Weekly Brain Update: practice makes perfect?

I thought about calling it Weakly Brain Update, as I found it difficult to relate any of the articles in the July 17 issue of the Journal of Neuroscience to the craft of knitting.  

July 17 issue of the Journal of Neuroscience: more about the cover can be found here

The article that was the source of the colorful cover of this week’s issue seemed like the only potential candidate: Nelson and colleagues examined the impact of practice testing on human memory in a paired-words task and linked better performance to increased activity in the parietal cortex.  It’s nice to see a brain imaging study that supports what we tell students all the time: one of the best ways to study is to practice taking a test on the material.  I’ll be sure to show my students the cover shot before I give the next exam!  I suppose I could relate this to the ability to memorize pattern repeats, but is that more of a procedural, motor memory?  Are we able to remember the repeats more accurately if we make an attempt to knit without the pattern in front of us, and make mistakes?  Actually, I think that does happen, and will happen a lot now that I have approached the 42-stitch repeat large motif of my current project:

 

I've modified the color combinations, based on issues that revealed themselves in the swatch.

After writing the initial draft of this post yesterday, I paid attention to what I was doing today as I began the 42-stitch repeat.  At first I found myself counting to keep track of my placement in the pattern: 1,3,1,1,1,1,1,3,1,1,3,7… It’s when I stopped counting that I made a mistake and had to go back a few stitches.  That would represent the practice test, and would be when the activity in my parietal cortex is at its peak.  Whether or not that is promoting my ability to remember the pattern, we’ll have to see.

 

I reached row 3 of the 42-stitch pattern before it was necessary to face reality and go to work this morning.

The three patterns line up very well.

Even though it was tough to relate this week’s articles to knitting, I can easily say how amazed I am at what neuroscientists are able to study.  For example, it is possible to switch out an amino acid to ever-so-slightly change the function of a protein so that it interacts differently with neighboring proteins.  Kazi and colleagues examined how channel proteins are structured so that they are able to select what gets across the neuron’s membrane.  Specific parts of the channel proteins form little gates that stick into the channel opening.  If the gate malfunctions, too many or not enough ions will cross the channel, affecting the cell’s ability to process signals from other cells.  Another article was about how variations in the shape of DNA in the prefrontal cortex can be used to predict the severity of symptoms of schizophrenia.  The DNA’s shape dictates how well a gene will get transcribed, and the shape can change depending on a person’s genetic make-up or their experiences.  

The article that I read most closely was about a process known as long-term depression (LTD).  LTD, and its counterpart, long-term potentiation (LTP) are widely recognized as cellular mechanisms for learning.  In conditioning a relationship is established between two events, often a noise and a foot shock such that the rat or mouse will learn to get scared when it hears the noise.  This relationship is represented in the brain as increased sensitivity of neurons in the amygdala (LTP) and is produced by an increase in the number of excitable receptors on the cell.  With more receptors, the cell’s response to another cell’s signal is enhanced, in this case leading to a greater fear response to the noise.  In this week’s article by Clem and Huganir, the opposite relationship between extinction and LTD was examined.  

Most of it was electrophysiology, where they used electrodes to stimulate neurons in a dish and then other electrodes to measure changes in excitability of other neurons in the same dish.  They were able to show that specific patterns of stimulation were able to decrease the number of excitable receptors that were expressed in the cells, but only if the neurons came from a mouse that had experienced extinction, in which the noise was presented repeatedly without the shock, until it no longer was scary.  Somehow that new experience changed the circuitry to be less sensitive, by reducing the number of available excitable receptors.  

Their goal was to uncover the cellular mechanism of extinction with the hope that other researchers would be able to improve the success of exposure-based therapies for post-traumatic stress disorder.  In these therapies a person is guided through sounds and sights related to a trauma, to restructure their memory into something less traumatic.  If the cellular changes that correspond to extinction can be worked out, it might reveal new strategies that would make this approach more successful, and maybe take less time in humans.