Biomedical subjects

Anders M Fjell

Publications and source records attributed to Anders M Fjell.

18 recordsLinked to original sources

PubMed2006

Accelerated age-related cortical thinning in healthy carriers of apolipoprotein E epsilon 4.

Effects of APOE genotype on age-related slopes of cortical thinning was estimated by measuring the thickness of the cerebral cortex on a point-by-point basis across the cortical mantle in 96 healthy non-demented volunteers aged 48-75 years. Fifty nine were APOE epsilon 4- (no epsilon 4 allele) and 37 were epsilon 4+ (1 or 2 epsilon 4 alleles). The genotype groups had similar age, sex and IQ. Two T(1)-weighted MP-RAGE sequences were averaged for each participant to yield images with high signal-to-noise ratio, and quantified using semi-automated analysis tools. epsilon 4 carriers had thicker cortex than non-carriers in several frontal and temporal areas in both hemispheres, but showed a steeper age-related decline in adjacent areas. Upon comparison of the epsilon 4-specific age-related thinning with previously published patterns of thinning in normal aging and Alzheimer's disease (AD), we conclude that APOE epsilon 4 may function to accelerate thinning in areas found to decline in aging (medial prefrontal and pericentral cortex), but also to initiate thinning in areas associated with AD and amyloid-beta aggregation (occipitotemporal and basal temporal cortex).

Aged↗

PubMed2006

The functional and structural significance of the frontal shift in the old/new ERP effect.

There is a lack of studies mapping electrophysiological event-related potentials (ERPs) to structural neuroanatomical characteristics. The aim of the present study was to integrate electrophysiological memory-related activity with cortical and hippocampal volume, as well as psychometric memory performance, in a life-span sample. More specifically, we wanted to investigate the functional significance of the often-observed frontal shift of ERP amplitude with increasing age and whether neuroanatomical characteristics can explain this shift. Sixty six healthy participants (20-78 years) went through a neuropsychological examination, MRI scans, and a visual recognition ERP task with verbal stimuli. The results showed that ERPs elicited in the recognition memory task (the old/new effect) correlated significantly with cortical volume, but not with hippocampal volume. Large cortex predicted more differentiated ERP activity and not just larger amplitude in general, implying more distinct and efficient retrieval. Furthermore, ERP amplitude, cortical volume, and hippocampal volume all predicted scores on a composite memory scale. All these relationship were dependent upon the common influence of age. Finally, the participants with the most anterior distribution of activity showed the poorest recognition memory performance. Neither cortical nor hippocampal volume were related to this frontal shift. It is concluded that the distribution of activity along the anterior-posterior axis in a memory paradigm may have functional but not neuroanatomical volumetric correlates. The functional correlates need not be restricted to the older age groups.

Adult↗

PubMed2006

Regional cortical thickness matters in recall after months more than minutes.

The aim of this study was to determine the role of regional cortical thickness in recall of verbal material over an extended time period. MRI scans of healthy adults of varying ages were obtained. Two scans were averaged per person to achieve high spatial resolution, and a semi-automated method for continuous measurement of thickness across the entire cortical mantle was employed. Verbal memory tests assessing recall after 5 min, 30 min, and a mean interval of 83 days were administered. A general linear model (GLM) of the effects of thickness at each vertex on the different memory indices was computed, controlling for gender, age, IQ, and intracranial volume. These analyses were repeated with hippocampal volume as an additional variable to be controlled for, to assess to which extent effects of cortical thickness were independent of hippocampal size. Minute effects of cortical thickness were observed with regard to shorter time intervals (5 and 30 min). However, even when controlling for the effects of hippocampal volume, higher recall across months was associated with thicker cortex of distinct areas including parts of the gyrus rectus, the middle frontal gyrus, the parieto-occipital sulcus and the lingual gyrus of both hemispheres. In addition, hemisphere-specific associations were found in parts of the right temporal and parietal lobe as well as parts of the left precuneus. This supports a unique and critical role of the thickness of distinct cortical areas in recall after months, more than after minutes.

Adult↗

PubMed2006

Interactive effects of APOE and CHRNA4 on attention and white matter volume in healthy middle-aged and older adults.

In the present study, we investigated age-related changes in interactions between efficiency of neuronal repair mechanisms and efficiency of cholinergic neurotransmission in the context of attentional orienting. In addition, we explored white matter volume changes as possible neuronal underpinnings. A sample of 230 healthy middle-aged (53-64 years) and older (65-75 years) adults was genotyped for polymorphisms of APOE and CHRNA4, a nicotinic receptor subunit gene. Participants were administered a visuospatial attention task involving letter discrimination with location cues of varying validity. Genotype effects on white matter volume were also investigated in a subset of participants who received MRI scans. APOE interacted with CHRNA4, such that APOE-epsilon4 carriers who were also CHRNA4 TT homozygotes showed disproportionately slowed reaction time (RT) following invalid location cues. The interaction was stronger in the middle-aged participants than in the older participants. There was also a trend for individuals with combined APOE-epsilon4/CHRNA4 TT genotypes to show both lower white matter volume and slower overall RT on the attention task The interaction of a neurotransmission gene (CHRNA4) and a susceptibility gene (APOE) suggests that the efficiency of neuronal repair mechanisms may modulate the cholinergic system to influence attentional function.

