According to researchers from MIT and City University London, trying to retain too much information in our working memory can cause communications problems among three areas of the brain that coordinate working memory.  Synchrony–how linked together neurons in the regions of the brain are–breaks down when working memory is overloaded, and the three areas no longer work together properly.

This is new research that was not specifically focused on neurofeedback, so it does not shed light on whether using neurofeedback training to improve synchrony might therefore improve working memory.  That said, most (not all) neurofeedback practitioners already are aware of the importance of synchrony in slower brainwaves, and those who practice whole-brain training automatically include synchrony and coherence training in their work.

For more information, a summary is available at Neuroscience News, http://neurosciencenews.com/brain-synchrony-working-memory-8887/  

The actual study, published in the journal Cerebral Cortex, is available here:  https://academic.oup.com/cercor/advance-article/doi/10.1093/cercor/bhy065/4955775