The main goal of Zhang's lab is to address how neural circuit dynamics give rise to neural codes to represent and process uncertain information, and how these produce perception, cognition, and behavior.

Neural circuit implementation of Bayesian (causal) inference  

The brain performs Bayesian (causal) inference to interpret the world and to infer the causal relations in the world. Bayesian (causal) inference underlies a wide spectrum of perceptual and cognitive processes, learning, and memory. It is a fundamental question in computational neuroscience how neural circuits implement Bayesian (causal) inference, and how neurons represent uncertainty information. We have conducted a series of theoretical studies along this line. Using multisensory cue integration as an example of Bayesian inference, we proposed that cue integration can be achieved in a decentralized circuit composed of several coupled brain areas (Zhang et al.,  J. Neurosci., 2016; NeurIPS 2013). We also identified that opposite neurons found in multisensory areas are able to perform casual inference in information integration (Zhang et al., eLife 2019; NeurIPS 2019, 2016). Recently we are studying how the Poisson spiking variability of cortical neurons drives distributed sampling-Based Bayesian inference in cortical circuits (Zhang, bioRxiv 2022; 2020).

Neural circuit dynamics

Neuronal responses are dynamic and have large response variability. It is important to study how interactions between neurons give rise to these dynamical and variable responses. We are particularly interested in two canonical circuit dynamics used in computational neuroscience: One is Continuous Attractor Neural Network which has been widely used to explain the processing of continuous stimulus (Zhang et al., 2016; 2012); Another is the Excitation-Inhibition balanced spiking network which internally generates large response variability. We are combining the main characteristics of the two canonical networks to study how the network exploits its internally generated variability to implement sampling-based Bayesian inference.

Other research directions

  • The principle of invariant and equivariant representations in neural circuits. 

  • Biological learning and synaptic plasticity.