| 1. |
- Bramao, Ines, et al.
(författare)
-
Encoding contexts are incidentally reinstated during competitive retrieval and track the temporal dynamics of memory interference
- 2022
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 32:22, s. 5020-5035
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to remember an episode from our past is often hindered by competition from similar events. For example, if we want to remember the article a colleague recommended during the last lab-meeting, we may need to resolve interference from other article recommendations from the same colleague. This study investigates if the contextual features specifying the encoding episodes are incidentally reinstated during competitive memory retrieval. Competition between memories was created through the AB/AC interference paradigm. Individual word-pairs were presented embedded in a slowly drifting real-word like context. Multivariate pattern analysis (MVPA) of high temporal-resolution electroencephalographic (EEG) data was used to investigate context reactivation during memory retrieval. Behaviorally, we observed proactive (but not retroactive) interference; that is, performance for AC competitive retrieval was worse compared to a control DE non-competitive retrieval, whereas AB retrieval did not suffer from competition. Neurally, proactive interference was accompanied by an early reinstatement of the competitor context and interference resolution was associated with the ensuing reinstatement of the target context. Together, these findings provide novel evidence showing that the encoding contexts of competing discrete events are incidentally reinstated during competitive retrieval and that such reinstatement tracks retrieval competition and subsequent interference resolution.
|
|
| 2. |
- Gaughwin, Philip, et al.
(författare)
-
Stage-Specific Modulation of Cortical Neuronal Development by Mmu-miR-134
- 2011
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 21:8, s. 1857-1869
-
Tidskriftsartikel (refereegranskat)abstract
- To realize the potential of microRNAs (miRs) as fine-tuning regulators of embryonic neuronal differentiation, it is critical to define their developmental function. Mmu-miR-134 (miR-134) is a powerful inducer of pluripotent stem cell differentiation. However, its functional role during embryonic, neuronal development is unknown. We demonstrate that mature, miR-134 transcript levels elevate during embryonic, neuronal differentiation in vitro and in vivo. To define the developmental targets and function of miR-134, we identified multiple brain-expressed targets including the neural progenitor cell-enriched, bone morphogenetic protein (BMP) antagonist Chordin-like 1 (Chrdl-1) and the postmitotic, neuron-specific, microtubule-associated protein, Doublecortin (Dcx). We show that, through interaction with Dcx and/or Chrdl-1, miR-134 has stage-specific effects on cortical progenitors, migratory neurons, and differentiated neurons. In neural progenitors, miR-134 promotes cell proliferation and counteracts Chrdl-1-induced apoptosis and Dcx-induced differentiation in vitro. In neurons, miR-134 reduces cell migration in vitro and in vivo in a Dcx-dependent manner. In differentiating neurons, miR-134 modulates process outgrowth in response to exogenous BMP-4 in a noggin-reversible manner. Taken together, we present Dcx and Chrdl-1 as new regulatory targets of miR-134 during embryonic, mouse, cortical, and neuronal differentiation and show a novel and previously undiscovered role for miR-134 in the stage-specific modulation of cortical development.
|
|
| 3. |
- Hahn, Andreas, et al.
(författare)
-
Association Between Earliest Amyloid Uptake and Functional Connectivity in Cognitively Unimpaired Elderly
- 2019
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 29, s. 2173-2182
-
Tidskriftsartikel (refereegranskat)abstract
- Alterations in cognitive performance have been noted in nondemented subjects with elevated accumulation of amyloid-β (Aβ) fibrils. However, it is not yet understood whether brain function is already influenced by Aβ deposition during the very earliest stages of the disease. We therefore investigated associations between [18F]Flutemetamol PET, resting-state functional connectivity, gray and white matter structure and cognitive performance in 133 cognitively normal elderly that exhibited normal global Aβ PET levels. [18F]Flutemetamol uptake in regions known to accumulate Aβ fibrils early in preclinical AD (i.e., mainly certain parts of the default-mode network) was positively associated with dynamic but not static functional connectivity (r = 0.77). Dynamic functional connectivity was further related to better cognitive performance (r = 0.21-0.72). No significant associations were found for Aβ uptake with gray matter volume or white matter diffusivity. The findings demonstrate that the earliest accumulation of Aβ fibrils is associated with increased functional connectivity, which occurs before any structural alterations. The enhanced functional connectivity may reflect a compensatory mechanism to maintain high cognitive performance in the presence of increasing amyloid accumulation during the earliest phases of AD.
|
|
| 4. |
- Harper, Luke, et al.
