Day 16: Memory: an inquiry

Dear Readers, 

Please accept my apologies for the late posting! I hope this will make up for it, as I think it is quite interesting....

Have you ever spent any time thinking about what memory is, exactly? How do we remember? How many different kinds of memory are there? Why do we remember some things and not others? Why do some things trigger spontaneous memories while other things require some digging around? 

I think we all take for granted the many things that our memory does for us on a daily, even momentary, basis. For example, take the simple task of walking from the kitchen to the living room. Muscle memory allows your limbs to move in the correct manner to get you from one point to the other; proprioception, or being able to interpret where your body is in space, allows you to get from one point to the other without falling down or bumping into every object you pass. Memory, both short- and long-term, allows you to remember and recognize the objects around you, and to know which way to go to get from one point to the other successfully. We don’t normally even think about these things - we just get up and walk from the kitchen to the living room.

Memory is such an amazing thing! Try to imagine life without it. To not be able to remember one second to the next. I have taken care of people in the hospital with advanced Alzheimer’s for whom that is their life. One patient would want to know if her book was there, even though it was in her hands, and she would ask over and over and over, “Is my book here?” even when no one was in the room, all day long.

As little as 20 years ago, imaging of the brain was limited to CAT scanning, angiography and a barbaric procedure called pneumoencephalogram, used to image the ventricles of the brain, in which the cerebrospinal fluid is drained and replaced with air; even a small leak of csf can cause a terrible headache. Imagine then, having ALL the csf drained from your brain and being replaced with oxygen or helium, then being placed in a torture device which would spin you around like a carnival ride,  even upside down, in order to get the injected gas into the various spaces or ventricles of the brain. The headache was so extreme, patients would actually scream in agony; the procedure often lasted 30 minutes or more, and the headache for 2-3 months while production of CFS caught up!

The physiology of memory is extremely complex and is still very poorly understood, but we have come a long, long way in the last 20 years. Many types of extremely sophisticated neuroimaging are available today, some of which are exquisitely sensitive and can show the chemical and electrical activity of the brain (called “functional” neuroimaging) as well as its structure.

These include:
CAT - computerized axial tomography
DOI - diffuse optical imaging
EROS - event-related optical signal
fMRI - functional magnetic resonance imaging
MEG - magneto ecephalography using SQUID (superconducting quantum interference devices
PET - positron emission tomography
SPECT - single positron emission computed tomography
(Notice all the acronyms - truncation devices used to help remember groups of words, and in this case, long words!)

 Many of these devices can be used to pinpoint with great accuracy metabolic and electrical activity in the brain while the patient is awake and being given tasks to do during the scan.  Stroke patients are scanned to determine which parts of their brains have been damaged; epilepsy patients are scanned to determine the source of aberrant brain activity that causes their seizures; patients with Alzheimer’s and other types of dementia are being studied to try to determine what is causing the degradation and loss of memory. It is a science still in its infancy, but has brought unprecedented progress to our understanding of the human brain.