The SEP entry on concepts is heavily committed to an RTM functionalism characterization of concepts as mental representations. But, it makes no real mention of alternatives to this position. Are there stronger competing theories of concepts as mental representations out there?
While the following may not directly answer your question, something there may lead to one.
I suggest taking a gander at Edouard Machery's 2005 Concepts Are Not a Natural Kind; he wrote a 2011 book in this strain of thought: Doing without Concepts. I took a "Philosophy of Neuroscience" course with Machery; I wrote a final essay Concepts Contain a Natural Kind, and he graded it well (this mostly gives you a tidbit about his character).
Fauconnier and Turner's The Way We Think: Conceptual Blending And The Mind's Hidden Complexities looks very interesting to me; WP's Conceptual blending has a bit of extra content.
Grossberg's 1999 The Link between Brain Learning, Attention, and Consciousness provides a possible model of consciousness, which offers a way to separate between concepts and percepts.
Both Kant & Deleuze talk about concepts. For Kant concepts are simply that which makes Intuitions intelligible to the Understanding; they are 'empty' placeholders which when full of the stuff of Intuition they become representations: a house is a concept, my house is a representation.
Deleuze argues that concepts are the productive ideas of philosophers - it is what a philosopher have to do if he wants to philosophise.