GSTM1 and obstructive sleep apnea syndrome: To investigate the effects of high-frequency stimulation of the habenula (Hb) on obstructive sleep apnea (OSA) induced by stimulation of the insular cortex Method. After OSA was induced by stimulating the insular cortex (Ic) with concentric stimulating electrodes at 100 Hz in rats, the Hb was stimulated at different frequencies (50 Hz, 120 Hz, 130 Hz, and 280 Hz).