Pro- and retrospective memory in late adulthood

Everyday tasks, such as getting groceries en route from work, involve two distinct components, one prospective (i.e., remembering the plan) and the other retrospective (i.e., remembering the grocery list). The present investigation examined the size of the age-related performance declines in these components, as well as the relationship between these components and age-related differences in processing resources. The subjects were 133 community-dwelling adults between 65 and 95 years of age. They completed a large battery of tests, including tests of pro- and retrospective memory as well as tests for indexing processing resources. The results showed similar age-related declines in pro- and retrospective memory. There was only a weak relationship between pro- and retrospective memory, and the age-related decline in processing resources was related more strongly to retro- than prospective memory.

Prospective memory: a new focus for research

Prospective memory is required for many aspects of everyday cognition, its breakdown may be as debilitating as impairments in retrospective memory, and yet, the former has received relatively little attention by memory researchers. This article outlines a strategy for changing the fortunes of prospective memory, for guiding new research to shore up the claim that prospective memory is a distinct aspect of cognition, and to obtain evidence for clear performance dissociations between prospective memory and other memory functions. We begin by identifying the unique requirements of prospective memory tasks and by dividing memory's prospective functions into subdomains that are analogous to divisions in retrospective memory (e.g., short- versus long-term memory). We focus on one prospective function, called prospective memory proper; we define this function in the spirit of James (1890) as requiring that we are aware of a plan, of which meanwhile we have not been thinking, with the additional consciousness that we made the plan earlier. We give an operational definition of prospective memory proper and specify how it differs from explicit and implicit retrospective memory and how it might be empirically assessed.

Letter cancellation performance across the adult life span

Letter cancellation tasks are paper and pencil tests widely used in clinical and research settings as quick measures of attention/concentration, visual-spatial scanning abilities, and visual-spatial dysfunctions such as spatial neglect. Despite their popularity, only a few studies have investigated effects of age on letter cancellation performance and no comprehensive large-scale adult life-span norms are available for any of the letter cancellation tasks. We have developed a letter cancellation test, and we report a normative data obtained from a partially stratified sample of 351 healthy adults between 18 and 91 years of age. The results show the expected large age-related decline in the speed of letter cancellation performance and no age-related differences in spatial distribution of cancellation errors. We also provide various equations for precise predictions of Cancel H test performance. The results of correlational analyses show high reliability and provide evidence for both convergent and divergent validity of our letter cancellation task.

Comparison of apraxia in corticobasal degeneration and progressive supranuclear palsy

OBJECTIVE

To describe ideomotor apraxia in patients with corticobasal degeneration and those with progressive supranuclear palsy, two parkinsonian disorders that are often misdiagnosed due to the overlap in their clinical features, and to determine whether systematic apraxia testing is useful for differential diagnosis.

METHODS

Fourteen patients fulfilling National Institute of Neurological Disorders and Stroke-Society for Progressive Supranuclear Palsy clinical criteria for progressive supranuclear palsy, 13 patients fulfilling modified Lang criteria for corticobasal degeneration, and 12 normal healthy control subjects were given the Test of Oral and Limb Apraxia, which was scored according to the Florida Apraxia Battery for occurrence of various types of apraxic errors.

RESULTS

Both patients with progressive supranuclear palsy and corticobasal degeneration committed a greater number of apraxic errors than normal healthy control subjects on both transitive and intransitive tasks (p < 0.001 in both cases), but apraxia was much more severe in patients with corticobasal degeneration than progressive supranuclear palsy (p < 0.001). The index of apraxia severity, in combination with the assessment of the two key features of progressive supranuclear palsy (falls and vertical gaze palsy), correctly classified all patients.

CONCLUSIONS

Patients with corticobasal degeneration show more severe ideomotor apraxia than patients with progressive supranuclear palsy, and systematic assessment of ideomotor apraxia facilitates the differential diagnosis between patients with progressive supranuclear palsy and those with corticobasal degeneration.

Suppression of vision by transcranial magnetic stimulation: a third mechanism

We recently reported three periods when single-pulse transcranial magnetic stimulation (TMS) of the occipital pole impaired performance on a forced-choice visual letter-identification task. TMS-induced suppression during these periods is best explained by a blink-associated covering of the pupils and by a direct interference with letter-processing neural activity. We now report TMS-induced suppression at times that seem too late for the suppression to be explained by the first mechanism and too early for the suppression to be explained by the second mechanism. The most likely explanation is a blink-associated interference with letter-processing neural activity.

Exacting assessments: do older adults fatigue more quickly?

