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Biomedical subjects

Lars Nyberg

Publications and source records attributed to Lars Nyberg.

At least 19 recordsLinked to original sources
PubMed2021

1q21.1 distal copy number variants are associated with cerebral and cognitive alterations in humans.

Low-frequency 1q21.1 distal deletion and duplication copy number variant (CNV) carriers are predisposed to multiple neurodevelopmental disorders, including schizophrenia, autism and intellectual disability. Human carriers display a high prevalence of micro- and macrocephaly in deletion and duplication carriers, respectively. The underlying brain structural diversity remains largely unknown. We systematically called CNVs in 38 cohorts from the large-scale ENIGMA-CNV collaboration and the UK Biobank and identified 28 1q21.1 distal deletion and 22 duplication carriers and 37,088 non-carriers (48% male) derived from 15 distinct magnetic resonance imaging scanner sites. With standardized methods, we compared subcortical and cortical brain measures (all) and cognitive performance (UK Biobank only) between carrier groups also testing for mediation of brain structure on cognition. We identified positive dosage effects of copy number on intracranial volume (ICV) and total cortical surface area, with the largest effects in frontal and cingulate cortices, and negative dosage effects on caudate and hippocampal volumes. The carriers displayed distinct cognitive deficit profiles in cognitive tasks from the UK Biobank with intermediate decreases in duplication carriers and somewhat larger in deletion carriers-the latter potentially mediated by ICV or cortical surface area. These results shed light on pathobiological mechanisms of neurodevelopmental disorders, by demonstrating gene dose effect on specific brain structures and effect on cognitive function.

Brain↗
PubMed2003

Predicting falls in residential care by a risk assessment tool, staff judgement, and history of falls.

BACKGROUND AND AIMS: It is of great importance to consider whether a tool's predictive value is generalizable to similar samples in other locations. Numerous fall prediction systems have been developed, but very few are evaluated over a different time period in a different location. The purpose of this study was to validate the predictive accuracy of the Mobility Interaction Fall (MIF) chart, and to compare it to staff judgement of fall risk and history of falls. METHODS: The MIF chart, staff judgement, and fall history were used to classify the risk of falling in 208 residents (mean age 83.2 +/- 6.8 years) living in four residential care facilities in northern Sweden. The MIF chart includes an observation of the ability to walk and simultaneously interact with a person or an object, a vision test, and a concentration rating. Staff rated each resident's risk as high or low and reported the resident's history of falls during the past 6 months. Falls were followed up for 6 months. RESULTS: During the follow-up period, 104 residents (50%) fell at least once indoors. Many of the factors commonly associated with falls did not differ significantly between residents who fell at least once and residents who did not fall. In this validating sample the predictive accuracy of the MIF chart was notably lower than in the developmental sample. A combination of any two of the MIF chart, staff judgement, and history of falls was more accurate than any approach alone; more than half of the residents classified as 'high risk' by two approaches sustained a fall within 3 months. CONCLUSIONS: Residents classified as 'high risk' by any two of the MIF chart, staff judgement, and history of falls should be regarded as particularly prone to falling and in urgent need of preventive measures.

Accidental Falls↗
PubMed2003

Prediction of falls among older people in residential care facilities by the Downton index.

BACKGROUND AND AIMS: Falls are frequent among older people living in residential care facilities. The aim of this study was to investigate the prediction accuracy of the Downton fall risk index among older people living in residential care facilities at 3, 6 and 12 months, and with two different definitions of falls. METHODS: Seventy-eight residents in one residential care facility, 56 women and 22 men, mean +/- SD age 81 +/- 6 years, participated in this study. Forty-seven percent of participants had dementia, 45% depression, and 32% previous stroke. Forty-one percent of participants used a walking device indoors, and the median score of the Barthel ADL Index was 16. At baseline, the Downton fall risk index was scored for each individual. A score of 3 or more was taken to indicate high risk of falls. Participants were followed up prospectively for 12 months, with regard to falls indoors. RESULTS: At 3, 6 and 12 months, and using a fall definition including all indoor falls, sensitivity ranged from 81 to 95% with the highest value at 3 months, and specificity ranged from 35 to 40%. The prognostic separation values ranged from 0.26 to 0.37. Within 3 months, the risk of falling was 36% in the high-risk group (index score > or = 3) and 5% in the low-risk group. The accuracy of predictions did not improve when applying a fall definition in which falls precipitated by acute illness, acute disease, or drug side-effects were excluded. CONCLUSIONS: Already after 3 months, the Downton fall risk index appears to be a useful tool for predicting falls, irrespective of their cause, among older people in residential care facilities.

