Figure 4.

Effects of hypercapnia on MEG fields evoked by tone pattern shifts. Root mean square of differential MEG activity evoked by rare tone pattern shifts when compared with control stimuli was averaged across five subjects. A: RMS activity was averaged across all sensors at each latency from 100 ms before stimulus onset to 600‐ms poststimulus. Note the increased amplitude during the normocapnic when compared with the hypercapnic periods at all latencies. B: Activity in each gradiometer channel was averaged between 100 and 500 ms after tone onset. Note the increased amplitude during the normocapnic when compared with the hypercapnic periods at all 204 sensors. The difference between normocapnic and hypercapnic activity was highly significant (see text).