1. An apparatus for categorizing objects said apparatus comprising a neural network having a plurality of cells, each cell comprising memory means for storing a state variable, said neural network further comprising a plurality of synaptic junctions, each of said synaptic junctions connecting cells of said network and having memory means for storing a synaptic strength variable and computer means to modify said synaptic strength variable in accordance with a heterocellular synaptic modification rule that includes both the passage of time and the values of the state variables of said cell and of those other cells having specific spatial locations with respect to said cell in three dimensional space.