LEARNING-RELATED ACTIVITY MODULATIONS OF LAYER 5 NEURONS IN MOUSE AUDITORY CORTEX

Auditory cortex (AC) plasticity plays a central role in not only sound analysis but also learning-related aspects such as reaction to sound cues. Furthermore, within the past few years layer-specific activity patterns during learning have been identified, with some studies relating deeper layers more strongly towards decision-making than supragranular layers. We investigated the activity of layer (L) 5 AC neurons using two-photon imaging during a Go/No-go learning paradigm over two weeks. Mice were trained to lick a waterspout in response to a target tone, while withholding when the foil tone was presented. Major subclass types of L5 pyramidal neurons are intratelencephalic (IT) and corticocollicular (CC) neurons, which project to cortical and subcortical areas, respectively. Selectivity analysis of CC neurons revealed shifts in both sound and choice selectivity, with neurons generally showing more pronounced selectivity for choices than sounds. Data from intratelencephalic L5 AC neurons exhibited shifts as well, but with profiles differing from CC neurons. We prior showed that L5 CC neurons display only a subtle topographic organization when compared to other L5 neuron types (Schmitt et al., 2023, Front Neural Circuit). However, we could not detect any sharpening of topographical organization of sound-evoked activity during the learning process, suggesting that weak tonotopy of CC neurons is not related to the behavioral relevance of sounds. Overall, both sound- and behavior-related activity shifts appear to be distinct within the different neuron types of L5 auditory cortex. Our data further underlines the importance of L5 AC neurons in auditory learning and decision-making.