The role of inhibitory processes in part-list cuing.

Providing a subset of studied items as retrieval cues can have detrimental effects on recall of the remaining items. In 2 experiments, the authors examined such part-list cuing impairment in a repeatedtesting situation. Participants studied exemplars from several semantic categories and were given 2 successive cued-recall tests separated by a distractor task of several minutes. Part-list cues were provided in the 1st test but not the 2nd. Noncue item recall was tested with the studied category cues (same probes) in the 1st test, but novel, unstudied retrieval cues (independent probes) in the 2nd test. The authors found detrimental effects of part-list cues in both the 1st (same-probe) test and the 2nd (independent-probe) test. These results show that part-list cuing impairment can be lasting and is not eliminated with independent probes. The findings support the view that the impairment was caused by retrieval inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Part-list cuing can be transient and lasting: The role of encoding.

The presentation of a subset of learned items as retrieval cues can have detrimental effects on recall of the remaining items. For 2 types of encoding conditions, the authors examined in 3 experiments whether such part-list cuing is a transient or a lasting phenomenon. Across the experiments, the detrimental effect of part-list cues was consistently found to be transient with a high degree of interitem associations and lasting with a low degree. These results indicate that the persistence of part-list cuing depends on encoding, thus challenging both strategy disruption and retrieval inhibition as general accounts of part-list cuing. A 2-mechanism account is provided according to which the 2 mechanisms mediate the effect in different encoding conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal memory in drug-naive, newly diagnosed Parkinson's disease. The retrieval deficit hypothesis revisited.

Objective: The retrieval deficit hypothesis on memory impairment in patients with Parkinson's disease (PD) implies a selective impairment in recall of learned material with normal encoding, retention, and recognition. This hypothesis has been challenged by new data. We have therefore investigated verbal memory and learning in a large sample of newly diagnosed, drug na?ve, non-demented patients with PD. Method: From a sample of patients with PD from the Norwegian ParkWest study, 133 PD patients and 133 controls matched on sex, age, and education were included. The California Verbal Learning Test-2 (CVLT-2) was used to assess verbal memory. Results: Patients performed significantly worse than controls on free and cued recall as well as on recognition memory. Patients used the semantic clustering learning strategy significantly less extensively than the controls and the learning slope of the PD patients was significantly less steep. There was no difference in retention when controlling for encoding. Patients did not perform better on the recognition measure or on cued recall (d-prime), as compared to free recall. Executive functions explained a substantial part of the memory deficits. Conclusions: This study suggests that memory impairment in drug na?ve early PD to a large degree is a deficit of learning/ encoding and not of retention or retrieval. An implication is that the retrieval deficit hypothesis should be moderated in its general form. Executive deficits and less extensive use of the efficient semantic clustering learning strategy had a strong impact on learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adjustments of conflict monitoring in Parkinson's disease.

Objective: In Stroop-like tasks, the detection of conflict triggers adjustments of cognitive control to reduce conflict in subsequent trials. The present study tested the hypothesis of an impaired modulation of conflict monitoring in Parkinson's disease (PD). Method: 18 PD patients and 18 healthy control (HC) participants performed a Stroop-like task in 2 conditions differing in terms of incongruent/congruent stimuli ratio. Results: HC participants demonstrated a sustained modulation of interference effect, the interference effect being decreased when the proportion of incongruent stimuli was high. A trial-by-trial analysis also showed that in the HC group, processing an incongruent stimulus reduced interference in the subsequent trial. Unlike controls, PD patients did not demonstrate any transient or sustained reduction of the interference effect. Conclusion: Within the framework of recent models, these results can be interpreted as an impairment of a proactive mode of cognitive control in patients with PD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced negative priming in Parkinson's disease.

In the ignored repetition paradigm, negative priming (NP) is defined as the increase in response time that occurs when the current target stimulus served as a distractor stimulus in the previous trial. In this study, 25 Parkinson's disease (PD) participants and 17 age-matched healthy controls (HCs) were tested using a touchscreen version of the ignored repetition task that allowed response time to be partitioned into response initiation and response execution segments. In both groups, NP effects were stronger in the response execution than in the response initiation segments. The most striking result was that the PD group showed larger NP effects overall than the HC group. In PD, clinical ratings of bradykinesia, but not tremor, were related to larger NP effects. Results indicate that in PD, disruption of dopamine neuromodulation diminishes response efficiency when action must be directed toward previously ignored information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interference effects from divided attention during retrieval in younger and older adults.

