Mona Lisa's smile: a hypothesis based on a new principle of art neuroscience. 
The smile on Mona Lisa's face remains enigmatous and a topic of much discussion in art circle over the centuries.  In this essay the author proposes a new principle of art neuroscience or the science of aesthetics namely 'dynamism' which artists often employ to impart an illusion of movement in their art works which are essentially static.  This illusion is possibly generated through imaginative thinking which involves frontal cortical activation in the viewer's brain coupled with activation of the motion area (area V5/MT) of the viewer's visual cortex.  It is suggested that this principle of dynamism is somewhat different from the previously described concept of kinetic art.  The author hypothesizes that the great painter Leonardo da Vinci very intelligently painted the angles of the mouth of Mona Lisa's face to evoke this illusion of movement (smile) to increase the aesthetic value of this great work of art.