Sensory maps and brain development the midbrain auditory nucleus had receptive fields independent of nature and intensity of the sound. Roger Sperry proposed a chemical gradient model for eye rotation and for neuronal wiring diagram. Retinal neurons and target cells had identification tags in the form of chemical gradients so that the projection of neurons would be orderly. For a topographic map of the visual world, the map first forms during neural development via molecular signals, such as chemospecific matching between molecular gradients. The molecular basis of sensory maps and brain development is a field that is being actively explored. The most recent work has
Electrical brain stimulation motor and sensory territories). EBS remains inextricably entwined with the work of Dr. Robert Galbraith Heath, Dr. Jose Delgado and Dr. Wilder Penfield. It's of interest that during cerebral localization studies, neurosurgeon Penfield could not elicit emotional reactions in humans, either by observing spontaneous epilepsy or by electrically stimulating the surface of the cerebral cortex. Neurophysiologist Dr. Jose Delgado noted a few exceptions to this rule. In contrast, EBS, via deeply implanted electrodes in localized areas of the brain (deep brain stimulation; DBS), elicited both pleasurable and aversive responses in laboratory animals and man as previously described. EBS could elicit