Accidental Falls↗
PubMed2003

Common prefrontal activations during working memory, episodic memory, and semantic memory.

Regions of the prefrontal cortex (PFC) are typically activated in many different cognitive functions. In most studies, the focus has been on the role of specific PFC regions in specific cognitive domains, but more recently similarities in PFC activations across cognitive domains have been stressed. Such similarities may suggest that a region mediates a common function across a variety of cognitive tasks. In this study, we compared the activation patterns associated with tests of working memory, semantic memory and episodic memory. The results converged on a general involvement of four regions across memory tests. These were located in left frontopolar cortex, left mid-ventrolateral PFC, left mid-dorsolateral PFC and dorsal anterior cingulate cortex. These findings provide evidence that some PFC regions are engaged during many different memory tests. The findings are discussed in relation to theories about the functional contribution of the PFC regions and the architecture of memory.

Adult↗
PubMed2003

Attention-related activity during episodic memory retrieval: a cross-function fMRI study.

In functional neuroimaging studies of episodic retrieval (ER), activations in prefrontal, parietal, anterior cingulate, and thalamic regions are typically attributed to episodic retrieval processes. However, these activations are also frequent during visual attention (VA) tasks, suggesting that their role in ER may reflect attentional rather than mnemonic processes. To investigate this possibility, we directly compared brain activity during ER and VA tasks using event-related fMRI. The ER task was a word recognition test with a retrieval mode component, and the VA task was a target detection task with a sustained attention component. The study yielded three main findings. First, a common fronto-parietal-cingulate-thalamic network was found for ER and VA, suggesting that the involvement of these regions during ER reflects general attentional processes. This idea is compatible with some of the interpretations proposed in the ER literature (e.g. postretrieval monitoring), which may be rephrased in terms of attentional processes. Second, several subregions were differentially involved in ER versus VA. For example, the frontopolar cortex and the precuneus were more activated for ER than for VA, possibly reflecting retrieval mode and processing of internally generated stimuli, respectively. Finally, the study yielded an unexpected finding: some medial temporal lobe regions were similarly activated for ER and VA. This finding suggests that the medial temporal lobes may be involved in indexing representations within the focus of consciousness, regardless of whether they are mnemonic or perceptual. Overall, the present results suggest that many of the activations attributed to specific cognitive processes, such as episodic memory, may actually reflect more general cognitive operations.

Adult↗
PubMed2003

Hemispheric asymmetries of memory: the HERA model revisited.

The hemispheric encoding/retrieval asymmetry (HERA) model is a process-specific description of experimental data provided by a large set of functional neuroimaging studies. According to HERA, left prefrontal cortex (PFC) is more involved than right PFC in episodic memory encoding, whereas right PFC is more involved than left PFC in episodic memory retrieval. Recently it has been claimed that this description does not hold for non-verbal materials. Here we propose a more precise formulation of HERA than previously, and argue that there is sufficient evidence to conclude that HERA, as reformulated, is true for both verbal and non-verbal materials.

Journal Article↗
PubMed2003

Fall and injury prevention in residential care--effects in residents with higher and lower levels of cognition.

OBJECTIVES: To evaluate the effectiveness of a multifactorial fall and injury prevention program in older people with higher and lower levels of cognition. DESIGN: A preplanned subgroup comparison of the effectiveness of a cluster-randomized, nonblinded, usual-care, controlled trial. SETTING: Nine residential facilities in Umeå, Sweden. PARTICIPANTS: All consenting residents living in the facilities, aged 65 and older, who could be assessed using the Mini-Mental State Examination (MMSE; n = 378). An MMSE score of 19 was used to divide the sample into one group with lower and one with higher level of cognition. The lower MMSE group was older (mean +/- standard deviation = 83.9 +/- 5.8 vs 82.2 +/- 7.5) and more functionally impaired (Barthel Index, median (interquartile range) 11 (6-15) vs 17 (13-18)) and had a higher risk of falling (64% vs 36%) than the higher MMSE group. INTERVENTION: A multifactorial fall prevention program comprising staff education, environmental adjustment, exercise, drug review, aids, hip protectors, and postfall problem-solving conferences. MEASUREMENTS: The number of falls, time to first fall, and number of injuries were evaluated and compared by study group (intervention vs control) and by MMSE group. RESULTS: A significant intervention effect on falls appeared in the higher MMSE group but not in the lower MMSE group (adjusted incidence rates ratio of falls P =.016 and P =.121 and adjusted hazard ratio P <.001 and P =.420, respectively). In the lower MMSE group, 10 femoral fractures were found, all of which occurred in the control group (P =.006). CONCLUSION: The higher MMSE group experienced fewer falls after this multifactorial intervention program, whereas the lower MMSE group did not respond as well to the intervention, but femoral fractures were reduced in the lower MMSE group.

