Sound improves neuronal encoding of visual stimuli in mouse primary visual cortex

In everyday life, we integrate visual and auditory information in routine
tasks such as navigation and communication. While concurrent sound can
improve visual perception, the neuronal correlates of audiovisual
integration are not fully understood. Specifically, it remains unclear
whether neuronal firing patters in the primary visual cortex (V1) of awake
animals demonstrate similar sound-induced improvement in visual
discriminability. Furthermore, presentation of sound is associated with
movement in the subjects, but little is understood about whether and how
sound-associated movement affects audiovisual integration in V1. Here, we
investigated how sound and movement interact to modulate V1 visual
responses in awake, head-fixed mice and whether this interaction improves
neuronal encoding of the visual stimulus. We presented visual drifting
gratings with and without simultaneous auditory white noise to awake mice
while recording mouse movement and V1 neuronal activity. Sound modulated
activity of 80% of light-responsive neurons, with 95% of neurons
increasing activity when the auditory stimulus was present. A generalized
linear model revealed that sound and movement had distinct and
complementary effects of the neuronal visual responses. Furthermore,
decoding of the visual stimulus from the neuronal activity was improved
with sound, an effect that persisted even when controlling for movement.
These results demonstrate that sound and movement modulate visual
responses in complementary ways, improving neuronal representation of the
visual stimulus. This study clarifies the role of movement as a potential
confound in neuronal audiovisual responses and expands our knowledge of
how multimodal processing is mediated at a neuronal level in the awake
brain.