(författare)
-
Prenatal Gyrification Pattern Affects Age at Onset in Frontotemporal Dementia
- 2022
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 32:18, s. 3937-3944
-
Tidskriftsartikel (refereegranskat)abstract
- The paracingulate sulcus is a tertiary sulcus formed during the third trimester. In healthy individuals paracingulate sulcation is more prevalent in the left hemisphere. The anterior cingulate and paracingulate gyri are focal points of neurodegeneration in behavioral variant frontotemporal dementia (bvFTD). This study aims to determine the prevalence and impact of paracingulate sulcation in bvFTD. Structural magnetic resonance images of individuals with bvFTD (n = 105, mean age 66.9 years), Alzheimer's disease (n = 92, 73.3), and healthy controls (n = 110, 62.4) were evaluated using standard protocol for hemispheric paracingulate sulcal presence. No difference in left hemisphere paracingulate sulcal frequency was observed between groups; 0.72, 0.79, and 0.70, respectively, in the bvFTD, Alzheimer's disease, and healthy control groups, (P = 0.3). A significant impact of right (but not left) hemispheric paracingulate sulcation on age at disease onset was identified in bvFTD (mean 60.4 years where absent vs. 63.8 where present [P = 0.04, Cohen's d = 0.42]). This relationship was not observed in Alzheimer's disease. These findings demonstrate a relationship between prenatal neuronal development and the expression of a neurodegenerative disease providing a gross morphological example of brain reserve.
|
|
| 5. |
- Hellerstedt, Robin, et al.
(författare)
-
Electrophysiological correlates of competitor activation predict retrieval-induced forgetting
- 2014
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 24:6, s. 1619-1629
-
Tidskriftsartikel (refereegranskat)abstract
- The very act of retrieval modifies the accessibility of memory for knowledge and past events and can also cause forgetting. A prominent theory of such retrieval-induced forgetting holds that retrieval recruits inhibition to overcome interference from competing memories, rendering these memories inaccessible. The present study tested a fundamental tenet of the inhibitory-control account: the competition-dependence assumption. Event-related potentials (ERPs) were recorded while participants engaged in a competitive retrieval task. Competition levels were manipulated within the retrieval task by varying the cue-item associative strength of competing items. In order to temporally separate ERP correlates of competitor activation and target retrieval, memory was probed with the sequential presentation of two cues: a category cue, to reactivate competitors, and a target cue. As predicted by the inhibitory-control account, competitors with strong compared to weak cue-competitor association were more susceptible to forgetting. Furthermore, competition-sensitive ERP modulations, elicited by the category cue, were observed over anterior regions and reflected individual differences in ensuing forgetting. The present study demonstrates ERP correlates of the reactivation of tightly bound associated memories (the competitors) and provides support for the inhibitory-control account of retrieval-induced forgetting.
|
|
| 6. |
- Johansson, Mikael, et al.
(författare)
-
When remembering causes forgetting: Electrophysiological correlates of retrieval-induced forgetting
- 2007
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 17:6, s. 1335-1341
-
Tidskriftsartikel (refereegranskat)abstract
- People tend to forget information that is related to memories they are actively trying to retrieve. On the basis of results from behavioral studies, such retrieval-induced forgetting is held to result from inhibitory control processes that are recruited to attenuate interference caused by competing memory traces. Employing electrophysiological measures of brain activity, the present study examined the neural correlates of these inhibitory processes as they operate. The results demonstrate that sustained prefrontal event-related potentials were 1) related to whether or not selective memory retrieval was required during reprocessing of previously studied words and 2) predictive of individual differences in the amount of forgetting observed in an ensuing recall test. The present findings give support to an inhibitory control account of retrieval-induced forgetting and are in accord with the view that prefrontal regions play an important role in the selection and maintenance of relevant memory representations at the expense of those currently irrelevant.
|
|
| 7. |
- Kokaia, Zaal, et al.
(författare)
-
Regulation of stroke-induced neurogenesis in adult brain--recent scientific progress.
