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PubMed2001

Working memory for location and time: activity in prefrontal area 46 relates to selection rather than maintenance in memory.

The role of the dorsal prefrontal cortex in working memory remains controversial. Influential proposals include a role in the maintenance of domain-specific information, and the processes of executive functions on remembered information. We used event-related functional magnetic resonance imaging to demonstrate a functional dissociation within prefrontal cortex in terms of the components of complex working memory tasks. The maintenance in working memory of spatial locations and their temporal order was associated with activation of area 8 and intraparietal cortex. In contrast, the selection of one location, according to its order, was associated with a distinct frontoparietal network, including dorsolateral prefrontal area 46, ventrolateral prefrontal cortex and anterior cingulate cortex and medial parietal cortex. The different contributions of these areas to selection are considered in the light of recent electrophysiological and lesion studies. We suggest a general role of the dorsolateral prefrontal area 46 in attentional selection, including selection from within working memory.

Adult↗

PubMed1999

Spatial working memory and reference memory of Brown Norway and WAG rats in a holeboard discrimination task.

To determine whether working memory (WM) and reference memory (RM) represent different aspects of spatial memory, albino WAG rats and the pigmented Brown Norway rats were tested in the acquisition, retention, and reversal of spatial orientation tasks in the holeboard, which allows the simultaneous assessment of WM and RM. Putative nonmnemonic factors, such as the speed of visiting the holes or the development of a search strategy (preferred sequence of visiting the baited set of holes) were also evaluated because they might influence WM and RM performance. The WM performance of Brown Norway rats was generally worse than that of the WAG rats. The reverse was true for the RM performance. Correlation analysis supported the notion that these two measures are independent. Differences in the speed of visiting the holes and in the development of a preferred sequence of visiting the baited set of holes could not explain the strain differences in WM and RM performance. Because spatial WM and RM appear to be independent measures in the holeboard, this task could be used to investigate whether different neural substrate(s) underlie these two memory components.

Animals↗

PubMed1992

Memory monitoring and memory performance: linked closely or loosely?

An experimental test of the metamemory hypothesis claiming a substantive positive relationship between memory monitoring and memory performance is provided. Forty-eight university students learned a set of abstract nouns. They were either instructed to make use of monitoring activities (experimental group), simply to learn the words (control-1) or to use non-metacognitive learning strategies (control-2). Prior to recall, the subjects had to predict the number of items they expected to remember. The experimental predictions were derived on two levels. First, prediction accuracy should be best for the experimental group. This is a necessary prerequisite for a valid test of the second prediction, namely that memory performance, too, should be best for the experimental group. Whereas the first prediction was confirmed, the second, vital for the metamemory hypothesis, was not. Thus, this hypothesis did not stand up to an experimental test, but would have been confirmed if tested by the correlation between prediction accuracy and memory performance.

Adult↗

PubMed1991

On the pharmacological phenocopying of memory mutations in Drosophila: alkylxanthines accelerate memory decay.

Theophylline and 3-isobutyl-1-methylxanthine, two cyclic nucleotide phosphodiesterase inhibitors, when fed to wild-type Drosophila adults, cause the rapid decay of learning index after training in a shock-odor learning paradigm. The drugs practically do not affect the olfactory acuity of flies, hence they influence the learning/memory process itself. The time courses of memory decay resemble those of the memory mutants rutabaga and amnesiac and, to a lesser extent, dunce2 and dunceM11. Theophylline further deteriorates the learning performance of dunceM11. Biochemical characterization of the inhibition of the two major phosphodiesterase isoenzymes in Drosophila by theophylline predicts only a slight inhibition of these enzymes in vivo, in accordance with the unchanged level of cAMP in wild-type fly heads during drug feeding. 8-Phenyltheophylline, an adenosine receptor antagonist in mammals, slightly retards memory decay in the wild-type. It is suggested that alkylxanthines induce memory decay in Drosophila by interfering with cAMP dynamics at more than one point of its metabolism.

