Table 1.

Estimated storage capacity of the monkey and rat hippocampus

	CA1			CA3			DG
	Monkey	Rat	Ratioe	Monkey	Rat	Ratioe	Monkey	Rat	Ratioe
Total cellsa	1,300	390	3.3	1,270	250	5.1	12,000	1,200	10
Active cellsb	50.1	144.3	0.35	36.2	50.5	0.72	50.4	32.4	1.56
Sparsityc	0.04	0.37	9.25	0.03	0.20	6.67	0.04	0.03	1.33
Storage capacityd	467	5	93.4	854	17	50.24	39294	951	41.32

^aEstimates (in thousands) obtained from Amaral and Lavenex (2007).

^bEstimates (in thousands) are the product of the proportion of active cells obtained here and the estimate of total cell number.

^cRatio of active cells to principal cells.

^dStorage capacity estimate for Hebb–Marr memory, $M_{\max }\le \frac{\text{ln}\left(0.5\right)}{\text{ln}\left(1-a^2\right)}$

^eRatio is presented as monkey/rat except in the case of sparsity, which is presented as rat/monkey to demonstrate more clearly how much sparser the coding in the monkey is.