| 1. |
- Becker, Nina, et al.
(författare)
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Structure-function associations of successful associative encoding
- 2019
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Ingår i: NeuroImage. - : Elsevier. - 1053-8119 .- 1095-9572. ; 201
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Tidskriftsartikel (refereegranskat)abstract
- Functional magnetic resonance imaging (MRI) studies have demonstrated a critical role of hippocampus and inferior frontal gyrus (IFG) in associative memory. Similarly, evidence from structural MRI studies suggests a relationship between gray-matter volume in these regions and associative memory. However, how brain volume and activity relate to each other during associative-memory formation remains unclear. Here, we used joint independent component analysis (jICA) to examine how gray-matter volume and brain activity would be associated during associative encoding, especially in medial-temporal lobe (MTL) and IFG. T1-weighted images were collected from 27 young adults, and functional MRI was employed during intentional encoding of object pairs. A subsequent recognition task tested participants' memory performance. Unimodal analyses using voxel-based morphometry revealed that participants with better associative memory showed larger gray-matter volume in left anterior hippocampus. Results from the jICA revealed one component that comprised a covariance pattern between gray-matter volume in anterior and posterior MTL and encoding-related activity in IFG. Our findings suggest that gray matter within the MTL modulates distally distinct parts of the associative encoding circuit, and extend previous studies that demonstrated MTL-IFG functional connectivity during associative memory tasks.
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| 2. |
- Eriksson, Johan, et al.
(författare)
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Rewiring the brain with repeated retrieval : A parametric fMRI study of the testing effect
- 2011
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Ingår i: Neuroscience Letters. - Amsterdam : Elsevier BV. - 0304-3940 .- 1872-7972. ; 505:1, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- The "testing effect" refers to the beneficial effects on memory performance from being tested, a phenomenon of potentially substantial implications in educational settings. While the effect itself is firmly established in previous research, little is known of related brain changes. Here we used fMRI and a parametric design to show that repeated successful retrieval during a memory acquisition phase leads to higher brain activity in the anterior cingulate cortex (ACC) at a subsequent test phase. The extent of ACC activity increase correlated across individuals with memory performance 5 months later. In relation to recent research that associates the ACC with memory consolidation processes, the present results suggest that the testing effect may operate at the systems level by enhancing consolidation of memory representations.
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| 3. |
- Gustavsson, Jonatan, et al.
(författare)
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The iron-dopamine D1 coupling modulates neural signatures of working memory across adult lifespan
- 2023
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Ingår i: NeuroImage. - : Elsevier. - 1053-8119 .- 1095-9572. ; 279
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Tidskriftsartikel (refereegranskat)abstract
- Brain iron overload and decreased integrity of the dopaminergic system have been independently reported as brain substrates of cognitive decline in aging. Dopamine (DA), and iron are co-localized in high concentrations in the striatum and prefrontal cortex (PFC), but follow opposing age-related trajectories across the lifespan. DA contributes to cellular iron homeostasis and the activation of D1-like DA receptors (D1DR) alleviates oxidative stress-induced inflammatory responses, suggesting a mutual interaction between these two fundamental components. Still, a direct in-vivo study testing the iron-D1DR relationship and their interactions on brain function and cognition across the lifespan is rare. Using PET and MRI data from the DyNAMiC study (n=180, age=20-79, %50 female), we showed that elevated iron content was related to lower D1DRs in DLPFC, but not in striatum, suggesting that dopamine-rich regions are less susceptible to elevated iron. Critically, older individuals with elevated iron and lower D1DR exhibited less frontoparietal activations during the most demanding task, which in turn was related to poorer working-memory performance. Together, our findings suggest that the combination of elevated iron load and reduced D1DR contribute to disturbed PFC-related circuits in older age, and thus may be targeted as two modifiable factors for future intervention.
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| 4. |
- Kalpouzos, Grégoria, et al.
