[Awareness in patients with mild cognitive impairment (MCI)]. / Ziekte-inzicht bij patiënten met een lichte cognitieve stoornis (MCI).

Patients with Mild Cognitive Impairment (MCI) run a higher risk for the development of a dementia. A disturbed awareness of deficits is a symptom of dementia and could be a predictor for the development of dementia in the assessment in the early stages of dementia. This awareness can be assessed by means of the discrepancy between the assessment of memory problems by patient and partner. In this study, the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE-N) was used to assess the level of awareness. The results show that the discrepancy score (the difference between the IQCODE-Nscore of the patient and the IQCODE-Nscore of the partner) was significantly higher for the 61 MCI-patients when compared to the 40 healthy elderly (p = 0,01). This suggests a diminished awareness in MCI-patients. Analysis of the range of the MCI-group shows that this is true for 60% of the patients. Patients with a disturbed awareness score significantly lower on the MMSE (p < 0,01) than patients with an intact awareness.

Metamemory and memory test performance in stroke patients.

Memory Self-Efficacy (MSE) has been shown to be related to memory performance and social participation in a healthy elderly population. This relation is unclear in stroke. As about 30% of all stroke survivors report memory complaints, there is an urgent need for effective treatment strategies. Before implementing MSE as a potential target in memory training, it should be examined whether the association between MSE and memory performance demonstrated in healthy elderly people also applies in stroke patients. This study therefore explored the predictive value of MSE on two kinds of memory tests in stroke patients; adjusted and unadjusted for age, gender, education and location of stroke. In 57 stroke patients, the Metamemory in Adulthood Questionnaire (MIA), an everyday memory test (RBMT) and a more traditional memory test (AVLT) were completed. The results show that MSE significantly predicts memory test performance on both memory tests (RBMT: beta = .34; p = .01 AVLT: beta = .28; p = .04). When adjusted for gender, age, education and location of stroke, the predictive value of MSE remained significant for the AVLT (RBMT: beta = .23; p = .07; AVLT: beta = .23; p = .05). The results support the hypothesis that MSE predicts test performance in stroke patients and, by consequence, enables improving memory performance in post-acute memory rehabilitation after stroke.

Discrimination learning in humans: role of number and complexity of rules.

Various types of discrimination learning tasks, such as so-called nonconditional, conditional, and biconditional tasks, are generally held to differ in complexity and to require different amounts of training. However, rather than a difference in rule complexity, between-task performance differences may reflect a difference in number of underlying rules. Accordingly, in the present study, human participants were subjected to tasks differing in number and/or complexity of rules. In Experiments 1 and 3, participants learned to differentially respond to visual-target stimuli, each of which was preceded by a visual feature. Conditions differed in the number of different features and in the informational value of individual features and/or targets. In Experiment 2, participants were fully informed about all relevant stimulus-response mappings prior to each trial. Performance accuracy was primarily determined by number of underlying rules in the initial phase of discrimination learning, especially when the time available for responding was restricted. However, when participants had attained a high accuracy level, performance was solely determined by rule complexity. Apparently, number and complexity of rules have a different weight, depending on the stage of discrimination learning.

Processing of emotionally toned pictures in dementia.

BACKGROUND: Apathy is a common symptom in dementia and is often associated with reduced emotional reactivity. This study examined whether reduced emotional reactivity can be demonstrated in dementia patients using a picture viewing task. METHODS: The viewing time of three different types of visual stimuli was measured in 24 elderly participants, half of which suffered from dementia. The participants had to make a target response to an emotionally neutral target stimulus that was intermixed with a frequently occurring non-target or 'background' stimulus and infrequently presented emotional stimuli. All participants could control the presentation time of each stimulus, but one half of the participants were explicitly instructed to perform the task quickly. RESULTS: The main measure was a ratio score in which the viewing time for emotional stimuli was expressed relative to the viewing time for the neutral non-target stimulus. Using this measure, the instigation of a time-pressure condition proved to significantly reduce the viewing time for emotional stimuli in the healthy subjects. Irrespective of time-pressure condition, the dementia patients showed a similar short viewing time for emotional stimuli as did the healthy subjects in the time-pressure condition. However, both dementia patients and healthy controls displayed longer viewing times for unpleasant than for pleasant stimuli. CONCLUSION: These results suggest the ability of the present task to reveal the simultaneous occurrence of an overall reduced interest for novel stimuli and an intact differential emotional reactivity to stimuli with a negative versus positive valence in the dementia patients.

Learned irrelevance and response perseveration in a total change dimensional shift task.

