Figure 2.

The 6‐s breath‐hold study of Subject 3 analysed using a Student's t‐test as if it were an 18‐s (a) and 30‐s (b) task. Considerable regions of significant activation (P _uncorrected < 0.0001) remain evident. c, d: Analysis of the complete time‐course of the same 6‐s breath‐hold study using the general linear model as implemented in SPM99, with motion‐correction parameters included in the model as confounds, and the task modelled with a canonical HRF convolved with a boxcar of task length 18 s (c) and 30 s (d). e: Significant activity was also seen in the short breath‐hold studies of other subjects, as demonstrated here for example in the 6‐s breath‐hold study of Subject 6, modelled in SPM99 (as described above) with a task length of 30 s. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com. Bright white replaces all color in print.]