Figure 3. Behavioral and neural signatures of variability.

. (A) Zebrafinches sing to conspecifics of the opposite sex (directed song) as well as in isolation (non-directed song). While only small acoustic differences are evident between these contexts, the underlying neural activity shows striking variability⁷². Adapted with permission from Hessler and Doupe⁷². (B) Head-fixed mice on a spherical treadmill spontaneously alternate between a stationary state and locomotion. Responses to identical visual stimuli result in approximately two-times greater response when the mouse is running. Without quantification of behavioral state, this would appear as unexplained variance^20,72. Adapted with permission from Niell and Stryker²⁰. (C) In recordings of monkeys performing a visual task over several hours, task performance and arousal (as measured by pupil diameter) vary slowly. This is accompanied by a slow drift in the first principal component of neural activity, evident at the population level⁷³. Adapted with permission from Cowley et al.⁷³.