Approaching finite-temperature phase diagrams of strongly correlated materials: a case study for V2O3

Examining phase stabilities and phase equilibria in strongly correlated materials asks for a next level in the many-body extensions to the local-density approximation (LDA) beyond mainly spectroscopic assessments. Here we put the charge-self-consistent LDA+dynamical mean-field theory (DMFT) methodology based on projected local orbitals for the LDA+DMFT interface and a tailored pseudopotential framework into action in order to address such thermodynamics of realistic strongly correlated systems. Namely a case study for the electronic phase diagram of the well-known prototype Mott-phenomena system V$_2$O$_3$ at higher temperatures is presented. We are able to describe the first-order metal-to-insulator transitions with negative pressure and temperature from the self-consistent computation of the correlated total energy in line with experimental findings.Comment: 12 pages, 15 figures, new data adde

Common and unique neural activations in autobiographical, episodic, and semantic retrieval

This study sought to explore the neural correlates that underlie autobiographical, episodic, and semantic memory. Autobiographical memory was defined as the conscious recollection of personally relevant events, episodic memory as the recall of stimuli presented in the laboratory, and semantic memory as the retrieval of factual information and general knowledge about the world. Our objective was to delineate common neural activations, reflecting a functional overlap, and unique neural activations, reflecting functional dissociation of these memory processes. We conducted an event-related functional magnetic resonance imaging study in which we utilized the same pictorial stimuli but manipulated retrieval demands to extract autobiographical, episodic, or semantic memories. The results show a functional overlap of the three types of memory retrieval in the inferior frontal gyrus, the middle frontal gyrus, the caudate nucleus, the thalamus, and the lingual gyrus. All memory conditions yielded activation of the left medial-temporal lobe; however, we found a functional dissociation within this region. The anterior and superior areas were active in episodic and semantic retrieval, whereas more posterior and inferior areas were active in autobiographical retrieval. Unique activations for each memory type were also delineated, including medial frontal increases for autobiographical, right middle frontal increases for episodic, and right inferior temporal increases for semantic retrieval. These findings suggest a common neural network underlying all declarative memory retrieval, as well as unique neural contributions reflecting the specific properties of retrieved memories

Dysfunctions in brain networks supporting empathy: An fMRI study in adults with autism spectrum disorders

The present study aimed at identifying dysfunctions in brain networks that may underlie disturbed empathic behavior in autism spectrum disorders (ASD). During functional magnetic resonance imaging, subjects were asked to identify the emotional state observed in a facial stimulus (other-task) or to evaluate their own emotional response (self-task). Behaviorally, ASD subjects performed equally to the control group during the other-task, but showed less emotionally congruent responses in the self-task. Activations in brain regions related to theory of mind were observed in both groups. Activations of the medial prefrontal cortex (MPFC) were located in dorsal subregions in ASD subjects and in ventral areas in control subjects. During the self-task, ASD subjects activated an additional network of frontal and inferior temporal areas. Frontal areas previously associated with the human mirror system were activated in both tasks in control subjects, while ASD subjects recruited these areas during the self-task only. Activations in the ventral MPFC may provide the basis for one's “emotional bond” with other persons’ emotions. Such atypical patterns of activation may underlie disturbed empathy in individuals with ASD. Subjects with ASD may use an atypical cognitive strategy to gain access to their own emotional state in response to other people's emotions

Grey and white matter correlates of recent and remote autobiographical memory retrieval:Insights from the dementias

The capacity to remember self-referential past events relies on the integrity of a distributed neural network. Controversy exists, however, regarding the involvement of specific brain structures for the retrieval of recently experienced versus more distant events. Here, we explored how characteristic patterns of atrophy in neurodegenerative disorders differentially disrupt remote versus recent autobiographical memory. Eleven behavioural-variant frontotemporal dementia, 10 semantic dementia, 15 Alzheimer's disease patients and 14 healthy older Controls completed the Autobiographical Interview. All patient groups displayed significant remote memory impairments relative to Controls. Similarly, recent period retrieval was significantly compromised in behavioural-variant frontotemporal dementia and Alzheimer's disease, yet semantic dementia patients scored in line with Controls. Voxel-based morphometry and diffusion tensor imaging analyses, for all participants combined, were conducted to investigate grey and white matter correlates of remote and recent autobiographical memory retrieval. Neural correlates common to both recent and remote time periods were identified, including the hippocampus, medial prefrontal, and frontopolar cortices, and the forceps minor and left hippocampal portion of the cingulum bundle. Regions exclusively implicated in each time period were also identified. The integrity of the anterior temporal cortices was related to the retrieval of remote memories, whereas the posterior cingulate cortex emerged as a structure significantly associated with recent autobiographical memory retrieval. This study represents the first investigation of the grey and white matter correlates of remote and recent autobiographical memory retrieval in neurodegenerative disorders. Our findings demonstrate the importance of core brain structures, including the medial prefrontal cortex and hippocampus, irrespective of time period, and point towards the contribution of discrete regions in mediating successful retrieval of distant versus recently experienced events