Thirty-six healthy participants received a discrimination learning task requiring the identification of a relevant stimulus dimension. After successful learning, the relevant dimension was shifted unannounced. All exemplars of the two dimensions presented after the shift were novel, implying a 'total change' design. In three experimental conditions, participants could either make only errors reflecting perseveration of responding to the former relevant dimension, continued ignoring of the former irrelevant dimension, or both. After the shift, the participants in the perseveration condition made fewer errors than did those in the other two conditions, which did not differ. These results imply a predominance of the learned irrelevance mechanism even when any direct transfer of learning about exemplars in the pre-shift phase is precluded.

More learned irrelevance than perseveration errors in rule shifting in healthy subjects.

The present experiments examined the extent to which two possible sources of error affect healthy subjects' performance in a rule-shift task. All 115 participants first received a discrimination learning task, in which a pair of different visual stimuli was presented on each trial, one of which had to be identified as 'correct.' Each stimulus varied in two dimensions: a task-relevant and a task-irrelevant dimension. Feedback on correctness was given after each choice. After eight successive correct choices, the nature of the task-relevant dimension changed: the post-shift learning phase. Two types of error can occur in this phase: continued responding to the former relevant, but now irrelevant, dimension, a perseverative error, and non-responding to the former irrelevant, but now relevant, dimension, an error due to learned irrelevance. Different groups received a post-shift task in which none, one, or both of these two types of error could affect performance. The number of incorrect choices in the post-shift phase was significantly affected by learned-irrelevance errors but not by perseverative errors. An associative-learning model incorporating feedback-induced changes in both associative strength and saliency of the elements comprising the stimuli can explain these results.

Motor performance in girls with Turner syndrome.

In order to validate the movement problems in daily life for girls with Turner syndrome (TS), as reported by teachers, parents, and the girls themselves, we examined whether these girls have impaired motor ability and a specific pattern of motor impairment. As TS phenotypes are characterized by a particular profile of normal Verbal IQ (VIQ) and lowered Performance IQ (PIQ), we investigated whether there is a significant correlation between intelligence scores and motor performance scores. Fifteen girls with TS (age range 5.8 to 12.5 years), of whom nine had 45 XO karyotype and six girls mosaic karyotype, were individually tested on the Movement Assessment Battery for Children (MABC; Henderson and Sugden 1992, Smits-Engelsman 1998), and the Wechsler Intelligence Scale-Revised (WISC-RN; Vander Steene et al. 1986). Mean percentile score on the MABC was 2.93 (range 1 to 8). Based on the total score of the MABC, none of the girls with TS fell into the 'normal' range; five patients were classified as 'at risk' and 10 as 'impaired'. Girls with TS made more errors and needed more time across all items tested; no specific profile of impairment was observed and no significant correlation between intelligence scores and motor performance scores was found. The results clearly demonstrate that girls with TS indeed experience a significant general motor impairment. The motor problems apparently cannot be attributed to cognitive problems.

Word frequency and word stem completion in Korsakoff patients.

Korsakoff patients are generally agreed to be impaired in conscious recollection, but whether their implicit memory performance is also affected is less certain. A deficit in novelty dependent encoding (i.e., elaboration learning) could account for both types of impairments and predicts a reduced implicit word frequency effect in the patients. This effect was examined with word stem completion in nineteen Korsakoff patients and nineteen healthy controls. The word frequency effect was larger in controls than in patients in absolute terms, but not reliably so. It is concluded that elaboration learning may be spared to some degree in Korsakoff amnesia, but, in line with the original reasoning by Korsakoff (1889/1996), it may only be engaged by the patients when they are continuously prompted to do so.

Proactive interference and temporal context encoding after diazepam intake.

Two experiments were designed to test whether the memory impairment induced by benzodiazepines (BZDs) is due to impaired memory for temporal context. In both experiments, subjects were administered either diazepam (15 mg oral) or placebo, and a standard BZD impairment on prose recall as well as a decreased subjective arousal was found. Key tasks to explore temporal context memory were an A-B A-C proactive interference paradigm and a list discrimination task. Initial learning of both groups on these tasks was broadly matched. In experiment 1, diazepam did not increase susceptibility to proactive interference using semantically related words. However, in experiment 2, using unrelated word pairs, diazepam markedly increased the number of prior list intrusions. Furthermore, after diazepam intake, subjects were clearly impaired in learning unrelated word pairs. Subjects after diazepam intake were not impaired in the list discrimination task. We conclude that (1) diazepam impairs the forming of new associations, whether this is the formation of links between two or more targets or between targets and context, (2) a temporal context encoding deficit cannot account for a broader diazepam-induced memory impairment.