The authors examined how retrieval, under divided attention (DA) conditions, is affected by the type of material in a concurrent task, and whether aging produces larger interference effects on memory. Young and old adults studied a list of unrelated words under full attention, and recalled them while performing either an animacy decision task to words or an odd-digit identification task to numbers. The animacy-distracting task interfered substantially with retrieval, and the size of the effect was not amplified in older compared with younger adults. DA using the odd-digit task did not produce as large an interference effect. These findings support the component-process model of memory, and pose problems for resource models of interference from DA at retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metamemory and prospective memory in Parkinson's disease.

Objective: Metamemory is integral for strategizing about memory intentions. This study investigated the prospective memory (PM) deficit in Parkinson's disease (PD) from a metamemory viewpoint, with the aim of examining whether metamemory deficits might contribute to PM deficits in PD. Method: Sixteen patients with PD and 16 healthy older adult controls completed a time-based PM task (initiating a key press at two specified times during an ongoing task), and an event-based PM task (initiating a key press in response to animal words during an ongoing task). To measure metamemory participants were asked to predict and postdict their memory performance before and after completing the tasks, as well as complete a self-report questionnaire regarding their everyday memory function. Results: The PD group had no impairment, relative to controls, on the event-based task, but had prospective (initiating the key press) and retrospective (recalling the instructions) impairments on the time-based task. The PD group also had metamemory impairments on the time-based task; they were inaccurate at predicting their performance before doing the task but, became accurate when making postdictions. This suggests impaired metamemory knowledge but preserved metamemory monitoring. There were no group differences regarding PD patients' self-reported PM performance on the questionnaire. Conclusions: These results reinforce previous findings that PM impairments in PD are dependent on task type. Several accounts of PM failures in time-based tasks are presented, in particular, ways in which mnemonic and metacognitive deficits may contribute to the difficulties observed on the time-based task. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Information processing speed and sentence comprehension in Parkinson's disease.

This study tests the hypothesis that sentence comprehension difficulty in Parkinson's disease (PD) is related in part to altered information processing speed that plays a crucial role in grammatical processing. The authors measured information processing speed in 32 PD patients without dementia using a lexical list-priming paradigm in which the interstimulus interval (ISI) between the prime and the target varied. Sentence comprehension accuracy was also assessed in 22 of these patients. Sentence comprehension accuracy for object-relative center-embedded sentences was impaired in a subgroup of PD patients. This subgroup of PD patients primed at an abnormally long ISI. Similarly, only PD patients who primed at a long ISI had greater difficulty understanding sentences with an object-relative clause than a subject-relative clause. Findings suggest that slowed information processing speed contributes to sentence comprehension difficulty in PD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition by familiarity is preserved in Parkinson's without dementia and Lewy-Body disease.

Objective: The retrieval deficit hypothesis states that the lack of deficit in recognition often observed in patients with Parkinson's disease is because of the low retrieval requirements of the task, given that these patients have retrieval and not encoding deficits. To test this hypothesis we investigated recognition memory by familiarity in Parkinson's patients and in patients with Lewy Bodies disease and Parkinson with dementia. Method: We analyzed to what extent the experimental groups were able to recognize by familiarity in a typical yes/no recognition memory task. The experimental groups were patients with early nondemented Parkinson's disease, advanced nondemented Parkinson's disease, demented Parkinson's patients, and patients with dementia with Lewy Bodies. We compared their performance with a group of young and another group of old healthy participants. The estimation of familiarity was made by analyzing recognition of word targets and distractors consisting of combinations of different letters in comparison with a condition in which targets and distractors were composed of similar letters, even though subjects were unaware of the independent variable. Results: The results indicate that familiarity was used at the same level by controls, patients with early Parkinson's disease and patients with dementia with Lewy Bodies. Although late Parkinson patients also used familiarity, its effect was only marginally significant. Patients with Parkinson's disease and dementia were not capable of using familiarity in recognition memory. Conclusions: Our results support the retrieval deficit hypothesis as Parkinson's patients without dementia show no deficit in a situation in which the retrieval requirements are minimal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selecting a response in task switching: Testing a model of compound cue retrieval.

How can a task-appropriate response be selected for an ambiguous target stimulus in task-switching situations? One answer is to use compound cue retrieval, whereby stimuli serve as joint retrieval cues to select a response from long-term memory. In the present study, the authors tested how well a model of compound cue retrieval could account for a complex pattern of congruency effects arising from a procedure in which a cue, prime, and target were presented on each trial. A comparison of alternative models of prime-based effects revealed that the best model was one in which all stimuli participated directly in the process of retrieving a response, validating previous modeling efforts. Relations to current theorizing about response congruency effects and models of response selection in task switching are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in mild Alzheimer's disease and early Parkinson's disease.

