Elizabeth L. Glisky

Source Memory in Older Adults: An Encoding or Retrieval Problem?

Source memory has been found to be more affected by aging than item memory, possibly because of declining frontal function among older adults. In 4 experiments, the authors explored the role of the frontal lobes (FLs) in source memory, the extent to which they may be involved in the encoding and/or retrieval of source or context, and the conditions under which the source memory deficit in older people may be reduced or eliminated. Results indicated that only a subset of older adults show deficits in source memory, namely those with below average frontal function, and these deficits can be eliminated by requiring people at study to consider the relation between an item and its context. These results provide convincing evidence of the importance of frontal function during the encoding of source and suggest that older adults with reduced FL function fail to initiate the processes required to integrate contextual information with focal content during study.

Learning and retention of computer-related vocabulary in memory-impaired patients: Method of vanishing cues

Several investigators have suggested that microcomputers might serve as useful external aids for memory-impaired patients. However, knowledge of basic computer vocabulary may be necessary for patients to use and benefit from a microcomputer. The present paper describes a procedure, the method of vanishing cues, which facilitated the acquisition of computer-related vocabulary in four memory-impaired patients. The method involves the systematic reduction of letter fragments of to-be-learned words across trials. Although learning was slow and strongly dependent on first-letter cues, all patients acquired a substantial amount of the vocabulary and eventually were able to produce the target words in the absence of fragment cues. Further, they retained the vocabulary over a 6-week interval and showed some transfer of the knowledge they had acquired. These findings suggest that memory-impaired patients may eventually be able to use a microcomputer as a prosthetic device.

COMPUTER LEARNING BY MEMORY-IMPAIRED PATIENTS: ACQUISITION AND RETENTION OF COMPLEX KNOWLEDGE*

Several investigators have shown that memory-impaired patients are capable of learning relatively simple information in both the laboratory and everyday life. The present research explored whether patients with memory disorders could also acquire complex knowledge--the domain-specific knowledge needed for operating and interacting with a microcomputer. The results indicated that patients with memory disorders of varying severity could learn to manipulate information on the computer screen, to write, edit and execute simple computer programs, and to perform disk storage and retrieval operations. The learning process, however, was slow relative to controls and the knowledge acquired appeared to be qualitatively different. Theoretical and practical implications of these findings are discussed.

Prospective memory: A neuropsychological study.

To examine the neuropsychology of prospective remembering, older adults were divided preexperimentally into 4 groups on the basis of their scores on 2 composite measures: one assessing frontal lobe function and the other assessing medial temporal lobe function. The groups reflected the factorial combination of high and low functioning for each neuropsychological system, and they were tested on an event-based laboratory prospective memory task. High-functioning frontal participants showed better prospective remembering than low-functioning frontal participants. There was no significant difference in prospective memory performance attributable to medial temporal functioning. The results support the theoretical notion that frontal lobe processes play a key role in prospective remembering. Discussion focuses on the particular components of prospective memory performance that frontal lobes might mediate.

Structural brain differences and cognitive functioning related to body mass index in older females

Little is known about the effect of obesity on brain structures and cognition in healthy older adults. This study examined the association between body mass index (BMI), regional volume differences in gray and white matter measured by magnetic resonance imaging (MRI), and cognitive functioning in older females. Participants included 95 community‐dwelling older females (ages 52–92 years) who underwent extensive neuropsychological testing and high‐resolution MRI scanning. Optimized voxel‐based morphometry techniques were employed to determine the correlation between BMI and regional gray and white matter volumes. Volumes of significant regions were then correlated with cognitive functioning. Higher BMI was associated with decreased gray matter volumes in the left orbitofrontal, right inferior frontal, and right precentral gyri, a right posterior region including the parahippocampal, fusiform, and lingual gyri, and right cerebellar regions, as well as increased volumes of white matter in the frontal, temporal, and parietal lobes, even when hypertension was considered. Compared to normal weight women, obese women performed poorer on tests of executive functioning. Smaller gray matter volume in the left orbitofrontal region was associated with lower executive functioning. Additionally, despite the lack of significant group differences in memory and visuomotor speed, gray and white matter volumes predicted performance on these measures. The results provide additional evidence for a negative link between increased body fat and brain functioning in older females. Hum Brain Mapp, 2010.

