Pronoun problem

pronoun problem

The passage below is from ‘the Blank Slate’ by Steven Pinker.

http://evolbiol.ru/blankslate/blankslate.htm

They use words, a grammar, and even phonological rules that combine meaningless gestures into meaningful signs, just as phonological rules in spoken languages combine meaningless sounds into meaningful words. Spoken languages, moreover, are partly modular: the representations for words and rules can be distinguished from the input-output systems that connect them to the ears and the mouth. The simplest interpretation, endorsed by Petitto and her colleagues, is that the cortical areas recruited in signers are specialized for language (words and rules), not for speech per se. What the areas are doing in deaf people is the same as what they are doing in hearing people.

I'd like to ask what the underlined 'them' stands for.
It seems to refer to 'the representations' in a sense, but it also seems to stand for 'words and rules' in another.

Hope for your replies.

Regards.