Accidental Falls↗
PubMed2003

Selective adult age differences in an age-invariant multifactor model of declarative memory.

Confirmatory factor analysis was used to test competing models of declarative memory. Data from middle-aged participants provided support for a model comprised of 2 2nd-order (episodic and semantic memory) and 4 1st-order (recall, recognition, fluency, and knowledge) factors. Extending this model across young-old and old-old participants established support for age invariance. Tests of group differences showed an age deficit in episodic memory that was more pronounced for recall than for recognition. For semantic memory, there was an increase in knowledge from middle to young-old age and thereafter a decrease. Overall, the results support the view that episodic memory is more age sensitive than semantic memory, but they also indicate that aging has differential effects within these 2 forms of memory.

Adult↗
PubMed2003

Cigarette smoking and cognitive performance in healthy Swedish adults.

BACKGROUND: The relationship between cigarette smoking and cognitive function was examined in healthy Swedish adults who were participants in the Betula Prospective Cohort Study of Aging, Memory, and Health. SUBJECTS: The data are from those individuals in the Betula study who were self-reported continuous smokers contrasted to those who reported never smoking cigarettes. DESIGN: The dependent variables were cognitive tasks that varied with respect to difficulty and the demand they placed on processing resources. RESULTS: Current smokers performed more poorly than never smokers on the more cognitively demanding tasks; namely, Block Design and free recall. CONCLUSIONS: The findings were interpreted in the light of the assumption that cigarette smoking may exert its greatest deleterious effect on those cognitive tasks that place the heaviest demands on processing resources.

Adult↗
PubMed2002

Decreased activity in inferotemporal cortex during explicit memory: dissociating priming, novelty detection, and recognition.

Studies of non-human primates have shown that activity in inferotemporal (IT) brain regions decrease over repeated stimulus exposure, a phenomenon known as repetition suppression. In the present study, repetition suppression was examined during recognition of personally experienced events (explicit memory). Brain activity was measured while subjects encoded and subsequently recognized scenic pictures. First, two recognition conditions were compared; one that mainly included familiar pictures and one that mainly included novel pictures. Responses derived from this contrast may reflect recognition memory, perceptual priming, or novelty detection. To test specifically for responses associated with recognition memory, subjects encoded a new set of pictures followed by two recognition tests. All test pictures had been presented during the course of the experiment, and the subjects identified pictures that appeared in the second encoding list. Since all pictures were familiar, repetition suppression was specifically associated with recognition memory. In the first contrast, relative change in brain activity was observed in inferotemporal, extra-striate, and hippocampal regions during recognition of familiar versus novel pictures. In the second contrast, decreased activity in IT cortex was found. The location of this region overlapped with that for the region identified in the first contrast, and a conjunction analysis showed that reduced activity in left IT cortex was common to both contrasts. These results suggest that repetition suppression in IT cortex reflects recognition memory, and that such a response is not a simple function of stimulus repetition but can be modulated by top-down processing.

Adult↗
PubMed2002

Memory functions and rCBF (99m)Tc-HMPAO SPET: developing diagnostics in Alzheimer's disease.

