We are told that the strogg - that is, any stroggified creatures - have no sense of individual self, as all strogg are controlled by the Nexus (via the neurocyte implant). This effect is supposed to kick in quickly after being activated as a strogg soldier (said Hannibal medic:"...higher brain functions seem to have completely atrophied..."). The process also erases ones personality, the individual is no longer aware of his situation in any way other than intended by the Nexus. However, we see and hear the tactical units talk, and see them making tactical decisions and signaling each other - if they were on "remote control" by the same entity (the Nexus), there would be no need for them to talk or signal, the Nexus would simply relay any info directly through the neurocyte, and they would also be steered in combat, based on their "experince" feeding back to it. Also, we hear lt. Voss pleading to be killed long after his stroggification has kicked in, suggesting that he is a conscious witness to his new body trying to kill Kane and that his higher brain functions are intact, just not in control.