Tailoring of variability in the lateral geniculate nucleus of the cat

Abstract

Variability is usually considered an unwanted component in a sensory signal, yet the visual system does not seem to filter out the noise. On the contrary, noise is 'tailored' to scale with the signal size. We show that this tailoring occurs in the lateral geniculate nucleus, preferentially in X-cells, which are the cells most likely to transmit pattern information. Tailoring the variability to the signal size may be the visual system's way of providing the right amount of variability for a signal of any magnitude at all times during the computation.

The structure and precision of retinal spike trains

“…As a result, many researchers have concentrated on estimates of the firing rate derived from averages over long time windows or multiple stimulus presentations (9,10). Measurements of response reliability have often focused on the trial-to-trial variance in this spike count: in the visual cortex, this variance is found to be greater than the mean (11,12), whereas similar experiments in the thalamus and retina have found variance-to-mean ratios both above and below one (13)(14)(15). The picture emerging from this work is that spike trains in the visual system are intrinsically stochastic; that, at best, one can determine the instantaneous probability that the neuron will fire, and that this firing rate depends in some smooth fashion on the sensory stimulus.…”

On the complex dynamics of intracellular ganglion cell light responses in the cat retina

“…The inverse effect can occur where, for example, chaotic oscillations in the G-potential are stabilized by the spike generating mechanism (e.g., Rajasekar and Laksmann 1991 investigated the possibilities of controlling chaos in Bonhoeffer-van der Pol oscillator). Such interactions might explain why the variability (noise) in spike trains in the LGN is lower than that in the retina (Levine 1994;Mukherjee et al 1994 ).…”

An analysis of visual detection by temporal probability summation

“…The relation between mean and variance function was also investigated by, e.g. Levine (1992) and Levine, Clelland, Mukherjee, and Kaplan (1996). These authors considered log-variance versus lograte plots, where rate means spike rate (recorded extracellularly in the optical tract of cats), and found that the variance increases faster for LGN-cells than for retinal ganglion cells.…”