SIGNS.

     The algorithm computes a similarity/connection matrix using the interface
     energy.  It then chooses the cluster pair with the highest connection
     strength, aggregates them, recalculates connection strengths, and then
     repeats the process.  Cluster aggregation is contingent on passing an
     interspike interval (ISI) test if SPIKES.SPIKETIMES is defined; if this
     test is not passed, the pair is not aggregated and aggregation continues.
     Aggregation stops when either (1) all 