During the late 1970s and early 1980s there was vigorous debate about the nature of visual mental imagery. One position (championed primarily by Pylyshyn, 1973, 1981) held that representations that underlie the experience of mental imagery are the same type as those used in language; the other position (which my colleagues and I supported, e.g., Kosslyn, 1980, 1994) held that these representations serve to depict, not describe, objects. The debate evolved over time... but always centred on the nature of the internal representations that underlie the experience of visualisation.

Stephen M. Kosslyn, "Mental images and the brain." Cognitive Neuropsychology 22.3-4 (2005): p. 333