Here are some stock slides on the connections between augmenting human cognition and biological rhythms I used during my time in the 
MIND Lab. The talk is called "Augmenting Cognition: dynamic modulation and biological rhythms", and dates from 2005. For more work in this area, see this technical paper: 
"Broad-Spectrum Mitigation and the Cognitive Neurobiological Interface: considering biological rhythms in Augmented Cognition", 
Proceedings of Human Factors, 2006.