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• Cyber Class Questions
• Learning Objectives
• Introduction
• Definitions/Main Concepts
• Neuropsychological Investigation of Memory
• Learning
• Procedural and Declarative Memory
• Retrieval Processes
• The Study of Age-Related Declines in Memory Functions
• Resource Theories of Age Differences in Aging
• Systems or Structural Theories of Memory and Aging
• Stage Theories of Memory and Aging
• Other Memory Distinctions
• Memory Strategies
• Conclusion
• Exercise
• Key Points

Learning Objectives

• To introduce the topic of memory and aging
• To understand the concept of memory, including its subtypes and various components.
• To explore the general methodological and theoretical approaches to memory and aging.
• To identify some of the current memory strategies to aid in information storage and recall.

Introduction

Given one of my theories that the more often a theme shows up in movies, the more it represents a primordial concern of humans, the complete loss of memory must rank right up there. You know the scene, while credits are still rolling, a man (and why are most movie amnesiacs male anyway?) with no identification, looking a bit confused but generally respectable wanders into a store/restaurant/bar/hospital and asks where he is. We then settle back waiting for the inevitable web of emotional and physical trauma underlying the memory loss to unravel.

But for any of us who have experienced what my older friends refer to as a "senior moment," I hear that even the transient inability to recall someone's name or a well-known phone number can be quite disquieting. While we have all heard the joke that everyday is a new one for someone with no memory, the joke loses its punch when we see someone lose their world as their memory fades.

The reality of being unable to recall who you are, where you live, and to whom you are related is truly one of our worst nightmares. What would it be like to forget where you grew up, what your personality was like and what you liked to do; what kind of a student you were and what your academic and/or vocational choices have been; if you viewed yourself as more artistic or more intellectual or both; what your religious, social, and/or political leanings have been; or even where you parked your car or placed your toothbrush?

As this imagined scenario suggests, our memory has a great deal to do with not only who we are, but also how we function on a day-to-day basis. Our memory serves as a type of signpost so that we know where we've been and where we are going. Barbara Meyerhoff describes memory as the basis for our human identity, with which we can both relive aspects of our past and create our personal history. In addition, memory facilitates our social exchanges and contributes to shared interpersonal history. It serves as means to multiple ends and provides the foundation for critical thinking and decision-making, thus impacting every facet of our lives. Memory is often used as the gauge by which cognitive functioning is measured. Intact memory allows us to function independently, care for ourselves and contribute to the world in which we live. Mildly or moderately impaired memory has a disorienting effect; severely impaired memory isolates us from emotionally or practically meaningful contact with the surrounding world, deprives us of a sense of personal continuity, and renders us passive and helplessly dependent. Thus it is no surprise that we value our memory and fear its possible decline as a result of illness, injury to the brain, or what is often perceived as the inevitable consequence of aging.

So what is this entity we call memory? How is it defined and what are its components? How does memory relate to overall cognitive functioning? What actually occurs in the brain to create a memory? How does memory function? How does information get into the brain, how is it stored, and how does it get retrieved? How is memory evaluated and assessed? What are our criteria for good versus poor memory? How do people vary in the kinds of information they remember? How is memory maintained and enhanced? What have we discovered about memory declines, particularly those related to both the normal processes of aging and pathological events/processes that occur with greater frequency in older age? Fine questions all, I'm sure you agree, but unless I'm Socrates you probably want some answers.

Psychologists began studying memory in the mid-19th century, with Ebbinghaus writing the first monograph in 1885. Ebbinghaus assessed retention of lists of nonsense syllables. He found very rapid forgetting in the first hour, which flattened out at about 30% for delays of up to two days. After that the rate of forgetting slowed markedly, but some forgetting was still apparent after a month. The 1880s have been described as a revolutionary decade for memory research because it marked the beginning of descriptions of memory disorders. Over a century later, although many mysteries remain regarding the complexity of memory, scientific understanding of the forms and processes of memory has markedly advanced. Novel approaches to the investigation of the neural basis of memory have accompanied the realization that memory is composed of different forms. These have included new theoretical developments, increased interest in brain function by cognitive psychologists, and the development and use of various brain imaging techniques.

Neuropsychological Investigation of Memory

The formal neuropsychological study of memory dates back to about 1915, when Karl Lashley embarked on a lifetime endeavor to identify the neural locations of learned activities.

In most of his experiments, he used animal models, removing portions of neocortex of the brain or making cuts of fiber pathways, hoping to prevent transcortical communication between the sensory and motor regions of the cortex. His desire to was interfere with specific memories, but after hundreds of experiments, he was largely unsuccessful in accomplishing his goals. In 1950, he wrote, "It is not possible to demonstrate the isolated localization of a memory trace anywhere in the nervous system. Limited regions may be essential for learning or retention of a particular activity, but the engram is represented throughout the region."