Your space or mine? : Mapping self in time

Peer reviewedPublisher PD

Functional Hemispheric (A)symmetries in the Aged Brain-Relevance for Working Memory

Functional hemispheric asymmetries have been described in different cognitive processes, such as decision-making and motivation. Variations in the pattern of left/right activity have been associated with normal brain functioning, and with neuropsychiatric diseases. Such asymmetries in brain activity evolve throughout life and are thought to decrease with aging, but clear associations with cognitive function have never been established. Herein, we assessed functional laterality during a working memory task (N-Back) in a healthy aging cohort (over 50 years old) and associated these asymmetries with performance in the test. Activity of lobule VI of the cerebellar hemisphere and angular gyrus was found to be lateralized to the right hemisphere, while the precentral gyrus presented left > right activation during this task. Interestingly, 1-Back accuracy was positively correlated with left > right superior parietal lobule activation, which was mostly due to the influence of the left hemisphere. In conclusion, although regions were mostly symmetrically activated during the N-Back task, performance in working memory in aged individuals seems to benefit from lateralized involvement of the superior parietal lobule.NORTE-01-0145-FEDER-000013, supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER), and was funded by the European Commission (FP7) “SwitchBox—Maintaining health in old age through homeostasis” (Seventh Framework Programme; Contract HEALTH-F2-2010-259772), by FEDER through the Competitiveness Factors Operational Programme (COMPETE) and by National Funds, through the Foundation for Science and Technology (FCT) under the scope of the project POCI-01-0145-FEDER-007038, by the Fundação Calouste Gulbenkian (Portugal; Contract Grant No: P-139977; project “TEMPO—Better mental health during ageing based on temporal prediction of individual brain ageing trajectories”) and by “PANINI—Physical Activity and Nutrition Influences In Ageing” (European Commission (Horizon 2020), Contract GA 675003); Fundação para a Ciência e a Tecnologia (FCT) (Grant Nos. SFRH/BD/52291/2013 to ME and PD/BD/106050/2015 to CP-N via Inter-University Doctoral Programme in Ageing and Chronic Disease (PhDOC), SFRH/BPD/80118/2011 to HL-A and SFRH/BD/90078/2012 to TCC); and FCT/MEC and ON.2–ONOVONORTE—North Portugal Regional Operational Programme 2007/2013, of the National Strategic Reference Framework (NSRF) 2007/2013, through FEDER (project FCTANR/NEU-OSD/0258/2012 to RM)info:eu-repo/semantics/publishedVersio

Deep Brain Stimulation of Nucleus Accumbens Region in Alcoholism Affects Reward Processing

The influence of bilateral deep brain stimulation (DBS) of the nucleus nucleus (NAcc) on the processing of reward in a gambling paradigm was investigated using H2[15O]-PET (positron emission tomography) in a 38-year-old man treated for severe alcohol addiction. Behavioral data analysis revealed a less risky, more careful choice behavior under active DBS compared to DBS switched off. PET showed win- and loss-related activations in the paracingulate cortex, temporal poles, precuneus and hippocampus under active DBS, brain areas that have been implicated in action monitoring and behavioral control. Except for the temporal pole these activations were not seen when DBS was deactivated. These findings suggest that DBS of the NAcc may act partially by improving behavioral control

Meditation and cognitive ageing: The role of mindfulness meditation in building cognitive reserve

Mindfulness-related meditation practices engage various cognitive skills including the ability to focus and sustain attention, which in itself requires several interacting attentional sub-functions. There is increasing behavioural and neuroscientific evidence that mindfulness meditation improves these functions and associated neural processes. More so than other cognitive training programmes, the effects of meditation appear to generalise to other cognitive tasks, thus demonstrating far transfer effects. As these attentional functions have been linked to age-related cognitive decline, there is growing interest in the question whether meditation can slow-down or even prevent such decline. The cognitive reserve hypothesis builds on evidence that various lifestyle factors can lead to better cognitive performance in older age than would be predicted by the existing degree of brain pathology. We argue that mindfulness meditation, as a combination of brain network and brain state training, may increase cognitive reserve capacity and may mitigate age-related declines in cognitive functions. We consider available direct and indirect evidence from the perspective of cognitive reserve theory. The limited available evidence suggests that MM may enhance cognitive reserve capacity directly through the repeated activation of attentional functions and of the multiple demand system and indirectly through the improvement of physiological mechanisms associated with stress and immune function. The article concludes with outlining research strategies for addressing underlying empirical questions in more substantial ways