Table 4.

The degree of convergence and divergence of principal cell numbers in the hippocampus.

Species	GCHIL	GCCA3	CA3CA1	CA1SUB
Dog	0.041	0.165	3.044	0.694
Pig	0.166	0.144	2.686	0.513
Human	0.087	0.152	4.194	0.379
Rhesus monkey	0.048	0.061	2.599	0.421
Marmoset	0.074	0.158	1.667	0.323
Cape mole-rat	0.143	1.122	0.717	0.756
Highveld mole-rat	0.09	0.639	0.898	0.766
Naked mole-rat	0.05	0.635	0.64	0.803
Muskrat	0.072	0.302	1.526	0.452
Bank vole	0.026	0.194	1.089	0.527
C57BL/6	0.029	0.263	1.31	0.719
DBA	0.028	0.361	1.113	0.722
House mouse	0.039	0.443	1.081	0.629
Brown rat	0.047	0.231	1.013	0.993
Harvest mouse	0.022	0.228	0.942	0.697
Yellow-necked mouse	0.054	0.313	1.608	0.396
Sand rat	0.061	0.46	1.221	0.481
Hamster	0.05	0.331	1.274	0.606
Cotton rat	0.045	0.301	1.49	0.423
Sengi	0.051	0.055	3.443	0.171

Functional connectivity of the principal cell numbers in the hippocampus can be expressed as a ratio of one cell population to the next one. Convergent ratios (many cells to few cells, white in the table) apply to the granule cells to hilus cells (GCHIL), granule cells to CA3 pyramidal cells (GCCA3), and CA1 pyramidal cells to subicular cells (CA1SUB). For example, C57BL/6 has a GCCA3 convergence ratio of 0.26 that means roughly four granule cells for each CA3 cell. Divergent ratios (few cells to many cells, gray background in the table) are found for CA3 pyramidal cells projecting to CA1 (CA3CA1). For example, C57BL/6 has a CA3CA1 divergence ratio of 1.3, which means 1.3 CA1 neurons for each CA3 neuron. Note that in particular the mole-rat species do not follow the overall convergence—divergence pattern, see Discussion. For data sources see Table 1.