The influence of clinical characteristics on prism adaptation training in visuospatial neglect: A post-hoc analysis of a randomized controlled trial.

Previous studies indicate that the effect of prism adaptation training (PAT) on unilateral neglect may depend on clinical characteristics. In this explorative work, we re-analyzed data from a previously conducted randomized controlled trial (N = 23) to investigate whether age, etiology, severity of motor impairments, and visual field deficits affect the efficacy of PAT. Additionally, we reviewed PAT studies that reported lesion maps and distinguished responders from non-responders. We transferred these maps into a common standard brain and added data from 12 patients from our study. We found patients suffering from subarachnoid bleeding appeared to show stronger functional recovery than those with intracranial hemorrhage or cortical infarction. Furthermore, patients with visual field deficits and those with more severe contralateral motor impairments had larger after-effect sizes but did not differ in treatment effects. In addition, patients with parietal lesions showed reduced recovery, whereas patients with lesions in the basal ganglia recovered better. We conclude that PAT (in its current form) is effective when fronto-subcortical areas are involved but it may not be the best choice when parietal regions are affected. Overall, the present work adds to the understanding on the effects of clinical characteristics on PAT.

On the relation between self-reported cognitive fatigue and the posterior hypothalamic-brainstem network.

BACKGROUND AND PURPOSE: Various causes have been suggested for multiple sclerosis (MS) related fatigue. Hypothalamus-brainstem fibres play a role in sleep-wake regulation and in hypothalamic deactivation during inflammatory states. Hence, they may play a role for experiencing fatigue by changing bottom-up hypothalamic activation. METHODS: Multiple sclerosis patients with and without self-reported cognitive fatigue and healthy controls were analysed with respect to the integrity of hypothalamus-brainstem fibres using diffusion-tensor imaging based tractography, focusing on the anterior, medial and posterior hypothalamic areas, controlling for clinical impairment and excluding participants with depressive mood. RESULTS: Multiple sclerosis patients without self-reported cognitive fatigue showed increased axial and radial diffusivity levels specifically for fibres connecting the right posterior hypothalamus with the right locus coeruleus, but not for the medial hypothalamus and the corpus callosum. Moreover, there were no differences between MS patients with and without fatigue in brain atrophy and lesion load, which could explain our results. CONCLUSION: Multiple sclerosis patients not experiencing fatigue show increased axial and radial diffusivity for fibres connecting the posterior hypothalamus and the brainstem, which might prevent bottom-up activation of the posterior hypothalamus and therefore downregulation of structures responsible for wakefulness and exploratory states of mind.

[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.

Conditional responding is impaired in chronic alcoholics.

Bechara (2003) describes a model for disturbances in executive functions related to addiction. This model involves deficits in decision-making and in suppressing pre-potent representations or response patterns. We tested this model in 29 individuals with long-term heavy alcohol dependency and compared their performance with that of 20 control subjects. Only individuals without memory impairment, with normal intelligence and normal visual response times were included. We examined word fluency, object alternation, spatial stimulus-response incompatibility, extra-dimensional shift learning and decision-making using the Gambling task. We subtracted the performance in a control condition from that of the executive condition, in order to focus specifically on the executive component of each task. Only the object alternation and incompatibility tasks revealed significant differences between the group of alcoholics and the control group. Moreover, response times in the object alternation task correlated with duration of alcohol dependency. The results do not argue in favor of a specific deficit in decision-making or in shifting between relevant representations. We conclude that long-term alcohol abuse leads to an impairment in conditional responding, provided the response depends on former reactions or the inhibition of pre-potent response patterns.

Depressive symptoms predict slow cognitive decline in mild dementia.

Depression may be a prognostic marker of subsequent cognitive decline in patients with dementia. Earlier investigations did not find support for this hypothesis, but these considered mainly syndromal depression. In this prospective study, 32 subjects with mild dementia were followed up for 12 months. The effects of GMS-AGECAT syndromal depression, subsyndromal depression and dimensions of depressive symptoms were studied. Higher levels of mood symptoms but not (sub)syndromal depression predicted slower cognitive decline during follow-up. It is hypothesized that the report of depressive symptoms by subjects with mild dementia reflects relative intactness of cognitive functions, not accounted for by cognitive screening instruments.

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.

Frontal lobe dysfunctions in Korsakoff's syndrome and chronic alcoholism: continuity or discontinuity?

The effect of long-term heavy alcohol consumption on brain functions is still under debate. The authors investigated a sample of 17 Korsakoff amnesics, 23 alcoholics without Korsakoff's syndrome, and 21 controls with peripheral nerve diseases, matched for intelligence and education. Executive functions were examined for word fluency, the modified Wisconsin Card Sorting Test, an alternate response task, and an "n-back" working memory task. Korsakoff amnesics, but not alcoholics, showed a marked memory impairment. They also scored lower in each of the executive tasks-the alcoholics only in the alternate response task. This task also correlated with the years of the alcohol dependency. First, the authors conclude that Korsakoff's syndrome is associated not only with a memory impairment but also with a global executive deficit. Second, the decline in the ability to alternate between different responses argues for a restricted neurotoxic effect of alcohol on some frontal lobe areas.

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.

Memory impairment in those who attempted suicide by benzodiazepine overdose.

BACKGROUND: A prospective study was conducted to investigate the presence of anterograde amnesia in those who attempted suicide by benzodiazepine overdose and to study the correlation with sedation. METHOD: In 43 patients who attempted suicide by taking benzodiazepines, memory was tested with a 15-word memory recall task. The immediate and delayed recall on the first day after admission (day 1) and 24 hours later (day 2) were rated. Each patient and the interviewer scored the patient's degree of sedation on a visual analogue scale. Patients also had to try to recognize, from photographs, the psychiatrist with whom they had spoken the day before. RESULTS: The ratings of immediate and delayed recall were significantly lower on day 1 than on day 2. Subjective ratings of sedation of the patients were not significantly higher than the ratings of the observer. Less than half of the patients recognized the psychiatrists and knew that they were the ones they had spoken to the day before. CONCLUSION: Anterograde amnesia is present in suicide attempters who take overdoses of benzodiazepines. The implications of this finding for the assessment of suicide attempters during admission are discussed.

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.