Measure of memory that requires you to remember specific information; fill in the blank test
The analysis of the anatomical and physical bases of learning and memory is one of the great successes of modern neuroscience. Thirty years ago little was known about how memory works, but now we know a great deal. This Chapter will discuss four issues that are central to learning and memory. First, what are the different types of memory? Second, where in the brain is memory located? One possibility is that human memory is similar to the memory chip in a personal computer (PC), which stores all the memory in one location. A second possibility is that our memories are distributed and stored in different regions of the brain. Third, how does memory work? What types of changes occur in the nervous system when a memory is formed and stored, are there particular genes and proteins that are involved in memory, and how can a memory last for a lifetime? Fourth, is the issue of importance to many people, especially as we age: How can memory be maintained and improved, and how can it be fixed when it is broken? Show 7.1 Types of Memory Psychologists and neuroscientists have divided memory systems into two broad categories, declarative and nondeclarative (Figure 7.1). The declarative memory system is the system of memory that is perhaps the most familiar. It is the memory system that has a conscious component and it includes the memories of facts and events. A fact like 'Paris is the capital of France', or an event like a prior vacation to Paris. Nondeclarative memory, also called implicit memory, includes the types of memory systems that do not have a conscious component but are nevertheless extremely important. They include the memories for skills and habits (e.g., riding a bicycle, driving a car, playing golf or tennis or a piano), a phenomenon called priming, simple forms of associative learning [e.g., classical conditioning (Pavlovian conditioning)], and finally simple forms of nonassociative learning such as habituation and sensitization. Sensitization will be discussed in detail later in the Chapter. Declarative memory is "knowing what" and nondeclarative memory is "knowing how".
7.2 Testing Memory
Everyone is interested in knowing how well they remember so let us take a simple memory test. The test (Figure 7.2) will present a list of 15 words, then there will be a pause and you will be asked whether you remember some of those words. Sorry, you have to put your pen down for this test and do not read further in the Chapter until you complete the test. This memory test called the DRM test after its creators James Deese, Henry Roediger and
Kathleen McDermott. It was not meant to be a trick, but to illustrate a very interesting and important feature about memory. We like to think that memory is similar to taking a photograph and placing that photograph into a filing cabinet drawer to be withdrawn later (recalled) as the “memory” exactly the way it was placed there originally (stored). But memory is more like taking a picture and tearing it up into small pieces and putting the pieces in different drawers. The
memory is then recalled by reconstructing the memory from the individual fragments of the memory. The reason so many individuals incorrectly believe that “sweet” was on the list is because there were so many other words on the list that had a sweet connotation. “Failing” this test is actually not a bad outcome. Individuals with Alzheimer’s disease generally do not say that “sweet” was on the list. They cannot make the normal associations involved in the recall of a memory. The word list gives insights into memory processing and retrieval, but it is not a really good test of “raw” memory ability because it can be affected by distortions and biases. To avoid these problems, psychologists have developed other memory tests. One is the object recognition test (Figure 7.3) to test declarative memory. This test is also good because, as we will see later, it can even be used on animals. The test involves presenting a subject with two
different objects and they are asked to remember those objects. There is a pause and then two objects are shown again, one of which is new and the other having been shown previously. Subjects are asked to identify the novel object, and to do so, they need to remember which one was shown previously. A somewhat related test is the object location test in which subjects are asked to remember the location of an object on a two-dimensional surface. Examples of nondeclarative memory, such as associative learning, can be tested by pairing one stimulus with another and later testing whether a subject has learned to make the association between the two stimuli. The classical example is the paradigm developed by the Russian physiologist Ivan Pavlov, which is now called classical or Pavlovian conditioning. In classical conditioning (Figure 7.4), a novel or weak stimulus (conditioned stimulus, CS) like a sound is paired with a stimulus like food that generally elicits a reflexive response (unconditioned response, UR; unconditioned stimulus, US) such as salivation. After sufficient training with contingent CS-US presentations (which may be a single trial), the CS is capable of eliciting a response (conditioned response, CR), which often resembles the UR (or some aspect of it).
7.3 Localization of Memory Now let us turn to this issue about where is memory located. There are three basic approaches.
A classic study on localization of memory was the result of surgery performed on Henry Molaison, a patient who was only known to the scientific community as “H.M.” until his death in 2008. H. M. is famous in neuroscience literature because his brain provided major insights into the localization of memory function. In the 1950’s, H.M. was diagnosed with intractable epilepsy, and while there are pharmacologic treatments, in some cases the only treatment is to remove the portion of the brain that is causing the seizures. Consequently, H.M.'s hippocampus was removed bilaterally. Figure 7.6 (right) is an MRI of a normal individual showing the hippocampal region, whereas Figure 7.6 (left) shows a MRI of patient H.M. after the removal of the hippocampus. Figure 7.6 Before the operation, H.M. had a fine memory, but after the operation, H.M. had a very severe memory deficit. Specifically, after the operation H.M.'s ability to form any new memories for facts and events was severely impaired; he had great
difficulty learning any new vocabulary words; he could not remember what happened the day before. So if H.M. had an interview the day following a previous interview, he would have little or no memory about the interview or events during it. This study clearly indicated that the hippocampus was critical for memory formation. But whereas H.M. had great difficulty forming new memories for facts and events, he still had all of his old memories for facts and events.
