Neural Signatures of Intransitive Preferences

It is often assumed that decisions are made by rank-ordering and thus comparing the available choice options based on their subjective values. Rank-ordering requires that the alternatives’ subjective values are mentally represented at least on an ordinal scale. Because one alternative cannot be at the same time better and worse than another alternative, choices should satisfy transitivity (if alternative A is preferred over B, and B is preferred over C, A should be preferred over C). Yet, individuals often demonstrate striking violations of transitivity (preferring C over A). We used functional magnetic resonance imaging to study the neural correlates of intransitive choices between gambles varying in magnitude and probability of financial gains. Behavioral intransitivities were common. They occurred because participants did not evaluate the gambles independently, but in comparison with the alternative gamble presented. Neural value signals in prefrontal and parietal cortex were not ordinal-scaled and transitive, but reflected fluctuations in the gambles’ local, pairing-dependent preference-ranks. Detailed behavioral analysis of gamble preferences showed that, depending on the difference in the offered gambles’ attributes, participants gave variable priority to magnitude or probability and thus shifted between preferring richer or safer gambles. The variable, context-dependent priority given to magnitude and probability was tracked by insula (magnitude) and posterior cingulate (probability). Their activation-balance may reflect the individual decision rules leading to intransitivities. Thus, the phenomenon of intransitivity is reflected in the organization of the neural systems involved in risky decision-making

rt-me-fMRI: a task and resting state dataset for real-time, multi-echo fMRI methods development and validation

Latest published: 04 Feb 2021A multi-echo fMRI dataset (N=28 healthy participants) with four task-based and two resting state runs was collected, curated and made available to the community. Its main purpose is to advance the development of methods for real-time multi-echo functional magnetic resonance imaging (rt-me-fMRI) analysis with applications in neurofeedback, real-time quality control, and adaptive paradigms, although the variety of experimental task paradigms supports a multitude of use cases. Tasks include finger tapping, emotional face and shape matching, imagined finger tapping and imagined emotion processing. This work provides a detailed description of the full dataset; methods to collect, prepare, standardize and preprocess it; quality control measures; and data validation measures. A web-based application is provided as a supplementary tool with which to interactively explore, visualize and understand the data and its derivative measures: https://rt-me-fmri.herokuapp.com/. The dataset itself can be accessed via a data use agreement on DataverseNL at https://dataverse.nl/dataverse/rt-me-fmri. Supporting information and code for reproducibility can be accessed at https://github.com/jsheunis/rt-me-fMR

The Hippocampus Is Coupled with the Default Network during Memory Retrieval but Not during Memory Encoding

The brain's default mode network (DMN) is activated during internally-oriented tasks and shows strong coherence in spontaneous rest activity. Despite a surge of recent interest, the functional role of the DMN remains poorly understood. Interestingly, the DMN activates during retrieval of past events but deactivates during encoding of novel events into memory. One hypothesis is that these opposing effects reflect a difference between attentional orienting towards internal events, such as retrieved memories, vs. external events, such as to-be-encoded stimuli. Another hypothesis is that hippocampal regions are coupled with the DMN during retrieval but decoupled from the DMN during encoding. The present fMRI study investigated these two hypotheses by combining a resting-state coherence analysis with a task that measured the encoding and retrieval of both internally-generated and externally-presented events. Results revealed that the main DMN regions were activated during retrieval but deactivated during encoding. Counter to the internal orienting hypothesis, this pattern was not modulated by whether memory events were internal or external. Consistent with the hippocampal coupling hypothesis, the hippocampus behaved like other DMN regions during retrieval but not during encoding. Taken together, our findings clarify the relationship between the DMN and the neural correlates of memory retrieval and encoding

Differentiële gevoeligheid van cellulaire membranen voor peroxidatieve processen. een elektronenmicroscopisch, histochemisch en cytochemisch onderzoek naar de invloed van vitamine E gebrek en röntgenstraling op de eendelever

Is er een differentiële gevoeligheid van de cellulaire membranen voor peroxidatieve processen? In dit proefschrift wordt een morfologisch, histochemisch en cytochemisch onderzoek beschreven naar de invloed die vitamine E, gebrek en röntgenstraling hebben op de ultrastructuur en de enzymactiviteiten van verschillende cellulaire membranen, zoals de plasmamembraan en de membranen van lysosomen, mitochondriën en endoplasmatisch reticulum. ... Zie: Samenvattin

Cortisol associated with hypometabolism across the Alzheimer's disease spectrum

Objective: Hypothalamic-pituitary-adrenal (HPA) dysregulation is proposed as a risk factor for Alzheimer's disease (AD). This cross-sectional study assessed relationships between plasma cortisol levels and neuroimaging biomarkers, specifically brain glucose metabolism and gray matter volume, across the AD spectrum. Methods: Cognitively normal older adults and patients with mild cognitive impairment (MCI) and AD dementia were included from the Alzheimer's Disease Neuroimaging Initiative. Participants (n = 556) were selected based on availability of baseline measures of plasma cortisol levels and gray matter volume, as estimated with magnetic resonance imaging. Within a subsample (n = 288), we examined brain glucose metabolism (n = 288) as with positron emission tomography. Relationships between plasma cortisol and AD neuroimaging biomarkers were assessed using regions-of-interest and voxel-wise analyses. Results: Across the entire cohort, higher plasma cortisol was also related to lower gray matter volume, most notably in the left lateral temporal-parietal-occipital regions. Importantly, higher plasma cortisol concentration was also related to hypometabolism, especially in lateral temporo-parietal and medial parietal regions. When stratified by diagnosis, these negative associations were most pronounced in MCI and AD patients. Interpretation: High plasma cortisol was associated with hypometabolism predominantly in AD-sensitive regions. Our results indicate that HPA axis activation could influence brain metabolism and exacerbate existing AD pathological processes. This is consistent with a notion that stress is a conceivable target for intervention to slow down AD progression. Future studies should delineate underlying pathological mechanisms and investigate if clinical or lifestyle interventions could alleviate negative actions of stress on AD

Cortisol associated with hypometabolism across the Alzheimer's disease spectrum

Objective: Hypothalamic-pituitary-adrenal (HPA) dysregulation is proposed as a risk factor for Alzheimer's disease (AD). This cross-sectional study assessed relationships between plasma cortisol levels and neuroimaging biomarkers, specifically brain glucose metabolism and gray matter volume, across the AD spectrum. Methods: Cognitively normal older adults and patients with mild cognitive impairment (MCI) and AD dementia were included from the Alzheimer's Disease Neuroimaging Initiative. Participants (n = 556) were selected based on availability of baseline measures of plasma cortisol levels and gray matter volume, as estimated with magnetic resonance imaging. Within a subsample (n = 288), we examined brain glucose metabolism (n = 288) as with positron emission tomography. Relationships between plasma cortisol and AD neuroimaging biomarkers were assessed using regions-of-interest and voxel-wise analyses. Results: Across the entire cohort, higher plasma cortisol was also related to lower gray matter volume, most notably in the left lateral temporal-parietal-occipital regions. Importantly, higher plasma cortisol concentration was also related to hypometabolism, especially in lateral temporo-parietal and medial parietal regions. When stratified by diagnosis, these negative associations were most pronounced in MCI and AD patients. Interpretation: High plasma cortisol was associated with hypometabolism predominantly in AD-sensitive regions. Our results indicate that HPA axis activation could influence brain metabolism and exacerbate existing AD pathological processes. This is consistent with a notion that stress is a conceivable target for intervention to slow down AD progression. Future studies should delineate underlying pathological mechanisms and investigate if clinical or lifestyle interventions could alleviate negative actions of stress on AD