1-Methyl-3-isobutylxanthine↗

PubMed2006

Eye movements and prospective memory: what the eyes can tell us about prospective memory.

In this study we used eye tracking methodology in combination with multi-element displays to examine the processes underlying event-based prospective memory in a visual search paradigm. In the task individuals searched for a different target stimulus (i.e., a letter) on each trial that could be present or absent, and made prospective responses to the letters D or M. The response accuracy data revealed that target hits were more frequent than prospective hits, and that there was no difference in response time for target and prospective responses. The eye tracking data revealed that both first and total fixation durations increased from distractors (stimuli that were neither targets nor prospective cues) to targets to prospective cues when a target or prospective response was made. These measures also revealed that the presence of a target in the display served to disrupt prospective memory. In addition, prospective memory misses resulted from a combination of failures to fixate the prospective cues and failures to engage in strategic processing of the prospective cues. These data demonstrate the utility of eye tracking methods in examining the processes underlying event-based prospective memory.

Analysis of Variance↗

PubMed2004

Visual imagery deficits, impaired strategic retrieval, or memory loss: disentangling the nature of an amnesic person's autobiographical memory deficit.

Conclusions about the duration of hippocampal contributions to our autobiographical record of personal episodes have come under intense scrutiny in recent years. Interpretation is complicated by such factors as extent and site of lesions as well as test sensitivity. We describe the case of an amnesic person, K.C., with large, bilateral hippocampal lesions who figured prominently in the development of theories of remote memory due to his severely impoverished autobiographical memory extending across his entire lifetime. However, the presence of lesions in higher-order visual cortex raises the possibility that K.C.'s retrograde autobiographical amnesia is mediated by loss of long-term visual images, whereas widespread frontal lesions suggest that his impairment may relate to deficits in strategic retrieval rather than storage. Normal performance on an extensive battery of visual imagery tests refutes the imagery loss interpretation. To test for deficits in strategic retrieval, we used a more formal autobiographical memory test requiring generation of personal events under varying levels of retrieval support. However, even with rigorous contextual prompting, K.C. produced few pre-injury recollections; all were schematic, lacking the richness of detail produced by control participants, raising doubt that his deficit is one of retrieval. Findings are discussed in the context of theories concerning the duration of hippocampal-neocortical interactions in supporting autobiographical re-experiencing. The approach we used to investigate the effects of different lesions on memory provides a framework for dealing with other patients who present with an interesting functional deficit whose neuroanatomical source is difficult to specify due to widespread lesions.

Amnesia↗

PubMed1994

Honoring the history of the Edward Jackson Memorial Lecture. The L Edward Jackson Memorial Lecture. Part 1.

The occasion of the 50th Edward Jackson Memorial Lecture provides an opportunity to look back on the history of the lecture that honors the memory of one of the most outstanding ophthalmologists of modern times. A review is provided as to how the lecture was established after Dr. Jackson's death in 1942 and how the memorial lecturers are chosen. There is a brief glimpse into the life, accomplishments, and personality of Dr. Jackson, and past Jackson lectures are highlighted to demonstrate the breadth of topics and their significance to the advancement of medicine and ophthalmology. In particular, two Jackson Memorial Lectures on the subjects of genetics and glaucoma are discussed since they fit well into the 40-year anniversary of the discovery, in 1953, of the DNA double helix.

Awards and Prizes↗

PubMed1994

Estimated prevalence of age-associated memory impairment derived from standardized tests of memory function.

Recent research on the prevalence of age-associated memory impairment (AAMI) has reflected considerable variability, with estimates ranging from 35% to 98%. This variability is attributed to (a) failure to employ the complete diagnostic criteria for AAMI and (b) failure to consider age as a variable in estimating prevalence. Analysis of published normative data on both standard clinical memory tests and computer-simulated everyday memory tests shows a clear increase in the percentage of persons meeting the AAMI memory performance criterion as a function of age. These data are offered as an upper-bound estimate of the prevalence of AAMI, by age decade.

