Maybe the attached publication by

Ma et al. (2014). Changing concepts of working memory. nature neuroscience, 17(3): 347-356

could give you some orientation?

Regards,

Klaus Blischke

Earlier work of monkey neurophysiology distinguished neuronal activities related to object and space based memory in the prefrontal cortex.

These are a few ERP studies that focus on the retrieval (or comparison) stage of change detection (including one from my lab):

Hyun, J.-S., Woodman, G. F., Vogel, E. K., Hollingworth, A., & Luck, S. J. (2009). The comparison of visual working memory representations with perceptual inputs. Journal of Experimental Psychology: Human Perception and Performance, 35(4), 1140–1160. http://doi.org/10.1037/a0015019

Ko, P. C., Duda, B., Hussey, E., Mason, E., Molitor, R. J., Woodman, G. F., & Ally, B. A. (2014). Understanding age-related reductions in visual working memory capacity: Examining the stages of change detection. Attention, Perception & Psychophysics, 76(7), 2015–2030. http://doi.org/10.3758/s13414-013-0585-z

For shameless promotion, my study looked at activity during both delay and retrieval, targeting different ERPs for these stages.

I hope that helps a little.