Impaired Acquisition and Rapid Forgetting of Patterned Visual Stimuli in Alzheimer's Disease

Whether or not rate of forgetting is accelerated in Alzheimer's disease (AD) is controversial. This study examined recognition of visual patterns in patients with AD and in controls at 10 min relative to a learning baseline measured after a 10-s delay (delayed recognition ratio, DRR). Comparable baseline performances were attained in the two groups by manipulating stimulus exposure times. Comparisons between 25 AD and 48 age-matched controls demonstrated lower DRR in AD when initial recognition, which was statistically worse in AD, was covariated. DRR was also lower in an analysis of subgroups closely matched on initial performance. The findings suggest that forgetting is accelerated in AD because multiple aspects of memory processing, including storage, are impaired.     

Impaired acquisition and rapid forgetting of patterned visual stimuli in Alzheimer's disease

Whether or not rate of forgetting is accelerated in Alzheimer's disease (AD) is controversial. This study examined recognition of visual patterns in patients with AD and in controls at 10 min relative to a learning baseline measured after a 10-s delay (delayed recognition ratio, DRR). Comparable baseline performances were attained in the two groups by manipulating stimulus exposure times. Comparisons between 25 AD and 48 age-matched controls demonstrated lower DRR in AD when initial recognition, which was statistically worse in AD, was covariated. DRR was also lower in an analysis of subgroups closely matched on initial performance. The findings suggest that forgetting is accelerated in AD because multiple aspects of memory processing, including storage, are impaired.     

Encoding process in delayed recall impairment and rate of forgetting in Alzheimer's disease

OBJECTIVE: To assess the role of impaired encoding in learning and in delayed recall disturbances, and to evaluate the rate of forgetting in AD. METHOD: Fifteen AD patients with mild or moderate dementia and 15 normal matched controls were assessed with the Buschke Selective Reminding Test. Delayed recall was evaluated after 30 minutes and after 24 hours. RESULTS: AD patients had a poorer performance across the six trials of the learning phase as well as in both delayed recall evaluations, with no difference between recall at 30 minutes and at 24 hours. CONCLUSION: Performance in the learning phase was as specific and almost as sensitive as the performance in delayed recall for AD diagnosis. Encoding impairment was responsible for poorer learning and rapid displacement of previous learned material in the AD group. Finally, we did not find a higher rate of forgetting in AD patients.     

Memory for the September 11, 2001, terrorist attacks one year later in patients with Alzheimer's disease, patients with mild cognitive impairment, and healthy older adults

Although there are many opportunities to study memory in patients with Alzheimer's disease (AD) in the laboratory, there are few opportunities to study memory for real world events in these patients. The September 11, 2001 terrorist attacks provided one such opportunity. Patients with AD, patients with mild cognitive impairment (MCI), and healthy older adults were given a telephone questionnaire in the initial weeks after the event, again three to four months later, and finally one year afterwards to evaluate their memory for the September 11, 2001 terrorist attacks. We were particularly interested in using the attacks as an opportunity to examine the decline of episodic memory in patients with AD, patients with MCI, and older adult controls over a period of months. We found that compared to healthy older adults, patients with AD and MCI showed impaired memory at the initial time point, more rapid forgetting from the initial to the three-month time point, and very similar changes in memory from the three-month to the one-year time point. We speculated that these findings were consistent with patients with AD and MCI showing initial impaired encoding and a more rapid rate of forgetting compared with healthy older adults, but that once the memories had been consolidated, their decay rate became similar to that of healthy older adults. Lastly, although memory distortions were common among all groups, they were greatest in the patients with AD.     

Verbal learning in Alzheimer's dementia.

Many recent findings in Western countries suggest that episodic recall is the most sensitive discriminator between patients with mild Alzheimer disease (AD) and the normal elderly, while semantic memory tends best to differentiate between moderate and severe AD patients. The present study is the first to examine in detail the episodic memory of Chinese AD patients in Hong Kong with a locally developed list learning test, comparing procedures that do or do not encourage the use of semantic organization. The performance of 28 AD patients was compared to that of 30 normal controls. AD patients did significantly worse in terms of acquisition and retention and also benefited significantly less from external organization cues. In the discriminant function analysis, the rate of forgetting in the random condition and the total retention score in the blocked condition were found to be the best predictors for differentiating between AD patients and controls. On the other hand, in the differentiation between mild and moderate AD, semantic clustering in the blocked condition was found to be the best predictor. Results of the present study were discussed in the light of the previous findings reported in the Western countries and the neuropathological changes of AD patients.     

