Author Note: Steven Lee Douglas, Iveta Rukere, Teather Smith, Lenka Valentine, Department of Psychology, Shepherd University
Correspondence concerning this article should be addressed to Steven Lee Douglas, Iveta Rukere, Teather Smith, Lenka Valentine, Department of Psychology, Shepherd University, Shepherdstown, West Virginia 25443.
In 1957, Scoville and Milner wrote a paper on “HM” who at the age of 27 years old had major brain surgery where doctors removed portions of his brain in an attempt to relieve serious seizures he suffered due to his epilepsy. According to the reports, surgery was successful in reducing the number of seizures he was having to the level that they could treat his remaining seizures with medication. What makes the case of “HM” so well known is that by removing the parts of the brain that included the hippocampus, he was no longer capable of storing short term memories. He was able to remember long term memories (LTM) from before his surgery but could no longer retain short term memory (STM). He was able to retain semantic memories (Baddeley, 1966) but could no longer record episodic memory (Tulving, 1972). In 1994 Tulving wrote about “KC” a young Canadian who in a serious motor accident damaged his temporal lobe. He lost all of his episodic memory. He was able to remember places but not what happened in those locations.
In 1977, Brown and Kulik, published research on Flashbulb Memory. They researched how well subjects could remember the assassination of President John F Kennedy in 1993. They determined that subjects had a stronger ability to remember details around where they were and what they were doing when they heard the news that the President was dead. They were not able to remember great details about what they were doing the day before. Neisser (1982) challenged earlier findings with questioning where people were when Pearl Harbor was attacked. His own memory recalled that he was at a baseball game at the time. This however is not possible since baseball season is over before December 8th. He could remember elements of news reports of the attack but not where he was at the time. Additional studies have been done on Flashbulb Memory using the Challenger explosion (McCloskey, Wible, and Cohen, 1988; Neisser and Harsch, 1992) and the terrorist attacks on 9/11 (Talarico and Rubin, 2003). In all of these studies, subjects were able to retain a great deal of information regarding the actual events but were not able to remember perfect details on what they were doing or where they were at the time. Another interesting factor that played a role in making proper retrieval possible is referred to as Confabulation (Wade & Tavris, 2011). The “Conditions of Confabulation” tell that a memory of an event can be influenced by other people’s memories that someone had overheard over time. In the case referred to here, a family member heard the same story so many times about someone else in the family knocking down a wall that they eventually believed that they had actually been there, when in fact they were not.
A person’s ability to pull from their Long Term Memory depends on how the memory was stored in the beginning. A method of memory retrieval was developed called “Material-induced Organization (Bower, Clark, Lesgold and Winzenz,, 1969) where common associations are used to enhance our memory. In a research experiment they determined that when grouping words together that had apparent relationships (i.e. boy/girl; orange/fruit) the subjects were able to recall 100% of 112 words after 4 sets of study and recall. They were allowed to study the words for 1 minute and then given 5 minutes to recall them. After 4 attempts they were able to recall 100% of the words. In a second control group they used word groups that held little obvious relationship. At the end of the 4 sets of study and recall, this group was not able to achieve higher than 60% recall. The more pieces available that are associated with an original memory the more reliable that memory will be.
The Power of Suggestion
To show how easily memory can be tainted, Lotus, Miller and Burns (1978) conducted a visual experiment with 30 slides depicting a Datsun car going through a stop sign (a 2nd control group saw as yield sign) and hitting a pedestrian. In questioning the participants as to what they could recall, suggestions were made in the questions in an attempt to mislead and distort their memory. By asking the control group that saw a stop sign, “When the car went through the yield sign, did it hit the pedestrian?” as many as 59% failed to answer correctly and could not recall the stop sign and replaced the memory with the suggestion made in the question.
In a study by Ceci and Bruck (1995), they found that the younger a child is the easier it is to change what they believe by using suggestive leading questions. In their research in a courtroom setting they found that it is possible to repeatedly suggest something has happened to a child and eventually the child will believe the suggestion was real. To what degree they are able to understand what they recall from the false information depends on their age. Studies found that the older the children are the less likely they will accept the false memories as their own. In a study by Poole and Lamb (1998) a little girl thought her privates referred to her elbows when the induced memory was regarding a visiting adult having touched children inappropriately.
Working memory (WM) provides temporary storage and manipulation of information that is necessary for cognition. Even though working memory has limited capacity at any given time, it has immense memory content in the sense that it acts on the brain’s nearly unlimited inventory of lifetime long-term memories. Using simulations, it has been shown that large memory content and functionality of working memory emerge spontaneously if the spike-timing nature of neuronal processing is taken into account. At this point, memories are represented by extensively overlapping groups of neurons that exhibit stereotypical time-locked spatiotemporal spike-timing patterns. These patterns are called polychromous patterns, and synapses that are forming polychromous neuronal groups (PNGs) are subject to associative synaptic plasticity in the form of both long-term and short-term spike-timing dependent plasticity. While long-term increased effectiveness is essential in PNG formation, short-term plasticity can temporarily strengthen the synapses of selected PNGs and lead to an increase in the spontaneous reactivation rate of these PNGs. This increased reactivation rate results in high interspike interval variability and irregular, yet systematically changing, elevated firing rate profiles within the neurons of the selected PNGs. (Szatmáry & Izhikevich, 2010)
Long Term Memory and Sleep Connection
Scientists in Germany conducted a research that examined the possible role of sleep in converting new experiences to long–term memory. Volunteers were placed in a rose-scented room where they played a computer version of a card game Memory. They had to remember locations of paired cards that were flashed on the screen for a few seconds. Later, while they were sleeping, researchers exposed the volunteers to rose fragrance, because odors can trigger memories. Volunteers performed better at the game when exposed to the scent during slow-wave sleep, and the brain imaging during slow-wave sleep showed that the scent cue activated the hippocampus, which is a region linked with memory (Choi, 2007).
