 
Summary: IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. IT31, NO. 4, JULY 1985 461
Information Capacity of the Hopfield Model
YASER S. ABUMOSTAFA AND JEANNINEMARIE ST. JACQUES
AbstractThe information capacity of general forms of memory is
formalized. The number of bits of information that can be stored in the
Hopfield model of associative memory is estimated. It is found that the
asymptotic information capacity of a Hopfield network of N neurons is of
the order N3 b. The number of arbitrary state vectors that can be made
stable in a Hopfield network of N neurons is proved to be bounded above
by N.
I. INTRODUCTION
I N CONTRAST to the standard model for memory,
where the amount of information storage is an explicit
quantity, the information capacity of certain models of
associative memory is a debatableissue.Associative mem
ory is a plausible model for biological memory, where a
large number of simple connected building blocks (neu
rons) act individually in an apparently random way, yet
collectively constitute an organ that does a specific com
plicated task in a robust manner. Apart from this biologi
