Skip to main content
. 2010 Jun 17;2:8. doi: 10.3389/fnene.2010.00008

Figure 2.

Figure 2

Theoretical curves derived from the theoretical framework in Table 1. (A) Equations 1 and 2 define contours (in red) of equal BOLD signal change in the CBF/CMRO2 plane, here illustrated for M = 8%. The contour of zero BOLD response has a slope slightly greater than 1 because of the way blood volume effects are included. (B) Equations 1, 3, and 4 define contours (in blue) of equal tissue pO2 change, calculated with the assumption that at baseline pTO2 = 25 mmHg. (C) Hypothetical CBF and CMRO2 responses to a simple stimulus are shown. These two responses define a trajectory in the CBF/CMRO2 plane, shown in (A,B) as the black curve. The points on the curve represent equal time increments in the evolving CBF and CMRO2 curves in (C). (D) The resulting BOLD and tissue pO2 responses are shown for the CBF and CMRO2 responses in (C). Note that in this example the CBF and CMRO2 responses are approximately in the ratio 2:1 (i.e., n ∼ 2), and this causes the trajectory to pass over and under the zero change contour of pTO2, leading to the complex dynamics in (D). In addition, the CBF response was constructed with a weak post-stimulus undershoot to illustrate that this can create a more pronounced undershoot in the BOLD signal. In this example the ratio of the undershoot to the peak response is only ∼8% for CBF, but ∼30% for the BOLD response.