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Mapping the functional organization of the superior colliculus in African mole-rats

Alireza Saeedi1, Pascal Malkemper1

1 Mapping the functional organization of the superior colliculus in African mole-rats

The superior colliculus (SC) is a highly conserved region of the mammalian midbrain that plays a crucial role in organizing and controlling sensory-guided behavior. The SC is controlling essential innate behaviors such as reorienting an organism toward objects of interest, arrest, and initiating escape or capture. The SC is organized into distinct layers. In most mammals, such as mice, rats, and monkeys, thick superficial layers process visual information related to motion and orientation, while the deep layers are known to be motor layers receiving multisensory information such as auditory and somatosensory signals [1, 2]. However, little is known about the functional organization of the SC in mammals with a degenerated visual system, as it is found in many fossorial rodents.  African mole-rats are subterranean rodents that spend their entire life in dark underground burrow systems with minimal visual information [3]. Anatomical tracing studies have shown that the superficial layers of the mole-rat SC that receive input from the retina are severely reduced [4]. This suggests that the functionality of SC might have evolved differently in mole-rats. In this study, we perform acute electrophysiological recording from the mole-rat SC to investigate its laminar functional circuitry and potential role in integrating multimodal sensory information. In the first experiment, we recorded 1010 single units from one mole-rat using a Neuropixels probe and tested responses to visual and auditory stimuli. 346 neurons were recorded from SC, and we found that about 13.5% of them responded to presented stimuli. Our preliminary results suggest the existence of multimodal encoding neurons in mole-rat SC, which respond to both visual and auditory stimulation. As SC receives input from different sensory organs, testing other stimulus modalities is needed to fully understand the functional organization of SC. Therefore, we plan to integrate air puff and olfactory stimulus into our study to reveal the functionalities of SC cells. References

  1. Basso, M.A. and P.J. May, Circuits for action and cognition: a view from the superior colliculus. Annual review of vision science, 2017. 3: p. 197-226.
  2. Wheatcroft, T., A.B. Saleem, and S.G. Solomon, Functional organisation of the mouse superior colliculus. Frontiers in neural circuits, 2022. 16: p. 792959.
  3. Burda, H., et al., Are naked and common mole-rats eusocial and if so, why? Behavioral Ecology and Sociobiology, 2000. 47: p. 293-303.
  4. Němec, P., H. Burda, and L. Peichl, Subcortical visual system of the African mole‐rat Cryptomys anselli: to see or not to see? European journal of neuroscience, 2004. 20(3): p. 757-768.

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