There are certain principles relating to the neural events that lead to perceptions of the various sensory experiences (Adrian 1947; Mountcastle 1975). Touch and vision have been most thoroughly investigated, but there is good reason to believe that all other sensory experiences are dependent upon similar neuronal mechanisms. Of necessity the crucial experimental investigation of sensory experiences must be carried out on conscious human subjects, but both the design and interpretation of these experiments are dependent on the wonderful successes that have attended investigations on animal, and particularly monkey, sensory systems in the last few decades. The powerful techniques designed for precision and selectivity of stimulation have been matched by microelectrode recording from single neurons. But just as importantly there has been the success in defining the neural pathways from receptor organs to cerebral cortex and within the cerebral cortex by precise anatomical investigations.