When mice actively locomote, visual signals in their primary visual cortex (V1) are strongly modulated[1]. This observation has fundamentally altered conceptions of a brain region previously assumed to be a passive image processor, and extensive work has followed, aimed at dissecting the sources, recipients, and functional consequences of running-correlated modulation [2-13]. However, it remains unclear whether visual processing in primates might similarly change during active locomotion. We therefore measured V1 activity in a nonhuman primate, the common marmoset (Callithrix jacchus), while they alternated between running and stationary. In contrast to the often large increases in mouse V1 during running, conventional metrics of response in marmoset V1 were barely distinguishable during running versus not running, with some slight decreases evident. However, by leveraging large-scale recordings, analysis of the latent variables driving population activity revealed a common mechanism in both species: trial-to-trial fluctuations of shared gain modulations were present across V1 in mice and marmosets. These gain modulations were larger in mice and were often positively correlated with running; they were smaller and more likely to be weakly negatively correlated with running in marmosets. Thus, population-scale gain fluctuations of V1 reflect a common principle of mammalian visual cortical function, but there are important quantitative differences in their magnitudes and correlations with behavior that yield distinct consequences for the relation between vision and action in primates versus rodents.

When mice run, activity in their primary visual cortex (V1) is strongly modulated. This observation has altered conception of a brain region assumed to be a passive image processor. Extensive work has followed to dissect the circuits and functions of running-correlated modulation. However, it remains unclear whether visual processing in primates might similarly change during locomotion. We measured V1 activity in marmosets while they viewed stimuli on a treadmill. In contrast to mouse V1, marmoset V1 was slightly but reliably suppressed during running. Population-level analyses revealed trial-to-trial fluctuations of shared gain across V1 in both species, but these gain modulations were smaller and more often negatively correlated with running in marmosets. Thus, population-scale gain fluctuations of V1 reflect a common feature of mammalian visual cortical function, but important quantitative differences yield distinct consequences for the relation between vision and action in primates versus rodents.

When mice run, activity in their primary visual cortex (V1) is strongly modulated. This observation has altered conception of a brain region assumed to be a passive image processor. Extensive work has followed to dissect the circuits and functions of running-correlated modulation. However, it remains unclear whether visual processing in primates might similarly change during locomotion. We measured V1 activity in marmosets while they viewed stimuli on a treadmill. In contrast to mouse V1, marmoset V1 was slightly but reliably suppressed during running. Population-level analyses revealed trial-to-trial fluctuations of shared gain across V1 in both species, but these gain modulations were smaller and more often negatively correlated with running in marmosets. Thus, population-scale gain fluctuations of V1 reflect a common feature of mammalian visual cortical function, but important quantitative differences yield distinct consequences for the relation between vision and action in primates versus rodents.