Normal release from proactive interference in untreated patients with Parkinson's disease.

The relationship of release from proactive interference (PI) to set-shifting, explicit free recall and language remains controversial. We tested 56 patients with Parkinson's disease (PD) who had never received medication and 37 matched normal control subjects on a test of PI release based on semantic category. The PD group showed normal PI release but impaired word recall. PI release was independent of impaired Wisconsin card-sorting test performance, language production, explicit memory, overall cognitive status and severity of depression. The results indicate dissociation between ability to benefit from semantic stimulus properties and processes of explicit memory, set-shifting and expressive language.     

Cued recall and release from proactive interference in Alzheimer's disease

Abstract

Two tasks were administered to 13 mildly to moderately impaired subjects who met clinical research criteria for AD, and 17 controls matched for age and education. In the first task, subjects were administered a cued recall test (Buschke, 1984). AD subjects were found to be variably impaired in their ability to perform the initial stimulus-processing procedure, which involved matching cues with referents. The subsequent cued recall test did not typically facilitate performance. In the second task, subjects were administered a release from proactive interference (PI) paradigm consisting of semantically related and unrelated word lists. AD subjects did not develop the expected proactive interference effect for the semantically related words or show a resulting “release from PI” on related word list recall compared to normal controls. Results are discussed in terms of the role of semantic processing in episodic memory tasks.     

Semantic memory is impaired in both dementia with Lewy bodies and dementia of Alzheimer's type: a comparative neuropsychological study and literature review

OBJECTIVE: To test the hypothesis that semantic impairment is present in both patients with dementia with Lewy bodies (DLB) and those with dementia of Alzheimer's type (DAT). METHODS: A comprehensive battery of neuropsychological tasks designed to assess semantic memory, visuoperceptual function, verbal fluency, and recognition memory was given to groups of patients with DLB (n=10), DAT (n=10) matched pairwise for age and mini mental state examination (MMSE), and age matched normal controls (n=15). RESULTS: Both DLB and DAT groups exhibited impaired performance across the range of tasks designed to assess semantic memory. Whereas patients with DAT showed equivalent comprehension of written words and picture stimuli, patients with DLB demonstrated more severe semantic deficits for pictures than words. As in previous studies, patients with DLB but not those with DAT were found to have impaired visuoperceptual functioning. Letter and category fluency were equally reduced for the patients with DLB whereas performance on letter fluency was significantly better in the DAT group. Recognition memory for faces and words was impaired in both groups. CONCLUSIONS: Semantic impairment is not limited to patients with DAT. Patients with DLB exhibit particular problems when required to access meaning from pictures that is most likely to arise from a combination of semantic and visuoperceptual impairments.     

Cued recall and release from proactive interference in Alzheimer's disease

Two tasks were administered to 13 mildly to moderately impaired subjects who met clinical research criteria for AD, and 17 controls matched for age and education. In the first task, subjects were administered a cued recall test (Buschke, 1984). AD subjects were found to be variably impaired in their ability to perform the initial stimulus-processing procedure, which involved matching cues with referents. The subsequent cued recall test did not typically facilitate performance. In the second task, subjects were administered a release from proactive interference (PI) paradigm consisting of semantically related and unrelated word lists. AD subjects did not develop the expected proactive interference effect for the semantically related words or show a resulting "release from PI" on related word list recall compared to normal controls. Results are discussed in terms of the role of semantic processing in episodic memory tasks.     

Are some memory deficits unique to lesions of the mammillary bodies?

The role of the mammillary bodies in human memory is still in debate. A recent model of human amnesia proposes similar functions for the mammillary bodies and the hippocampus. But the main evidence for this model comes from animal studies using the delayed non-matching to sample paradigm. We describe a patient who developed a severe memory impairment after surgical removal of a germinoma. Postsurgical high resolution MRI revealed bilaterally shrunken mammillary bodies and an infarct of the left mammillary body. There were no other relevant lesions. Neuropsychological testing showed mildly impaired frontal lobe functions (executive functions, working memory and word fluency), almost intact learning and recognition, but severely impaired free and delayed recall. Experimental investigations revealed a reduced but preserved release of proactive interference and a pronounced impairment of recency and source judgments. We conclude that the mammillary bodies do play a prominent role in human memory, although the role differs slightly from that of the hippocampus.     

Release from proactive interference: determinants of performance and neuropsychological correlates.