Episodic memory in patients with focal frontal lobe lesions

Episodic memory was evaluated in patients with unilateral, frontal lobe damage and matched controls using a list- method directed forgetting paradigm. Directed forgetting instructions (forget vs. remember the word), encoding instructions (learn vs. judge the word) and test format (recall vs. recognition) were manipulated in order to explore how variations in encoding and retrieval affect verbal memory. Controls demonstrated a normal directed forgetting effect in recall and less directed forgetting in recognition. Patients with left frontal (LF) damage did not show directed forgetting in either recall or recognition and patients with right frontal (RF) damage showed directed forgetting in recall, but not in recognition. Furthermore, the LF group recalled significantly more of the judge than learn words, suggesting that this group's performance improves by providing them with an encoding strategy. Conversely, the RF group's performance did not depend on encoding instructions and their recognition memory was impaired relative to the other two groups when they were instructed to judge the words. Our results suggest that (a) patients with LF damage show deficits in the rehearsal of to-be-remembered information, (b) whereas patients with RF damage show impairments in recognition memory. Furthermore, both patient groups show a lack of directed forgetting when familiarity-based processes guide performance.     

Further characterization of patients with amnesia after cardiac arrest: preserved recognition memory

We observed that patients with amnesia after cardiac arrest had preserved recognition memory despite profound loss of recall memory. In the present study, rate of forgetting was measured in six amnesic subjects for both recall and recognition memory of verbal material. The data show that recall decayed significantly faster for the amnesic subjects than for controls, whereas the rate of forgetting for recognition memory was comparable in both groups. Dissociation between recall and recognition performance is a feature of the amnesic syndrome after cardiac arrest.     

Material-specific memory loss in probable Alzheimer''s disease.

This study extends previous work analysing functional dissociations occurring in patients with Alzheimer's disease (AD) by demonstrating that material-specific memory loss is common. The pattern of neuropsychological dysfunction in 191 patients with probable AD was examined and 13% presented with material-specific memory loss. Thirteen patients had impaired immediate verbal recall, but normal non verbal recall and 12 had impaired non verbal recall and normal verbal memory. These patterns appeared to be related to a specific memory deficit and were probably not secondary to associated cognitive impairments. These data confirm earlier observations that the memory defect in AD can be material-specific, and suggest that these patterns of impairment should be viewed as a focal sparing of function.     

Assessment of free and cued recall in Alzheimer’s disease and vascular and frontotemporal dementia with 24-item Grober and Buschke test

Alzheimer’s disease (AD), vascular dementia (VaD) and frontotemporal dementia (FTD) are the most common forms of dementia. It is well known that memory deficits in AD are different from those in VaD and FTD, especially with respect to cued recall. The aim of this clinical study was to compare the memory performance in 15 AD, 10 VaD and 9 FTD patients and 20 normal controls by means of a 24-item Grober-Buschke test [8]. The patients’ groups were comparable in terms of severity of dementia. We considered free and total recall (free plus cued) both in immediate and delayed recall and computed an Index of Sensitivity to Cueing (ISC) [8] for immediate and delayed trials. We assessed whether cued recall predicted the subsequent free recall across our patients’ groups. We found that AD patients recalled fewer items from the beginning and were less sensitive to cueing supporting the hypothesis that memory disorders in AD depend on encoding and storage deficit. In immediate recall VaD and FTD showed a similar memory performance and a stronger sensitivity to cueing than AD, suggesting that memory disorders in these patients are due to a difficulty in spontaneously implementing efficient retrieval strategies. However, we found a lower ISC in the delayed recall compared to the immediate trials in VaD than FTD due to a higher forgetting in VaD.     

Neuropsychological functioning in elderly patients with schizophrenia and Alzheimer's disease

Cognitive functioning was compared in elderly patients with schizophrenia, elderly patients with probable Alzheimer's disease (AD), and matched healthy controls using a brief neuropsychological battery. Both schizophrenia and AD patients demonstrated marked impairment as compared to controls, with the profile of neuropsychological deficits in both disorders appearing remarkably similar. Only visual confrontation naming, verbal delayed recall, and rate of forgetting (i.e. savings score) significantly differentiated between the two patient groups, with AD patients showing poorer overall recall and more rapid forgetting of verbal information over delay. In addition, schizophrenia subjects showed a significantly greater deficit in visual confrontation naming than the AD group. The relationship of neuropsychological function and clinical symptoms of schizophrenia subjects was also examined. Results showed that word list learning, delayed recall, and rate of forgetting correlated most strongly with positive and negative symptoms. Recent neuropathological studies have indicated abnormalities in specific subfields of the hippocampal formation in schizophrenia that are also severely affected in AD. Though the specific histopathology of the two disorders differs, abnormalities in the common sites may underlie the common neuropsychological profile.     

