Beta rhythms play a role in synaptic plasticity.

Zanos, S., Rembado, I., Chen, D., & Fetz, E. E. (2018). Phase-Locked Stimulation during Cortical Beta Oscillations Produces Bidirectional Synaptic Plasticity in Awake MonkeysCurrent Biology.

Super-cool paper by Andreas Nieder and crew.  Frontal-parietal beta synchrony encodes the most recent numerical input.  Theta synchrony distinguishes between different numerosities held in working memory.  The spiking of mixed-selectivity neurons multiplexed both task-relevant and irrelevant stimuli but they were separated in different phases of theta oscillations.  Powerful support that neural oscillations functionally organize spiking activty.

Jacob, S. N., Hähnke, D., & Nieder, A. (2018). Structuring of Abstract Working Memory Content by Fronto-parietal Synchrony in Primate CortexNeuron99(3), 588-597.

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.

More evidence for mixed-selectivity in the cortex.  This time with voxels in the human brain.

Jackson, J., & Woolgar, A. (2018). Adaptive coding in the human brain: Distinct object features are encoded by overlapping voxels in frontoparietal cortex. Cortex.

Read more about mixed selectivity:
Rigotti, M., Barak, O., Warden, M.R., Wang, X., Daw, N.D., Miller, E.K., & Fusi, S. (2013) The importance of mixed selectivity in complex cognitive tasks. Nature, 497, 585-590, doi:10.1038/nature12160. View PDF »        

Fusi, S., Miller, E.K., and Rigotti, M. (2016) Why neurons mix: High dimensionality for higher cognition.  Current Opinion in Neurobiology. 37:66-74  doi:10.1016/j.conb.2016.01.010. View PDF »

Enhanced prefrontal-hippocampal spike-LFP coupling during learning of a spatial strategy (but not other strategies).

Negrón-Oyarzo, I., Espinosa, N., Aguilar, M., Fuenzalida, M., Aboitiz, F., & Fuentealba, P. (2018). Coordinated prefrontal–hippocampal activity and navigation strategy-related prefrontal firing during spatial memory formationProceedings of the National Academy of Sciences, 201720117.

A computational model of visual categorization in cortex that has properties similar to our lab’s results.  It must be true.

Abe, Y., Fujita, K., & Kashimori, Y. (2018). Visual and Category Representations Shaped by the Interaction Between Inferior Temporal and Prefrontal CorticesCognitive Computation, 1-16.

Big-ass survey of cortex by Gray and crew:

Dotson, N. M., Hoffman, S. J., Goodell, B., & Gray, C. M. (2018). Feature-Based Visual Short-Term Memory Is Widely Distributed and Hierarchically OrganizedNeuron.

Nice paper by Bressler and colleagues showing that top-down influences on visual cortex are mediated by beta-band oscillations.

Richter, C. G., Coppola, R., & Bressler, S. L. (2018). Top-down beta oscillatory signaling conveys behavioral context in early visual cortex. Scientific reports, 8(1), 6991.

Further reading on beta oscillations mediating top-down processing:
Buschman, T.J. and Miller, E.K. (2007) Top-down versus bottom-up control of attention in the prefrontal and posterior parietal cortices. Science. 315: 1860-1862  View PDF »

Bastos, A.M., Loonis, R., Kornblith, S., Lundqvist, M., and 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.  View PDF


Nice result from Buschman Lab.  Error-correcting dynamics introduce bias into working memory while reducing noise.

Error-correcting dynamics in visual working memory
Matthew F Panichello, Brian DePasquale, Jonathan W Pillow, Timothy Buschman

The Department of Brain and Cognitive Sciences at MIT award Earl Miller the 2017 Award for Excellence in Graduate Teaching.