The Wickens (1970) modification of the Brown-Peterson short-term memory task has been used to investigate release from proactive interference (PI) in a number of memory-impaired groups. It has been suggested that failure to release from PI is observed only in patients with compromise of both memory and 'frontal-lobe' functions. The present study examined performance on this paradigm in patients with schizophrenia (SC), a neuropsychiatric disorder which typically includes both frontal and mnemonic impairments. Patients with SC were found to exhibit significantly less release from PI than normal controls. It was determined through correlational analyses that average Trial 1 performance on this task could predict performance on all subsequent trials, indicating that 'release' from PI may measure the same psychological process as the Brown-Peterson task, which does not include a release condition. Trial 1 performance in the SC group was correlated with a wide range of neuropsychological measures, but after the effect of full scale IQ was partialled out, only correlations with measures of memory and measures of frontal-lobe function remained significant. The results support previous formulations of the neuropsychological concomitants of release from PI, but suggest that failure to release on this paradigm may be secondary to a significant compromise of the ability to perform the Brown-Peterson task. It is proposed that the experimental design constraints necessary to elicit a failure to release from PI in any patient group may limit the utility of this measure, and that Brown-Peterson performance may be a more reliable index of the neuropsychological functions involved.     

Release from proactive interference: Determinants of performance and neuropsychological correlates

Abstract

The Wickens (1970) modification of the Brown-Peterson short-term memory task has been used to investigate release from proactive interference (PI) in a number of memory-impaired groups. It has been suggested that failure to release from PI is observed only in patients with compromise of both memory and 'frontal-lobe' functions. The present study examined performance on this paradigm in patients with schizophrenia (SC), a neuropsychiatric disorder which typically includes both frontal and mnemonic impairments. Patients with SC were found to exhibit significantly less release from PI than normal controls. It was determined through correlational analyses that average Trial 1 performance on this task could predict performance on all subsequent trials, indicating that 'release' from PI may measure the same psychological process as the Brown-Peterson task, which does not include a release condition. Trial 1 performance in the SC group was correlated with a wide range of neuropsychological measures, but after the effect of full scale IQ was partialled out, only correlations with measures of memory and measures of frontal-lobe function remained significant. The results support previous formulations of the neuropsychological concomitants of release from PI, but suggest that failure to release on this paradigm may be secondary to a significant compromise of the ability to perform the Brown-Peterson task. It is proposed that the experimental design constraints necessary to elicit a failure to release from PI in any patient group may limit the utility of this measure, and that Brown-Peterson performance may be a more reliable index of the neuropsychological functions involved.     

Different error pattern of episodic and semantic memory in Alzheimer's disease and Parkinson's disease with dementia

To evaluate the possible differences in memory dysfunction we analysed the episodic and semantic memory of patients with Alzheimer's disease (AD) and Parkinson's disease (PD) with dementia, and age-matched normal controls (NC). The memory was examined with story recall tests, list learning test with Buschke selective reminding method and category naming test. Both AD and PD groups committed more prior-story intrusion errors as compared with the NC subjects, but only the AD patients committed more extra-story intrusion errors. Both patient groups committed more extra-list intrusion errors than the NC group. Furthermore, the AD patients made more extra-list intrusion errors and recognized more false positive targets than the PD patients did. The results suggest that AD and PD patients have different patterns of memory dysfunction. The AD patients seem to perform poorly because of their inability to inhibit irrelevant information and because of increased sensitivity to interference, whereas the deficits of PD patients only reflect sensitivity to proactive interference.     

Memory interference in multiple sclerosis.

To explore verbal memory impairments associated with multiple sclerosis (MS), we compared proactive and retroactive interference effects on the California Verbal Learning Test (CVLT; Delis et al., 1987) in a sample of 83 community-residing individuals with MS and 80 healthy participants. Individuals with MS demonstrated normal accumulation of proactive interference (PI), but attenuated release from PI relative to healthy individuals. Furthermore, accumulation of retroactive interference (RI) at short-delay free recall (SDFR) was intensified for those with MS as compared to healthy participants. Interestingly, accumulation of RI predicted long-term memory (LTM) only for participants with MS. These findings suggest that individuals with MS may experience particular difficulty when required to use semantic properties of information flexibly to facilitate verbal LTM.     

