A central question in sensory neuroscience is how neurons represent complex natural stimuli. This
process involves multiple steps of feature extraction to obtain a condensed, categorical representation
useful for classification and behaviour. It has previously been shown that central auditory neurons in
the starling have composite receptive fields composed of multiple features. Whether this property is
an idiosyncratic characteristic of songbirds, a group of highly specialised vocal learners, or a generic
property of sensory processing, is unknown. To address this question, we have recorded responses
from auditory cortical neurons in mice, and characterised their receptive fields using mouse ultrasonic
vocalisations (USVs) as a natural and ethologically relevant stimulus and pitch-shifted starling songs
as a natural but ethologically irrelevant control stimulus. We have found that these neurons display
composite receptive fields with multiple excitatory and inhibitory subunits. Moreover, this was the
case with either the conspecific or the heterospecific vocalisations. We then trained the sparse filtering
algorithm on both classes of natural stimuli to obtain statistically optimal features, and compared the
natural and artificial features using UMAP, a dimensionality-reduction algorithm previously used to
analyse mouse USVs and birdsongs. We have found that the receptive-field features obtained with
both types of the natural stimuli clustered together, as did the sparse-filtering features. However, the
natural and artificial receptive-field features clustered mostly separately. Based on these results, our
general conclusion is that composite receptive fields are not a unique characteristic of specialised
vocal learners but are likely a generic property of central auditory systems.