Although Lashley was largely correct in his prediction, only 3 years later, a neurosurgeon by the name of William Scoville inadvertently made one of the most influential discoveries in the study of memory when he operated on the now-famous patient, H.M. H.M. had a history of severe generalized (bilateral) epileptic seizures that had become virtually unresponsive to even large doses of antiseizure medications. Dr. Scoville, in an effort to stop the seizures, performed a bilateral medial temporal resection, which is to say that he removed brain matter, including the amygdala and hippocampus, on both sides of H.M.'s brain. To keep our movie metaphors going, "Groundhog Day" resulted. H.M. was unable to retain most new information without extensive repetition, even though his overall IQ remained above average (118 on the Wechsler Adult Intelligence Scale), his perceptual functioning remained intact, and his memory for events that occurred prior to his surgery was good. So not only were the events of each day largely forgotten, H.M. would often forget what happened hours, or in some cases, minutes before. He is known to have remarked,

"Everyday is alone in itself, whatever enjoyment I've had and whatever sorrows I've hadáAt this moment everything looks clear to me, but what happened just before?" (Milner, 1970)

Thus the case of H.M., who was subsequently followed and studied for more than 35 years, revolutionized the study of memory in that it shifted the emphasis from a search for the location of memory to an analysis of the process of storing memories. Support for the role of the temporal lobes in memory, which had first been proposed around the turn of the century, was increased. Further, increased recognition was given to the fact that there are different classes of memory (H.M. exemplifies one class of memory loss), and that these different types of memory may be more independent than originally thought.

Learning

The first step on our way to a memory is getting the information into the brain. The acquisition and/or encoding of new information through experience or practice is typically referred to as learning, a process whereby attention, perception, and processing of information via various sensory modalities are incorporated. Considered the foundation of memory, learning encompasses complex processes by which experiences change our nervous system, and hence, our memory and ultimately our behavior. Now, a thorough discussion of the various theories and types of learning are beyond the bounds of this lecture. However, before we leave this area, we will touch on some of the common tenets of learning. Carlson discusses learning as occurring in four basic forms:

Perceptual learning is, in simple terms, the establishment of changes within the sensory systems of the brain. It involves learning to recognize and categorize stimuli that have been seen and/or previously experienced. Each of our sensory systems (seeing, hearing, smelling, touching, and tasting) engages in perceptual learning. Perceptual learning appears to be accomplished primarily by changes in the corresponding sensory association cortex. For example, learning to recognize complex visual stimuli involves changes in the visual association cortex; learning to recognize complex auditory stimuli involves changes in the auditory association cortex, etc.

The Human Brain

Stimulus-response learning involves learning to perform a certain behavior when a particular stimulus is present, thus establishing connections between sensory perception and movement circuits. The movement could be an automatic response, such as a defensive reflex, or it could be a complicated sequence of movements. Stimulus response learning includes two major classes of learning that psychologists have studied extensively: classical conditioning and instrumental conditioning. (We'll send you to Psychology 101 to brush up on those learning theories.)

Motor learning is a special form of stimulus response learning wherein establishment of changes occurs within motor systems with sensory guidance from the environment. Generally, the more novel the movement behavior, the more the neural circuits in the motor systems of the brain must be modified.

Relational learning involves learning the complex relations among stimuli in such a way that we are able to make complex connections. For example, if we were to go for a walk in the dark of night and feel a first drop of rain on our cheek, we can imagine what a drop of rain might look like, and what it sounds like when it hits certain objects. Thus the neural circuits in the somatosensory cortex that recognize the feel of a raindrop on the skin have come to be interconnected to the appropriate circuits in the visual and auditory association cortexes. There are several types of relational learning: spatial learning (perception of spatial location), episodic learning (remembering ordered sequences of events), and observational learning (learning by watching and imitating, which requires us to remember what someone else does and how they did it, and the relationship between our own and the other person's movements).

Procedural and Declarative Memory

After information has been encoded it then has to be stored. Most memory research has focused on two main memory systems: procedural (nondeclarative) memory and declarative memory, and of these, declarative memory has received greater attention. Larry Squire, a neuropsychologist at UCSD breaks down memory as follows:

Procedural (nondeclarative) memory is generally not what people refer to when they mention experiencing problems with their memory, as this type of memory is largely unconscious. Mishkin and Petrie (1984) refer to this as "a habit system", a memory system that includes retention of well-ingrained or "overpracticed" abilities such as the capacity to walk, talk, dress, eat, etc. Procedural memory is a "hearty" memory that tends to be preserved even in most amnestic patients; it is generally the last domain to decline in such cognitive degenerative illnesses as Alzheimer's disease.

There are several categories of procedural memory that have been recognized, all of which can be classified under a broader subdivision of memory referred to as implicit memory. Implicit memory is generally defined as "knowledge that is expressed in performance without the subjects' phenomenal awareness that they possess it" (Schacter et al., 1988), and the term is often used synonymously with procedural memory. Explicit memory is the inverse of implicit memory, in that it is available to conscious awareness and usually involves an intentional recollection process.

