Patrick S. R. Davidson

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.

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.

Does lateral parietal cortex support episodic memory? Evidence from focal lesion patients

Although neuroimaging and human lesion studies agree that the medial parietal region plays a critical role in episodic memory, many neuroimaging studies have also implicated lateral parietal cortex, leading some researchers to suggest that the lateral region plays a heretofore underappreciated role in episodic memory. Because there are very few extant lesion data on this matter, we examined memory in six cases of focal lateral parietal damage, using both clinical and experimental measures, in which we distinguished between recollection and familiarity. The patients did not have amnesia, but they did show evidence of disrupted recollection on an anterograde memory task. Although the exact mechanisms remain to be elucidated, lateral parietal damage appears to impair some aspects of episodic memory.

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.

Is flashbulb memory a special instance of source memory? Evidence from older adults

Flashbulb memories (FMs) are vivid, stable memories for the reception of arousing, consequential news. Although such memories have been found in people of all ages, in the only examination of age differences to date, Cohen, Conway, and Maylor (1994) reported that older adults were less likely than young adults to experience a FM. We hypothesised that FM would be impaired in older adults with reduced frontal lobe (FL) function. To test this hypothesis, we asked older adults, who had been characterised according to FL function, to recall details of the moment that they first heard the news about the deaths of Princess Diana and Mother Teresa. Long-term retention was tested 6 months later. Details concerning the reception of the news about Princess Dianas death were retained better than those associated with Mother Teresas death. Importantly, there was no evidence that memory for these contextual details was related to FL function. A measure of medial temporal lobe function, derived from neuropsychological tests of episodic memory, was also not associated with memory for the reception events, although it was associated with memory for the details of an everyday autobiographical event. We speculated that emotionally arousing autobiographical memories may be qualitatively different from everyday memories and may involve the amygdala.

Frontal lobe contributions to recognition and recall: Linking basic research with clinical evaluation and remediation

The role of the human frontal lobes in episodic memory is becoming better understood, thanks mainly to focal lesion and neuroimaging studies. Here we review some recent findings from basic research on the frontal lobes in memory encoding, search, and decision-making at retrieval. For each of these processes, researchers have uncovered cases in which frontal memory impairments can be attenuated by various task manipulations. We suggest ways in which these findings may inform clinical evaluation and rehabilitation of memory problems following frontal damage.

Verbal fluency, trail making, and Wisconsin Card Sorting Test performance following right frontal lobe tumor resection.

Three commonly used clinical tests of frontal-executive function are verbal fluency, the Trail Making Test, and the Wisconsin Card Sorting Test, but few lesion studies of regional specificity within the frontal lobe (FL) exist for them. We examined 20 patients with right FL tumor resection, and mapped their damage to explore brain–behavior relations with greater precision. Across tests, the patients performed poorly and they also showed a deficit in switching but not clustering in verbal fluency. Within the right FL, however, we found none of the regional differences reported in studies of mixed-etiology FL patients, possibly due to the gradual neural reorganization that can occur with brain tumors. We discuss the importance of etiology in examining brain–behavior relations.

Flashbulb Memories for September 11th can be Preserved in Older Adults

ABSTRACT Flashbulb memories (FMs) are vivid, long-lasting memories for the source of surprising, arousing news. Laboratory studies have consistently found that older adults, especially those with below-average frontal lobe (FL) function, are impaired in source memory relative to young. We tested memory for the source of news concerning the September 11th terrorist attacks in older adults with high or low frontal lobe function and in young people. We found no age differences in source memory a year after the event and no differences related to FL function. Flashbulb memories may be different from usual cases of source memory because of their emotional content, personal importance, or social relevance.

Effects of emotion on item and source memory in young and older adults.

Emotional experiences are easier to remember than neutral ones, but whether memory for all aspects of an experience is improved by emotion remains unclear. Some researchers have argued that the influence of emotion on memory is different for item than for source information, whereas others have argued that emotion affects both similarly. Also, whether item and source memory are affected by emotion in older people in the same way as in young people is currently unclear. We examined item and source memory for emotional and neutral materials in young and older adults. Memory for emotional items was superior to memory for neutral items, whereas there was no difference in source memory. Overall, item and source memory were poorer in older people than in young people, but emotion seemed to have a similar effect on both age groups. Although emotional content was remembered better than neutral content, this benefit did not apply to source memory. However, varying the emotionality of the source (i.e., the voice in Experiment 3) improved memory for the source, and this effect was greater in young than in older people. Tone of voice had no effect on item memory in older people, but the effect was variable in the young and may depend on the extent to which the tone of voice moderates the interpretation of the content.

Source Memory in the Real World: A Neuropsychological Study of Flashbulb Memory

A flashbulb memory (FM) is a vivid, enduring memory for how one learned about a surprising, shocking event. It thus involves memory for the source of event information, as opposed to memory for the event itself. Which brain regions are involved in FM, however, is uncertain. Although medial temporal lobe/diencephalic (MTL/D) damage impairs content or item memory, frontal lobe (FL) damage has been associated with impaired source memory. One would therefore expect that FM should depend on the FLs, although two recent reports do not support this idea. In the current study, we examined memory for the events of September 11th, and memory for the source of that information, in MTL/D patients, FL patients, and healthy subjects. Only the MTL/D patients were impaired in long-term memory for the event itself, measured after a 6 month retention interval. The FL patients, on the other hand, showed a selective deficit in source memory, although their memory for the target event was unimpaired. MTL/D and FL structures appear to play different roles in memory for flashbulb events. This research was supported by fellowships from the Natural Sciences and Engineering Research Council of Canada and the Canadian Institutes of Health Research to P. D., a National Institute on Aging grant (AG 14792) to E. G., and a National Institute on Neurological Disease and Stroke grant (NS 26985) to the Memory Disorders Research Center at Boston University and the Boston VA Healthcare System. We thank Lee Ryan for access to healthy participants; Lis Nielsen, Jasmeet Pannu, Pamela Perschler, and Sheryl Reminger for help contacting participants; Mick Alexander, Kelly Sullivan Giovanello, and David Schnyer for providing lesion data on the patients from Boston; Michael Robinson and Andrea Soulé for assistance with data collection, entry, and analysis; and members of the Memory Interest Group at the University of Arizona for helpful comments on a preliminary report. Preliminary findings were presented at the 2003 International Neuropsychological Society meeting in Honolulu, HI.