Neural Sensory Processing Group

The dynamical regime of sensory cortex: stable dynamics around a single stimulus-tuned attractor account for patterns of noise variability
Neuron (2018)
G Hennequin, Y Ahmadian*, D B Rubin*, M LengyelŦ, and KD MillerŦ


Correlated variability in cortical activity is ubiquitously quenched following stimulus onset, in a stimulus-dependent manner. These modulations have been attributed to circuit dynamics involving either multiple stable states («attractors») or chaotic activity. Here we show that a qualitatively different dynamical regime, involving fluctuations about a single, stimulus-driven attractor in a loosely balanced excitatory-inhibitory network (the stochastic «stabilized supralinear network»), best explains these modulations. Given the supralinear input/output functions of cortical neurons, increased stimulus drive strengthens effective network connectivity. This shifts the balance from interactions that amplify variability to suppressive inhibitory feedback, quenching correlated variability around more strongly driven steady states. Comparing to previously published and original data analyses, we show that this mechanism, unlike previous proposals, uniquely accounts for the spatial patterns and fast temporal dynamics of variability suppression. Specifying the cortical operating regime is key to understanding the computations underlying perception.

On the cover: The variability of cortical responses reveals fundamental properties of the dynamics of the underlying circuit. In this paper, we use patterns of stimulus-dependent variability in visual cortex to identify specific circuit mechanisms that generate and control response variability. The cover image is a photograph of a so-called «Chladni pattern»: as a sound makes a metal plate vibrate, high- and low-variability regions of the plate are revealed as regions repelling and attracting small grains of rice. Much like in the cortex, patterns of variability arise as an interplay between the «stimulus» (the sound) and the dynamics of the medium (the plate). Photograph by Gergő Orbán, with help from Miklós Vass, Máté and Dávid Lengyel. Artwork by Guillaume Hennequin.