Declarative memory involves the ability to learn and remember information, objects, and events. Declarative memory encompasses the acquisition, retention, and retrieval of knowledge that can be consciously and intentionally recollected (Cohen & Squire 1980). Such knowledge includes memory for events (episodic memory) or facts (semantic memory) (Tulving 1983).

That is a distinction can be made between episodic, or event memory (which refers to a person's own experiences that are unique and localizable in time and space), and semantic memory (which refers to what is learned as knowledge, typically timeless and nonlocalizable, and likely does not directly relate to a person's experiences). Learning the alphabet or the contents of this course would be semantic memory.

Declarative memory is a catchall phrase, as you will soon see, and encompasses a wide variety of memory processes. This is the kind of memory to which people usually refer when they claim to be having memory problems. It has also been described as "the mental capacity of retaining and reviving impressions, or of recalling or recognizing previous experiencesá" (Stein, 1966). Now, a multitude of theories about stages and/or processing levels of declarative memory have been advanced, but for the sake of providing a framework for conceptualizing and understanding normal memory processes and how memory may become dysfunctional with advancing age (and/or illness/injury), we will focus on two succeeding stages: short-term memory, and then long-term memory. Then we will address more aspects and elements of declarative memory, particularly when it comes to retrieval of information and pathological brain conditions that may interfere with declarative memory.

You will likely recall from your previous studies that memory for stimuli that have just been perceived, such as a telephone number received from a 411 operator, or directions to a certain establishment, is called short-term memory. Memory for things that are remembered for a long period of time such as your own phone number or the route to your home is called long-term memory. These types of memory require different processes.

Short-term memory can hold only a limited amount of information. To demonstrate, read the following numbers to yourself just once, then close your eyes and recite them back:

6 7 1 9 0 4 6

You probably had no trouble remembering them. Now try doing the same with the following, again go through them ONLY ONCE before you close your eyes:

9 4 8 2 0 7 6 1 7 5 2 3

Very few people can repeat 11 numbers, at least not without utilizing some means, such as rehearsal, to make the information "stick" in memory. We'll talk more about rehearsal later.

First, let's talk more about aspects of short-term memory. As referred to earlier in the encoding aspect of our information-processing model, the process begins with registration or sensory memory, which retains large quantities of incoming information momentarily (1-2 seconds at most). Registration includes the determination of what information is to be held, even briefly. Of course, numerous aspects of perception and response predisposition (e.g. mood and attention-focus) play into what information gets registered. At this point, the information is either further processed or it quickly decays and is "lost".

Immediate memory, the actual first stage of short-term memory storage, temporarily holds information retained from the registration process. Immediate memory has a limited capacity, as was demonstrated earlier. Most individuals are able to manage about 7 bits (+ 2) of information at any given time (thus the 7-digit phone number). Although there is some contention that there are differences between immediate memory and working memory, the primary function of both is to "hold information in mind, or to internalize information, and to use that information to guide behavior without the aid of, or in the absence of external cues" (Goldman-Rakic, 1993). Another term you may hear in conjunction with immediate memory is primary memory. Primary memory is synonymous with simple immediate span of attention that extinguishes promptly with distraction and is therefore repeatedly replaced. Early stage Alzheimer's patients, for example, may exhibit a relatively intact working memory, but a very tenuous primary memory.

Research evidence suggests that information in immediate memory is temporarily maintained in "reverberating neural circuits", which are self-containing neural networks that sustain a nerve impulse by channeling it repetitively through the same network (Shepherd and Koch, 1990). It appears that, if not transformed into a more durable biochemical organization for longer lasting storage, the electrochemical activity that constitutes the immediate memory trace spontaneously dissolves and the memory is not preserved. For example, you will not remember verbatim the previous sentence, even though you just read it, unless you happen to be one of those rare people with truly "photographic" memory.

Rehearsal is any repetitive mental procedure that prolongs the duration of a memory trace. With rehearsal, a memory trace may be retained for hours, and the likelihood that a given bit of information will be permanently stored increases.

Some kinds of short-term memory appear to last longer than immediate memory, but seem to be gone within a few hours or a few days (much like what sometimes happens when we cram for an exam, learning the material for immediate recall, or as some students call it, "regurgitation", but then we are unable to hold onto much of the vast amount of information once the exam is done). Some researchers propose that these are actually "newly laid" long-term memories, but that they are relatively vulnerable to interference effects.

