To achieve a better understanding of the parallel information processing th
at takes place in the nervous system, many researchers have recently begun
to use multielectrode techniques to obtain high spatial- and temporal-resol
ution recordings of the firing patterns of neural ensembles. Apart from the
complexities of acquiring and storing single unit responses from large num
bers of neurons, the multielectrode technique has provided new challenges i
n the analysis of the responses from many simultaneously recorded neurons.
This paper provides insights into the problem of coding/decoding of retinal
images by ensembles of retinal ganglion cells. We have simultaneously reco
rded the responses of 15 ganglion cells to visual stimuli of various intens
ities and wavelengths and analyzed the data using discriminant analysis. Mo
dels of stimulus encoding were generated and discriminant analysis used to
estimate the wavelength and intensity of the stimuli. We find that the gang
lion cells we have recorded from are non-redundant encoders of these stimul
us features. While single ganglion cells are poor classifiers of the stimul
us parameters, examination of the responses of only a few ganglion cells gr
eatly enhances our ability to specify the stimulus wavelength and intensity
. Of the parameters studied, we find that the rate of firing of the ganglio
n cells provides the most information about these stimulus parameters, whil
e the timing of the first action potential provides almost as much informat
ion. While we are not suggesting that the brain is using these variables, o
ur results show how a population of sensory neurons can encode stimulus fea
tures and suggest that the brain could potentially deduce reliable informat
ion about stimulus features from response patterns of retinal ganglion cell
populations. (C) 2000 Elsevier Science B.V. All rights reserved.