Executive functioning is high-level thought found in a part of the brain called the frontal cortex (just behind the forehead).
The best way to describe this role of our brains is to think about the jobs of corporate executives. What do they do? They set goals, make decisions, solve problems, organize information, and follow through on tasks. They act quickly in a crisis and exercise impulse control (okay, some CEOs are famous for blowing their tops and aren't that great at the other things either, but let's just work with this definition...)
Before chemo (B.C.), they may have competently juggled a household, kids and work, kind of like Martha Stewart but without the designer oven. Now multitasking becomes impossible. Forget about listening to their kids while the TV is on, it's not going to happen. They may have a hard time retrieving information. Sometimes they wish they hadn't said those things to their bosses, or worse, their mothers-in-law. They have trouble making decisions, keeping track of things, and planning ahead.
Why does this happen? Because the connections between the front areas of their brains and deeper brain circuits are impaired.
How did they get impaired? Was it really the chemotherapy? The hormonal therapy? The anesthesia at surgery? The steroids? The cancer itself? A genetic predisposition? What we know is what has been documented in studies (mostly with breast cancer and lymphoma survivors). And chemotherapy appears at least partially responsible. But the drugs also could be part of a cascade of events that affect the way we think. The science is fascinating and you'll hear more about that later.
For now, look for part 3 in this series on the cognitive domains of "chemo brain." Next up: INFORMATION PROCESSING SPEED, perhaps the most common deficit of all.