Memory impairment differs in frontotemporal dementia and Alzheimer's disease

The aim of this study was to assess short-term and long-term explicit memory and implicit memory in frontotemporal dementia (FTD; frontal variant) and to compare FTD and Alzheimer's disease (AD) patients with similar severity of dementia. Fifteen FTD patients [mean age: 68 years; Mini-Mental State (MMS): 24], 30 probable AD patients (mean age: 72 years; MMS: 23) and 12 healthy subjects participated in the study. The three groups were comparable in terms of gender and educational level. Short-term memory was assessed with the digit span and Corsi block-tapping tests. Explicit verbal memory was assessed with the Grober and Buschke test, and implicit memory with a verbal priming task and a fragmented picture test. FTD patients demonstrated a genuine memory deficit with impaired digit span, encoding deficit and retrieval strategy difficulties, but preserved implicit verbal and visual priming. Memory patterns differed in AD and FTD: short-term memory and free recall were similarly decreased in FTD and AD but cues provided more benefit to FTD than to AD; encoding was more impaired and the forgetting rate was faster in AD than in FTD; priming was lower in AD than in FTD. AD patients with clinical and imaging frontal lobe dysfunction tended to have lower memory performance and to differ even more from FTD patients than AD patients without frontal lobe dysfunction.     

Immediate and delayed memory performance in schizophrenia spectrum patients: use of matched tasks

Rapid forgetting has been observed in long-term schizophrenic patients in the past. In this study, the rate of forgetting was assessed in short-term schizophrenic, schizophreniform and schizoaffective patients who had positive symptoms in the past, and in schizophreniform patients who never had positive symptoms. Four groups of patients representing these distinctions and a group of normal controls were assessed using immediate and delayed recall tasks, while controlling for effects of discriminating power of tasks, using matched-task methodology. The results showed that all schizophrenia spectrum patients with positive symptoms showed rapid forgetting as compared to schizophreniform patients with negative symptoms and normal controls. It is concluded that better immediate than delayed recall characterizes schizophrenia spectrum patients who have had positive symptoms. However, schizophrenia spectrum patients with negative symptoms may be qualitatively different from patients with positive symptoms in showing a slower rate of forgetting. The results support the hypothesis that there is at least one and possibly two brain dysfunctions affecting memory in schizophrenia.     

Better preservation of memory span relative to supraspan immediate recall in Alzheimer's disease

It is suggested that Alzheimer's disease (AD) patients are able to recall more items on the digit span task than on immediate free recall from a supraspan word list. Two experiments were undertaken to verify this assertion and to understand the basis of the putative span/supraspan discrepancy. The first experiment, involving 35 mildly or moderately demented AD patients, confirmed that digit span significantly exceeded immediate recall from a 10-item supraspan word list. Although digit span also exceeded supraspan recall in 38 elderly non-demented control subjects, the discrepancy was significantly greater within the AD group. In a second experiment, 19 AD cases and 20 controls were assessed with a word span task that used nouns matched by frequency and word length to nouns on the supraspan task. The magnitude of the span/supraspan discrepancy was reduced, indicating that part of the initial discrepancy was due to differences in stimulus items (digits versus common nouns). As before, AD subjects recalled more words on the span task than the supraspan task. However, in striking contrast, NC subjects recalled more words on the supraspan task, further indicating that AD patients are particularly impaired on supraspan recall. Using combined data from 106 subjects in both experiments, digit span performance correlated significantly with supraspan recall for NC but not AD subjects. Moreover, within the AD group the magnitude of the discrepancy was inversely related to a working memory measure derived from the backward digit span. The magnitude of the span/supraspan discrepancy correctly classified 88% of patients with mild dementia and 74% of controls. Results indicate that AD patients are specifically vulnerable to information overload inherent in the supraspan task, a view consistent with the perspective that AD is characterized by prominent disturbances in working memory.     

Prose memory deficits associated with schizophrenia

Memory of contextual information is essential to one's quality of living. This study investigated if the different components of prose memory, across three recall conditions: first learning trial immediate recall, fifth learning trial immediate recall, and 30-min delayed recall, are differentially impaired in people with schizophrenia, relative to healthy controls. A total of 39 patients with schizophrenia and 39 matched healthy controls were recruited. Their prose memory, in terms of recall accuracy, temporal sequence, recognition accuracy and false positives, commission of distortions, and rates of learning, forgetting, and retention were tested and compared. After controlling for the level of intelligence and depression, the patients with schizophrenia were found to commit more distortions. Furthermore, they performed poorer on recall accuracy and temporal sequence accuracy only during the first initial immediate recall. On the other hand, the rates of forgetting/retention and recognition accuracy were comparable between the two groups. These findings suggest that people with schizophrenia could be benefited by repeated exposure to the materials to be remembered. These results may have important implications for rehabilitation of verbal declarative memory deficits in schizophrenia.     

Patterns of verbal memory performance in mild cognitive impairment, Alzheimer disease, and normal aging.

