Learning and Memory

The Secrets of Learning and Memory: Attentiveness, encoding and retrieval strategies.

Andrew P Mallon

Brown University, MPPB, 75 Waterman Street, Providence, RI. 02912

Abstract

In order to memorize and recall information the brain is required to perform several key tasks at several physiological and behavioral stages. We have investigated the impact of environmental factors and physiological states on two aspects of cognitive function. In doing so we consciously tried to mimic strategies that are realistically attainable and reproducible in study habits.

We tested the working memory component of the central executive functions using the n-back test and the short- and long-term memory using the Sperling word list test. Under control conditions 19 healthy volunteers were administered these tests and split into pairs to form two groups that contained subjects with the same range of ability, a control group and a test group that scored an average of 62.83 ±3.43%, n=10 and 62.41±2.49%, n=9 respectively. Ten days later the groups underwent different regimens and were retested. We found that the test group significantly outperformed the control group on tests of the central executive and short-term memory.  Two days later the subjects were again asked to recall as many of the words as they could, again the test group significantly outperformed the control group suggesting that long-term memory had also been improved. The impact of several variables are postulated to have worked synergistically to produce such a profound effect. We postulate that the significant factors in the regimens were that the test group was fasting and well rested leading to an increased level of attention and had the optimum opportunity of encoding the information in the same environment as the test was administered.

These simple techniques could be adopted to aid in mental tasks and maximize cognitive powers.

Introduction

The central nervous system (CNS) is responsible for many varied tasks including the reception of sensation, the coordination of muscles to produce movements, and the homeostatic regulation of body function. However, the most fascinating aspect of the CNS is its ability to learn new facts, collate, plan and then act upon that information. It is the vastly superior aptitude that human beings have for this function that greatly separates them from every other species. Of key importance in our cognitive ability is the central executive functions found in the large dorsal prefrontal cortex that allow us to consciously consider information and make plans. Also, notable in humans are the extensive cortical areas that provide the capability to encode and retrieve memories and skills that can persist from a few seconds to a lifetime. This has freed humans from living a moment to moment existence based on instincts and their immediate environment as found in other species.

There has been a great deal of research investigating what strategies can improve memory and there are several products available that claim to improve memory. Several factors are thought to be important including exercise level, diet, rest, stress and caffeine intake. However, there is little consensus on how significant each variable is either alone or in combination to elicit improvements. We have used a control study environment based closely on the real experience of students and designed a test environment designed to be more conducive to effective learning. We have found that this learning environment was able to produce a significant increase in central executive function, short- and long-term memory retrieval.

Methods and Results

The nineteen subjects for this experiment were aged 14-17 years that were screened and vetted for confounding factors including alcohol, tobacco, medical and psychological conditions.

Initially, the subjects were given two tests in control conditions. The first test was the n-back test, where the subjects were read a randomized list of integers from 1-9. When the integer ‘3’ was read, the subjects were instructed to write down the integer that had been read out five steps previously. For example, in the example series 8, 4, 2, 8, 6, 2, 1, 5 and 3, the integer five steps prior to ‘3’, is ‘8’.

Subsequently, the subjects underwent the Sperling word list test. In this test, a list of twenty neutral words were displayed and read in a random sequence. Each word was displayed for two seconds, at the end of the series the screen was blanked and the subjects were instructed to hold the words in their memory. After two minutes they were asked to write down as many of the twenty words as they could remember. The subjects were then split into two groups that contained pairs of participants with similar test scores producing two groups of approximately equal initial ability, age and gender split. The subject’s names were assigned random letters of the alphabet to blind the results from the investigators.

Fig 1 Initial scores for group 1 and group 2.

Bar graph showing the initial test scores of the subjects after they had been paired into two groups of nearly equal ability. The control group initially scored 45.5±3.45% in the word list, 50±8.33% in the n-back test and 62.8±3.43% on average across several tests (n=10). The test group scored 47.78±2.06% on the word list, 63.89±4.39% in the n-back test and 55.83±2.64% (n=9) on average overall.

 Ten days later the subjects were split into two groups and assigned to either the control group or the test group. The control group was asked to interrupt their sleeping and reduce the amount they would normally attain the night before they were to be tested. On the day of the test they were asked to eat normally and were also provided with ample amounts of pizza, chips and chocolate milkshake immediately prior to testing, at 3.30pm.

This group was placed in a separate classroom than the test group. During the test a radio was playing on low volume in the background. Prior to the start of the tests the subjects were informed that a surprise exam for the course they were taking would be administered the next day, causing some stress. The students were then given the n-back test and their answers were recorded. They were then read and shown a list of twenty new words as described above. During the two minute break they were moved to an adjoining classroom to join the test group where all subjects wrote down as many words as they could remember.

