Figure 6. Mediolateral gradient of neural drive to the parasternal intercostal muscles.

Data from recordings in medial and lateral portions of the second parasternal intercostal space for five subjects. A, the duration of the phasic inspiratory activity is indicated relative to total inspiratory time ((T_I−T_O)/T_I percentage), shown as mean ± s.e.m.B, data for the mean (± s.e.m.) inspiratory peak firing rate at the medial and lateral locations. There was no difference in the onset of activity, or the discharge frequency of motor units recorded from the two locations in the second parasternal intercostal. C, the percentage of total units with tonic activity, recorded from medial and lateral portions of the second parasternal intercostal space. The occurrence of tonic activity was similar at the two sites.