How memory improves; How memory works
Q: It would be nice to complete WonderQuest's memory series with
suggestions for memory improvement based on sound scientific data. N.L.
Some place, World
 Hiking
at Eagle Creek, Oregon for fun. Photo courtesy of Kelvin Kay and Wikipedia.
A: The best way to improve our memories seems to be to increase the
supply of oxygen to the brain, which we can do by aerobic exercising. Walking for three hours each week
suffices, as does swimming or bicycle riding.
Such aerobic exercise has helped elderly people switch between mental tasks,
concentrate better and improve their short-term memory, says Arthur Kramer of
the University of Illinois, Urbana, commenting on a number of studies.
Moreover, we now know why. Kramer and his team studied 59 healthy
volunteers 60 to 79 years old, and found that aerobic exercise increased the
number of neurons in their brains and the number of connections between neurons.
Exercising the brain, itself, isn't as helpful as we might hope.
Several big-name researchers (Columbia, Harvard, Brown, John Hopkins University,
the University of Pennsylvania and the Mount Sinai School of Medicine) formed a
consortium in 1992. They spent $11.4 million on studies researching memory loss due to aging. The upshot: intervention
programs they devised produced only modest temporary improvement.
Furthermore, results showed "training in a specific task did not lead to
improvement in memory capacity overall."
However, if we train in a particular task we want to improve — like
remembering names — then perhaps it doesn't matter whether or not we've
increased our overall memory capacity. At least, we can remember names
better. Also, we can keep up the training, so it lasts as long as we
please.
Perhaps even more interesting: the consortium found memory improvement or
maintenance depends highly on the individual. What works for some may not
work for others.
I've listed some memory guides under Further Reading. These guides
present a variety of ideas, so you can pick and choose what might help you.
I've also included some demos of a program designed to improve mental skills.
The demos are humbling but also fun.
And, if you want to know just how poor your memory is (and how little we
pay attention to details), I've included a 'police sketch' program.
First put away all pictures and mirrors, without peeking. Then use the
sketch program
to select the right features, and assemble them into a reasonable picture of
your face. Now, try to picture, with the sketch program, a close friend or
relative. By the way, you can stretch features with the mouse.
Not easy, eh?
Further Reading
How memory
works, part 1, WonderQuest
How memory
works, part 2, WonderQuest
Aerobic exercise training increases brain volume in aging humans,
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences
61:1166-1170 (2006)
Exercise shown to reverse brain deterioration brought on by aging, University
of Illinois, Urbana, November 2006
10 research-proven tips for a better memory, Harvard Health Beat
Improving your memory: tips and techniques for memory enhancement,
wwwlHelpGuide.org
How to remember names better, 43 folders
MindFitness
demos
Police sketch,
FlashFace
Q: How do we store memories in our brain? How do we
recall memories? Rajeev, Bangalore, India
The cortex and its various lobes. Short-term memory activates regions in the frontal lobe (shown in blue); the parietal lobe (yellow) holds tactile sensations and maps
of the space around us. The occipital lobe (red) is a vision area; the
temporal lobe (dark yellow) contains auditory areas and the hippocampus.
Drawing from Gray's Anatomy.
Two weeks ago we considered how information flows through the brain, and how the
brain places a new short-term memory into long-term memory. Last week we
described how neuron networks store and retrieve memories. This week
concludes
our memory series by seeing how hippocampus synapse molecules change to define a network path and, hence, a
pattern and memory.
The action takes place in the border region (called a synapse) between two
neurons. A synapse is a small molecular-size gap (20 to 40 nanometers
across) between two neuron cells and the cell membranes of both neurons at
the gap. A nanometer is one billionth of a meter (or yard). This
tiny region between neurons in the hippocampus is where a memory-defining path
is born.
Neurons carry information across the brain in the form of electrical pulses.
One neuron fires a
signal, which propagates down its tail-like axon to the synapse. Chemical messengers
at the synapse carry the disturbance across the synapse, and change the
potential difference across the cell membrane of the second neuron. If the change is great enough (about
15 mV), the second neuron fires
an outgoing signal (peak of +30 mV). So far, so good. That's how signals go down a
neuron network. But there's more to establishing a long-term pattern.
The first neuron cell fires an electrical impulse. The
impulse propagates down the tail of the neuron (called an axon) to the
synapse. Neurotransmitter molecules
cross the gap, and stimulate the outgoing neuron to fire, thus (if the stimulus
exceeds the neuron's firing threshold) sending an
impulse farther down the line. Drawing courtesy of Bruno Dubuc and http://thebrain.mcgill.ca/,
modified by the author. Click here for an
animation showing
how a neuron fires, courtesy of Bruno Dubuc and here for the
firing
voltages and mechanisms, courtesy of Eric Chudler.
For a preferred path, we need frequent-firings. If the incoming neuron
fires frequently enough so that the outgoing neuron's cell membrane receives
many jolts in a short period of time, the jolts excite the outgoing neuron's
membrane long enough to elevate the voltage across the cell membrane for a
sustained time. That's the ticket: jacking up the voltage for a
goodly time. Five thousand or more molecules and ions drift and bop their
way across the gap to the outgoing neuron. Molecules bond with molecules
on the outgoing side. Each bonding releases energy. Activity
avalanches into a frenzy of catalytic-induced growth. New proteins are
born, which create new synapses, which define a new network.
The net result is to raise the resting potential in the outgoing neuron's
membrane for a long period. The elevated resting potential makes it easier
for an incoming signal to exceed the neuron's firing threshold voltage and,
therefore, to fire the outgoing neuron. The synapse is strengthened, can
fire more efficiently and a new preferred path is created.
Please click here for the
details of how
molecules change to establish a network path.
Note: The content of the site "The Brain from Top to Bottom" is
under
copyleft. , which allows free
access to the material. I am in debt to Bruno Dubuc and his excellent
primer.
Further Reading:
How memory
works, part 1, WonderQuest
How memory
works, part 2, WonderQuest
The brain from top to bottom by Bruno Dubuc, Canadian
Institutes of
Neuroscience, Mental Health, and Addiction
Medical, Science and
Nature Images by Scott Camazine
Neuroscience for kids by Eric Chudler, University of Washington
Brain
Facts and Figures by Eric Chudler, University of Washington
MIT team discovers memory mechanism, Science Daily, Feb. 9, 2004
Gene manipulation in mouse and applications to the study of memory, RIKEN,
the Institute of Physical and Chemical Research, Brain Science Institute
Requirement for Hippocampal CA3 NMDA receptors in associative memory recall,
RIKEN, the Institute of Physical and Chemical Research, Brain Science
Institute
Learn
like a human, Numenta, IEEE Spectrum, March 2007
Spatial
short-term memory pinpointed in human brain, National Health Institutes,
1998.
Capacity limit of visual short-term memory in human posterior parietal cortex,
Nature, 2004.
(Answered March 26, 2007)
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