Specifically, he had all his childhood memories, and all of his memories prior to the operation. This type of memory deficit is called anterograde amnesia. (In contrast, retrograde amnesia refers to loss of old memories.) The studies on H.M. clearly indicated that whereas the hippocampus is critical for the formation of new memories, it is not where the old memories are stored. It is now known that those old memories are stored in
other parts of the brain, such as in the frontal cortex. The process by which an initially labile memory is transformed into a more enduring form is called consolidation. This process involves the memory being stored in a different part of the brain than the initial site of its encoding. H.M. was also interesting in that while his ability to form new memories for facts and events was severely impaired, he could form new memories for skills and habits. While
he could form new memories for skills and habits, he did not know that he had the skills! He had no awareness of the memory; he couldn’t declare that he had it. This finding clearly indicated that the memory for skills and habits are not formed in the hippocampus. Collectively, we learned from these studies on H.M. and other patients that memory is distributed throughout the nervous system, and different brain regions are involved in mediating different types of
memory. Figure 7.7 summarizes many decades of research on the anatomical locus of memory systems. The medial temporal lobe and structures like the hippocampus are involved with memories for facts and events; the striatum is involved with memories for skills and habits; the neocortex is involved with priming; the amygdala is involved with emotional memories; and the cerebellum with simple forms of associative learning. Lower brain regions and the spinal cord contain even simpler forms of learning. In summary, memory is not stored in a single place in the brain. It is distributed in different parts of the brain.
7.4 Mechanisms of Memory Model systems to study memory mechanisms
Much of what has been learned about the neural and molecular mechanisms of learning and memory have come from the use of so called “model systems” that are amenable to cellular analyses. One of those model systems is illustrated in Figure 7.8A. Aplysia californica is found in the tidal pools along the coast of Southern California. It is about six inches long and weighs about 150 grams. At first glance it is an unpromising looking creature, but neuroscientists have exploited the technical advantages of this animal to gain fundamental insights into the molecular mechanisms of memory. Indeed, the pioneering discoveries of Eric Kandel using this animal were recognized by his receipt of the Nobel Prize in Physiology or Medicine in 2000. Aplysia have three technical advantages. First, it exhibits simple forms of nondeclarative (implicit) learning like
classical (Pavlovian) conditioning, operant conditioning and sensitization. Second, Aplysia have a very simple nervous system. Compared to the 100’s of billions of nerve cells in the human brain, the entire nervous system of this animal only has about 10,000 cells. Those cells are distributed in different ganglia like the one illustrated in Figure 7.8B. Each ganglia like this one has only about 2,000 cells, yet it is capable of mediating
or controlling a number of different behaviors. This means that any one behavior can be controlled by 100 neurons or even less. One has the potential of working out the complete neural circuit underlying a behavior, and then, after training the animal, the neural circuit can be examined to identify what has changed in the circuit that underlies the memory. Third, the ganglia contain neurons that are very large. Figure 7.8B shows a ganglion
under a dissecting microscope. It is about 2mm in diameter. The spherical structures throughout the ganglia are the cell bodies of individual neurons. Each neuron is identifiable and has a unique localization and function. A related advantage is that individual neurons can be removed and placed in culture medium where they can survive for many days. Indeed, multiple neurons can be removed from the ganglia and they reestablish their normal synaptic connections, thereby providing
a very powerful experimental system to study the physiology of nerve cells and the properties of the connections between them. Figure 7.8C shows an example of a sensory neuron (small cell to the right) and a motor neuron (large cell to the left) in culture. In the micrograph it is possible to see the shadow of a microelectrode that has impaled the sensory neuron, and the shadow of a microelectrode that has impaled a motor neuron for performing intracellular
recordings. Sensitization, a simple form of nondeclarative learning amenable to detailed cellular analyses
Figures 7.9 and 7.10 illustrate a simple behavior exhibited by the animal and a simple form of learning called sensitization. The animal is tested by stimulating its tail with a weak electric shock (7.9) or a weak mechanical tap (7.10). These stimuli elicit defensive reflex withdrawals of the body, which includes the tail and nearby sites such as the gill and a fleshy spout called the siphon. In response to test stimuli delivered every five minutes, the withdrawals are fairly reliable. They are about the same duration each time (Figures 7.9B, C, 7.10A). But if a strong noxious stimulus (e.g., an electric shock) is delivered to another part of the animal such as its body wall, subsequent test stimuli to the tail give enhanced responses (Figure 7.9B and 7.10B). This is an example of a simple form of learning called sensitization. It is defined as the enhancement of the response to a test stimulus as a result of delivering a strong generally noxious stimulus to the animal. In a sense, the animal is learning that it is in a “fearful” environment. Sensitization is a ubiquitous form of learning that is exhibited by all animals including humans. Neural circuit and mechanisms of sensitization
Which measure of memory is used on a test?Explicit memory is assessed using measures in which the individual being tested must consciously attempt to remember the information. A recall memory test is a measure of explicit memory that involves bringing from memory information that has previously been remembered.
What are the 3 ways we measure memory?Measures of Forgetting and Retention
Researchers measure forgetting and retention in three different ways: recall, recognition, and relearning.
What are the 4 types of memory?There is much that researchers do not understand about human memory and how it works. This article explores the types of memory and what a person can do to improve their recall.. working memory.. sensory memory.. short-term memory.. long-term memory.. What are the 3 types of memory?The three major classifications of memory that the scientific community deals with today are as follows: sensory memory, short-term memory, and long-term memory.
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