"But I'm not aware of neurology having identified anything remotely resembling multiple cores or hyperthreading in the human or animal brain."
And yet here you sit, typing and breathing and seeing and thinking about what you're having for dinner tonight while your digestive system continues to work on lunch and your heart continues to beat.
Sounds more like a bunch of specialized hardware controllers than several general-purpose cores. If you want to do something as simple as counting while thinking about something else, the only way is to (ab)use your visual or auditory processors.
And yet here you sit, typing and breathing and seeing and thinking about what you're having for dinner tonight while your digestive system continues to work on lunch and your heart continues to beat.