Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - VestibVis (Visual and vestibular processing in secondary visual cortex)

Teaser

Spatial navigation requires the coordinated interaction of several cerebral tasks, including visuo-spatial processing, spatial cognition and episodic memory. While navigating within a complex environment, one constantly needs to estimate self-motion relative to the...

Summary

Spatial navigation requires the coordinated interaction of several cerebral tasks, including visuo-spatial processing, spatial cognition and episodic memory. While navigating within a complex environment, one constantly needs to estimate self-motion relative to the surroundings. Visual cues related to object motion during navigation can provide information about direction, but these cues signal a mixture of information relative to the motion of both object and observer, which may be ambiguous.
Despite evidence in primates and rodents that using visual cues in combination with vestibular information improves self-motion perception, the neuronal circuitry and cellular mechanisms supporting this multisensory representation of space remain elusive.
We are studying how mice combine visual and vestibular information with their internal representation of space and study the underlying neuronal networks, in a neuronal population at the intersection of sensory input and internal models of space.
Virtual reality (VR) environments are a key tool for this type of research, as by controlling the external, sensory information allows us to interfere with processes to build a mechanistic, causal understanding of how the brain works. One drawback of current VR systems is the lack of vestibular stimulation during navigation thus disabling the brain’s internal compass (the head-direction system). We have developed a novel VR system prototype which overcomes this fundamental limitation.

The outcome of this study is important for society because the ability to navigate within a complex environment is compromised by a range of neuronal dysfunctions. These involve damage to central brain regions, which can occur following strokes, tumours, during ageing, or in Alzheimer’s disease, which frequently leave patients experiencing spatial disorientation. A better understanding of the physiological underpinnings of the neural circuits involved in these phenomenons is a crucial step to understand what goes wrong following injury or diseases.

Our objectives were:
- to characterize the functional responses of this cell population to visual and vestibular input,
- to study their activity during spatial navigation
- to develop the appropriate novel tools to this end

Work performed

We have characterised the behaviour of layer 5 pyramidal neurons in the V2 area of the visual cortex in response to a range of visual stimuli, and in response to active and passive rotations. To achieve this goal, we have introduced a novel method to provide stimulation of the head-direction system during a spatial navigation task in a VR environment, a more natural stimulus compared to the currently used VR systems.

Final results

We have developed a VR-compatible animal platform which can both actively and passively be rotated, allowing for naturalistic engagement of the HD system. The encoding of vestibular information can be studied using passive rotations, while naturalistic navigation can be studied using active rotations. At the same time, the animal’s head remains fixed, allowing electrical or optical access to the brain.
We believe this more naturalistic engagement of the HD system in VR will be of interest for the large scientific community using VR setups to study rodent behaviour.