Fig. 1. Constraining fluctuations near stimulus-evoked response trajectories may yield robust representations.

In the cartoons (A and B), we consider the space of all possible neural responses. Each axis in the space is the response of a given neuron, and the dimensionality of the space is equal to the number of neurons in the population. Within this space, we consider the dynamical trajectories of the evoked neural responses. The cartoons show both the mean response trajectories (solid line), and two example trajectories — observed on different trials (dashed lines) — generated in response to 2 different stimuli. In (A), the variability is structured such that responses to each stimulus remain close to the mean trajectory. For contrast, in (B), the trial-by-trial fluctuations are more spread out from the mean trajectory. Accordingly, the responses to different stimuli in (B) overlap more — and thus the stimulus identity is more ambiguously encoded in the neural activities.