Figure 12.

Tuning manifold concept. The firing rate distribution for Idle can be overlapping that of Reach and Hold for each unit alone (bottom and left). When plotted together (top right), the firing rates during Reach and Hold tend to fall on a manifold (dashed line) because they are correlated with each other by following a common tuning function, a common driver. However, Idle firing rates follow a different correlation pattern. Unit 1 has a higher-than-average rate and unit 2 a lower-than-average rate during Idle, so the Idle cluster (black oval) separates from the manifold.