 Concurrently, the test group was instructed to ensure that they were well rested all night and that they ate nothing on the day of the test. They were allowed to have one banana if they were uncomfortable. However, all but 2 subjects who had the small morning snack, managed to fast until the time of the test at 3.30pm. At which point they were all hungry. They were also given a calorie free drink containing 80mg of caffeine 30 minutes before the testing began.

The test group was kept in the same classroom which they were accustomed to and the room was kept silent. They were administered the n-back test and the scores were recorded. Then they were given the word list with the advice to read out the words to themselves to make use of both the auditory memory buffer and to associate the words with images as the thought about them to better use the visual memory buffer. At the end of the reading the control group returned to the classroom and after two minutes all the students wrote down as many words as they could recall.

[At the end of this phase of the testing the test groups hunger was relieved with cold pizza, warm milkshake and potato chips.]

Two days later the subjects were again asked to recall as many of the word list as they could remember to test the impact on long term memory storage. As shown in Figure n the test group significantly outperformed the control group on every test. This demonstrates a clear advantage was acquired by the test group in these tests.

Bar graph showing the test scores of the subjects after they had been paired into two groups of nearly equal ability. The control group scored 45±4.71% in the word list, 50±9.86% in the n-back test (n=10). The Test group scored 71.11±2.74% on the word list, 77.8±6.51% in the n-back test (n=9)

Fig 3 Second experimental phase scores for group 1 and group 2.

Bar graph showing the test scores of the subjects after they had been paired into two groups of nearly equal ability. The control group scored 38±8.67% in the word list (n=10). The Test group scored 61.67±7.07% on the word list (n=9).

Discussion

 This investigation, rather than considering one parameter in isolation, recreated the collection of variables that are commonly found acting in concert in study and test environments. The tests that were utilized were designed to gauge the most important aspects of learning and memory. A combination of heightened attentiveness in the central executive allows for the best understanding and acquisition of information that then leads to the effective encoding into short and long term memory for subsequent recall.

There are several variables which we consider most significant in the difference seen in this experiment. The fasting state of the test group as compared to the satiated control groups had a direct impact upon cognitive ability. It has been previously demonstrated that when the stomach is empty it releases a hormone, ghrelin, that travel through the bloodstream and acts on the brain to improve attention. This is a logical evolutionary and survival progression. When a human is hungry it becomes more alert and thus more likely to spot a source of food. When a human has had a full meal, blood flow can be diverted to the gastrointestinal tract and away from the muscles and rest of the body. When we have had a big meal the body is shut down and often the brain automatically instigates a sleep cycle to allow for this. It is widely perceived that the brain needs glucose to work and lack of glucose actively circulating in the blood is deleterious to cognitive function but this is clearly not the case. The majority of glucose released into the blood from digestion is rapidly sequestered into the liver as glycogen by the action of insulin. In the brain there are very numerous specialized cells called glia which surround nerve cells and store large quantities of glucose to feed them.

 The test group also had the advantage of being well rested this was also a significant variable for the central executive which is dependent upon attentiveness and wakefulness.

If the brain is poorly rested it is unable to concentrate on acquiring information and it is not encoded from sensory systems into short and long term memory but is quickly forgotten. Being well rested, taking frequent and effective breaks and not studying in mammoth sessions can improve this condition.

 The effect of environment in this experiment should not be underestimated. The test group had the advantage of being in the same environment during very stage of the tests. The environmental cues are very effective in aiding recall of memory. Simply changing classrooms is enough of a change to produce a detriment on memory recall. This phenomenon is seen in many types of learning. Trying to study in an environment that

is radically different from the testing environment will result in problems with recall. Constructing a study environment as close to the testing area as possible or in the testing area will improve memory recall. This includes the removal of all sensory stimuli: sounds, smells, sights, touch and taste.

 Additionally the distraction of background noise results in problems with maintaining attention and confusing the environmental cues associated with the initial encoding of the memory. The brain uses environmental cues to aid in the recall of appropriate learned information depending on where it was encoded. Any deviation from this impairs memory recall and the association of new information into a pre-formed network of older memories.

 The use of caffeine in the test group was to increase attentiveness. However, the small dosage and lack of time to allow for delivery of an effective dose suggests that its contribution was minimal. Additionally, we would not recommend adopting a regime of learning that requires the regular use of pharmacological agents. The short term benefits of such a strategy are offset by the long term cost and dependence that it would entail.