  We tested the hypothesis that simple exercises may significantly increase
cerebral blood flow (CBF) and/or cerebral oxygenation. Eighteen subjects
ranging in age from nineteen to thirty nine participated in a four-stage study
during which measurements of end tidal CO_2 (EtCO2 - by capnometer) and local
brain oxygenation (by near-infrared spectroscopy (NIRS) sensor) were taken. The
four stages were 1) baseline, 2) breathing exercises, 3) solving an arithmetic
problem, and 4) biofeedback. During the breathing exercises there was a
significant increase in EtCO2 indicating a significant increase in global CBF.
The increase in global CBF was estimated on the basis of a theoretical model.
During the arithmetic and biofeedback tasks there was a significant increase in
the local (Fp1) oxygenation, but it varied between the different participants.
The results may lead to new clinical applications of CBF and brain oxygenation
monitoring and behavioral control. We foresee future more detailed
investigations in the control of CO2 in brain circulation in specific regions
of the brain involved in cognition and memory.
