Living matter, as brain tissue, can be regarded as a kind of material, which can be studied using the tools of condensed matter physics and statistical mechanics \cite{Kasza_2007}. A universal theory of this kind of condensed matter should provide a catalogue of the generic behaviours, such as nonequilibrium phases and phase transitions \cite{Ramaswamy_2010}. Some phase transitions of active matter have successfully been described by Ginzburg-Landau theory referring there to  exotic properties which active matter can mimic,  such as superfluidity, sound modes, long-range order, and Nambu-Goldstone modes. This shows that active matter, like  condensed matter, can not only be understood by the symmetry breaking theory of Landau but can also resemble phase transitions which are only known in low-temperature physics; a remarkable capability of active matter. Other phases of active matter behave like liquid crystals where internal motion can result in the formation of emergent dynamic structures, including topological defects at which local order breaks down. Topological defects in those materials show remarkable dynamics like movements in a céilí dance fashion \cite{Doostmohammadi_2018}. Recent studies in living tissue have shown that topological defects seem to influence cell behaviour. In neural progenitor cell cultures, defects can control cell movement \cite{Kawaguchi_2017}. More drastically, it has been shown that compressive stresses induced by orientational ordering and defects in the epithelium provide a physical trigger for cell death \cite{Saw_2017}. From those findings, we can conclude that topological defects of nematic origin exist in brain tissue, and that they can probably move around.