"Bushy Brains" Function Longer and Better

Did you know that a healthy brain is like a fat bush with lots of slender, criss-crossing branches? That's the fascinating image drawn by reporter Lauran Neergaard of the Associated Press in an article explaining brain function and what happens to the brain as we age. (See our October 16, 2007 post.)

As we learn, branchlike tentacles grow from the ends of the brain's cells, like shoots sprouting from a seed, crossing and overlapping to create communication connections. The more we learn, the more branches and the more connections. In other words, we develop a "bushy" brain.

As we age, the brain cells (or seeds) don't die as they do in Alzheimer's Disease, but their branches often shrivel to skinny twigs. Without the multiple intertwining branches that enable communication, cells are less connected and have a harder time sending and receiving messages. For example, you may know someone's name but not be able to recall it.

Aging targets a different part of the brain's memory center, the hippocampus, than Alzheimer's. Interestingly, the brain has developed two methods of fighting the changes caused by aging. The curiosity, scientists say, is that brains are highly individual regarding which method they use to heal themselves and the extent to which healing occurs, if it does.

• Bushy brains. Some brains have developed so many connectors, or branches, that they remain largely unaffected by the ravages of age or even Alzheimer's damage. "Striking autopsy studies have found that between 20% and 40% of older people who displayed no confusion actually had brains riddled with Alzheimer's trademark plaques," wrote Neergaard. Apparently, their brains had developed so many connections that even the death of some neurons from Alzheimer's left plenty of neurons still able to maintain normal brain function. This ability of the brain to maintain function in the face of attack is called "cognitive reserve."
  


• By-pass brains. Some brains simply by-pass damaged or dead brain cells and neural pathways. If a pathway stops functioning, the brain finds an alternate pathway to maintain communication. "Brain scans show younger people tend to use different neural networks than older people when performing the same task," Neergaard wrote. Scientists speculate that when neural pathways break down as we age, the brain may seek out alternate routes used during our younger years. There is also evidence that the brain may build new pathways when old ones cease to function.