Alzheimer's disease (AD) is a primary degenerative disease of the brain. The prevalence increases with age, with devastating consequences for the individual and society. The aim of this study was to evaluate whether patients with early AD show an altered regional cerebral blood flow (rCBF) compared with control persons. Furthermore, we aimed to investigate the correlation between rCBF in sublobar volumes of the brain and performance on memory tests. Memory tests were chosen to evaluate episodic and semantic memory. Fourteen patients (aged 75.2+/-8.8 years) with early AD and 15 control persons (aged 71.4+/-3.2 years) were included. rCBF measurements with single-photon emission tomography (SPET) using technetium-99m hexamethylpropylene amine oxime (HMPAO) were performed. The rCBF (99m)Tc-HMPAO SPET images were spatially transformed to fit a brain atlas and normalised for differences in rCBF (Computerised Brain Atlas software). Cortical and subcortical volumes of interest (VOIs) were analysed and compared. Compared with the controls, AD patients showed a significantly lower rCBF ratio in temporoparietal regions, including the left hippocampus. The diagnostic sensitivity and specificity for AD were high in temporoparietal regions. AD patients had significantly reduced performance on semantic and, in particular, episodic memory tests compared with age-matched normative data, and their performance on several episodic tests correlated with rCBF ratios in parietal and temporal regions, including the left hippocampus. The correlation between rCBF ratio and level of episodic memory performance suggests that abnormalities in rCBF pattern underlie impaired episodic memory functioning in AD.

Aged↗
PubMed2002

Fall and injury prevention in older people living in residential care facilities. A cluster randomized trial.

BACKGROUND: Falls and resulting injuries are particularly common in older people living in residential care facilities, but knowledge about the prevention of falls is limited. OBJECTIVE: To investigate whether a multifactorial intervention program would reduce falls and fall-related injuries. DESIGN: A cluster randomized, controlled, nonblinded trial. SETTING: 9 residential care facilities located in a northern Swedish city. PATIENTS: 439 residents 65 years of age or older. INTERVENTION: An 11-week multidisciplinary program that included both general and resident-specific, tailored strategies. The strategies comprised educating staff, modifying the environment, implementing exercise programs, supplying and repairing aids, reviewing drug regimens, providing free hip protectors, having post-fall problem-solving conferences, and guiding staff. MEASUREMENTS: The primary outcomes were the number of residents sustaining a fall, the number of falls, and the time to occurrence of the first fall. A secondary outcome was the number of injuries resulting from falls. RESULTS: During the 34-week follow-up period, 82 residents (44%) in the intervention program sustained a fall compared with 109 residents (56%) in the control group (risk ratio, 0.78 [95% CI, 0.64 to 0.96]). The adjusted odds ratio was 0.49 (CI, 0.37 to 0.65), and the adjusted incidence rate ratio of falls was 0.60 (CI, 0.50 to 0.73). Each of 3 residents in the intervention group and 12 in the control group had 1 femoral fracture (adjusted odds ratio, 0.23 [CI, 0.06 to 0.94]). Clustering was considered in all regression models. CONCLUSION: An interdisciplinary and multifactorial prevention program targeting residents, staff, and the environment may reduce falls and femoral fractures.

Accidental Falls↗
PubMed2002

Similarities and differences in the neural correlates of episodic memory retrieval and working memory.

Functional neuroimaging studies have shown that different cognitive functions activate overlapping brain regions. An activation overlap may occur because a region is involved in operations tapped by different cognitive functions or because the activated area comprises subregions differentially involved in each of the functions. To investigate these issues, we directly compared brain activity during episodic retrieval (ER) and working memory (WM) using event-related functional MRI (fMRI). ER was investigated with a word recognition test, and WM was investigated with a word delayed-response test. Two-phase trials distinguished between retrieval mode and cue-specific aspects of ER, as well as between encoding/maintenance and retrieval aspects of WM. The results revealed a common fronto-parieto-cerebellar network for ER and WM, as well as subregions differentially involved in each function. Specifically, there were two main findings. First, the results differentiated common and specific subregions within the prefrontal cortex: (i) left dorsolateral areas were recruited by both functions, possibly reflecting monitoring operations; (ii) bilateral anterior and ventrolateral areas were more activated during ER than during WM, possibly reflecting retrieval mode and cue-specific ER operations, respectively; and (iii) left posterior/ventral (Broca's area) and bilateral posterior/dorsal areas were more activated during WM than during ER, possibly reflecting phonological and generic WM operations, respectively. Second, hippocampal and parahippocampal regions were activated not only for ER but also for WM. This result suggests that indexing operations mediated by the medial temporal lobes apply to both long-term and short-term memory traces. Overall, our results show that direct cross-function comparisons are critical to understand the role of different brain regions in various cognitive functions.

Adult↗
PubMed2002

Genetic variation in memory functioning.

