Frequency domain characterizing ‘EEG-like’ signature in Octopus vulgaris

Functional analogies between cephalopod molluscs and vertebrate brains and complex cognitive abilities support the existence of sentience and some sort of primary consciousness in these invertebrates. Recent studies have revealed both evoked and spontaneous neural signals from areas of the octopus’ brain using different approaches (i.e., two-photon calcium imaging of optic lobes, OLs; Neuropixels probes in the supraoesophageal mass, SEM). EEG-like signatures characterizing neural dynamics in octopus have been reported in these studies. By using Ag/AgCl subcutaneous electrodes placed in correspondence of OLs and SEM we recorded neural signals in live – lightly sedated - Octopus vulgaris and detected Visually Evoked and Resting State Potentials. Amplitudes and frequency band powers (1-40 Hz) are compared between light-off and light-on conditions. Spectrograms and Power spectral densities show an increase in power for all the frequency spectra during the light-on condition, compared to light-off. In both cases the total power of the bioelectrical signals is mainly distributed across low frequency bands, i.e. Delta, Theta and Alpha. This is the first time a minimally invasive approach is utilized to study neural dynamics in a cephalopod brain, providing findings that reveal analogies with mammals and humans. This investigation supports the identification of hallmarks of conscious states in cephalopods.