Our dual Perspectives “debate” paper re: Does persistent spiking hold memories “in mind” (i.e., working memory):
Paper and link to opposing paper: Working Memory: Delay Activity, Yes! Persistent Activity? Maybe Not

Press release: To understand working memory, scientists must resolve this debate

Our two cents:
Surprised this became a debate.  All we are saying is that if you look at delay activity more closely (on single trials) it’s bursty. Something else (synaptic weight changes) could be helping. Adding synaptic mechanisms saves energy and confers functional advantages.
Lundqvist, M., Rose, J., Herman, P., Brincat, S. L., Buschman, T. J., & Miller, E. K. (2016). Gamma and beta bursts underlie working memory. Neuron, 90(1), 152-164.

And it leaves room for network rhythms that may underlie executive control of working memory.
Bastos, A. M., Loonis, R., Kornblith, S., Lundqvist, M., & Miller, E. K. (2018). Laminar recordings in frontal cortex suggest distinct layers for maintenance and control of working memory. Proceedings of the National Academy of Sciences, 201710323.

Lundqvist, M., Herman, P., Warden, M. R., Brincat, S. L., & Miller, E. K. (2018). Gamma and beta bursts during working memory readout suggest roles in its volitional control. Nature Communications, 9(1), 394.

Yuri Buzsaki pointed out that his lab reported that in PFC working memories are maintained by internally generated cell assembly sequences. The few persistently firing neurons were interneurons.
Fujisawa S, Amarasingham A, Harrison MT, Buzsáki G.
Nat Neurosci. 2008.

Also, the idea that synaptic weight changes help maintain working memories is not altogether new.  Goldman-Rakic suggested such a mechanism.  Her lab found that sparse firing in the PFC produces temporary changes in synaptic weights.  Importantly, if neurons firing too fast, inhibitory mechanisms kick in and you don’t get the weight changes. See:

Wang, Y., Markram, H., Goodman, P.H., Berger, T.K., Ma, J., and Goldman-Rakic, P.S. (2006). Heterogeneity in the pyramidal network of the medial prefrontal cortex. Nat. Neurosci. 9, 534–542.

But, hey, don’t take our word for it:  Look at memory delay activity on single trials and tell us what *you* see.

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. ekmillerlab.mit.edu