(författare)
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Higher Striatal Iron Concentration is Linked to Frontostriatal Underactivation and Poorer Memory in Normal Aging
- 2017
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Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 27:6, s. 3427-3436
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Tidskriftsartikel (refereegranskat)abstract
- In the brain, intracellular iron is essential for cellular metabolism. However, an overload of free iron is toxic, inducing oxidative stress and cell death. Although an increase of striatal iron has been related to atrophy and impaired cognitive performance, the link between elevated iron and altered brain activity in aging remains unexplored. In a sample of 37 younger and older adults, we examined whether higher striatal iron concentration could underlie age-related differences in frontostriatal activity induced by mental imagery of motor and non-motor scenes, and poorer recall of the scenes. Higher striatal iron concentration was linked to underrecruitment of frontostriatal regions regardless of age and striatal volume, the iron-activity association in right putamen being primarily driven by the older adults. In older age, higher striatal iron was related to poorer memory. Altered astrocytic functions could account for the link between brain iron and brain activity, as astrocytes are involved in iron buffering, neurovascular coupling, and synaptic activity. Our preliminary findings, which need to be replicated in a larger sample, suggest a potential frontostriatal target for intervention to counteract negative effects of iron accumulation on brain function and cognition.
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| 5. |
- Kalpouzos, Grégoria, et al.
(författare)
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Impact of negative emotion on the neural correlates of long-term recognition in younger and older adults
- 2012
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Ingår i: Frontiers in Integrative Neuroscience. - : Frontiers Media SA. - 1662-5145. ; 6:74, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Some studies have suggested that the memory advantage for negative emotional information over neutral information (“negativity effect”) is reduced in aging. Besides the fact that most findings are based on immediate retrieval, the neural underpinnings of long-term emotional memory in aging have so far not been investigated. To address these issues, we assessed recognition of neutral and negative scenes after 1- and 3-week retention intervals in younger and older adults using functional magnetic resonance imaging. We further used an event-related design in order to disentangle successful, false, and true recognition. This study revealed four key findings: (1) increased retention interval induced an increased rate of false recognitions for negative scenes, canceling out the negativity effect (present for hit rates only) on discrimination in both younger and older adults; (2) in younger, but not older, adults, reduced activity of the medial temporal lobe was observed over time for neutral scenes, but not for negative scenes, where stable or increased activity was seen; (3) engagement of amygdala (AMG) was observed in older adults after a 3-week delay during successful recognition of negative scenes (hits vs. misses) in comparison with neutral scenes, which may indicate engagement of automatic processes, but engagement of ventrolateral prefrontal cortex was unrelated to AMG activity and performance; and (4) after 3 weeks, but not after 1 week, true recognition of negative scenes was characterized by more activity in left hippocampus and lateral occipito-temporal regions (hits vs. false alarms). As these regions are known to be related to consolidation mechanisms, the observed pattern may indicate the presence of delayed consolidation of true memories. Nonetheless, older adults’ low performance in discrimination of negative scenes could reflect the fact that overall, after long delays of retention, they rely more on general information rather than on perceptual detail in making recognition judgments.
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| 6. |
- Kalpouzos, Gregoria, et al.
(författare)
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Local brain atrophy accounts for functional activity differences in normal aging
- 2012
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 33:3, s. 623.e1-
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Tidskriftsartikel (refereegranskat)abstract
- Functional brain imaging studies of normal aging typically show age-related under-and overactivations during episodic memory tasks. Older individuals also undergo nonuniform gray matter volume (GMv) loss. Thus, age differences in functional brain activity could at least in part result from local atrophy. We conducted a series of voxel-based blood oxygen level-dependent (BOLD)-GMv analyses to highlight whether age-related under-and overrecruitment was accounted for by GMv changes. Occipital GMv loss accounted for underrecruitment at encoding. Efficiency reduction of sensory-perceptual mechanisms underpinned by these areas may partly be due to local atrophy. At retrieval, local GMv loss accounted for age-related overactivation of left dorsolateral prefrontal cortex, but not of left dorsomedial prefrontal cortex. Local atrophy also accounted for age-related overactivation in left lateral parietal cortex. Activity in these frontoparietal regions correlated with performance in the older group. Atrophy in the overrecruited regions was modest in comparison with other regions as shown by a between-group voxel-based morphometry comparison. Collectively, these findings link age-related structural differences to age-related functional under-as well as overrecruitment.
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| 7. |
- Kalpouzos, Gregoria, et al.
