Biological look at smell and taste

The olfactory and gustatory senses are chemosensory responses, which operate using receptors encoded by a number of recently identified genes. Smells and tastes are represented by combinations of receptors activated by molecular-stimuli. Because the brain processes these neural representations fairly directly, they are perceived synesthetically and result in an enduring memory, unaltered by interference from later experiences. Smells and tastes are endowed with positive or negative emotional valence. This valence could be seen as an incentive to take some sort of action, depending on the approach-avoidance polarity, the result of behavior learned sensorially (smells) or determined genetically (tastes). Unconscious perception and implicit memory are significant aspects of chemosensory function.