Lexical and semantic priming deficits in patients with Alzheimer's disease

Two experiments utilizing priming procedures examined the status of semantic memory in demented and amnesic patients. In the first investigation, lexical priming was assessed in patients with dementia of the Alzheimer type (DAT), Huntington's Disease (HD), alcoholic Korsakoff's syndrome (KS), and in intact control subjects. Subjects were first exposed to a list of words in a rating task and then required to complete three-letter stems with the "first word that comes to mind". Half of the stems could be completed with the previously presented words and the other half were used to assess baseline guessing rates. Recall and recognition of incidentally exposed words was also assessed. Although all three patient groups were impaired on tests of recall and recognition, only the DAT patients exhibited a priming deficit on the stem-completion task. In the second experiment, DAT, HD, and intact control subjects were administered a semantic priming test which required the subject to "free associate" to the first words of previously presented semantically associated word pairs. The results for this association task showed that DAT patients were significantly less likely to produce the second word of the semantically related pair than were the other subject groups. The results of these two experiments suggest that the memory capacities of DAT patients are characterized by a breakdown in the structure of semantic memory and that this impairment is evident on some "automatic" as well as "effortful" processing tasks.     

Episodic and semantic memory in alzheimer's disease and progressive supranuclear palsy: A comparative study

Abstract

We compared 13 patients with dementia of the Alzheimer's type (DAT) and 9 progressive supranuclear palsy (PSP) patients, matched by age, sex, education, and the overall level of cognitive deterioration, measured by using the Dementia Rating Scale, and 12 normal controls. The results of this study confirm that the pattern of cognitive deterioration of PSP patients differs from that of DAT patients. While episodic memory is severely affected early in the course of DAT, it appears to be relatively spared in PSP. In contrast to previous suggestions, we found no evidence for differentially rapid forgetting in DAT, although we did confirm relatively preserved recognition memory in PSP. We had predicted that the performance of the DAT group on tests of semantic memory (the Boston Naming Test, the ADA Synonym Judgement Test, and the Pyramids and Palm Trees Test) would be worse than that of the PSP group. However, there was, in fact, no difference on any of these measures, except that the PSP patients showed a significantly greater deficit on the Synonym Judgement Test. We suggest that the underlying cause of the semantic memory impairment might, however, be different in the two pathologies.     

Differing neuropsychological and neuroanatomical correlates of abnormal reading in early-stage semantic dementia and dementia of the Alzheimer type

Individuals with semantic dementia (SD) were differentiated neuropsychologically from individuals with dementia of the Alzheimer type (DAT) at very mild-to-mild stages (clinical dementia rating 0.5 or 1). A picture naming and recognition memory experiment provided a particularly useful probe for early identification, with SD individuals showing preserved picture recognition memory and impaired naming, and DAT individuals tending to show the reverse dissociation. The identification of an early SD group provided the opportunity to inform models of reading by exploring the influence of isolated lexical semantic impairment on reading regular words. Results demonstrated prolonged latency in both SD and DAT group reading compared to a control group but exaggerated influence of frequency and length only for the SD group. The SD reading pattern was associated with focal atrophy of the left temporal pole. These cognitive-neuroanatomical findings suggest a role for the left temporal pole in lexical/semantic components of reading and demonstrate that cortical thickness differences in the left temporal pole correlate with prolonged latency associated with increased reliance on sublexical components of reading.     

Are Some Memory Deficits Unique to Lesions of the Mammillary Bodies?

The role of the mammillary bodies in human memory is still in debate. A recent model of human amnesia proposes similar functions for the mammillary bodies and the hippocampus. But the main evidence for this model comes from animal studies using the delayed non-matching to sample paradigm. We describe a patient who developed a severe memory impairment after surgical removal of a germinoma. Postsurgical high resolution MRI revealed bilaterally shrunken mammillary bodies and an infarct of the left mammillary body. There were no other relevant lesions. Neuropsychological testing showed mildly impaired frontal lobe functions (executive functions, working memory and word fluency), almost intact learning and recognition, but severely impaired free and delayed recall. Experimental investigations revealed a reduced but preserved release of proactive interference and a pronounced impairment of recency and source judgments. We conclude that the mammillary bodies do play a prominent role in human memory, although the role differs slightly from that of the hippocampus.     

Proactive interference in a semantic short-term memory deficit: role of semantic and phonological relatedness

Previous research has indicated that patients with semantic short-term memory (STM) deficits demonstrate unusual intrusions of previously presented material during serial recall tasks (Martin and Lesch, 1996). These intrusions suggest excessive proactive interference (PI) from previous lists. Here, we explore one such patient's susceptibility to PI. Experiment 1 demonstrated patient M.L.'s extreme susceptibility to PI using a probe recognition task that manipulates the recency of negative probes (the recent negatives task). When stimuli consisted of letters, M.L. showed greatly exaggerated effects of PI, well outside of the range of healthy control participants. Experiment 2 used a variation of the recent negatives task to examine the relative contribution of semantic and phonological relatedness in PI. This task manipulated semantic and phonological relatedness of probes and recently presented list items. Relative to healthy control participants, patient M.L. showed exaggerated interference effects for both phonological and semantically related probes, both for probes related to the current list and for probes related to the previous list. These data have important implications for theories of semantic STM deficits. Specifically, these data suggest that it is not the rapid decay of semantic representations that is responsible for difficulties in short-term recall, but rather the abnormal persistence of previously presented material. We propose that this susceptibility to PI is the result of a deficit in control processes acting on STM.     

