A neuronal link was present in the brain of a mycelial network-traveling species refereed to as tardigrades by Starfleet. The same brain pattern was also present in Paul Stamets after he engaged in eugenic manipulation to be able to engage with the network like the tardigrade.
Micropatterns in the neurons of its frontopolar cortex formed a such a link, which acted as an internal trans-dimensional portal to, theoretically, any universe accessible through the mycelial network. (DIS: "The Wolf Inside")