Long-term memory (sometimes called "secondary" memory) refers to the storage component of our information-processing system. The process of memory storage, consolidation, may transpire rapidly, or persist for relatively longer periods of time without requiring additional conscious involvement. Long-term memory storage involves a number of processes occurring at the cellular level, such as neurochemical alterations in the neuron and at the synapse between nerve cell endings, increased branching out of the dendrites of the cell structures to increase the number of contacts made with other cells (Bailey & Kandel, 1985; Mayes, 1988), and possible "pruning" of some connections that have not been used (Singer, 1990). These cellular processes of learning and memory are of particular interest in the process of the aging brain, particularly when we consider the effects of continuing intellectual challenge, or lack thereof, in the brain of older adults. As discussed briefly earlier, researchers have concluded that there is not a single storage site for stored memories, rather memories result from neuronal connections and interconnections from many cortical and subcortical centers (Squire, 1987). Storage and retrieval of memories appear to take place according to principles of association, with different brain systems playing different roles in memory. Therefore, a breakdown in the capacity to store and/or retrieve information may involve any number of brain sites and/or communication pathways between sites. And how and where the breakdowns occur results in distinctive memory disorders.

Recent memory is a clinical term referring to consolidated information stored within the last few hours, days, weeks, or even months, whereas remote memory dates from early childhood. However, it is realistically impossible to ascertain where recent memory ends and remote memory begins in intact individuals. The sub classification tertiary memory is sometimes used in discussing memory states associated with aging, as older adults may exhibit relatively stronger and more accessible memory for experiences and acquired knowledge from their earlier years than recently learned information (Kasniak et al., 1986).

Retrieval Processes

Memory deficits or difficulties assume many different forms. Besides the overriding distinctions between short- and long-term memory, individuals may display deficits that are specific to the nature of the information to be learned, i.e. material specific. Deficits may be specific to either verbal or nonverbal information or to motor-skill, or may involve a combination of these modalities. Neuropsychologists are able to perform detailed evaluations in order to determine what sensory modalities, knowledge categories, and/or output mechanisms may be affected by brain injury or disease, or by the normal process of aging. For example, a common memory battery, the Wechsler Memory Scale (now in it's third edition) tests both short-term and long-term memory for verbal material (e.g. word lists, logical prose material) and nonverbal material (e.g. faces, relatively simple drawings). Most neuropsychological evaluations also include motor skills testing, such as drawing and writing, Grooved Pegboard, hand dynomometer, and/or tests of praxis, or recall of deliberate movements employed in the execution of simple and complex motor acts, such as combing one's hair, stirring, standing, etc.

Some loss or diminished access to information, both remote and recently acquired, occurs normally and continuously in all individuals. Forgetting rates vary according to many variables, such as the relevance or meaningfulness of the material for the person, individual conceptual styles, and psychological factors, such as affective (mood) correlates and stress levels. A number of hypotheses have been presented as to what the processes of forgetting might be. Even Freud had an opinion on this, proposing that we don't really forget anything; rather the information becomes inaccessible to the conscious mind because of the mind's tendency to repress some memories.

Others suggest that what is "forgotten" is actually lost from memory because of a replacement effect, and/or because of interference by other more recently or "vividly learned" information (Squire, 1987), or because of disuse (the old "use it or lose it" principle). What seems likely is that both processes, both psychodynamic suppression/repression of unwanted or unneeded memories and organic dissolution may be at work in the normal "forgetting" process. A highly simplified but useful schematic of how memory is mediated in the brain is provided by Posner and Raichle. While a full discussion of the neuroanatomical substrates of memory is beyond this lecture's scope, suffice it to say that numerous areas of the brain are involved in different types and modalities of memory.

The Study of Age-Related Declines in Memory Functions

Anecdotal evidence suggests that, by far, more older than younger adults complain of memory problems. Although a large and continually growing body of research has validated many of these age-related differences in memory functioning, results are not always easy to decipher and/or to compare. As we have seen in our opening discussion, the complex nature of memory makes it difficult to determine what aspect(s) of memory may be involved in quality of performance.

We're going to spend some time reviewing major methodological and theoretical issues in the study of memory and aging. First, a word about research methodology. There are primarily two research methods used to investigate age differences in memory. The first is referred to as interaction research. This method involves utilization of different age groups, manipulating task or stimulus variables, while looking for statistical interactions between the manipulated variables and age. For a better understanding of interactions visit http://www.statsoff.com The main difficulty with this type of design is that memory is simply too complex to be chronicled by basic two-way interactions. In addition, cognitive mechanism(s) responsible for any observed interactions can only be inferred because most of these studies fail to include independent measures of the theoretical constructs. Nevertheless, interaction studies have provided increasing refinements in the specification of age-differences in memory. For example, initial published results reported the absence of age differences in aspects of memory such as recognition versus recall, implicit versus explicit, semantic versus episodic, etc., only to be later revised following more complex analysis suggesting that the two-way interactions between age and the specified condition were found to vary according to another condition or variable.

Another (increasingly prevalent) methodology is individual-difference research. This research involves using statistical procedures such as correlation techniques to identify the cognitive mechanism(s) responsible for age-related variance in memory performance. First investigators collect independent measures of some theoretical construct that is reputed to underlie age differences in memory. Then the extent to which these measures covary with memory performance is examined using various statistical techniques. The value of this methodology is that different memory factors such as working memory, verbal learning and recall, and attention, as well as non-memory variables such as age, education, and health conditions can be directly related to possible underlying memory mechanisms. Of course, as in any good research, the measures used to operationalize the constructs must have good reliability and validity.