Primary memory and secondary memory in dementia of the Alzheimer type

Abstract

Free recall of word lists was investigated in a sample of 47 patients with dementia of the Alzheimer type (DAT) and 31 normal controls of equivalent age and education. Recall was divided into primary memory (PM) and secondary memory (SM) components based on the number of items intervening between presentation and recall. The findings were as follows: (1) the patients showed a greater deficit on the SM than on the PM measure; (2) there was little evidence of proactive interference in the patient group; (3) the PM and SM measures were independent in the controls but not in the patient group; and, (4) the size of patients' PM deficit increased linearly with increasing items between presentation and attempted recall. These results suggest that the memory disorder of DAT is partially the result of defective PM.     

Encoding processes in social anxiety

According to current theories, memory processes play an important role in the maintenance of social fears. However, the empirical evidence regarding memory processes in social anxiety is controversial, and little is known about specific memory processes, such as encoding. The present study employs a release from proactive interference (RPI) technique to explore encoding-related processes in social anxiety. Eighty-four high and low socially anxious college students participated in the RPI task. The main hypothesis was that RPI effects that involve socially threatening words are greater in high than in low socially anxious subjects. Contrary to this hypothesis, however, greater RPI effects were found in low rather than in high socially anxious subjects if a social threat dimension was encoded. This suggests that low socially anxious individuals show more specific encoding strategies of threatening information than high socially anxious individuals.     

Proactive interference in short-term recall by aphasic,brain-damaged nonaphasic and normal subjects

Aphasic, brain-damaged nonaphasic and normal subjects performed a short-term recall task, and groups were compared with regard to (1) the amount of proactive interference occurring in short-term memory and (2) amount of proactive interference release occurring in short-term memory as a result of changing stimulus material. The aphasic subjects had, in general, mild communication problems. Results were that groups demonstrated approximately the same degrees of proactive interference and proactive interference release. However, the aphasic subjects were able to recall fewer items than the other subjects. The relatively poor recall by the aphasic subjects appeared due to factors operating within trials during the recall task.     

Vulnerability to proactive semantic interference and progression to dementia among older adults with mild cognitive impairment

There is evidence that vulnerability to proactive semantic interference may be an early manifestation of early Alzheimer's disease and other neurodegenerative disorders. At present, there is a paucity of data regarding the extent to which such deficits relate to the progression of cognitive deficits and to clinically significant endpoints such as dementia. In this study, we followed 76 older adults, initially diagnosed with mild cognitive impairment, for a period of up to 3 years. Twenty-seven of these individuals (35.5%) progressed from mild cognitive impairment to dementia. An examination of baseline neuropsychological performance indicated lower baseline scores for object memory among those progressing to dementia. However, baseline Mini-Mental State Examination scores, delayed memory for passages, delayed visual memory, letter fluency, category fluency, Trails B and Block Design did not differ among study groups. In contrast, the Semantic Interference Test, a measure susceptible to vulnerability to proactive semantic interference showed the greatest baseline differentiation between those who progressed and those who did not progress to dementia. Further, scores on this measure predicted future progression to dementia with high accuracy. Vulnerability to proactive interference may be an early manifestation of an early dementing process and may have utility in predicting future progression to dementia.     

A comparison of the information processing deficits of patients with Huntington's chorea and Korsakoff's syndrome.

Patients with Huntington's Chorea and alcholic Korsakoff's disease were compared on six tests of short-term memory (STM) and of encoding capacity. While the alcoholic Korsakoff patients demonstrated STM disorders related to an increase sensitivity to proactive interference (PI) and to failures in semantic encoding, the Chorea patients had a different pattern of deficits. The Chorea patients, like the Korsakoffs, had STM deficits, but their memory performance did not improve with reductions in PI, and they had different types of encoding deficits than did the Korsakoff patients. These results demonstrate that information processing tasks can be used to empirically differentiate amnesic patients with normal I.Q.'s from patients with dementia-related memory impairments.