The author does not suggest that “most” cognition depends on independent modules located in different parts of the brain. In fact, the author questions the modular theory of mind and suggests it might not be correct.

Actually, the modular theory of mind is compatible with the view that parts of the brain that are not engaged in a specific cognitive task might still use oxygen. The modular theory would simply say that after we subtract the baseline oxygen use from the oxygen use during a cognitive task, the remaining difference is associated solely with the cognitive task. This doesn’t imply that other parts of the brain have “close to zero” oxygen use.”

This is supported, because if it were not true, the “subtractive method” underlying an fMRI would not work. fMRIs depict “differential rate of oxygen use.” There’s a baseline level of use throughout the brain. This level is subtracted from the oxygen use during a cognitive task. The resulting difference, after subtracting the baseline, is represented in a brain scan by areas that “light up.” In order for areas to light up, those areas must be using oxygen at a higher rate than the rest of the brain.

The author doesn’t suggest that the baseline measurements of oxygen use show regions of the brain with “high metabolic activity at all times.” Perhaps there’s only low or medium metabolic activity at the baseline; we have no reason to think otherwise.

The author never suggests that brain scans during anger will show several different regions with metabolic activity. It’s possible brain scans will show only one part lit up; the author would suggest that this doesn’t indicate anger comes from only that part of the brain. Anger might still involve other areas of the brain even if only 1 part lights up.