Aged↗

PubMed2005

Selective increase of cortical thickness in high-performing elderly--structural indices of optimal cognitive aging.

The aim of this study was to identify cortical areas important for optimal cognitive aging. 74 participants (20-88 years) went through neuropsychological tests and two MR sessions. The sample was split into two age groups. In each, every participant was classified as "high" or "average" on fluid ability tests and on neuropsychological tests related to executive function. The groups were compared with regard to thickness on a point-by-point basis across the entire cortical mantle. The old high fluid performers had thicker cortex than the average performers in large areas of cortex, while there was minimal difference between the groups of high vs. average executive function. Furthermore, the old group with high fluid function had thicker cortex than the young participants in the posterior cingulate and adjacent areas. Further analyses showed that the latter was a result of a complex aging pattern, differing between the two performance groups, with decades of cortical thickening and subsequent thinning.

Adult↗

PubMed2005

Age-dependent changes in distribution of P3a/P3b amplitude and thickness of the cerebral cortex.

With increasing age, the electrophysiological event-related potentials P3a/P3b tend to get a more frontal maximum. The cognitive significance of this so-called frontal shift is not known, but hypotheses have focused on changes in the integrity of the frontal lobes. The aim of the present study was to test how the thickness of the cerebral cortex is related to the frontal shift. Well screened elderly participants went through a visual three-stimuli oddball-task, a battery of neuropsychological tests and magnetic resonance imaging scans. It was found that participants with frontocentral maxima had a thicker cerebral cortex in distinct areas than participants with parietal maxima, both for P3a and for P3b, while the parietal P3b participants had a thicker cortex in the anterior cingulate. This is the first study to demonstrate that age-dependent changes in the scalp distribution of electrophysiological activity are related to differences in thickness of the cerebral cortex.

Aged↗

PubMed2005

Age-sensitivity of P3 in high-functioning adults.

In their interesting paper, Daffner et al. [Daffner KR, Ryan KK, Williams DM, Budson AE, Rentz DM, Scinto LFM, et al. Age-related differences in novelty and target processing among cognitively healthy high performing adults. Neurobiol Aging 2005;26:1283-95] argue that previous studies have found changes in ERP components in response to novel and target stimuli due to two methodological factors: (1) lack of control for differences in level of cognitive status between age groups, and (2) not controlling for a non-specific age-related processing difference for all stimulus types (standards, targets, and novel). The questions raised by Daffner et al. are interesting, but based on existing literature, their conclusion seems premature. In the following, we will present examples from empirical literature as well as re-analyses of some of our own work to illustrate problematic aspects of Daffner et al.'s position.

Age Factors↗

PubMed2005

Effects of age on volumes of cortex, white matter and subcortical structures.

The effect of age was investigated in and compared across 16 automatically segmented brain measures: cortical gray matter, cerebral white matter, hippocampus, amygdala, thalamus, the accumbens area, caudate, putamen, pallidum, brainstem, cerebellar cortex, cerebellar white matter, the lateral ventricle, the inferior lateral ventricle, and the 3rd and 4th ventricle. Significant age effects were found for all volumes except pallidum and the 4th ventricle. Heterogeneous age responses were seen in that age relationships for cortex, amygdala, thalamus, the accumbens area, and caudate were linear, while cerebral white matter, hippocampus, brainstem, cerebellar white, and gray matter, as well as volume of the lateral, inferior lateral, and 3rd ventricles showed curvilinear relationships with age. In general, the findings point to global and large effects of age across brain volumes.

Adult↗

PubMed2005

Cortical volume and speed-of-processing are complementary in prediction of performance intelligence.

The rationale for the present study was to investigate the relationship between cortical volume, the latency of the ERP component P3a (as a measure of speed-of-processing), and performance intelligence (not adjusted for age differences). Seventy-one participants aged 20-88 years underwent a visual 3-stimuli oddball ERP task, an MRI-scan, and intelligence testing. P3a latency and cortical volume shared 9% variance (p<.05) and both were significantly related to performance intelligence (R2=.26 and .40, respectively). The amount of explained variance increased significantly (to R2=.51) when both measures were used as simultaneous predictors. When a path diagram was constructed including age as an exogenous variable, P3a latency and cortical volume both significantly predicted performance intelligence, but were no longer related to one another. The main conclusion from the study is that speed and size are complementary in prediction of performance intelligence, and the theoretical implications are discussed.

