The authors suggest a hybrid model of working memory.  The current focus of attention is encoded by spiking activity.  Other items held in the working memory that are not the current focus of attention are held by temporary changes in synaptic weights per the activity-silent models of Lundqvist and Stokes.

Manohar, S. G., Zokaei, N., Fallon, S. J., Vogels, T., & Husain, M. (2017). A neural model of working memorybioRxiv, 233007.

For more on activity-silent models, 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 »

Stokes, M., Buschman, T.J., and Miller, E.K. (2017) Dynamic coding for flexible cognitive control.  The Wiley Handbook of Cognitive Control, The Wiley Handbook of Cognitive Control, Edited by Tobias Egner, John Wiley & Sons, (Chichester, West Sussex, UK). View PDF

Wasmuht, D. F., Spaak, E., Buschman, T. J., Miller, E. K., & Stokes, M. G. (2017). Intrinsic neuronal dynamics predict distinct functional roles during working memorybioRxiv, 233171.

Stokes, M. G. (2015). ‘Activity-silent’working memory in prefrontal cortex: a dynamic coding frameworkTrends in Cognitive Sciences19(7), 394-405.

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.