Grandmother Cells, Symmetry, and Invariance: How the Term Arose and What the Facts Suggest

Abstract

By the late 1960s, recording from sensory pathways had shown that single neurons can be much more sensitive, selective, and reliable than had previously been recognized. The term grandmother cell started as a fanciful name for a high-level neuron that might enable us to experience complex perceptions and discriminate among them. The concept included invariance of response for changes in some variables as well as selectivity of response for others, together with the idea that these cells are created by processing at a hierarchy of levels. This chapter first outlines the discoveries that eventually led to the general acceptance that such cells really exist. It then discusses hierarchical processing, the evolution of the cortex, and ideas about the new behavioral faculties that evolved with it. Finally it points to the enormous, unaccounted for number of neurons in the cortex and suggests that this plays a major role in enhancing our ability to exploit symmetry and invariance in our environment.