The RETINA AND olfactory bulb are organized in an orderly manner, consisting of a few major classes of neurones. Synaptic operations are well defined, and can be examined in relation to a functional context. Furthermore, the retina and olfactory bulb are very similar in their synaptic organization and operation to those neurones in the central parts of the brain, and external sensory stimuli are processed into a form that can serve as the basis for sensory perception by higher centres. Recent electrophysiological and molecular studies have revealed the detailed receptor mechanisms of the bipolar cell and mitral and tufted (M/T) cells in information processing of external sensory signals.