<prompt> Stimulation of which of the following areas of brain is experimentally used to control intractable painPeriaqueductal grey matterMesencephalonSubthalmic nucleusMedical fore brain bundle  <response>: ganongs review of medical physiology 24th edition . mesencephalic periaqueductal grayPAG is pa of descending pathway that modulates pain transmission by inhibition of primary afferent transmissiion in the dorsal horn of spinalcord PAG neurons project directly to and activate two groups of neurons in brainstem:neurons in nucleus raphe magnus and in rostral ventromedial medulla . neurons from both region project to dorsal horn and inhibit dorsal horn neuron activity. 