In the context of discussing specific research findings regarding age-related memory differences, we'll address three main theories related to memory and aging: resource theories, systems or structural theories, and stage theories.

Resource Theories of Age Differences in Memory

Resource theories propose that there are a number of mechanisms that account for age differences in memory. The first is environmental support. According to Craik (1994), age differences are likely to be found when a given memory task fails to provide sufficient environmental support, thus requiring the individual to utilize more self-initiated processes in order to remember. So, for example, one of the reasons given for increased dependence on recognition (versus recall) in aging memory is that the former provides greater environmental, or contextual support, whereas the latter requires self-initiated search processing in order to retrieve the information. In one experiment, Craik & McDowd (1987) had subjects perform a secondary task involving choice reaction times while they also performed a series of either recall or recognition paired associate tasks. Results indicated that even when performance levels on the recognition and recall tasks were equated, large age differences were found on recall but not on recognition. In addition, reaction times on the secondary task were lengthened with the recall task compared to the recognition task, and this effect was further inflated for the older age cohort.

A related theory is that the size of the age difference on memory tasks depends on the extent to which the tasks require deliberate processing, which requires self-initiated cognitive effort, rather than automatic processing, which functions independently of effort or even attention, much like procedural memory discussed earlier. This hypothesis comes mainly from the work of Hasher and Zacks (1991) who suggested that age differences would be evidenced only on tasks requiring deliberate processing.

That is a distinction can be made between automatic and more effortful memory. The former involves relatively more passive acquisition and later retrieval of information, whereas the latter requires more active, effortful processing of the information. Clinically, differences can be seen when a person with some sort of brain deficit or damage (such as is common in Alzheimer's disease, head trauma, multiple sclerosis) is able to immediately recall digits (e.g. counting from 1 to 20) or days of the week without difficulty, but they show inhibited performance when asked to count or say the days of the week backwards, a task requiring increased processing.

his theory has received support from the literature on priming, which is purported to be a more automatic or implicit measure of memory. An example of priming is presenting the subject with fragments of a word learned earlier such as g e _ _ra_ ion. A large body of research suggests that there are greater age-related memory differences when explicit rather than implicit memory measures are used. You may wish to read reviews on aging and implicit memory in Graf (1990) and Kausler (1994).

One of the problems encountered in this area of research is difficulty measuring the extent of automatic versus deliberate processing in a given task, for there is generally a great deal of overlap in the ways in which individuals handle information, using both processes. While Jacoby (1991) has noted that both implicit and explicit memory task performances are influenced by both processes, (which he refers to as "familiarity" and "deliberate recollection"), his group has developed a procedure for separating these processes, with resulting conclusions that older adults have deficits only in the latter (Jacoby et al., 1993).

Taking the processing hypotheses to a greater level of specificity, a third theory recognizes failure to integrate context. This theory of age-related memory differences suggests that older adults have greater difficulty integrating the memory context with the information they are trying to remember, thus diminishing the cues they will need for later retrieval. Evidence supporting this long-standing hypothesis is mixed. A number of studies show age differences in memory for context. For example, geriatric adults have shown relatively greater inability to identify whether a word was presented to them auditorily or visually (Lehman & Mellinger, 1986), or which voice presented a list of words (Ferguson et al., 1992). However, other investigators have reported that the degree to which deliberate processing is required to integrate the focus item (the item to be remembered) and the context is an important determinant of whether age differences are observed in failure to integrate context. Again, when more effortful integration is required, age differences are observed, but when less proactive integration is necessary, age differences are smaller.

The failures of inhibition hypothesis proposed by Asher and Zacks (1988) suggests that older adults exhibit processing resource limitations because of inefficient inhibition of "task-irrelevant thoughts". Because of failure to inhibit off-task thoughts, there is purportedly less working memory capacity for on-task processing.

Significant, reliable age differences have been found in working memory (see for example, Salthouse, 1991). A general working memory hypothesis is that older adults show less ability to multi-task, or specifically, to simultaneously perform a cognitive task while trying to remember some of the information for a later memory task. And aging appears to adversely affect free recall more so than cued recall, with free recall considered a higher-demand working memory task requiring self-initiated processing, When working memory is broken down into its supposed components (e.g. storage, processing, and other aspects of executive functioning), processing thus appears to be the most sensitive to age differences.

Another hypothesis focuses on reduced perceptual speed as accounting for many, if not most age-related differences in memory. It is obvious that most older adults are slower, with slower responses not simply due to motor slowing. Researchers have reported declines in several aspects of sensory perception related to aging, including reduced odor detection and identification, decreased subjective sensory thermoregulatory (sense of heat and cold) perception, and reduced visual perception and detection of objects from their background. Aging also appears to affect the more numerous processing steps required for the analysis of higher-level visual stimuli. Thus it is not surprising that perceptual speed is a strong consideration in memory research.