Biology of Memory
The biology of memory refers to the biological changes that occur to the brain as memories are created. Memories fall into two categories: long-term and short-term. Biological changes occur in the brain each time a memory is created, however those changes are different depending on the kind of memory. The kinds of biological changes to the brain that occur involve both chemical and structural changes at the level of synapses – the point where a transmission of a nerve impulse from one nerve cell to another occurs.
In the case of short-term memory the brain neurons are temporarily altered. Studies have shown that brain neurons show an increase or decrease in readiness to release neurotransmitter molecules (chemical substances that transmit nerve impulses across a synapse – the space between nerve cells) into a synapse for a short amount of time when an animal is developing a short-term memory.
When developing a long-term memory lasting structural changes occur in the brain. It is believed that these changes take time to develop fully. This time period is called consolidation and can last several weeks or years in human beings. While the exact biochemical and molecular changes involved have not been defined, it is believed that through stimulation receiving brain neurons become more receptive to the next signal that comes a long and the brain structure is altered allowing for dendrite growth and an increase in the number of synapses.
Human memory is a complex phenomenon, and involves several areas of the brain. Short-term memory mostly takes place in the frontal and pre-frontal parts of the brain. The hippocampus and the cortical structures around it are mostly responsible for long-term memories. The hippocampus thus plays a fundamental role in episodic, semantic and spatial memory. Emotional memory appears to involve another structure of the limbic system besides the hippocampus. This structure is the amygdala. Procedural memory, such as knowing how to ride a bike, does not appear to involve the hippocampus at all. Instead, procedural memory appears to be associated with modifications in the cerebellum, the basal ganglia, and the motor cortex.
It is also believed that hormones can also affect the brain’s ability to store memories. Hormones released by the adrenal glands during stress and emotional arousal can enhance memory, however; extreme amounts can have the opposite effect. No one knows exactly how the brain stores information, how different memory circuits link up to one another or how information is located and retrieved by the brain. There is still much to be learned about the biology of the brain.
How We Remember
Information must be encoded in order to be remembered. This is done by encoded information. An example of effortful encoding is studying. Rehearsing is also an effective technique for remembering information. There are three significant ways of rehearsing information in order create lasting memories: Maintenance rehearsal (rote memorization), elaborative rehearsal (making associations between already stored information and new information), and deep processing (the process of meaning rather than simply the physical or sensory features of a stimulus).
Reading, reciting and reviewing are examples of elaborate and deep processing and more effective tools for encoding information than just reading and rereading or studying alone. Retrieval practice such as testing also increases the ability of persons to recall information that has been memorized. In addition to elaborative rehearsal, deep processing and strategies such as reading reciting and reviewing, people who want to increase their ability to remember use formal strategies or tricks to help encode information in order to store and retain it. These are called mnemonic devises.
Why We Forget
Forgetting isn’t really a bad thing, it is actually a phenomenon. Imagine if you remembered every detail of every minute of our lives. Failing to remember something doesn’t mean the information is gone forever. Sometimes the information is there only we cannot access it. Other reasons we forger is something called repression, which is where we push a memory out of reach, because we do not want the feelings associated with the feelings.
A classic experiment, conducted to study the interference in forgetting. The experiment was conducted with only two subjects, they we both taught the same thing. After learning, one group slept while the other preformed their normal routine. The results showed the group who slept, retained more information longer. Two types of interference are proactive interference and retroactive interference (Loftus, 1980).
Decay theory is information in the memory that eventually disappears if the information is not accessed. The term decay theory was first coined by Edward Thorndike in his book “The Psychology of Learning” in 1914. This simply states that if a person does not access and use the memory representation they have formed the memory trace will fade or decay over time. One of the biggest criticisms of decay theory is that it cannot be explained as a mechanism and that is the direction that the research is headed.
Childhood amnesia, despite being a universal human experience, was only first formally studied in 1893 by the psychologist Caroline Miles in her article “A study of individual psychology”, published in the American Journal of Psychology. In 1904 G. Stanley Hall noted the phenomenon in his book Adolescence, but it was Sigmund Freud who offered one of the first, most famous, and most controversial descriptions and explanations of childhood amnesia when he tied the phenomenon in with psychoanalysis. Childhood amnesia is the inability to remember the events and experiences that occurred during the first three years of life. Sigmund Freud’s theories of psychosexual development are highly intertwined with childhood experiences. In what is now published as The Standard Edition of the Complete Psychological Works of Sigmund Freud, Freud theorized that childhood amnesia is the result of the mind’s attempt to repress memories of traumatic events that, according to Freud, necessarily occur in the psychosexual development of every child. This would lead to the repression of the majority of the memories of the first years of life. Freudian theory, including his explanation for childhood amnesia, has been criticized for extensive use of anecdotal evidence rather than scientific research, and said to frequently permit multiple interpretations.
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