Extending these molecular changes to functional outcomes, Tkacs et al. (2007) demonstrated that hypoglycemia at 2.4–2.6 mM doubled wake time to 48%, fragmented non-REM sleep, and increased Fos expression in orexin neurons from 8.7% to 37% directly linking orexin activation to heightened arousal and vigilance during energy crises. Here, FOS is linked to Hypoglycemia.