Alzheimer's disease (AD) and Parkinson's disease (PD) impair working memory (WM). It is unclear, however, whether the deficits seen early in the course of these diseases are similar. To address this issue, the authors compared the performance of 22 patients with mild AD, 20 patients with early PD and without dementia, and 112 control participants on tests of inhibition, short-term memory, and 2 commonly administered tests of WM. The results suggest that although mild AD and early PD both impair WM, the deficits may be related to the interruption of different processes that contribute to WM performance. Early PD disrupted inhibitory processes, whereas mild AD did not. The WM deficits seen in patients with AD may be secondary to deficits in other cognitive capacities, including semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nicotine effects on general semantic priming in Parkinson's disease.

In young healthy nonsmokers, effects of nicotine on semantic processing have been observed under strategy-based priming procedures but not under more general priming procedures (Holmes, Chenery, & Copland, 2008; Holmes, Chenery, & Copland, 2010). Effects of nicotine under general priming procedures, however, may be mediated by baseline priming levels that are below optimum such as when compromised by disease. Nicotinic mechanisms may be involved in the cognitive sequalae of Parkinson's disease (PD). Evidence suggests that semantic processing may be compromised in PD but the potential benefit of nicotinic stimulation is unknown. This study investigated the effects of nicotine on semantic processing in nonsmokers with PD (n = 12) and nonsmoking matched controls (n = 17) using general priming procedures. Specifically, an automatic priming task (0.15 relatedness proportion, RP, and 200 ms stimulus onset asynchrony, SOA) and a controlled priming task (0.8 RP and 1000 ms SOA) were used. Prime-target category relation (category related, noncategory related) was also manipulated. Transdermal nicotine patches (7 mg/24 h) were administered in a double-blind, placebo-controlled, crossover design. For the automatic task, nicotine did not influence priming effects for PD. Unexpectedly, compromised automatic priming for controls was ameliorated. For the controlled task, nicotine influenced priming effects for PD but not controls. The patterns of priming and nicotine effects across the tasks suggest an age-related slowing of the rate of semantic activation for controls, which may be exacerbated in PD. Overall, the findings indicate that nicotine can improve compromised semantic processing in PD, and also influence semantic processing in healthy older individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A differential deficit in time- versus event-based prospective memory in Parkinson's disease.

Objective: The aim of the current study was to clarify the nature and extent of impairment in time- versus event-based prospective memory in Parkinson's disease (PD). Prospective memory is thought to involve cognitive processes that are mediated by prefrontal systems and are executive in nature. Given that individuals with PD frequently show executive dysfunction, it is important to determine whether these individuals may have deficits in prospective memory that could impact daily functions, such as taking medications. Although it has been reported that individuals with PD evidence impairment in prospective memory, it is still unclear whether they show a greater deficit for time- versus event-based cues. Method: Fifty-four individuals with PD and 34 demographically similar healthy adults were administered a standardized measure of prospective memory that allows for a direct comparison of time-based and event-based cues. In addition, participants were administered a series of standardized measures of retrospective memory and executive functions. Results: Individuals with PD demonstrated impaired prospective memory performance compared to the healthy adults, with a greater impairment demonstrated for the time-based tasks. Time-based prospective memory performance was moderately correlated with measures of executive functioning, but only the Stroop Neuropsychological Screening Test emerged as a unique predictor in a linear regression. Conclusions: Findings are interpreted within the context of McDaniel and Einstein's (2000) multiprocess theory to suggest that individuals with PD experience particular difficulty executing a future intention when the cue to execute the prescribed intention requires higher levels of executive control. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Prospective memory impairment in individuals with Parkinson's disease.

This study investigated prospective memory and its relationship to executive and memory functions in persons with Parkinson's disease (PD). Twenty-three individuals with PD and 25 healthy comparison participants participated in the study. In the prospective memory tasks, participants were asked to execute 3 actions after 20 min (time-based condition) or after a timer ring (event-based condition). A score was computed for the correct recall of the intention to perform the actions (prospective component) and for the correct execution of the actions (retrospective component). Participants with PD also received an extensive neuropsychological test battery. PD participants were less accurate than comparison participants in the prospective component of the time-based but not the event-based task. Individuals with PD were also impaired on the retrospective component of both tasks. In the PD group, a general trend toward significant correlations was found between performance level on the prospective memory component of the time-based task and scores on executive and working memory measures. These results document that prospective memory is impaired in PD possibly in relation to a dysregulation of cognitive functions associated with frontal systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is implicit sequence learning impaired in Parkinson's disease? A meta-analysis.

