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.

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.

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.

[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.

Consistency of ear advantage: an improvement due to increase in presentation rate.

In this study data are reported on the reliability of scores of ear advantages obtained in two dichotic tasks, viz. category monitoring and rhyme monitoring. Stimuli were presented at a much higher rate than in earlier reported experiments. This procedure appears to be effective in producing acceptable reliable results with respect to both the direction and the magnitude of ear advantage scores. Furthermore, the data on responses to individual target words are discussed. It appears that neither stimulus characteristics of the target words alone nor strategies of the subjects can explain the major part of variation in reaction times and ear differences. It is suggested that the combination of the stimulus characteristics of the target word and of the word simultaneously presented to the other ear is a major factor determining response latencies.

Stroop interference and disorders of selective attention.

Fourteen patients with right-hemisphere CVA and 8 patients with a left-hemisphere CVA were examined for selective attention deficits using a variant of the Stroop color-word task: the picture-word interference task. Experiments 1 and 2 first compared the performance of the two patient groups and a control group in three tasks of increasing difficulty: picture-word detection, word reading, and picture naming. The results showed that (a) the two patient groups were significantly slower than the control group, but did not differ from each other, and (b) the difference in mean RT between the two patient groups and the control group did not increase with task difficulty. In Experiment 3, the subjects were required to name pictures while ignoring accompanying distractors: nonletter symbols, unrelated words or semantically related words. In this task, the right hemisphere patients showed a much larger semantic interference effect than both the left hemisphere patients and the control group. It is argued that this finding most probably reflects problems in visual selective attention with the right hemisphere patients.

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.

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.

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.

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.

Predominant right leg dysfunction without asymmetric muscle inflammation in CD1 Swiss mice with coxsackievirus B1-induced myositis.

To establish the existence of predominant right leg involvement in Coxsackievirus B1-induced myositis (CB1 myositis) 189 neonatal CD1 Swiss mice were inoculated with 300 pfu CB1, and regularly observed for posture, mobility, and gait. After 2 and 4 weeks, quantitative comparison of motor dysfunction of right and left leg yielded an asymmetry score; on light microscopy mononuclear cell infiltration and muscle fiber necrosis were quantified in bilateral hamstring muscles, using a five-grade scale (0-4). Motor asymmetries were seen during acute viral myositis as soon as hind leg dysfunction appeared, and animals with a predominant dysfunction of one leg preserved that preference throughout the observation period. At 2 weeks, mice with predominant right leg dysfunction (n = 34) significantly outnumbered those with predominant left leg dysfunction (n = 11) (p = 0.01). At 2 and 4 weeks, infiltration and necrosis in hamstrings from legs with predominant dysfunction were not higher than in those from contralateral legs, and infiltration in right-sided hamstrings was not higher than in left-sided ones, nor was infiltration at 4 weeks. At 4 weeks right-sided muscles were more necrotic (mean +/- SD, 1.8 +/- 1.5) than left-sided muscles (1.1 +/- 1.2; p = 0.03). In the absence of predominant inflammatory disease of the right leg, we interpret the hind leg asymmetry as a preferential use of the left leg, due to left-leggedness, and suggest that in CD1 Swiss mice left-leggedness is associated with increased susceptibility to CB1 myositis.

Effects of diazepam on encoding processes.

Benzodiazepines are known to induce amnesic effects. To specify these effects more precisely, 40 healthy volunteers were given 15 mg diazepam or placebo. Effects on a chain of encoding operations were investigated: activation of memory representations, spreading of activation, semantic encoding and organizational processes. The diazepam group performed tasks consistently slower, although spreading of activation and semantic encoding were not affected by diazepam. Rather, diazepam subjects benefited less from opportunities to organize to-be-learned material. It is suggested that cognitive processes are slowed down after diazepam intake. This may also have implications for the organization of to-be-learned material.

Recognition of derivations in Broca's aphasics.

A well-known feature of Broca's aphasia is the problem of handling "small words." It has been claimed that patients show these problems in both language production and language perception. The traditional dichotomy of "function" words and "content" words is probably not a good description of the classes of words that are affected and intact. It has long been recognized that not only do Broca's aphasics have problems with free closed class morphemes, but that also bound morphemes, such as verb inflections, are often omitted in spontaneous speech. The question arises whether all bound morphemes, being members of the closed class category, are difficult to process for Broca's aphasics. Using a lexical decision task the recognition of derivational word forms was studied in Broca's aphasics and two control groups. The pattern of results is very similar in the three groups. Derivational word forms are recognized as lexical items independent of the stem. It is concluded that Broca's aphasics can process derivational affixes appropriately. The consequences of this conclusion for the characterization of the class of "small" words are discussed.

Paragrammatic speech without a comprehension deficit? A case report.

In this article we present a case report of a patient, who had a peculiar pattern of language use following a stroke. The two most prominent features were language switches during spontaneous speech in the first months postonset, when the patient mixed English, German, and French words and utterances into his mother tongue (Dutch); clearly disturbed speech output, showing signs of word-finding problems and paragrammatism but hardly any paraphasias, while at the same time no evidence of a language disturbance could be obtained with standard clinical aphasia tests.

Bilingual language processing after a lesion in the left thalamic and temporal regions. A case report with early childhood onset.

This case study concerns an 18-year-old bilingual girl who suffered a radiation lesion in the left (dominant) thalamic and temporal region when she was 4 years old. Language and memory assessment revealed deficits in auditory short-term memory, auditory word comprehension, nonword repetition, syntactic processing, word fluency, and confrontation naming tasks. Both languages (English and Dutch) were found to be affected in a similar manner, despite the fact that one language (English) was acquired before and the other (Dutch) after the period of lesion onset. Most of the deficits appear to be related to verbal (short-term) memory dysfunction. Several hypotheses of subcortical involvement in memory processes are discussed with reference to existing theories in this area.

[Causes of the slowing-down of cognitive processes in aging: the noise hypothesis]. / Oorzaken van cognitieve verlangzaming bij veroudering: ruishypothesen.

A typical phenomenon accompanying aging is the slowing down of cognitive processes. This slowing down may be considered to affect only specific aspects of information processing or it may be looked upon as a general property. As yet there exists no generally accepted explanation of this phenomenon. There is disagreement about the exact localisation and the physiological basis of the slowing down. However, a number of hypotheses has been formulated. These hypotheses have in common that the slowing down is attributed to a form of 'noise', either at neuronal level or at psychological level. We discuss several of these noise-related theories and their predictions and review the empirical basis for each of them. It is concluded that the different hypotheses do not exclude each other and that slowing down of cognitive processes can be observed at different levels of information processing.

[Hemisphere differences in aging: an artifact]. / Hemisfeerverschillen in veroudering: een artefact.

The observation that language processes in particular resist aging relatively well, gave rise to the hypothesis that the right hemisphere declines more rapidly than the left. In this review we discuss results from different lines of research relevant to this issue. It appears that the hypothesis is based on methodologically weak studies. Factors such as task characteristics, familiarity with stimulus materials and practice effects have been controlled insufficiently in the past and they may well explain the observed effects. Moreover, no clear neuropathological differences between the hemispheres have been reported. Therefore, it seems reasonable not to assume differential rates of aging for the two hemispheres.