# The Geometry of Layer 2/3 Cortical Sound Processing in Slow Wave Sleep

## TL;DR

This study explores how sound processing in the brain changes during sleep, finding that while sound representations are preserved, intermittent disconnections occur.

## Contribution

The study reveals that sleep preserves sound representation geometry but introduces intermittent sensory disconnections through coordinated neural modulations.

## Key findings

- Sleep dampens sound responses but preserves sound representation geometry distinct from spontaneous activity.
- Response dampening is coordinated across neurons and varies during sleep, with failures more common during high spindle-band activity.
- Sensory disconnection during sleep occurs intermittently, suggesting alternating surveillance and internal processing.

## Abstract

During wake, sound‐evoked and spontaneous neural activity of the auditory cortex evolves in distinct subspaces, whereas anesthesia disrupts sound responses and merges these spaces. To evaluate if similar modifications of sound representation geometry explain sensory disconnection during sleep, large neural populations of the mouse auditory cortex are followed across slow‐wave sleep and wakefulness. It is observed that sleep dampens sound responses but preserves the geometry of sound representations such that they remain separate from spontaneous activity. Moreover, response dampening is strongly coordinated across neurons and varied throughout sleep, spanning from fully preserved response patterns to population response failures on a fraction of sound presentations. These failures rarely occurred in wakefulness and are more common during high spindle‐band activity. Therefore, in sleep, the auditory system preserves sound feature selectivity up to the cortex for detailed acoustic surveillance but concurrently implements an intermittent gating mechanism leading to local sensory disconnections.

Sleep is associated with a sensory disconnection whose mechanisms remain elusive. Large neuronal population recordings in the auditory cortex revealed that, in NREM sleep, the neural code for sounds is highly similar to wakefulness, but coordinated modulations of neuron responsiveness intermittently disconnect the local cortical networks from sensory information. This suggests an alternation between surveillance and internal processing in sleep.