- 2006
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 16, s. 162-167
-
Tidskriftsartikel (refereegranskat)abstract
- Stroke induced by middle cerebral artery occlusion in adult rodents induces the formation of new neurons in the damaged striatum, a region that normally does not show neurogenesis. Here we describe recent findings on the regulation of neurogenesis after stroke, in particular regarding the duration of the neurogenic response and the influence of age, as well as the molecular mechanisms influencing migration and survival of the new neurons. We also discuss some crucial issues that need to be addressed in the further exploration of this potential self-repair mechanism after damage to the adult brain.
|
|
| 8. |
- Lövdén, Martin, et al.
(författare)
-
Performance-Related Increases in Hippocampal N-acetylaspartate (NAA) Induced by Spatial Navigation Training Are Restricted to BDNF Val Homozygotes
- 2011
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 21:6, s. 1435-1442
-
Tidskriftsartikel (refereegranskat)abstract
- Recent evidence indicates experience-dependent brain volume changes in humans, but the functional and histological nature of such changes is unknown. Here, we report that adult men performing a cognitively demanding spatial navigation task every other day over 4 months display increases in hippocampal N-acetylaspartate (NAA) as measured with magnetic resonance spectroscopy. Unlike measures of brain volume, changes in NAA are sensitive to metabolic and functional aspects of neural and glia tissue and unlikely to reflect changes in microvasculature. Training-induced changes in NAA were, however, absent in carriers of the Met substitution in the brain-derived neurotrophic factor (BDNF) gene, which is known to reduce activity-dependent secretion of BDNF. Among BDNF Val homozygotes, increases in NAA were strongly related to the degree of practice-related improvement in navigation performance and normalized to pretraining levels 4 months after the last training session. We conclude that changes in demands on spatial navigation can alter hippocampal NAA concentrations, confirming epidemiological studies suggesting that mental experience may have direct effects on neural integrity and cognitive performance. BDNF genotype moderates these plastic changes, in line with the contention that gene-context interactions shape the ontogeny of complex phenotypes.
|
|
| 9. |
- Padilla, Nelly, et al.
(författare)
-
Breakdown of Whole-brain Dynamics in Preterm-born Children
- 2020
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 30:3, s. 1159-1170
-
Tidskriftsartikel (refereegranskat)abstract
- The brain operates at a critical point that is balanced between order and disorder. Even during rest, unstable periods of random behavior are interspersed with stable periods of balanced activity patterns that support optimal information processing. Being born preterm may cause deviations from this normal pattern of development. We compared 33 extremely preterm (EPT) children born at < 27 weeks of gestation and 28 full-term controls. Two approaches were adopted in both groups, when they were 10 years of age, using structural and functional brain magnetic resonance imaging data. The first was using a novel intrinsic ignition analysis to study the ability of the areas of the brain to propagate neural activity. The second was a whole-brain Hopf model, to define the level of stability, desynchronization, or criticality of the brain. EPT-born children exhibited fewer intrinsic ignition events than controls; nodes were related to less sophisticated aspects of cognitive control, and there was a different hierarchy pattern in the propagation of information and suboptimal synchronicity and criticality. The largest differences were found in brain nodes belonging to the rich-club architecture. These results provide important insights into the neural substrates underlying brain reorganization and neurodevelopmental impairments related to prematurity.
|
|
| 10. |
- Pereira, Joana B., et al.
(författare)
-
Abnormal structural brain connectome in individuals with preclinical Alzheimer's disease
- 2018
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 28:10, s. 3638-3649
-
Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease has a long preclinical phase during which amyloid pathology and neurodegeneration accumulate in the brain without producing overt cognitive deficits. It is currently unclear whether these early disease stages are associated with a progressive disruption in the communication between brain regions that subsequently leads to cognitive decline and dementia. In this study we assessed the organization of structural networks in cognitively normal (CN) individuals harboring amyloid pathology (A+N-), neurodegeneration (A-N+), or both (A+N+) from the prospective and longitudinal Swedish BioFINDER study. We combined graph theory with diffusion tensor imaging to investigate integration, segregation, and centrality measures in the brain connectome in the previous groups. At baseline, our findings revealed a disrupted network topology characterized by longer paths, lower efficiency, increased clustering and modularity in CN A-N+ and CN A+N+, but not in CN A+N-. After 2 years, CN A+N+ showed significant abnormalities in all global network measures, whereas CN A-N+ only showed abnormalities in the global efficiency. Network connectivity and organization were associated with memory in CN A+N+ individuals. Altogether, our findings suggest that amyloid pathology is not sufficient to disrupt structural network topology, whereas neurodegeneration is.
|
|
