Tickling and the Brain By Dr Silvia Helena

Tickling and the Brain By Dr. Silvia Helena Cardoso Please, see comments on each slide 1 1

Tickling Fascinating instance of the Normal child Congenitally blind child Chimpanzee • Connection between playfulness, laughter and social bonding • Almost always produces laughter • Tickling and laughter evolved in part to help us relate to others 2

Anatomy of Tickling Brain Skin Axon Touch receptors Sensory cortex (Area that registers touch) Thalamus Spinal cord Anterior Spinothalamic Tract Nerve cell Sensory ganglion Tickling stimulates touch receptors in the skin. These receptors, when stimulated carry information in sensory neurons that goes to the spinal cord. Then this information travels up to the sensory cortex via the thalamus. 3 The sensory cortex is involved in processing information from the skin.

The big enigma of We do not laugh when we tickle ourselves, only when other people tickle us. 4

Why is it impossible to tickle ourselves? 5

Cerebellum Brain region that helps to control voluntary movement and balance Predicts the sensory consequences of movements - supplying the brain with information that reduces the sensation of touch information. 6

Charles Darwin 1809 -1882 “For tickling to be effective, you must not know the precise point of stimulation in advance” 7

. Somatosensory cortex Cerebellum When you try to tickle yourself, your cerebellum sends to your somatosensory cortex precise information on the position of the tickling target and therefore what sensation to expect. . 8

Robotic arm Experiment using robotic arms to tickle people. It is as effective as real people in provoking laughter. Subject tickling himself. He couldn’t make himself laugh. 9

f. MRI Touch’s area Somatosensory cortex Part of the brain that registers touch To compare brain activity when a subject's hand was tickled by an experimenter or by himself. f. MRI detected more neuronal activity in somatosensory cortex, when people were tickled than when they tickled themselves. Somatosensory cortex helps interpret external stimuli registered by nerve endings that sense touch. 10