Adolescent↗

PubMed1992

Reports of real and false memories: the relevance of hypnosis, hypnotizability, and context of memory test.

Thirty high- and 30 low-hypnotizable subjects saw slides of a purse snatching and then imagined seeing the slides in hypnosis or waking conditions. The experimenter suggested the offender had a moustache (true), wore a scarf (false), and picked up flowers (false). Memory was tested by the experimenter after the suggestion, by another experimenter during an inquiry session, and again by the 2nd experimenter after the experimenter appeared to end the session. Hypnotizability, but not hypnosis, was associated with false memory reports; more high-than low-hypnotizable subjects reported false memories. The context of testing influenced true and false memory reports; fewer reports occurred in an informal rather than a formal test context.

Adult↗

PubMed1993

Desperately seeking memories of the first few years of childhood: the reality of early memories.

How far back into their childhoods can people remember? Previous research suggests that people's earliest memories date back to the ages of 3 or 4 years. J. A. Usher and U. Neisser (1993, this issue) reported that some events, like the birth of a sibling and a planned hospitalization, can be readily remembered if they occurred at age 2. However, the bits and pieces of such memories that were obtained in their research may not be indicative of genuine episodic memory. An alternative hypothesis is that these apparent memories are the result of educated guesses, general knowledge of what must have been, or external information acquired after the age of 2.

Adult↗

PubMed1990

Portal aspects of memory overlay in psychoanalysis. An object relations contribution to screen memory phenomena.

Distortion in screen memories illustrates the unique manner in which part-object representations unite perceptions from different temporal periods. "Portal" aspects of a given source memory designate anachronistic distortions borrowed from perceptions at a subsequent time when the source memory and its full emotional significance attempted access to consciousness. The unconscious perception of recall at the subsequent occasion is represented by the appearance of portal details in the source dream. The portal concept is related to object relations theory and the psychology of memory.

Adult↗

PubMed2000

Individual differences in memory span: the contribution of rehearsal, access to lexical memory, and output speed.

Rehearsal speed has traditionally been seen to be the prime determinant of individual differences in memory span. Recent studies, in the main using young children as the subject population, have suggested other contributors to span performance, notably contributions from long-term memory and forgetting and retrieval processes occurring during recall. In the current research we explore individual differences in span with respect to measures of rehearsal, output time, and access to lexical memory. We replicate standard short-term phenomena; we show that the variables that influence children's span performance influence adult performance in the same way; and we show that lexical memory access appears to be a more potent source of individual differences in span than either rehearsal speed or output factors.

Adult↗

PubMed2003

Recognition memory in Alzheimer's disease. A demonstration of a remarkable memory capacity in Alzheimer's disease.

A compelling feature of human memory is its striking capacity. Under certain circumstances, subjects can remember large amounts of information even with brief exposure at study. This investigation shows that this ability is preserved even in severely impaired Alzheimer's disease patients, and this holds implications for the clinical management of amnesic patients. To this date, demonstrations of preserved learning and memory capacity in Alzheimer's disease and amnesia have been confined to implicit memory tasks. Since the present results were obtained in an explicit memory task, the finding also holds implications for the understanding of amnesia.

Alzheimer Disease↗

PubMed2002

The locus of "memory displacement" is at least partially perceptual: effects of velocity, expectation, friction, memory averaging, and weight.

When observers are asked to localize the final position of a moving target, the judged position is usually displaced from the actual position. It has been suggested that mental processes derived from a number of invariant and noninvariant principles produce the mislocalization in memory. In this study, the effects of velocity, expectation, friction, memory averaging, and weight were reconsidered, and evidence was accumulated that supports the alternative view that the distortions arise to a large degree at a perceptual level. Effects of velocity and expectation were present when observers still perceived a persisting image of the target. It is suggested that the active reorienting of the perceptual organs explains the distortions. Furthermore, distortions of the perceived center of a visible stimulus may explain effects that have previously been attributed to memory averaging and mental analogues of weight. Thus, the locus of memory displacement is at least partially perceptual.