OBJECTIVE: Individuals with mild cognitive impairment (MCI) typically demonstrate memory loss that falls between normal aging (NA) and Alzheimer disease (AD), but little is known about the pattern of memory dysfunction in MCI. METHOD: To explore this issue, California Verbal Learning Test (CVLT) performance was examined across groups of MCI, AD, and NA. RESULTS: MCI subjects displayed a pattern of deficits closely resembling that of AD, characterized by reduced learning, rapid forgetting, increased recency recall, elevated intrusion errors, and poor recognition discriminability with increased false-positives. MCI performance was significantly worse than that of controls and better than that of AD patients across memory indices. Although qualitative analysis of CVLT profiles may be useful in individual cases, discriminant function analysis revealed that delayed recall and total learning were the best aspects of learning/memory on the CVLT in differentiating MCI, AD, and NA. CONCLUSIONS: These findings support the position that amnestic MCI represents an early point of decline on the continuum of AD that is different from normal aging.     

Learning and forgetting new names and objects in MCI and AD

We studied how subjects with mild cognitive impairment (MCI), early Alzheimer's disease (AD) and age-matched controls learned and maintained the names of unfamiliar objects that were trained with or without semantic support (object definitions). Naming performance, phonological cueing, incidental learning of the definitions and recognition of the objects were tested during follow-up. We found that word learning was significantly impaired in MCI and AD patients, whereas forgetting patterns were similar across groups. Semantic support showed a beneficial effect on object name retrieval in the MCI group 8 weeks after training, suggesting that the MCI patients’ preserved semantic memory can compensate for impaired episodic memory. The MCI group performed equally well as the controls in the tasks measuring incidental learning and recognition memory, whereas the AD group showed impairment in this respect. Both the MCI and the AD group benefited less from phonological cueing than the controls. Our findings indicate that word learning is compromised in both MCI and AD, whereas long-term retention of newly learned words is not affected to the same extent. Incidental learning and recognition memory seem to be well preserved in MCI.     

Verbal recall and recognition abilities in patients with Wilson's disease

Tests of memory and verbal fluency were administered to 19 neurologically impaired Wilson's patients, 12 non-neurologically impaired Wilson's patients and 15 normal control subjects. Wilson's patients with neurologic disease recalled significantly fewer words on the delayed recall version of the Rey Auditory Verbal Learning Test than control subjects (p less than .05) but they showed no impairment on the recognition version of this test. On a verbal fluency test (FAS) requiring the subject to retrieve items from different categories, Wilson's patients with neurologic disease generated significantly fewer words than control subjects (p less than .01). Results suggest that retrieval memory is mildly impaired in the neurologic WD group but rate of learning and rate of forgetting is normal.     

Recognition memory span in mildly and moderately demented patients with Alzheimer's disease

An abbreviated form of Moss et al.'s (1986) Recognition Span Test (RST) was administered to patients with mild or moderate dementia of the Alzheimer type (DAT) and to intact control (NC) subjects. Memory spans for verbal (i.e., words), spatial and configurational (i.e., faces) information were assessed. Delayed recall (15 s and 2 min) of the words used on the verbal recognition span was also determined. The results showed that both DAT patient groups were impaired on the three recognition tasks and that the spatial and verbal forms differentiated the mildly from the moderately demented patients. The mean overall recognition span scores (spatial + verbal + facial) differentiated between DAT patients and intact controls, with 37 of the 39 patients falling beyond the 95% confidence limits derived from the control subjects' scores. On verbal recall, both the mildly and moderately demented patients were severely impaired and evidenced a very rapid rate of forgetting between the 15-s and 2-min recall attempts. These findings suggest that the RST is not only highly sensitive to memory disorders in the early stages of DAT but also effective in discriminating among various stages of this disorder.     

Verbal learning and forgetting in patients with temporal lobe epilepsy

Studies comparing non-surgical patients with left or right temporal lobe epilepsy (TLE) have shown irregular differences in verbal learning and memory. We assessed the performance of unoperated patients with epileptogenic temporal lobe lesions or cryptogenic TLE using a selective reminding procedure for the learning of a word list, and five delayed trials for the recall of learned words. On the selective reminding procedure, patients with left TLE were found to be more impaired than those with right TLE and controls, in agreement with the role of the left temporal lobe in verbal learning. The patients with right TLE were more impaired than the controls, possibly due to the semantic organization of the word list The rate of forgetting learned words was similar in the patient and control groups, suggesting that patients with left TLE can normally retain and/or retrieve stored items. These data support the hypothesis that distinct functional systems subserve learning and memory. Comparisons of the patient subgroups with epileptogenic lesions (hippocampal sclerosis or low-grade glioma) and those with cryptogenic TLE did not reveal any significant difference in learning or in memory, suggesting that epileptiform activity could affect verbal performance as a detectable temporal lesion.