To determine whether neuropsychological testing is fatiguing, and whether it is more fatiguing to older than younger adults, 351 healthy, community living adults, between 18 and 91 years of age, completed a 3 to 4 hour battery of tests focusing on sensation, perception, attention, memory and knowledge. The battery included 3 critical tests: one for assessing the speed of making simple reactions and two for assessing the speed of making decisions. For half of the participants, the critical tests were administered only once, at the end of the session; for the remaining participants, the critical tests were given at the beginning and end of the session. The results show no evidence of fatigue effects with participants from any age group. In view of the type and variety of instruments in our battery, we believe our results will generalize to a wide range of testing situations. The participants in our study were healthy adult volunteers, however, and thus we recommend caution in generalizing the results to clinical populations.

Plasticity revealed by transcranial magnetic stimulation of early visual cortex

We applied single-pulse transcranial magnetic stimulation (TMS) to the occipital pole of healthy subjects while they performed a forced-choice visual letter-identification task. We found three separate periods when TMS suppressed performance; the first period is best explained by TMS-induced blinking whereas the last two periods are best explained by TMS-induced disruption of letter-processing in the early visual cortex. Unexpectedly, we also found that TMS-induced suppression progressively disappeared during three weeks of repeated TMS experiments. However, it was only suppression during the last two periods that disappeared; suppression during the first period remained undiminished. When subjects were then presented with dimmer letters, suppression reappeared. The most likely explanation is a practice-induced increase in neuronal activity in the early visual cortex.

Timing of activity in early visual cortex as revealed by transcranial magnetic stimulation

To determine the timing of visual processing in the early visual cortex, we applied single pulse transcranial magnetic stimulation to the occipital pole of healthy subjects while they were engaged in a forced-choice visual letter-identification task. We found two separate periods of activity, the first ranging from 20 to 60 ms after the onset of the visual stimulus, and the second ranging from 100 to 140 ms after the onset of the visual stimulus. We suggest that these two periods reflect necessary activity in V1, before and after re-entry.

Two periods of processing in the (circum)striate visual cortex as revealed by transcranial magnetic stimulation

To determine the timing of visual processing in the (circum)striate visual cortex, we examined the effect of single pulse transcranial magnetic stimulation over the occipital pole of healthy subjects who were engaged in a forced-choice visual letter identification task. Single letters, subtending a visual angle of 0.35 degrees, were foveally presented for 10 ms and were immediately followed by a mask. We investigated 30 different delays (d), defined as the time between the onset of the visual stimulus and the onset of the magnetic stimulus, from d = -100 ms to d = +190 ms, and 4 different midsagittal coil positions (x), defined as the distance between the lower edge of the coil and the upper edge of the inion, from x = 1 cm to x = 7 cm. Three out of four subjects showed three distinct delay intervals (dips) at which application of TMS resulted in an impairment of the task. The first dip was centred around d = -50 ms and occurred independently of the coil position; the second dip was centred around d = 0 ms and was elicitable only with the two lowest coil positions; the third dip was centred around d = 100 ms and was also elicitable only with the lower coil positions. In the fourth subject, only the first and the third dip were found. We conclude that there are two distinct periods when the activity in the (circum)striate visual cortex is necessary for the identification of visually presented letters.

Caregiving in progressive supranuclear palsy

BACKGROUND

Basic issues regarding factors influencing progressive supranuclear palsy (PSP) patient caregiver burden remain unresolved, including whether and how disease severity and duration influence caregiver burden.

OBJECTIVE

To examine the relation between PSP patient caregiver burden and disease severity, describe the time course of caregiver burden in relation to disease progression, and identify the contribution of other factors (e.g., patient memory and behavioral problems, caregiver gender) to caregiver burden.

METHODS

Mail survey of 180 caregivers of PSP patients (living at home and cared for by nonprofessionals) who were members of the Society for Progressive Supranuclear Palsy. The survey included the Burden Interview, an instrument measuring caregiver burden by inquiring how they feel about different aspects and demands of caregiving.

RESULTS

Caregiver burden was related to both PSP disease severity (r = 0.40) and disability/need for assistance (r = 0.43). The relation between burden and disease duration was nonlinear, following the same time course as disease severity; the burden increased during the first 18 months postdiagnosis and leveled off thereafter. Women reported more burden than men (caregiver sex delta r2 = 0.05), even after controlling for disease severity and duration (delta r2 = 0.22) and patient gender (delta r2 < 0.01; NS), patient depression (delta r2 = 0.09), and aggressiveness (delta r2 = 0.02).

CONCLUSION

Burden in PSP is related to disease severity, disease duration, and caregiver gender (even after controlling for patient's memory, patient depression, and aggression).

Progressive supranuclear palsy: a survey of the disease course

BACKGROUND

The most accurate knowledge about progressive supranuclear palsy (PSP) comes from small sample studies that preclude precise estimation of the proportion of PSP patients affected with various symptoms and the examination of factors predicting survival time.

OBJECTIVE

To describe the course of PSP in a large clinically diagnosed sample of PSP patients and to identify factors predicting survival time.

METHODS

We surveyed the caregivers of 318 living and 119 deceased patients with progressive supranuclear palsy. The main outcome measures were a principal symptom severity questionnaire and a signs and symptoms questionnaire.