The work of Salthouse has consistently shown that older adults perform significantly more slowly when the cognitive complexity of a task increases, thus impacting perception, processing, recall, and other aspects of memory. In Salthouse's 1993 study, perceptual speed accounted for over 80% of the age-related variance in the recall measures. Speed of performance and working memory have been shown to be important considerations of age differences in memory. In fact, they are likely constructs that underlie cognitive performance in general and may be a good marker of a number of fluid intellectual measures.

As we review the six resource hypotheses for age-related memory differences discussed above, it is important to keep in mind that the function highlighted by each hypothesis does not stand in opposition to the others, or that each is independent of the others. Rather the similarities and overlaps outweigh the differences. Older adults appear to experience increased sensitivity to environmental support, deficits in deliberate processing, failures in integrating context, and failures of inhibition, working memory, and perceptual speed. Researchers in these areas clearly recognize the ongoing need to tease out reliable independent measures of the constructs they desire to investigate, as well as to increase understanding of how these various components work in concert with one another to impact memory.

Systems or Structural Theories of Memory and Aging

The ways in which we theoretically and scientifically approach significant investigative questions related to age differences in memory is established by how we conceptualize memory. In general there have been two main veins of conceptualization directing research on aging and memory. As previously discussed, the first presupposes that there are age differences in processing effectiveness due to disparities in processing resources. The second is the conjecture that age differences are attributable to specific memory systems or structures. Considering this second tenet, the goal of research is to figure out whether the different systems are affected differently by aging.

To briefly review the memory systems we covered, there is short-term memory (current information processing) and long term memory that is based on past experiences. Most research based on conceptualization of memory, and memory difficulties, as specific to memory systems or structures attempt is to find differential age effects that are restricted to one system but not another. So, for example, age differences have been reported in explicit memory (recall), but not in procedural (implicit) memory in subjects (Park & Shaw, 1992), and in working memory (reading span), but not in primary memory (digit span; Wingfield et al., 1988). One of the problems with this research approach is that scientists aren't yet sure how to deal with smaller or larger age differences between different memory systems. For example, several studies have found age differences in implicit memory, but they are smaller differences than those found with select explicit memory tasks (Hultch et al., 1991).

Stage Theories of Memory and Aging

A popular trend in the 1970s and 80s was to look for age differences between the different stages of encoding, storage, and retrieval. However, current research concentrates more on specifics within the stages themselves.

The main assumption in research on age-related encoding differences is that age differences are primarily due to older adults' less elaborate processing, and that these differences should be reduced when the nature of processing is controlled during encoding. However, study results have been inconclusive. For example, some studies report that increased elaboration at the encoding stage show greater effects for younger subjects (e.g. Puglusi & Park, 1987), others show a greater benefit for older adults (e.g. Park et al., 1990) and some show virtually equal effects (Park, Puglisi & Smith 1986). You'll notice that even the same investigators have diverse findings across studies. Craik & Jennings (1992) took a closer look at these different studies and suggested that there may not be a linear relationship between elaboration during the encoding process and age. Specifically, this group proposed that younger adults may show initial improvement but level out at asymptote, whereas older adults don't show improvement at the beginning but then begin to improve, eventually reaching the same level of asymptote. As you might guess, this configuration would result in very different patterns of findings depending on where on the memory elaboration dimension the particular sampling occurred.

Research that has focused on potential age-related differences that occur in memory at the storage stage generally shows that no differences exist between younger and older adults on this factor. For example, these conclusions were drawn as a result of assessing semantic organization with a free-association test, using both pictures (Puglisi et al., 1987) and words (Burke & Peters, 1986). The idea behind utilization of this procedure is that possible differences in the way information is stored or represented in memory could be elucidated in the resulting pattern of free association. There is some argument that because older adults demonstrate some problems with verbal fluency/word finding, that this may be an age-related storage problem; however, Light (1992) and others argue that this is likely more due to lexical access than organizational deficits.

In focusing specifically on the stages, probably the toughest aspect of this has been attempting to look at retrieval effects separately from potential age-related encoding differences. For example, research shows that greater age differences exist on free recall than recognition between older and younger adults. But is this a retrieval problem, as is often assumed, or, based on what we discussed earlier in regard to relative processing deficiencies in older adults, could this be a problem of processing when the memory material is presented? Whitte's group (1993) has suggested that relational or organizational processing is more difficult for older adults. If this is so, then the relatively better performance on recognition may result from a reduced need for organizational encoding when engaging in recognition rather than recall.

Tip of The Tongue, by Dave Coverly

One interesting aspect of retrieval problems is the old familiar "tip-of the tongue" phenomenon (problems retrieving a well-known word or familiar name), which we all experience from time to time. This experience has been shown to be more prominent in older than younger adults (Burke & Laver, 1990). But, similar to younger adults, most of the time older adults are eventually able to recall what it was they wanted to say, indicating that this is a temporary condition. I don't know of any research that has looked at differences in eventual retrieval time between older and younger adults.

