Memory dynamics in sheared non-brownian suspensions

We use a rheometer to study memories in a soft material that stays far from equilibrium: a non-Brownian, neutrally buoyant suspension. This system learns the strain amplitude of oscillatory shear, forming a specific memory (memory state) that can be recalled. Inspired by a suite of simple memory tasks in neuroscience experiments, we study the dynamics of these memory states over time as the system is perturbed and its inputs are varied. Our results include how the transient response to oscillatory shear with one amplitude depends on prior oscillatory training with another amplitude, and how robust memories are to slight perturbations that are orthogonal to the oscillatory shear. Our approach demonstrates how memory in this mechanically-driven system can function similarly to an organism's perceptual memory, allowing an agent to judge a stimulus in the context of the past, or ignore a stimulus while attending to another.