On the basis of a review of the literature the contribution of genetic factors for individual differences in memory performance is discussed. Explorations of such influences on memory have just begun. Most of those studies that have been conducted in order to find a quantitative trait locus for memory have focused on ApolipoproteinE (ApoE). One form of this gene is strongly associated with cardiovascular disease in middle age and to late-onset Alzheimer's disease. Some studies have demonstrated an association between ApoE and memory even in non-demented individuals. Other studies have failed to demonstrate this association. Based on data from a prospective cohort study (Betula) in our own laboratory, we have assessed and examined associations between three different forms of ApoE and performance on episodic memory tests. Cross-sectional comparisons revealed non-significant differences in episodic memory performance between carriers of the three alleles. Analyses of change scores in longitudinal data revealed that allele epsilon 4 was related to a lower level of memory performance than alleles epsilon 2 and epsilon 3. This effect was most pronounced in tasks providing cognitive support at both encoding and retrieval, suggesting a deficit in utilizing such support in carriers of the epsilon 4 allele.

Aging↗
PubMed2002

Individual differences in memory enhancement by encoding enactment: relationships to adult age and biological factors.

Numerous studies have demonstrated an age-related decline in episodic memory performance. However, both younger and older adults benefit from various kinds of encoding support, suggesting that memory functioning remains plastic in older age. The present review is concerned with encoding support in the form of enactment. Memory for simple commands is substantially higher if the commands are enacted during encoding than only read/heard. Such memory enhancement has been demonstrated for many age groups and patient groups, suggesting that it is a general effect. Analysis of the results from 1000 participants ranging in age between 35 and 80 years revealed that about 5% of the participants had low memory performance after enacted encoding and showed no enactment effect. The majority of these were older. Comparisons of participants that did or did not show an enactment effect for a select set of biological and neuropsychological factors provided tentative evidence that a failure to benefit from encoding enactment reflects a dysfunctional motor system. This is in agreement with findings from recent functional neuroimaging studies that associate the enactment effect with motor areas in the brain. Variation in the ability to benefit from encoding enactment is discussed in relation to an age-related decline in dopamine function.

Aging↗
PubMed2002

Brain imaging of human memory systems: between-systems similarities and within-system differences.

There is much evidence for the existence of multiple memory systems. However, it has been argued that tasks assumed to reflect different memory systems share basic processing components and are mediated by overlapping neural systems. Here we used multivariate analysis of PET-data to analyze similarities and differences in brain activity for multiple tests of working memory, semantic memory, and episodic memory. The results from two experiments revealed between-systems differences, but also between-systems similarities and within-system differences. Specifically, support was obtained for a task-general working-memory network that may underlie active maintenance. Premotor and parietal regions were salient components of this network. A common network was also identified for two episodic tasks, cued recall and recognition, but not for a test of autobiographical memory. This network involved regions in right inferior and polar frontal cortex, and lateral and medial parietal cortex. Several of these regions were also engaged during the working-memory tasks, indicating shared processing for episodic and working memory. Fact retrieval and synonym generation were associated with increased activity in left inferior frontal and middle temporal regions and right cerebellum. This network was also associated with the autobiographical task, but not with living/non-living classification, and may reflect elaborate retrieval of semantic information. Implications of the present results for the classification of memory tasks with respect to systems and/or processes are discussed.

Adult↗
PubMed2002

Falls among frail older people in residential care.

AIMS: A prospective study was carried out to investigate the incidence, circumstances, and injuries from falls among frail older people living in three different types of Swedish residential care settings. METHODS: The settings were senior citizens' apartments, an old people's home, and a group dwelling for people with dementia. The falls were registered during the three-year study period on a semi-structured fall report, and injurious falls were categorized according to severity. RESULTS: In total 428 falls occurred among 121 residents. The incidence rate of falls at the group dwelling was twice the rates of the old people's home and senior citizens' apartments (4282 compared with 1709 and 2114 falls per 1000 person-years respectively). Some 27% of the falls occurred during the night (2100h to 0600h) and 28% were related to a visit to the lavatory. The presence of acute disease at the time of a fall was diagnosed in 23% of the falls. Some type of injury occurred in 118 falls (28%) and 36 of these (8%) led to moderate or serious injuries. In total 48 fractures were diagnosed. CONCLUSIONS: In a preventive programme for falls and injuries in residential care settings, areas of particular interest should include falls after mealtimes and falls at night, conditions of acute diseases, rising up from sitting, walking, and activities in progress, especially visits to the lavatory.

Accidental Falls↗