocution is discussed. 

It is as if the two experiences, electrocution in the electric chair and the experience of ECT, have become one in Esther Greenwood's mind. We are made to feel that she has perhaps, during the ECT, experienced what she was speculating on in the first paragraph of the novel when she wrote, 'I couldn't help wondering what it would be like, being burned alive all along your nerves'.

The overt use of 'unmodified' ECT as a punishment occurs in Ken Kesey's 1962 novel One Flew Over the Cuckoo's Nest which is set in an Oregon asylum. The novel was later made into a film  in which Jack Nicholson plays the part of the character subjected to the unjustified ECT.