The Readings for the Week of Jan 29th

The main focus of this week’s readings are models of memory. Memory models have been constructed to explain how things like phone numbers, facts, and important events become stored in our long-term memory. There are several models but most of them follow a similar blue print called the Modal Model of memory. In this model, information received from the environment goes through several processing steps before it has the possibility of being stored in one’s long-term memory. Richard Atkinson and Richard Shiffrin developed the Dual Store Model, which follows the modal model blueprint. The first stop for an external stimulus is the sensory register, which is based on the nature of the information. For example if the stimulus is visual, it enters a visual sensory register. One question I had about this stage was what happens when a stimulus has both auditory and visual properties? Is the information processed simultaneously or separately?

The second stop is short-term store (STS) which has a limited capacity. The short-term memory storage’s capacity explains why information is lost and why information stays here for only a short period. It is during this stage that the information from the stimulus is further analyzed and processed. For example, if one sees the word dog, the word’s case, its letters, how it is said, and its meaning are all processed. One may also associate this word with life experiences to strengthen its meaning. This stage is crucial because the longer the information stays in STS the more likely it is to be stored in the long-term memory store. Rehearsal also increases the likelihood that information will be stored. Without the short-term memory store, the information we get from external stimuli can never become concrete and be stored in our long-term memory.

Reading about this second memory stage made me to think about patients with amnesia. We read last week that anterograde amnesia is when a person cannot form new memories because they are unable to transfer events from their short-term to their long-term memories. This is commonly seen in people with brain damage and in soap operas. This type of amnesia can be either temporary or permanent. The second type of amnesia, anterograde amnesia, is the inability to form new memories. Anterograde amnesia is commonly seen as a permanent condition and not a temporary one. This led me to ask the following question: Does temporary anterograde amnesia exist? After doing some research on Wikipedia, I found an entry that discussed the types of anterograde amnesia. It was here that I found about the term traveler’s amnesia which is the name given to temporary anterograde amnesia. Traveler’s amnesia can be caused by the intake of certain medications (Benzodiazepines and imidazopyridines) and the consumption of a large amount of alcohol. Wikipedia also introduced me to a second type of temporary anterograde amnesia called amnesia automatis. Amnesia automatis is caused by the consumption of alcohol and prescription drugs simultaneously. Those who suffer from this type of amnesia suffer memory blackout and do very strange things that they later do not remember doing. These strange actions are done automatically by amnesiac without any thought, which is why sometimes they do not know how they did these things.

The last and final stage of memory/information processing is long-term storage (LTS). The capacity of this storage is infinite and it is here where information like our childhood memories and factual knowledge is stored. The memories stored here have already been processed thoroughly and are not usually forgotten. One exception to the permanency of the memories in this storage is if one suffers from retrograde amnesia.

This week’s reading also discusses the serial position curve, which is based on data collected from free recall tasks. During this task, people see a list of letters or numbers and are asked to recall them afterwards. The plot of this data revealed that people remember the items presented first and last better than the items in the middle of the list. The terms used to explain this trend are the primacy and recency effect. The primacy effect is when a person remembers the first few items of a list and the recency effect is the opposite. It is when a person remembers the last items presented on a list.

This curve, the recency effect, and the primacy effect have been introduced in almost every psychology course I have taken. During these classes, I just accepted the fact that the recency and primacy effect exist without testing it myself. This is what led me to search for internet memory experiments that administered free recall tasks and analyzed the information from this task. After some extensive googling, I finally found a website that lets you take the experiment. The first time I did this experiment, I recalled the items in the middle of the list the best. I do not know what this means, but it disproves the recency and primacy effect. My serial position curve also looked nothing like the one in the textbook. It was shaped more like a bell curve. Factors that I thought could have affected my results could be the way the experiment itself was made or my own bias.

If you want to take the memory experiment go this website:
http://www.essex.ac.uk/psychology/experiments/memtask.html

Just Take A Nap...

During midterms or finals, have you ever felt that you do not remember what you studied only a few hours ago? Do you sometimes have to review the same information repeatedly for it to stick? I know I have felt this way a couple of times during a semester and have taken ginkgo biloba to help improve my memory. Psychologist Elizabeth Gould from Princeton University has found what causes many college student memory problems. In her study on sleep-deprived rats, she noticed that growth of cells in the hippocampus decreased. This decrease in the genesis of cells impedes the formation of new memories

So what exactly caused the cell production to decrease? Gould found that there was an indirect relationship between the level of the stress hormone corticosterone in the hippocampus and the production of neurons. This means that as the amount of stress hormone in the rats increases, the rate of brain cell production in the hippocampus decreases. To confirm this relationship, Gould removed the sleep deprived rats adrenal glands in order to halt the production and accumulation of the stress hormone. These rats were able to produce new neurons normally which meant that the relationship was correct.

