Somatotopy of mechanosensory neurons in the stellate ganglion of the squid. ©CrookLab
A new manuscript from the lab was posted this week on Biorxiv, the preprint server for Biology, titled “Somatotopic organization of mechanosensory afferents in the stellate ganglion of the squid, Euprymna”. This study describes the first clear evidence for somatotopic arrangement of sensory neuronal cell bodies in a cephalopod ganglion, and describes also the first published report of live calcium imaging of mechanosensory activity in cephalopods. Cephalopod neurons have been exceptionally hard to characterize with standard electrophysiology techniques due to their small size. In this study, calcium dye injected into the stellate ganglion in situ allows for observation of firing of individual neurons in response to touch on distinct areas of the mantle, which is innervated by the stellar nerves emanating from the ganglion. Along with retrograde tracing from individual stellar nerves, the live calcium imaging data demonstrates clear somatotopy of mechanosensory neuron cell bodies in the stellate ganglion. This is the first functional evidence for somatotopy in any cephalopod and the first identification of a neuronal subtype through functional imaging. Funding to our lab from the Frontiers Group of the Allen Foundation is allowing our lab to continue to refine these techniques, to apply to octopus arms and other neuronal tissues.