Layer 5 and 6b extratelencephalic neurons encode distinct sound features in auditory cortex

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cortical Circuitry

Background:

• Extratelencephalic (ET) neurons in auditory cortex layers 5 and 6b are crucial for corticofugal outputs and auditory plasticity.
• While ET neuron subtypes innervate similar targets, their distinct physiological and molecular properties suggest specialized functions.
• In vivo response properties of these ET neuron subtypes remain largely uncharacterized.

Purpose of the Study:

• To elucidate the in vivo response properties of layer 5 and layer 6b extratelencephalic neurons in the auditory cortex.
• To compare the encoding of diverse acoustic stimuli by these two distinct neuronal populations.

Main Methods:

• Utilized a projection-defined viral strategy for selective GCaMP8s expression in auditory cortex layer 5 and 6b ET neurons in mice.
• Recorded in vivo calcium activity in awake mice during presentation of various acoustic stimuli.
• Employed unsupervised clustering to analyze neuronal response motifs and tuning profiles.

Main Results:

• Layer 5 ET neurons showed predominantly sound-evoked excitation, higher sparseness, and greater reliability compared to layer 6b ET neurons.
• Layer 6b ET neurons frequently exhibited sound-evoked suppression, especially for complex stimuli, and displayed lower reliability.
• Distinct tuning profiles were observed: layer 5 favored monotonic intensity tuning and simple frequency tuning, while layer 6b showed complex tuning and stronger functional coupling.

Conclusions:

• Layer 5 and layer 6b ET neurons constitute complementary corticofugal processing streams.
• Layer 5 ET neurons convey selective acoustic feature representations, whereas layer 6b ET neurons transmit integrative corticofugal signals.
• These findings reveal distinct descending channels that enrich cortical control over subcortical auditory processing.