Motor Cortical Projections to Auditory and Vocal Regions Expanded in Alston’s Singing Mouse vs. Lab Mouse

A research paper published in Nature has documented a specific and substantial expansion of orofacial motor cortical projections in the Alston’s singing mouse compared with the laboratory mouse. The study examined the Alston’s singing mouse (Scotinomys teguina), which exhibits a striking vocal behaviour absent in the laboratory mouse (Mus musculus).

Researchers used bulk tracing and serial two-photon tomography to map motor cortical projections throughout the brain of the singing mouse.

They performed high-throughput DNA sequencing of more than 76,000 barcoded neurons. The analyses revealed expansion of orofacial motor cortical projections to an auditory cortical region and the midbrain periaqueductal grey, both implicated in vocal behaviours.

Analyses of projection motifs of individual orofacial motor cortical neurons showed preferential expansion of exclusive projections to the auditory cortical region in the singing mouse.

@Nature reported that the results suggest selective expansion of ancestral motor cortical projections may lead to behavioural divergence over short timescales. The paper cites references 10 and 11 linking enhanced cortical control over vocalizations to a preadaptation for human language.

The approach of comparing recently diverged species with substantial behavioural divergences can be readily generalized across other model clades to discover quantitative rules of neural circuit evolution, according to the study.

Elucidating how modifications in neural circuit architecture drive behavioural innovation remains a key challenge in neuroscience and evolutionary biology. In mammals, the neocortex is posited to play a crucial part in facilitating rapid behavioural innovations.

Although changes in long-range connectivity have been proposed to underlie such innovations, these hypotheses remained largely untested quantitatively because of the lack of high-throughput neuronal projection data at single-neuron resolution across species.

It was published in Nature. The study compared the Alston’s singing mouse to the laboratory mouse throughout its mapping of neural differences.