The implications of Gould’s study are that sleep deprivation and stress are the reasons why we have difficulty remembering or learning things. For this reason, we should not force ourselves to study for exams when we are exhausted. No amount of ginkgo biloba or B complex can substitute for a good night sleep. If you have to study under these stressful conditions then just take a short nap to restore your energy.

The above information comes form the article "Can't remember what you just read? Take a nap." By Andy Coghlan. The article can be found here: http://www.newscientist.com/channel/being-human/brain/mg19225804.400-cant-remember-what-you-just-read-take-a-nap.html

Readings Week of Jan 22

This week’s readings includes some more historical background, sensory memory and an overview of brain structure and function. The focus of the historical background portion of the reading was Hermann Ebbinghaus. His main contribution was that he saw psychological research as something that can be studied scientifically and experimentally. Through this type of research, Ebbinghaus discovered the forgetting curve which indicates that when one learns something (ie memorizes things on a list) there is a huge initial drop in performance after only a few minutes, but this drop in performance is minimal after more time passes. This is great news for college students who hope to retain some of the information they learn through out their undergraduate careers.
The second portion of the reading focuses on sensory memory, which is where we store all of sensory experiences. Two studies help us see how sensory memory works. George Sperling performed the first study. This study tests information persistence of sensory memory, which is defined as being able to extract information about a stimulus even after it is gone. In his study, Sperling showed subjects a series of letters in numbers organized neatly into columns and row. At first, he showed them the series of characters and asked them to recall what they saw. On average people could report 4 letters/numbers but these subjects told him that they could see more, but they were unable to recall them. Hearing this feedback from his earlier subjects made Sperling revise his study by giving subjects a cue that would indicate which row they needed to recall (known as partial report). He plotted this data and found out that partial report gave subjects an advantage only when the cue was given within 500ms.
The second study was performed by Haber and Standing. This study examines stimulus persistence of sensory memory, which is when a stimulus seems to persist even after the stimulus is absent. In their study Haber and Standing, showed subjects a visual stimulus and asked them if they perceive it as a continuous or discontinuous. Subjects reported that they saw a continuous stimulus, when the duration of the blinking of stimulus was 250-300ms. People experience this persistence of stimulus in their daily lives when they hear a high pitch sound and continue to hear it ringing in their ears even after it is gone.
The third part of the reading, I think is the most interesting part. I think this section is interesting because we learn about the brain. The brain is interesting both functionally and structurally. The part of the brain that we will get know inside and out in this class is the hippocampus because it is said to play a very important role in memory. This section of the readings is also interesting because it discusses the two types of amnesia: retrograde and anterograde. I never get tired of learning about amnesia. People with retrograde amnesia do not remember the events prior to them getting the amnesia. The way that I remember this type of amnesia is by thinking about “retro” fashion and how it is in the past. Those with anterograde amnesia can not form new memories. Whenever I think about this type of amnesia, the first thing that comes to mind is the film Memento. In this movie, the protagonist Leonard Shelby who suffered from anterograde amnesia had to tattoo his new memories on his body in order to remember them. Every time I learn about amnesia, all I can think about is how hard it should be for the family members of amnesiacs.

The Memory Molecule

The article "Memories are made of this molecule..." from the magazine New Scientist (Jan 13-19 2007) discusses how memories are formed at the molecular level. The molecule that is the focus of this article is called TrkB. It is found on the surface of brain cells in the hippocampus and is involved in the initiation of signaling pathways of a memory/learning process called long-term potentiation (LTP). In LTP, the strength of the connections between brain cells are increased as they are used more and more. Scientists from Italy and Spain who studied mice, recently discovered the involvement of TrkB in LTP. These scientists measured the LTP activity in the hippocampus of mice that were learning to blink whenever they heard a tone. Normal mice learned this without a problem, but mice with abnormal TrkB failed to learn to respond to the tone and initiate LTP. This study showed scientists that TrkB does play an important role in memory/learning and in long-term potentiation (LTP) initiation.

I found this article very interesting because it introduced new research on memory that I was not aware of. When I think about memory, the first thing that comes to mind is models and not actual molecules in the brain. This article gives a biological approach to memory. I believe that the next step in this research is to see if TrkB abnormalities are involved in memory disorders. If researchers find that TrkB plays a role in memory deterioration, then the second step is to find out how the abnormality occurred and how it can be corrected. This can lead to great advances in medicine, which can drastically change the lives of those who suffer from disorders like Alzheimer’s.

The entire article can be found here:
http://www.newscientist.com/channel/being-human/mg19325864.500-memories-are-made-of-this-molecule.html