# Inter- and intrahemispheric sources of vestibular signals to V1

## TL;DR

The study reveals two pathways through which head motion signals from the vestibular system reach the primary visual cortex, helping maintain stable vision during movement.

## Contribution

The discovery of two distinct pathways—via the pulvinar and contralateral visual cortex—transmitting head motion signals to V1.

## Key findings

- V1 receives head movement signals from the ipsilateral pulvinar and contralateral visual cortex.
- The pulvinar encodes head movement variables like direction, velocity, and acceleration.
- The pulvinar provides a subcortical computation of head movement variables before reaching V1.

## Abstract

Information about head motion is fundamental to the visual interpretation of our environment. Indeed, head motion signals originating from the vestibular system robustly modulate activity in the visual cortex (VC). Despite this profound modulation, however, we still do not know how these signals reach the VC. Furthermore, we have only a very rudimentary understanding of what aspects of head motion are transmitted. We found that two distinct pathways deliver head motion signals to the primary VC: the pulvinar nucleus of the thalamus and the contralateral VC. These pathways provide complementary directional information about head movements, revealing how the brain integrates movement-related signals within visual circuits that might help maintaining stable vision during motion.

Head movements are sensed by the vestibular organs. Unlike classical senses, signals from vestibular organs are not selectively conveyed to a dedicated cortical area but are broadcast throughout the cortex. This distributed processing pattern reflects the fundamental role of vestibular information in contextual modulation across diverse cortical computations. Surprisingly, the routes taken by vestibular signals to reach the cortex are still largely uncharted. Here, we show that the primary visual cortex (V1) receives real-time head movement signals—direction, velocity, and acceleration—from the ipsilateral pulvinar and contralateral visual cortex (VC). The ipsilateral pulvinar provides the main head movement signal, with a bias toward contraversive movements (e.g., clockwise movements in left V1). Conversely, the contralateral VC provides head movement signals during ipsiversive movements. Crucially, head movement variables encoded in V1 are already encoded in the pulvinar, suggesting that those variables are computed subcortically. Thus, the convergence of inter- and intrahemispheric signals endows V1 with a rich representation of the animal’s head movements.