PET Scan studies: right hemisphere is more activated when the learner is feeling depressed or stressed. Left Hemisphere is more engaged when learner is experiencing a healthy optimism about life and the future. (Jensen, Eric. Brain-Based Learning (Revised). CA: The Brain Store, 2005.)
Under acute stress, the two hemispheres of the brain become disconnected. Laughter improves creativity and problem-solving, and activates the limbic system in the brain, connecting the right and left sides. It helps you do more whole brain work. (O’Donnell, Sinara Stull. Laugh More at Work To Ease Office Stress.