n. an interaction observed between the center and the surround regions of receptive fields, particularly those of visual, photoreceptor cells and somatosensory neurons. When the center of a receptive field is stimulated, it elicits an opposite response in that of the surrround or periphery. This causes some neurons to depolarize at the center or to hyperpolarize at the surround, while other neurons exhibit exactly the opposite reaction. See on response. Also off reponse.