Memory and executive function in older adults: relationships with temporal and prefrontal gray matter volumes and white matter hyperintensities

Forty-eight healthy adults aged 65-85 were recruited for structural magnetic resonance scans after an extensive neuropsychological battery that ensured a high degree of variability across the sample in performance on long-term memory tests, and on tests traditionally thought to rely on prefrontal cortex. Gray matter volumes were measured for three gyri in the frontal lobe (superior, middle, inferior), six gyri in the temporal lobe (superior, middle, inferior, fusiform, parahippocampal, and hippocampus), and the occipital lobe. Gray matter volumes declined across the age range evaluated, but with substantial regional variation--greatest in the inferior frontal, superior temporal, and middle temporal gyri but negligible in the occipital lobe. Both memory performance and executive function declined as the number of hyperintense regions in the subcortical white matter increased. Memory performance was also significantly correlated with gray matter volumes of the middle frontal gyrus (MFG), and several regions of temporal neocortex. However, the correlations were all in the negative direction; better memory performance was associated with smaller volumes. Several previous reports of significant negative correlations between gray matter volumes and memory performance are described, so that the possible reasons for this surprising finding are discussed.

Neuropsychological correlates of recollection and familiarity in normal aging

The dual-process model of recognition memory proposed by Jacoby (1991; see also Mandler, 1980) postulates the existence of two independent components of recognition memory: a conscious retrieval process (recollection) and an automatic component ( familiarity). Older adults appear to be impaired in recollection, but findings with respect to familiarity have been mixed. Studies of the brain bases of these components, using neurological patients, have also been inconclusive. We examined recollection and familiarity, using the process dissociation procedure, in older adults characterized on the basis of both their frontal and their medial temporal lobe function. Findings suggest that only some older adults, depending on their neuropsychological status, are impaired in recollection and/or familiarity: Recollection seems to involve both frontal and medial temporal lobe function, whereas familiarity appears to be dependent only on function associated with the medial temporal lobes.

Do young and older adults rely on different processes in source memory tasks? A neuropsychological study.

Source memory has consistently been associated with prefrontal function in both normal and clinical populations. Nevertheless, the exact contribution of this brain region to source memory remains uncertain, and evidence suggests that processes used by young and older adults may differ. The authors explored the extent to which scores on composite measures of neuropsychological tests of frontal and medial temporal function differentially predicted the performance of young and older adults on source memory tasks. Results indicated that a frontal composite measure, consistently associated with source memory performance in older adults, was unrelated to source memory in young adults, although it was sensitive to a demanding working memory task. The memory composite score, however, predicted performance in the young group. In addition, item and source memory were correlated in young but not older people. Findings are discussed in terms of age-related differences in working memory and executive functions, and differential binding processes necessary for item and source memory. The requirement to integrate item and source information at encoding appears to place greater demands on executive or working memory processes in older adults than in younger adults.

Acquisition of domain-specific knowledge in organic amnesia: Training for computer-related work

Abstract In previous research we demonstrated that memory-impaired patients can acquire some forms of complex domain-specific knowledge in the laboratory. The present study explored further the kind of complex knowledge that amnesic patients can acquire in the laboratory, and examined whether such knowledge could be applied in an important domain of everyday life. A severely amnesic patient was taught, in the laboratory, the knowledge and skills needed to perform a complex computer data-entry job. Subsequently, she was able to perform the job in the real-world work environment as quickly and as accurately as experienced data-entry employees. Successful job training appeared to depend on (a) the use of a training technique, the method of vanishing cues, that engaged the patients preserved learning abilities, (b) extensive repetition of all procedures, and (c) explicit and direct training of all components of the job.

MEMORY CONJUNCTION ERRORS IN YOUNGER AND OLDER ADULTS: EVENT-RELATED POTENTIAL AND NEUROPSYCHOLOGICAL DATA

In a study/recognition paradigm, new words at test were recombinations of studied syllables (e.g. BARLEY from BARTER and VALLEY), shared one syllable with studied words, or were completely new. False alarm rates followed the gradient of similarity with studied items. Event-related potentials to the three classes of false alarms were indistinguishable. False alarms elicited different brain activity than did hits, arguing against the idea that conjunction errors occur during encoding and are later retrieved liked genuine memories. In Experiment 2, with healthy older adults, neuropsychological tests sensitive to frontal lobe function predicted false alarm rate, but not hit rate. Performance on standardised memory scales sensitive to medial temporal/diencephalic function influenced the pattern of false alarm rates across the three classes of new words. The experiments suggest that false alarms to conjunction lures are not similar to true recollections, but are products of faulty monitoring at retrieval.