If somebody says, "I feel sleepy," then another may say, "So am I." However, if the first statement is negative, can neither be used in replacement of so? If not, how should the second statement be constructed?
Saying "So am I" is just like saying "I am so," right? I just didn't think that neither can be used since it's a conjunction unlike so which is an adverb in this case so I don't know if it's ok to use "Neither am I" in formal writings.