Adult↗

PubMed2005

Age does not increase rate of forgetting over weeks--neuroanatomical volumes and visual memory across the adult life-span.

The aim of the study was to investigate whether age affects visual memory retention across extended time intervals. In addition, we wanted to study how memory capabilities across different time intervals are related to the volume of different neuroanatomical structures (right hippocampus, right cortex, right white matter). One test of recognition (CVMT) and one test of recall (Rey-Osterrieth Complex Figure Test) were administered, giving measures of immediate recognition/recall, 20-30 min recognition/recall, and recognition/recall at a mean of 75 days. Volumetric measures of right hemisphere hippocampus, cortex, and white matter were obtained through an automated labelling procedure of MRI recordings. Results did not demonstrate a steeper rate of forgetting for older participants when the retention intervals were increased, indicating that older people have spared ability to retain information in the long-term store. Differences in neuroanatomical volumes could explain up to 36% of the variance in memory performance, but were not significantly related to rates of forgetting. Cortical volume and hippocampal volume were in some cases independent as predictors of memory function. Generally, cortical volume was a better predictor of recognition memory than hippocampal volume, while the 2 structures did not differ in their predictive power of recall abilities. While neuroanatomical volumetric differences can explain some of the differences in memory functioning between younger and older persons, the hippocampus does not seem to be unique in this respect.

Adult↗

PubMed2005

Basic information processing of neurotics and stables: an experimental ERP approach to personality and distractibility.

The aim of the study was to investigate the effects of level of neuroticism on electrophysiological event-related potentials (ERPs) to different kinds of stimuli. The neuroticism items from the NEO-PI-R were administered to 168 female, right-handed undergraduates between 19 and 29 years of age. 20 highly neurotic and 22 highly stable persons underwent an ERP task that was designed to be a combination of an auditory P3a and a visual P3b oddball task. No significant differences in the P3a and P3b were detected. It is concluded that highly neurotic and highly stable persons do not differ in fast neurocognitive processing of neutral stimuli, and that cognitive differences between the groups may be located at another level in the sequence of information processing stages.

Adult↗

PubMed2005

Age-differences in verbal recognition memory revealed by ERP.

Seventy-four participants (aged 20-82 years) went through a continuous performance recognition memory task with multiple repetitions of words and non-words while ERPs were recorded from the scalp. The old/new ERP effect (the difference in activation to stimuli correctly recognized as old and stimuli correctly recognized as new) for words but not non-words declined with increasing age in a linear pattern, but the relationship between the old/new effect and age varied throughout the ERP time window. Differences in topography between age groups were manifested in a frontal shift in activation for older age groups. Further, the data point to differences in semantic versus non-semantic processing across the adult life span, and it is concluded that specific cognitive memory processes are differentially involved at different ages.

Adult↗

PubMed2004

Thinking styles in relation to personality traits: an investigation of the Thinking Styles Inventory and NEO-PI-R.

This study is an investigation of the Sternberg-Wagner Thinking Style Inventory (TSI), with regard to cross-cultural replication and relation to the five-factor personality model (FFM). TSI and NEO-PI-R were administered to 107 participants from USA and 114 participants from Norway. Inter-correlations between NEO-PI-R dimensions and TSI-scales and factors were not very strong, few exceeding 0.40, and the correlations were in predicted directions. Joint factor analyses of TSI and NEO-PI-R showed that TSI covers variance that NEO-PI-R does not explain. Thus, it is argued that the thinking styles give an independent contribution beyond FFM dimensions. However, TSI did not relate to FFM in the same manner in the two samples. Finally, the TSI-scales and factors were replicable across samples by Procrustes rotation. The question whether thinking style may be regarded as a valid and reliable construct is discussed.

Cross-Cultural Comparison↗

PubMed2004

Life-span changes in P3a.

The relationship of visual P3a to age was investigated in a life-span sample. The aims of the study were (1) to assess to what extent P3a, relative to P3b, decreases with increasing age; (2) To assess at which recording sites the relationship between P3a and age is strongest; (3) to investigate whether the relationship between P3a and age is best described as linear or nonlinear. One hundred and three well-functioning adults, 20-92 years old, were given a health interview, a battery of neuropsychological tests, and performed a visual three-stimuli oddball ERP task yielding both a P3a and a P3b. P3a and age was moderately correlated, with coefficients reaching.53 (Cz) and -.52 (Pz) for latency and amplitude, respectively. P3b was to a much lesser extent related to age. Generally, the age-P3a relationship was strongest at midline and central electrodes. Finally, the relationship between age and P3a was best described as linear. P3a seems selectively more impaired with age than P3b, but this impairment seems less pronounced at Fz than at Cz and Pz. There is a need for complex theoretical integration of these and previous findings.

