Plaut and McClelland (2010) and Quian Quiroga and Kreiman both challenged my characterization of localist and distributed representations. They also challenged the biological plausibility of grandmother cells on conceptual and empirical grounds. This reply addresses these issues in turn. The premise of my argument is that grandmother cells in neuroscience are the equivalent of localist representations in psychology. When defined in this way, grandmother cells are biologically plausible, given the neuroscience to date. By contrast, the neurophysiology is shown to be inconsistent with the distributed representations often learned in existing parallel distributed processing (PDP) models, and it poses a challenge to PDP theories more generally. (Contains 1 figure and 2 footnotes.)