AI Insight
Researchers used two-photon calcium imaging in mice to investigate how different excitatory neuron populations in the primary auditory cortex represent sounds in the presence of background noise. They found that superficial layer 2/3 neurons showed strong noise-dependent responses, while deeper layer 5 neurons, particularly intratelencephalic (IT) neurons, maintained more stable, noise-invariant representations of sounds. This reveals a functional division where deep cortical layers preferentially carry noise-resistant sound information that can support perception in noisy environments.
Why it matters
Understanding how the brain filters out background noise to recognize important sounds could inform development of better hearing aids and cochlear implants. This research may also help explain why some individuals struggle more than others with hearing in noisy environments and could guide therapeutic approaches for auditory processing disorders.
Understand the Science
by Tomas Suarez Omedas, Ross S. Williamson
Neurons in the auditory system must represent behaviorally relevant sounds in the presence of background noise (BN) to support noise-invariant perception and behavior. Although the primary auditory cortex (ACtx) has been implicated in constructing noise-invariant representations, it remains unclear which excitatory subpopulations within ACtx carry out this transformation from noise-dependent to noise-invariant coding. To address this, we presented pure tones with and without continuous BN to head-fixed mice and used two-photon calcium imaging to record sound-evoked activity from three major excitatory subpopulations in ACtx: layer (L)2/3 intratelencephalic (IT) neurons, L5 IT neurons, and L5 extratelencephalic (ET) neurons. L2/3 IT neurons exhibited strong noise dependence at the level of single-neuron responses, pairwise interactions, and population representations. In contrast, deep-layer pathways showed greater noise invariance, with L5 IT neurons preserving stable representations most consistently and L5 ET neurons exhibiting more limited invariance at the population level. These findings reveal a functional division of labor in ACtx, in which superficial neurons remain noise-dependent and deep-layer broadcast pathways, particularly L5 IT, preferentially carry noise-invariant representations, suggesting that excitatory subpopulations contribute differentially to the construction and propagation of noise-invariant codes.
Source: Noise-invariant representations of sound emerge along the canonical cortical hierarchy