Brain fog could be caused by stressors impacting the prefrontal cortex (PFC).

Neuroinflammation drives kynurenic acid production, from kynurenine by kynurenine aminotransferase isozymes (KAT II), which blocks N-methyl-D-aspartate (NMDA) receptors, reducing the dorsolateral prefrontal cortex (dlPFC) neuronal firing needed for higher cognition.

N-acetylcysteine (NAC) works by inhibiting KAT II to reduce production of kynurenic acid.

https://medicine.yale.edu/news-article/potential-new-treatment-for-brain-fog-in-long-covid-patients/