Dov Michaeli
First posted 9/22/11 on The Doctor Weighs In
Yesterday The President gave his usually eloquent speech, this time to the U.N. General Assembly. At one point, if you listened closely, you would have detected slight hesitation, an almost mperceptible pause, and then…the flub. Here is the text:
“This week, America signed an agreement with the World Health Organization to affirm our commitment to meet this challenge. And today, I urge all nations to join us in meeting the… pause…HWO’s goal of making sure all nations have core capacities to address public health emergencies in place by 2012. That is what our commitment to the health of our people demands.”
Was it a lip of the tongue, or a “senior moment”? Cable TV pundits would probably have a field day with it (Republicans –“he’s losing it!!!” Dems –“A slip of the tongue, and compared to W’s mastery of his brain-tongue connection, he is doing quite well”). To me, the short pause speaks volumes. I think I know what went through his mind in that fraction of a second: “HWO… doesn’t sound right… oh, well, need to go on with the speech”. A minor cognitive dissonance, then pushing on. I would have gotten around the problem by enunciating the full name (World Health Organization), or some other substitute. That’s a trick that all seniors who have had their moments are using.
But wait, am I letting the President off too easily? Could it be an early sign of the dreaded Alzheimer’s? Just listen carefully and watch closely President Reagan’s tapes of his last years in the White House. How could we miss it at the time? The answer, my friend, is written in the hippocampus.
The Neurobiology of senior moments
One of the scientists who explored this problem is Carol Barnes, Director of the Evelyn F. McKnight Brain Institute at the University of Arizona (and a holder of two pilot licenses, to boot). In an
article in the September 2011 issue of The Scientist (appropriately titledSecrets of Aging) there are some fascinating facts. Long-term memory is stored in a structure sea horse-shaped structure called the hippocampus.Different kinds of memory are stored in different regions of this structure. Spatial memory (where am I? how do I get to the grocery store?) resides in an area
called the dentate gyrus. In it there are neurons called granule cells. During memory formation synapses between these neurons become stronger, a physiological process called long-term potentiation or LTP, which biochemically involves protein synthesis, and this extra protein goes toward formation of thicker and more abundant connections between the cells. This strengthening gradually declines, unless the particular memory is reinforced, by repetition, for example (I can find my way to the grocery store with my eyes closed, but where did I leave the car keys?). In 2-3 year old rats (equivqlent to 70-80 year human oldsters) these connections, and the memories transmitted through them, fade significantly faster than in young rats. The same is true for monkeys. And whether you believe in Darwin or in Adam and Eve, our brains look and function in a similar way.
To make things a bit more complicated, biology operates as a Ying/Yang system: every action is dampened by a counter-action. As you would expect, there is a process that actively suppresses LTP (called Long-Term Depression, or LTD), which is more active in old animals, thus contributing to the faster loss of memory.
Now we are ready to understand what’s happening in a “senior moment”. A given memory resides in a circuit of neurons, each neuron contributing a bit of information which gets integrated into a whole (I left the key in the glove compartment). Now what happens if the cell that “owns” the glove compartment bit of information is slow in delivering it to the circuit? You know that you
are looking for the key (memory bit: key), you know that it is in the car (memory bit: car), but where? You are stumped for a moment –the senior moment. Of course, this is misoversimplified (to illustrate George W’s hopelessly tangled verbal neurons) but you get the picture.
Is this early Alzheimer’s Disease
Emphatically not! In a “senior moment” the loss of memory is momentary, in AD it is permanent. On the micro level the mechanism is completely different; In AD there is an accumulation of a protein, beta amyloid, that is toxic to cells. The destruction is widespread, and the effects are equally devastating. And, according to Dr. Barnes’ research, AD destroys primarily CA1 cells in the hippocampus, not the granule cells.
And yes, there are ways to counteract episodes of momentary memory loss: focus and repetition. When you put the key in the glove compartment, make a “mental note” of it. And try to always leave
the key in the same place –repeating the same memory circuit will thicken the connection between the cells, and will make you look like a memory genius.
Dov Michaeli MD PhD is a basic scientist who writes on the life sciences at The Doctor Weighs In.
Care And Cost 