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Authors & Affiliations
Vojko Pjanovic, Jacob Zavatone-Veth, Ann Hermundstad, Paul Masset, Sander Keemink, Michele Nardin
Abstract
Uncertainty is a fundamental aspect of the natural environment. Computing with uncertain information is important not only for encoding and decoding stimuli in early sensory areas, but also for
more complex downstream inference and integration. The head-direction (HD) system is a prominent
example of this, where noisily encoded angular velocity estimates need to be inferred and integrated
into a circular attractor to keep track of the heading direction. The brain may employ sampling-based
methods to perform inference, where neural activity reflects samples from the posterior probability
distribution. However, how sampling-based methods might be linked with the attractor dynamics of
HD computations is poorly understood. Here, we derive a spiking neural network with local nonlin-
earities that performs sampling-based inference and integration of noisily encoded inputs. To this end,
we extend the sampling capabilities of a class of spiking networks --- previously constrained to sampling from Gaussian distributions --- to the exponential family distributions. We describe the precise
requirements at the network, cellular, and synaptic levels for sampling from distributions with different
moment functions, and implement sampling-based inference of latent stimuli encoded by noisy Poisson
neurons. We then use this to develop a model for the HD system, in which inferred angular velocities
are integrated on a ring-shaped prior. The model bridges sampling-based inference with attractor dynamics and provides concrete, testable predictions about correlated subthreshold voltages, short- and
long-term neural activity correlation patterns, and statistics of bump movement. Our work showcases
how sampling-based computations could be used in higher-order brain areas, paving the road for bridging probabilistic methods with attractor dynamics in spiking neural networks. Moreover, we offer an
alternative perspective on the neural computations responsible for orientation and navigation, providing
testable predictions about neural activity that can be examined in future neuroscientific experiments.