The aim of the present study was to examine impairment of implicit learning in Parkinson's disease (PD) by means of a meta-analysis of studies that used the serial reaction time (SRT) task. The authors performed a systematic review and meta-analysis of published journal articles (1987-2005) that used the SRT task with patients with PD. The principal outcome measures used to compare studies were (a) the difference in reaction time between the last block of ordered sequence trials and the randomized block for PD and control participants and (b) fixed and random effects pooled estimates by the inverse weighting method. Six studies, including 67 patients with PD, met the inclusion criteria. The meta-analysis showed that implicit learning was impaired in PD, relative to healthy controls, with a standardized mean difference of 0.73 (95% confidence interval = 0.38, 1.07). Implicit sequence learning appears to be impaired in patients with PD. Some common methodological weaknesses and limitations in the reporting of statistical data are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

No retrieval-induced forgetting using item-specific independent cues: Evidence against a general inhibitory account.

Retrieval practice with particular items from memory can impair the recall of related items on a later memory test. This retrieval-induced forgetting effect has been ascribed to inhibitory processes (M. C. Anderson & B. A. Spellman, 1995). A critical finding that distinguishes inhibitory from interference explanations is that forgetting is found with independent (or extralist) cues. In 4 experiments, the authors tested whether the forgetting effect is cue-independent. Forgetting was investigated for both studied and unstudied semantically related items. Retrieval-induced forgetting was not found using item-specific independent cues for either studied or unstudied items. However, forgetting was found for both item types when studied categories were used as cues. These results are not in line with a general inhibitory account, because this account predicts retrieval-induced forgetting with independent cues. Interference and context-specific inhibition are discussed as possible explanations for the data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease.

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integration of auditory and kinesthetic information in motion: Alterations in Parkinson's disease.

The main aim in this work was to study the interaction between auditory and kinesthetic stimuli and its influence on motion control. The study was performed on healthy subjects and patients with Parkinson's disease (PD). Thirty-five right-handed volunteers (young, PD, and age-matched healthy participants, and PD-patients) were studied with three different motor tasks (slow cyclic movements, fast cyclic movements, and slow continuous movements) and under the action of kinesthetic stimuli and sounds at different beat rates. The action of kinesthesia was evaluated by comparing real movements with virtual movements (movements imaged but not executed). The fast cyclic task was accelerated by kinesthetic but not by auditory stimuli. The slow cyclic task changed with the beat rate of sounds but not with kinesthetic stimuli. The slow continuous task showed an integrated response to both sensorial modalities. These data show that the influence of the multisensory integration on motion changes with the motor task and that some motor patterns are modulated by the simultaneous action of auditory and kinesthetic information, a cross-modal integration that was different in PD-patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The independent influence of apathy and depression on cognitive functioning in Parkinson's disease.

Objective: The purpose of the present study was to examine the independent influence of symptoms of depression and apathy, two of the most common neuropsychiatric symptoms in Parkinson's disease (PD), on executive functioning and memory in PD patients using measures designed to discriminate between these symptoms. Method: Participants included 68 nondemented, idiopathic PD patients, ages 56–82 years. The Apathy Evaluation Scale—Self-Rating and select items of the Beck Depression Inventory II were used to assess symptoms of apathy and depression, respectively. Cognitive function was assessed using the Wisconsin Card Sorting Test and Hopkins Verbal Learning Test—Revised. Correlations and hierarchical regressions were conducted to investigate the relationships between apathy, depression, and cognitive function. Hierarchical regression analyses were conducted to evaluate the degree of influence of depression and apathy on cognitive function. Results: Results revealed that symptoms of apathy, but not depression, were significantly and negatively associated with executive functioning. Immediate memory was significantly and negatively associated with both apathy and depression. However, apathy accounted for additional variance in memory performance after controlling for depression at a level approaching significance. Conclusions: Apathy is not only associated with cognitive impairment, but also with impaired daily functioning, caregiver burden and distress, medication noncompliance, and increased mortality. Differentiating apathy and depression, understanding their unique effects, and appropriately identifying apathy symptoms in patients have robust implications for the development of neuropsychological models of these effects in PD as well as practical implications in guiding improvements to patient care and enhancing quality of life in patients and caregivers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)