Although research related to memory and aging once focused more prominently on stage theories, resource theories discussed previously seem to be the hot ticket these days. This is primarily because the hypotheses on which current studies are based are appropriately more focused on processing characteristics in different age groups, thus providing a better depiction of effects seen at both encoding and retrieval.

Other Memory Distinctions

Most research on memory and aging has been dominated by use of verbal materials. However, as we've noted, there are other memory distinctions to consider, such as memory for nonverbal information like spatial locations and directions, faces, and scenes. With few exceptions, older adults show declines in spatial memory, such as where an object appeared in one of four quadrants, where to locate objects in a room after performing various tasks in that room, and remembering where to place objects in a 3-dimensional model. Memory for faces and for map routes has also been shown to weaken with age. Research related to memory for activities and actions has had equivocal results, depending on specific tasks. It is generally suggested that older adults have problems when trying to remember which complex activity they had performed earlier; however, fewer age differences have been found in recall of simple actions. Kausler (1994) has suggested that the reason for smaller age differences in memory for actions and activities when compared to verbal recall is the independence of rehearsal in performing the actions (as performing an activity automatically encodes it).

A clear trend in memory aging research has been the melding of the behavioral study of memory with neuropsychological research examining underlying brain mechanisms and functions. For example, read the following abstract:

Rabbitt P. Lowe C. (2000). Patterns of cognitive ageing. Psychological Research. 3(3-4):308-16.

"Neuroanatomical evidence suggests that normal ageing affects some brain areas, and the "local" functions they support, earlier and more severely than others. Changes appear to be especially marked in the hippocampus, temporal association and prefrontal cortex. Evidence from classical neuropsychological studies suggests that these brain areas are associated with memory and "executive" functions, respectively. We may, therefore, expect that tests purported to measure these functions may be disproportionately affected in old age and that there may be evidence for some separation of these functions even within neurologically normal populations. What we also know, however, is that measures reflecting general fluid ability also decline with increasing age, so any hypothesis relating to specific "local" deficits must acknowledge and account for any "globar" changes in performance. Volunteers (n = 162) aged between 60-80 years who had completed the Cattell and Cattell Culture Fair Intelligence Test (CCF) completed the Cambridge Automated Neuropsychological Test Battery (CANTAB). The CANTAB has been administered to several patient populations and tests from the battery have been shown to be sensitive to damage in both temporal and prefrontal areas (Owen et al., 1996). Results from the test battery showed that both the Paired Associate Learning and Spatial Recognition tests were the most sensitive to normal ageing even when CCF is accounted for. In contrast, this performance on the "executive" tests, shown to be sensitive to frontal lobe damage was not related to age, and CCF scores predicted performance on these tests. These results are discussed in relation to theories of cognitive ageing and patterns of change and in relation to several important methodological and theoretical considerations for the study of executive function.

Memory Strategies

As you recall from our discussion, a memory goes through several stages where information gets associated and obtains meaning on its way to longer-term storage. Thus if information becomes degraded or only partially integrated into an individual's knowledge base during memory processing, this would have profound implications for all aspects of memory, including accurate information retrieval. A number of strategies have been devised to help memory, increase the depth of processing of information, and thereby serve to aid in learning and subsequent recall of the information.

Repetition: Repeating information that is heard or read has been shown to improve later recall of the information. Repetition is usually verbal, either writing the information down (sometimes repeatedly), or verbalizing it to oneself or aloud. This strategy can also be used with nonverbal material such as maps, directions, diagrams, or even "doodles". This strategy works well if one needs to keep information in mind for a relatively brief period of time, like repeating a phone number an operator has given you when you can't seem to find a pen and paper.

Use it in a sentence: Verbal material to be remembered, such as a word or names of people or places one wants to remember, can be placed in a sentence, thus providing a greater context and likelihood of recall or at least recognition.

Rhyme it, or create a song out of it: Most of us learned our English alphabet this way. An old song (from the 60s maybe?) called "The Name Game" used this principle. "áLet's try David: David David bobavid banana fanna fofavid. Me my momavid. David."

Give it a "face"/Association: Similar to some of the other strategies, the principle behind this strategy is to make meaningful connections between the information in working memory and information already known.

Mnemonic: This is another related concept, because it again has to do with association. Most students are familiar with mnemonic devices, as this strategy is often helpful in remembering lengthy or more complex information. Some of you might remember a mnemonic for recalling the names of the planets in their order of proximity to the sun (before the discovery of many more planets):

Many Very Energetic Monkeys Jumped Sideways Under Nuts (Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune).

These are just a few of the devices prescribed for memory enhancement. Other methods abound.

Conclusion

Memory is not a unitary process. While I think that memory is an area in which I have a relative amount of expertise, trying to put together a structured logical lecture made me realize what a hodgepodge of conceptual and empirical approaches are currently used. I'm sure our approaches are going to keep changing as well. And the link between understanding memory and being able to do anything about memory ability is a whole other ballgame. Not to sound overly pessimistic but until we have more comprehensive and testable theories of memories, it is probably overly optimistic to think we will escape the ill effects aging has on memory.