(författare)
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Memory Self-Efficacy Beliefs Modulate Brain Activity when Encoding Real-World Future Intentions
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:9, s. e73850-
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Tidskriftsartikel (refereegranskat)abstract
- Background: While the use of different cognitive strategies when encoding episodic memory information has been extensively investigated, modulation of brain activity by memory self-efficacy beliefs has not been studied yet.Methodology/Principal Findings: Sixteen young adults completed the prospective and retrospective metamemory questionnaire, providing individual subjective judgments of everyday memory function. The day after, using functional magnetic resonance imaging, the participants had to memorize real-world intentions (e. g., return a book to the library), which were performed later on in a virtual environment. Participants also performed offline cognitive tasks evaluating executive functions, working memory, and attention. During encoding, activity was found in medial temporal lobe, left prefrontal cortex, medial parietal regions, occipital areas, and regions involved in (pre) motor processes. Based on results from the questionnaire, the group was split into low and high memory self-efficacy believers. Comparison of encoding-related brain activity between the 2 groups revealed that the low memory self-efficacy believers activated more the hippocampus bilaterally, right posterior parahippocampal cortex, precuneus, and left lateral temporal cortex. By contrast, more activity was found in dorsal anterior cingulate gyrus for the high-memory believers. In addition, the low-memory believers performed more poorly at feature binding and (at trend) manipulating visuospatial information in working memory.Conclusion/Significance: Overall, these findings indicate that memory self-efficacy beliefs modulate brain activity during intentional encoding. Low memory self-efficacy believers activated more brain areas involved in visuospatial operations such as the hippocampus. Possibly, this increase reflects attempts to compensate for poor performance of certain neurocognitive processes, such as feature binding. By contrast, high-memory believers seemed to rely more on executive-like processes involved in cognitive control.
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| 8. |
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| 9. |
- Kalpouzos, Grégoria, et al.
(författare)
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Neurocognitive systems related to real-world prospective memory.
- 2010
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Ingår i: PLOS ONE. - San Francisco : Public library of Science. - 1932-6203. ; 5:10, s. e13304-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Prospective memory (PM) denotes the ability to remember to perform actions in the future. It has been argued that standard laboratory paradigms fail to capture core aspects of PM.METHODOLOGY/PRINCIPAL FINDINGS: We combined functional MRI, virtual reality, eye-tracking and verbal reports to explore the dynamic allocation of neurocognitive processes during a naturalistic PM task where individuals performed errands in a realistic model of their residential town. Based on eye movement data and verbal reports, we modeled PM as an iterative loop of five sustained and transient phases: intention maintenance before target detection (TD), TD, intention maintenance after TD, action, and switching, the latter representing the activation of a new intention in mind. The fMRI analyses revealed continuous engagement of a top-down fronto-parietal network throughout the entire task, likely subserving goal maintenance in mind. In addition, a shift was observed from a perceptual (occipital) system while searching for places to go, to a mnemonic (temporo-parietal, fronto-hippocampal) system for remembering what actions to perform after TD. Updating of the top-down fronto-parietal network occurred at both TD and switching, the latter likely also being characterized by frontopolar activity.CONCLUSION/SIGNIFICANCE: Taken together, these findings show how brain systems complementary interact during real-world PM, and support a more complete model of PM that can be applied to naturalistic PM tasks and that we named PROspective MEmory DYnamic (PROMEDY) model because of its dynamics on both multi-phase iteration and the interactions of distinct neurocognitive networks.
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| 10. |
- Kompus, Kristiina, et al.
(författare)
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The size of the anterior corpus callosum correlates with the strength of hemispheric encoding-retrieval asymmetry in the ventrolateral prefrontal cortex
- 2011
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Ingår i: Brain Research. - Amsterdam : Elsevier BV. - 0006-8993 .- 1872-6240. ; 1419, s. 61-67
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Tidskriftsartikel (refereegranskat)abstract
- Functional lateralization of episodic memory processes in the frontal lobe is an area of intense study in the field of cognitive neuroimaging. Yet, to date there is insufficient knowledge of what role the interhemispheric structural connectivity plays in this lateralized organization. We analyzed functional and structural magnetic resonance imaging data from healthy adult volunteers who performed an associative encoding and retrieval task. We examined the relationship between functional voxel-based relative asymmetry of encoding and retrieval in the frontal lobes and the size of the anterior corpus callosum (antCC; corrected for brain size). The size of the antCC was strongly associated to the relative encoding-retrieval asymmetry in the ventrolateral prefrontal cortex (BA 47). These findings show that the functional asymmetry of episodic memory processes in the frontal lobes is associated with the structural connectivity between the hemispheres.
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