Dual task performance after diazepam intake: can resource depletion explain the benzodiazepine-induced amnesia?

It was tested whether a depletion in resources can account for the benzodiazepine-induced memory impairment. In two experiments, it was examined whether dividing attention had a disproportionately detrimental effect on learning semantically related and unrelated word pairs after diazepam intake. Word pairs had to be learned in both a single task condition and while performing a visual discrimination task concurrently (dual task condition). Moreover, the complexity of the visual discrimination task was manipulated systematically. Diazepam (15 mg, orally) or placebo was administered in a double-blind, between-subjects design. Subjects after diazepam intake were clearly impaired in learning unrelated word pairs, but not in learning related word pairs. Dividing attention in the dual task condition was associated with a reduction in learning unrelated word pairs, but this was not disproportionately reduced after diazepam intake. Moreover, the magnitude of resource depletion did not correlate with the severity of the diazepam-induced memory impairment. In general, the pattern of results does not support the hypothesis that a depletion of resources can explain the benzodiazepine-induced memory impairment.

Shifting behavior: an analysis of response patterns of Parkinson patients in discrimination learning.

Parkinson patients often show decreased performance on what is generally referred to as "shift tasks." This does not necessarily imply that Parkinson patients have problems with shifting, since task performance reflects not only shifting but also other factors. Using a discrimination learning task, we analyzed response patterns to determine the decision rules used. As well, we varied the manner of problem alternation (implicit versus explicit) and the type of problem alternation (extradimensional versus intradimensional shifts). In accordance with the literature, we found that Parkinson patients needed more trials to solve the problems. However, the response patterns of the Parkinson patients and controls were practically the same. An important finding was that Parkinson patients did not hold on longer to a rule, which was correct in a former problem, than controls did. Therefore, we concluded that Parkinson patients are able to shift from one decision rule to another.

A model and diagnostic measures for response time series on tests of concentration: historical background, conceptual framework, and some applications.

Based upon classical hypotheses about accumulating mental fatigue and distraction and its effect on response times, put forward in late 19th and early 20th century papers, a mathematical model is proposed for response times on tests of speed and concentration. The model assumes the random occurrence of very short distractions during information processing. It explains fluctuation and the increasing trend in response times on successive equivalent task units and leads to some simple diagnostic RT measures of speed and concentration as alternatives to the mean RT. A review is given of several experimental applications of the model, with subjects with and without concentration problems, using cancellation and digit addition tasks. The results demonstrate the potential usefulness of the model and the diagnostic measures derived from it. As predicted by the model, prolonged task performance yields an increasing trend in RT mean and variance that can be strongly reduced by giving very short resting periods very frequently, and to a lesser extent also by task alternation, but not by simply motivating the subjects to concentrate. Some practical implications for the administration and scoring of tests of speed and concentration are discussed, as well as limitations of the present results and the complementary relation of our approach to popular ones such as "stage analysis."

Categorization of arithmetic word problems by normals, frontal and posterior-injured patients.

An important stage in the solution of mathematical word problems is the formation of a global internal representation of the problem. There is ample evidence that the recognition of problem schemata or problem types plays a major role in this representation stage. In the present study, a sorting task is used in order to examine the knowledge of arithmetical word-problem schemata in a group of normals, a group of patients with frontal lesions, and a group of patients with left posterior brain lesions. Quantitative and qualitative analyses show that normals classify the word problems according to principles that are essential for problem solving. These analyses also reveal that the general sorting dimensions of the frontal and the left posterior brain-damaged groups, as measured by a multidimensional scaling procedure, are similar. Cluster analysis shows that both groups base their sorting behavior mainly on superficial text characteristics, such as the objects found in the various word problems. The implications of these differences in sorting behavior for arithmetical word-problem solving are discussed.

The internal representation of arithmetical word problem sentences: frontal and posterior-injured patients compared.

Patients with frontal and left posterior brain lesions have severe difficulties in arithmetical word problem solving. In the present study the origin of these difficulties is investigated from an information-processing perspective. Following this perspective the first stage in word problem solving consists of a translation of individual sentences to an internal representation. This translation process is examined in 30 frontal patients, 10 left posterior-injured patients, and 10 healthy controls with a recognition and a sentence-picture matching task. In addition, the relationship between sentence representation and arithmetical word problem solving is studied. The results suggest that error rates in the translation of different types of arithmetical word problem propositions differ substantially in our three groups. A relationship between translation skills and arithmetical word problem solving ability is also found.