Lateralization of insular cortex activation during high and low intensity exercise

The insular cortex has been implicated as an important cortical site of cardiac regulation. It has been proposed that one insula may regulate cardiac parasympathetic activity while the other regulates sympathetic activity. Our purpose was to determine if hemispheric differences in insular activation exist for low and high intensity exercise using single photon emission computed to mography (SPECT) and magnetic resonance imaging (MRI). Four healthy men (24±2 yr) were studied during: seated rest; low intensity cycling (LIC); and high intensity cycling (HIC). For each condition, regional cerebral blood flow was measured via i.v. injection of 20mCi Tc99m-ECD (Neurolite). Individual SPECT and MRI data were aligned and percent changes in radioactivity from rest were calculated for each subject. Resting HR was 68 . During HIC (HR = 156±3 bpm), there was right insular activation (8.5±1.1%; P<0.05) with a trend for activation of the left (4.7±1.0%; P>0.05). These findings suggest that the left insula may be more involved in cardiac vagal withdrawal, while the right insula may be more involved in increased sympathetic activity during higher intensity exercise.