There is a growing consensus that there may be more to working memory than simple maintenance of spiking.  On a single-trial, moment-to-moment basis, memory delay spiking is sparse, not sustained.  Instead, spiking may produce changes in synaptic weights and that is where the working memories are actually stored.

Trübutschek, D., Marti, S., Ojeda, A., King, J. R., Mi, Y., Tsodyks, M., & Dehaene, S. (2017). A theory of working memory without consciousness or sustained activity. Elife, 6.

For further reading see:
Lunqvist, M., Rose, J., Herman, P, Brincat, S.L, Buschman, T.J., and Miller, E.K. (2016) Gamma and beta bursts underlie working memory.  Neuron, published online March 17, 2016. View PDF »

About the Author

The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior.