Summary: LETTER Communicated by Michael Shadlen
The Effect of Correlated Variability on the Accuracy of a
L. F. Abbott
Volen Center and Department of Biology, Brandeis University, Waltham, MA 02454-
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology,
Cambridge, MA 02139, U.S.A.
We study the impact of correlated neuronal ring rate variability on the
accuracy with which an encoded quantity can be extracted from a pop-
ulation of neurons. Contrary to widespread belief, correlations in the
variabilities of neuronal ring rates do not, in general, limit the increase
in coding accuracy provided by using large populations of encoding neu-
rons. Furthermore, in some cases, but not all, correlations improve the
accuracy of a population code.
In population coding schemes, the activities of a number of neurons jointly
encode the value of a quantity. A frequently touted advantage of popula-
tion coding is that it suppresses the effects of neuronal variability. The ob-