RESULTS

The estimated age of PSP symptom onset depends critically on how symptom onset is defined, with estimates differing by as much as 1.5 years. Men and women were represented equally (51.6% versus 48.4%) in the living sample, but men formed 61.8% of the deceased sample. Men were diagnosed later than women following symptom onset (33.4 versus 24.1 months) and died earlier following the diagnosis (37.0 versus 47.6 months). Motor and visual symptoms appeared first, followed by emotional and personality problems, cognitive impairment, and sleep changes. Whereas motor symptoms eventually affected almost every patient, emotional/personality and cognitive symptoms did not. The early onset, presence of falls, slowness, and inability to move eyes downward early in the development of the disease predicted survival time.

CONCLUSION

PSP is a rapidly progressive disease dominated by motor symptoms, and it affects men more frequently than women.

Color-Word Stroop test performance across the adult life span

In the Color-Word Stroop test (CWST), the basic task is to name the ink color of rows of XXXs, and performance in this condition is compared with performance in naming the ink-color of color words under conditions where word meanings and ink colors mismatch or are incongruent (e.g., the word red printed in green ink). The present study investigated whether Stroop test interference, defined as the cost associated with ink-color naming in the incongruous stimulus condition versus in the basic color-naming condition, provides positive evidence for a kind of processing qualitatively different than that which is required for color naming or for word reading. Does the pattern of age-related differences in Stroop interference force the conclusion that the incongruous condition taps a qualitatively different kind of processing than that required for color naming or for word reading? We gave the CWST to 310 healthy adults. Their performance in each condition of the test replicates and extends previous findings. Structural equation modeling of the data showed a significant, direct link between age and performance in the latent factor associated with the incongruent condition. However, this direct link with age produced a relatively small increase in the model's fit; it amounted to only a .024 increase in the proportion of variance explained in the incongruent condition. In light of this small direct influence due to age, the most parsimonious explanation of our findings is that age effects in Stroop interference are due to age-related slowing (which is also indexed by color naming and by word reading) primarily; the findings do not provide evidence for a qualitatively different kind of processing that declines with age.

Color- and picture-word Stroop tests: performance changes in old age

The Stroop test comes in different variations, but all of them index performance on a basic task, like color or picture naming, when it is carried out by itself versus when it is performed in the presence of conflicting or incongruent stimuli. The present study examined the hypothesis that Stroop interference--the cost of performing one task in the presence of another--is a general as opposed to a test-specific index of cognitive flexibility. A second goal was to examine changes in Stroop test performance in old age. A group of 129 healthy older adults (> or = 65 years of age) were assessed on the color- and picture-word Stroop test, as well as on a battery of neuropsychological tests. Subjects' performance on each card of both Stroop tests, and various derived (differences and ratios) scores, were used to prepare age-group norms. The use of the norms is illustrated with findings from previous studies. Regression analyses showed age-changes in several aspects of Stroop test performance. Hierarchical multiple regression analyses, and causal modeling showed an age effect on Stroop interference only on the picture-word test but not on the color-word test. Exploratory factor analysis of the Stroop data and the neuropsychological test data revealed different factor loadings for the color- and picture-word test. The combined findings suggest that the color- and picture-word Stroop test measure different cognitive functions, at least in old age.

Episodic spatial memory in adulthood

Two experiments examined age-related differences in memory for spatial location information in a museum exhibit (Experiment 1) and in a secretarial office (Experiment 2). In Experiment 1, subjects were the visitors to the exhibit (N = 302, 15-74 years of age), and memory was assessed using a map test. In Experiment 2, subjects were 64 young adults (M = 21.2 years) and 32 older adults (M = 71.2 years), and memory was assessed using both a map test and a relocation test. The relocation test required subjects to replace the to-be-remembered targets where they appeared at study. Experiment 1 showed an age-related decline in spatial memory performance, and it placed the onset of this decline in the sixth decade of life. Experiment 2 showed an age-related decline on both tests, but age effects were smaller on the relocation test than on the map test, and when subjects knew that spatial memory would be tested than when they were not informed.

Episodic spatial memory in adulthood

Two experiments examined age-related differences in memory for spatial location information in a museum exhibit (Experiment 1) and in a secretarial office (Experiment 2). In Experiment 1, subjects were the visitors to the exhibit (N = 302, 15-74 years of age), and memory was assessed using a map test. In Experiment 2, subjects were 64 young adults (M = 21.2 years) and 32 older adults (M = 71.2 years), and memory was assessed using both a map test and a relocation test. The relocation test required subjects to replace the to-be-remembered targets where they appeared at study. Experiment 1 showed an age-related decline in spatial memory performance, and it placed the onset of this decline in the sixth decade of life. Experiment 2 showed an age-related decline on both tests, but age effects were smaller on the relocation test than on the map test, and when subjects knew that spatial memory would be tested than when they were not informed.