Here's a non-paywalled article from a few years earlier where this technique was developed: "Working Memory Modulates Glutamate Levels in the Dorsolateral Pref

Here's a non-paywalled article from a few years earlier where this technique was developed: "Working Memory Modulates Glutamate Levels in the Dorsolateral Prefrontal Cortex during 1H fMRS" (2018) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5845718/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5845718/ > "We interpret elevated glutamate levels during working memory task performance to reflect increased metabolic activity and excitatory neurotransmission driven by working memory-related demands." Practically, it might be beneficial to take cognitive breaks before exhaustion sets in, as well as improve blood flow and oxygen delivery - i.e. get up, walk around, drink some water, meditate for a few minutes etc. on a regular basis. I imagine a full eight hours of solid sleep is needed for a complete return to baseline, although vivid dreams might interfere with recovery.