MAPPING SENSORY SPECIALIZATIONS TO LIFE UNDERGROUND: ELECTROPHYSIOLOGICAL RECORDINGS FROM THE MOLE-RAT MIDBRAIN

The sensory systems of animals are shaped by the specific demands and constraints of their ecological niches. Subterranean mammals represent an extreme adaptation, as they live in dark, acoustically constrained tunnel systems throughout their lives. While the peripheral sensory specializations of these species have been well characterized, little is known about how different sensory modalities are represented in the brain.
We focused on the midbrain tectum, a key area for multisensory processing across vertebrates, to examine how visual and auditory information is processed in the African mole-rat. Using Neuropixels probes, we recorded single-unit activity from the superior colliculus (SC), inferior colliculus (IC), and surrounding cortical and subcortical structures, including the periaqueductal gray (PAG). In the SC, we found that auditory-evoked spiking responses occurred across all layers, while visual responses were weaker and limited to the superficial layers. We also identified multimodal neurons in the SC that responded to both visual and auditory stimuli. In contrast, neurons in the IC and PAG were exclusively responsive to auditory stimulation.
In summary, we established a methodological foundation for future investigations of sensory processing in subterranean mammals. Additionally, we observed consistent patterns that suggest modality-specific organization, including a predominance of auditory responses, reduced visual responsiveness, and signs of multisensory integration in subcortical structures. Notably, these findings contrast with surface-dwelling rodents such as mice, in which visual processing is more prominent in the superior colliculus. These results demonstrate that the adaptations to a subterranean environment in mole-rats are also reflected in their midbrain sensory organization.