Acceleration↗

PubMed1991

Problem-oriented training promotes spontaneous analogical transfer: memory-oriented training promotes memory for training.

Spontaneous analogical transfer is the use of information from one problem to solve another problem, without an explicit hint to use the previous information. The results of five experiments were that if subjects tried to solve a training problem before hearing its solution, or tried to explain a training story's solution before hearing the correct explanation, spontaneous transfer was more likely than it was if subjects had studied the same training passage for memory before hearing its solution or explanation. The advantage of problem-oriented processing over memory-oriented processing occurred even though solution attempts nearly always failed, and the advantage was not reduced if the target problem was tested 15 min later rather than immediately after training. We propose that problem-oriented processes performed at study are appropriate processes to use at test. Further support for the account comes from subjects' memory for the training passages; the advantage for problem-oriented processing on solution tasks was mirrored by an equally substantial advantage for the memory-oriented subjects on a recall task.

Adult↗

PubMed2001

The Word Completion Memory Test (WCMT): a new test to detect malingered memory deficits.

In recent years, much research has focused on developing tests to detect malingering. A drawback of existing tests is their poor ability to detect malingerers possessing more "sophisticated" knowledge of neuropsychological deficits. The current study presents preliminary validation data on a new measure, the Word Completion Memory Test (WCMT), which is the first malingering test to utilize a sophisticated coaching methodology in its development. The WCMT was administered to control participants, memory-impaired patients, and coached simulators. The coached simulators were provided with specific information about and examples of memory deficits commonly experienced following closed head injury (CHI; e.g., anterograde vs. retrograde amnesia). They also read a detailed scenario describing the lifestyle and motivations likely experienced by CHI litigants, and then practiced their roles by taking a quiz about their deficits. Results showed that 93% of coached simulators and 100% of control and memory-impaired participants were correctly classified by the WCMT.

Journal Article↗

PubMed1996

Interaction of perirhinal cortex with the fornix-fimbria: memory for objects and "object-in-place" memory.

Four monkeys (Macaca mulatta) were trained preoperatively in an automated object-in-place memory task in which they learned 20 new scenes in each daily session. In the object-in-place memory task, the correct, rewarded response in each scene is to a particular object of a pair, which always occupies a particular position in a unique background that has been generated using randomly chosen colors and shapes. Each animal then underwent two surgeries, with a period of testing after each. In the first, control surgery, each animal had either a unilateral lesion of the perirhinal cortex or unilateral fornixfimbria transection, combined with section of the body and splenium of the corpus callosum and the anterior commissure (to prevent interhemispheric transfer of visual information). The disconnection was completed in the second surgery, after which all animals had a unilateral perirhinal cortex ablation in one hemisphere, unilateral fornix-fimbria transection in the contralateral hemisphere, and partial forebrain commissurotomy. The monkeys performance was compared for the learning of 200 scenes, preoperatively and after each surgery. After control surgery, the animals were mildly impaired on the object-in-place task. After disconnection, the animals showed a severe impairment in object-in-place memory. We conclude from this that, in episodic memory, the perirhinal cortex provides input of visual object information to the subiculum, hippocampus, and fornix.

Animals↗

PubMedDate not supplied

[Memory complaints and anxiety. Apropos of 40 patients attending a specialized memory consultation].

This study reports results of the specialized memory consultation based on 2 successive examinations, one by a neurologist, the other by a psychologist, of 40 anxious subjects with or without social phobias. Traumatic events were frequent and we observed Alzheimer's disease in the family of 41.9% of subjects. Anxious subjects obtained a high score in Mac Nair questionnaire [44.05 (16,49)]. Their principal complaints were attentional difficulties. They obtained normal but low performances for free recall of 10 pictures, logical memory (QM), and inverse span. Mac Nair score was only correlated with logical memory score. Standardized psychometric evaluation showed short-term memory difficulties. Attention seems to be unstable and anxious individuals have relatively limited attentional resources. They are preoccupied by their anxiety and thus have less ability to focus on tasks.

Adult↗