Table 2 BHIs derived from NIRS signals. Population averaged values of the BHI and of the slope of the O2Hb and CO2Hb concentration signals derived from the NIRS data (all the values are expressed in μ mol/l/s). The first and the second rows report the BHIs derived from the concentration changes of oxygenated and reduced hemoglobin, the third and fourth rows report the slopes of the time course of the concentration signals during the BH phase (all the values are expressed as mean/sd). The second column reports the first species probability error of a Student's t – test to test the BHI and the slope values against zero (i.e. against no modification induced by the BH) with a confidence level equal to 95%.