Grandmothers Galore?

I've been reading some work by a mathematician who is trying to model
the internal structure of ANN's by assuming that the network consists
entirely of grandmother cells, one feature one unit. Any complex
feature represented by the network is a hierarchical combination of
these units and all of the units used for a particular feature are
logically necessary. Now, I've only read a few textbooks on ANN's, but
this strikes me as a rather unusual approach. Is it a common
simplifying assumption?

TIA,
Wendell