Her undeveloped frontal lobes will not mature until her mid or late twenties, she is controlled in large part by her instincts and basic emotions related to survival. She had no impulse control, is not rational, has a short attention span, and cannot understand the concept of waiting for a reward-food-that will come later. Her brain is telling her one thing: she must eat now.
Try the same experiement with a marathon runner who is just reaching the finish line. He would rather slap you in the face than try to solve a simple algebra problem. With its energy stores almost completely depleted, his brain is hoarding whatever's left for the region essential to survival: the primitive limbic brain, which operates autonomous functions, like keeping his heart and lungs opearting, and regulates basic emotions like fear. His brain has switched off the luxurious, sophisticated frontal lobe, which enables problem-solving and other higher cognitive functions that make us human, including the ability to evaluate options in order to make judgement calls. For the exhausted marathon runner, these more refined skills simply aren't as essential as the basic brain functions that will keep him alive, so they into a kind of hibernation until there is enough energy for them to spring back.
Short-term memories are processed differently in the brain than long-term memories, so people with dementia can often remember events that happened in their childhoods but have trouble recollecting what they had for breafast that day. Long-term memories are tucked away in our brains for safekeeping with strong emotional attachments tied to them, since they may be useful for survival. Short-term memories appear to be more like temporary factoids waiting to be categorized and evaluated. If importantnt, they'll be stored. If they're unimportant, they're not tagged for retention and will vanish.
Normally, the brain is able to sort through the sensor information that comes at it and prioritize what's important and what can be ignored. When this filtre mechanism doesn't work, the brain can be become overwhelmed by all the information it's trying to process, like a computer bombarded by too much data. The brain can no longer distinguish between what it's safe to ignore, like the sounds of distant traffic or the sensation of wind on your face as you walk along, versus what is important, like the honking of the car that's about to hit you. The horrible jumble of noises and sights ans smells can be very upsetting. When faced the significant sensory overload, some people have a reaction akin to a panic attack, like what I experience at the supermarket.
The brain has a remarkable ability to heal itself after various kinds of injuries and assaults, a capacity that amazes sceintist and doctor. Even patients with severe brain damage can sometimes recover nearly fully. While it's clear that excellent medical care and therapy can assist in recovery from a brain injury, how the healling process works remains unknown. Neurons in the brain do not as a rule regenerate. Experiments in mice have shown that a limited number of new neurons may grown in the hippocampus, the part of the brain that stores memories and one of the first regions affected by Alzheimer's disease. But it's probably an insignificant number of neurons, and it's unclear whether they ever become fully functional. It's also unknown if the same phenonmenon occurs in teh human hippocampus. We do know that in the brain regions critical for thinking, such as the prefontal cortex, the neurons that emerged in infancy and probably even before remain the same throughout a person's life.
The fact that we retain the same neurons from the beginning to the end of our lives may be one reason we can consider ourselves "ourselves." What may change, however, are the connections bewteeen cells and among brian regions. Some connections grow stronger; some wither; some are damaged. If a region of the brain becomes impaired, new connections between cells may grow and hep us recover some or most of the disable function. But does that modify who we are?
I Google the general definition of the word and learn that survivor means a person who remains alive, carries on depsite hardships or trauma, perserveres, and remains funcitonal or usable. This sounds a lot more inspiring, especially the last part, "functional and usable."
In the foreseeable future, and perhpas for as long as I live, there will be more brain scans, more tests, and the anxiety of waiting for results. There may be unexpected, undesirable findings followed by more treatments. I am competing with a particulary wicked and perverse opponent, an illness that is very hard to beat. It feels like an Ironman competition that demands, in addition to the latest scientific achievements, an iron will, body and mind. In this race, I'm not rushing to the finish line because there isn't one. There are no medals or trophies to earn, no accolades, no cheering. There is only the deep satisfaction of another day lived, another day with the people I love.