Key Points

Ebbinghaus' Forgetting Curve (1885) began the formal study of memory.

Memory involves a combination of related functions and systems by which humans register, retain, store and retrieve information.

The information processing approach has been used to study learning and memory in terms of encoding, storage and retrieval.

Neuropsychological investigations on memory include

• Karl Lashley's animal work demonstrating no single locations for memories, and
• William Scoville's surgery on H.M., producing a subsequent deficit in H.M.'s short but not long term memory with removal of the amygdala and hippocampus.

Learning, or the acquisition and/or encoding of new information, includes

• Perceptual learning--changes in the sensory systems of the brain; especially sensory association cortex
• Stimulus-response learning--learning to perform a certain behavior when a particular stimulus is present; classical conditioning (e.g., Pavlov's dogs), instrumental learning (dog obedience school)
• Motor learning--learning/changes that occur within motor systems; e.g., riding a bike
• Relational learning--learning complex relationships among stimuli; e.g., spatial learning, episodic learning, observational learning--Galen's description of this last type makes me think of the ballroom dancing lessons my husband took me to a few years ago--hilarious and fun.

Procedural (nondeclarative, implicit) memory describes memory processes for which we have no awareness. For example, the habit system and overpracticed abilities fall into this category.

Declarative memory is remembering that is conscious and effortful, such as recalling a list of names or words. This is further divided into

• episodic memory--memory for events, facts within a temporal context (e.g., who were you with and what did you eat for dinner last night?)
• semantic memory--memory for facts, knowledge (e.g., your abc's).

The two major conceptualizations of stage or processing levels of declarative memory are short-term and long-term memory.

Short-term memory can be further divided into

• registration or sensory memory--information retained momentarily (1 to 2 s)
• immediate memory--the first stage of actual memory storage; bits of information 7 (plus or minus 2) held for processing; note this could also describe working memory,
• primary memory.

Rehearsal is any mental procedure that prolongs the duration of the memory trace.

Long-term (secondary) memory refers to the storage component of the information processing system. The process of memory storage, called consolidation, involves

• neurochemical alterations in neurons and synapses
• increased branching of dendrites
• possible pruning of some connections

Long-term memory includes

• recent memory--information stored within hours, days, weeks, months
• remote (tertiary) memory--e.g., early childhood memories.

The two primary mechanisms of memory retrieval are recall and recognition. Recall is an active search process whereas recognition involves cues or triggers to facilitate remembering (e.g., multiple choice tests).

Forgetting varies depending on the amount of information to be recalled, relevance of the information to the individual, individual conceptual styles, and psychological factors such as mood or stress. Some hypotheses related to the process of forgetting are

• repressed memories (Freud)
• replacement of information (L. Squire)
• disuse ("use it or lose it").

Two methodological designs used to study age-related decline in memory function are

• interaction research--looking for age by memory performance interactions
• individual-differences research--looking for multiple variables that may contribute to or are associated with particular patterns of performance

Three main theories address age-related memory differences: resource theories, systems or structural theories, and stage theories.

Resource theories of age-related memory differences can be grouped into six general hypotheses, all proposing that age differences in memory are due to disparities in some aspect of information processing resources:

• environmental support--older compared to younger adults are more sensitive to the amount of contextual or environmental support (cues) supplied in the retrieval process
• deliberate processing--self-initiated cognitive effort, as opposed to automatic processing, which requires little or no effort or attention (Hasher & Zacks,1991); note that this is similar to the distinction between explicit and implicit (e.g., priming) memory
• failure to integrate context--the idea that older compared to younger adults have more trouble integrating the context of the learning situation with the information they are trying to remember
• failures of inhibition--the idea that older compared to younger adults have more difficulty inhibiting stimuli that are irrevelant to the task at hand
• working memory hypothesis--older adults appear less able to multi-task, suggesting age declines in the the processing component of working memory
• perceptual speed--sensory speed, not just motor processing, is slower in older compared to younger adults

Systems or structural theories of aging propose that there are age differences in specific memory systems or structures. For example, explicit vs. implicit memory, working vs. primary memory.

Stage theories of memory and aging focus research on either encoding, storage and/or retrieval.

• Encoding--theories in this area propose that age differences are due to less elaborate processing at encoding by older adults.
• Storage--current research suggests there may be no age differences in this stage.
• Retrieval--older adults show larger deficits on recall vs. recognition paradigms. "Tip-of-the-tongue" phenomena are more frequent in older than younger adults.

Memory for nonverbal information, e.g., spatial locations and directions, faces, and scenes, also show age-related declines.

Memory strategies include rehearsal, elaboration or association, for example:

• repetition
• use it in a sentence
• rhyme or create a song out of it
• give it an association or "face"
• mnemonic--"many very energetic monkeys jumped sideways under nuts"