Adult↗

PubMed2003

The relationship between P3 and neuropsychological function in an adult life span sample.

The relationship of P3 to age and neuropsychological performance was investigated in a sample of 71 well-functioning adults ranging in age from 21.8 to 94.7 years. ERPs were recorded while the participants performed an auditory two-stimuli oddball task in which the rare tones were to be counted. The Wechsler Abbreviated Scale of Intelligence (WASI) and the digit span subtest from the Wechsler Adult Intelligence Scale-R (WAIS-R) were administered. Regression analyses showed significant, linear effects of age on P3 latency and amplitude. Significant relationships between P3 and neuropsychological measures were found, in that P3 latency correlated moderately in predictable ways with scores on matrices, block design, and digit span. Overall, these relationships are best characterized by a linear function, but a non-linear component is involved in the relationship between P3 latency and fluid tests. Finally, a linear relationship between ERP components and age was found, while a curvilinear relationship was found between age and block design and matrices, respectively. There appears to be either partially different functions or structures underlying performance on these tests, the P3 component and performance on neuropsychological tests, or one must assume some variant of a multiplicative, as opposed to an additive, model of cognition.

Adult↗

PubMed2003

Effects of auditory stimulus intensity and hearing threshold on the relationship among P300, age, and cognitive function.

OBJECTIVE: Although P300 is regarded as cognitive or endogenous, studies have demonstrated that stimulus intensity influences the component. To isolate effects of hearing from cognition, two experiments were designed to compare the effects of variation in stimulus intensities with naturally occurring differences in hearing thresholds. METHODS: In experiment 1, 18 participants were tested with 5 auditory oddball event-related potential (ERP) paradigms with different intensities. In experiment 2, an auditory oddball ERP task was completed by 3 groups of participants with different hearing thresholds (n=57). P300 was then correlated with block design and matrices from Wechsler's abbreviated scale of intelligence. RESULTS: At Cz and Pz, manipulation of intensity had less effect on P300 than the observed differences between groups with different hearing thresholds. At Fz, however, the effect of manipulations of stimulus intensity was greater than the effect of naturally occurring differences in hearing thresholds. P300 still correlated in predicted directions with cognitive tests after correcting for the estimated effect of differences in hearing. CONCLUSIONS: The results indicate that P300 is an index of cognitive function even when the relationship is corrected for perceptual differences, at least at posterior scalp areas.

Acoustic Stimulation↗

PubMed2003

On the topography of P3a and P3b across the adult lifespan--a factor-analytic study using orthogonal procrustes rotation.

The purpose of this study was to investigate whether the activity distribution of P3a and P3b across the scalp changes with age or remains identical. 103 well-functioning adults, 20-90 years, performed a visual three-stimuli oddball ERP task yielding both a P3a and a P3b. The sample was divided into three age groups: 20-44 years, 45-69 years, and 70-90 years. The P3as and P3bs from 20 electrodes were subjected to principal component factor analyses. The unrotated factor matrices from the three different age groups were then compared using orthogonal Procrustes rotation to maximize congruence, and Tucker's coefficient of congruence was used as index of similarity. The results showed that less variance in latency than in amplitude was explained by three factors. Further, for amplitude, the factor structure remained the same for both P3a and P3b across different age groups, implying that the structure of the neurophysiological generation of the P3 amplitude operates similarly at different ages. For P3a and P3b latency the congruence coefficients were weaker, implying that when it comes to latency, the neural generators or parts of the generator circuits are differentially susceptible to the influence of age. It is speculated that a possible reduced temporal synchronicity across electrodes could result in less predictable shifts of the clustering of P3 latency, and may explain the presently observed factor variability with age. Implications of the findings and the utility of Procrustes rotation in ERP studies are discussed.

Adult↗

PubMed2002

One-year test-retest reliability of auditory ERPs in young and old adults.

The reliability of ERP measures was investigated in a sample covering the adult life span (n = 59, age 21-92). This sample was divided into a young and an old group. ERPs to an auditory two-stimuli oddball task were recorded in the sample at two occasions separated by 12-14 months (T1 and T2). The recordings of T1 were split in half, to assess within session reliability. Correlations were calculated for N1, P2 and P3 peak latency and amplitude, for average amplitude during 50 ms epochs within the defined P3-window 250-550, and for average amplitude in successive 15 ms epochs from 1 to 705 ms. The results show that amplitude measures were more reliable than the latency measures at all electrodes. Time window/epoch amplitude measures yielded reliabilities in the same range as peak amplitude. Reliabilities peaked around the conventionally studied N1, P2 and P3, and this is seen as a validation of the components. In general, the old group exhibited weaker P3 peak latency reliabilities than the young group. However, many of these differences did not reach statistical significance. Implications of the findings are discussed.

Adult↗