| 1. |
- Adams, Rick A., et al.
(författare)
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Variability in Action Selection Relates to Striatal Dopamine 2/3 Receptor Availability in Humans : A PET Neuroimaging Study Using Reinforcement Learning and Active Inference Models
- 2020
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 30:6, s. 3573-3589
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Tidskriftsartikel (refereegranskat)abstract
- Choosing actions that result in advantageous outcomes is a fundamental function of nervous systems. All computational decision-making models contain a mechanism that controls the variability of (or confidence in) action selection, but its neural implementation is unclear-especially in humans. We investigated this mechanism using two influential decision-making frameworks: active inference (AI) and reinforcement learning (RL). In AI, the precision (inverse variance) of beliefs about policies controls action selection variability-similar to decision 'noise' parameters in RL-and is thought to be encoded by striatal dopamine signaling. We tested this hypothesis by administering a 'go/no-go' task to 75 healthy participants, and measuring striatal dopamine 2/3 receptor (D2/3R) availability in a subset (n = 25) using [C-11]-(+)-PHNO positron emission tomography. In behavioral model comparison, RL performed best across the whole group but AI performed best in participants performing above chance levels. Limbic striatal D2/3R availability had linear relationships with AI policy precision (P = 0.029) as well as with RL irreducible decision 'noise' (P = 0.020), and this relationship with D2/3R availability was confirmed with a 'decision stochasticity' factor that aggregated across both models (P = 0.0006). These findings are consistent with occupancy of inhibitory striatal D(2/3)Rs decreasing the variability of action selection in humans.
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| 2. |
- Andin, Josefine, 1979-, et al.
(författare)
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Working Memory for Signs with Poor Visual Resolution : fMRI Evidence of Reorganization of Auditory Cortex in Deaf Signers
- 2021
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 31:7, s. 3165-3176
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Tidskriftsartikel (refereegranskat)abstract
- Stimulus degradation adds to working memory load during speech processing. We investigated whether this applies to sign processing and, if so, whether the mechanism implicates secondary auditory cortex. We conducted an fMRI experiment where 16 deaf early signers (DES) and 22 hearing non-signers performed a sign-based n-back task with three load levels and stimuli presented at high and low resolution. We found decreased behavioral performance with increasing load and decreasing visual resolution, but the neurobiological mechanisms involved differed between the two manipulations and did so for both groups. Importantly, while the load manipulation was, as predicted, accompanied by activation in the frontoparietal working memory network, the resolution manipulation resulted in temporal and occipital activation. Furthermore, we found evidence of cross-modal reorganization in the secondary auditory cortex: DES had stronger activation and stronger connectivity between this and several other regions. We conclude that load and stimulus resolution have different neural underpinnings in the visual–verbal domain, which has consequences for current working memory models, and that for DES the secondary auditory cortex is involved in the binding of representations when task demands are low.
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| 3. |
- Cacciaglia, Raffaele, et al.
(författare)
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APOE-ε4 Shapes the Cerebral Organization in Cognitively Intact Individuals as Reflected by Structural Gray Matter Networks.
- 2020
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Ingår i: Cerebral cortex. - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 30:7, s. 4110-4120
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Tidskriftsartikel (refereegranskat)abstract
- Gray matter networks (GMn) provide essential information on the intrinsic organization of the brain and appear to be disrupted in Alzheimer's disease (AD). Apolipoprotein E (APOE)-ε4 represents the major genetic risk factor for AD, yet the association between APOE-ε4 and GMn has remained unexplored. Here, we determine the impact of APOE-ε4 on GMn in a large sample of cognitively unimpaired individuals, which was enriched for the genetic risk of AD. We used independent component analysis to retrieve sources of structural covariance and analyzed APOE group differences within and between networks. Analyses were repeated in a subsample of amyloid-negative subjects. Compared with noncarriers and heterozygotes, APOE-ε4 homozygotes showed increased covariance in one network including primarily right-lateralized, parietal, inferior frontal, as well as inferior and middle temporal regions, which mirrored the formerly described AD-signature. This result was confirmed in a subsample of amyloid-negative individuals. APOE-ε4 carriers showed reduced covariance between two networks encompassing frontal and temporal regions, which constitute preferential target of amyloid deposition. Our data indicate that, in asymptomatic individuals, APOE-ε4 shapes the cerebral organization in a way that recapitulates focal morphometric alterations observed in AD patients, even in absence of amyloid pathology. This suggests that structural vulnerability in neuronal networks associated with APOE-ε4 may be an early event in AD pathogenesis, possibly upstream of amyloid deposition.
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| 4. |
- Dall'orso, Sofia, 1992, et al.
(författare)
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Cortical Processing of Multimodal Sensory Learning in Human Neonates
- 2021
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 31:3, s. 1827-1836
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Tidskriftsartikel (refereegranskat)abstract
- Following birth, infants must immediately process and rapidly adapt to the array of unknown sensory experiences associated with their new ex-utero environment. However, although it is known that unimodal stimuli induce activity in the corresponding primary sensory cortices of the newborn brain, it is unclear how multimodal stimuli are processed and integrated across modalities. The latter is essential for learning and understanding environmental contingencies through encoding relationships between sensory experiences; and ultimately likely subserves development of life-long skills such as speech and language. Here, for the first time, we map the intracerebral processing which underlies auditory-sensorimotor classical conditioning in a group of 13 neonates (median gestational age at birth: 38 weeks + 4 days, range: 32 weeks + 2 days to 41 weeks + 6 days; median postmenstrual age at scan: 40 weeks + 5 days, range: 38 weeks + 3 days to 42 weeks + 1 days) with blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (MRI) and magnetic resonance (MR) compatible robotics. We demonstrate that classical conditioning can induce crossmodal changes within putative unimodal sensory cortex even in the absence of its archetypal substrate. Our results also suggest that multimodal learning is associated with network wide activity within the conditioned neural system. These findings suggest that in early life, external multimodal sensory stimulation and integration shapes activity in the developing cortex and may influence its associated functional network architecture.
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| 5. |
- Darki, F, et al.
(författare)
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Inter-Individual Differences in Striatal Connectivity Is Related to Executive Function Through Fronto-Parietal Connectivity
- 2020
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Ingår i: Cerebral cortex (New York, N.Y. : 1991). - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 30:2, s. 672-681
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Tidskriftsartikel (refereegranskat)abstract
- The striatum has long been associated with cognitive functions, but the mechanisms behind this are still unclear. Here we tested a new hypothesis that the striatum contributes to executive function (EF) by strengthening cortico-cortical connections. Striatal connectivity was evaluated by measuring the resting-state functional connectivity between ventral and dorsal striatum in 570 individuals, aged 3–20 years. Using structural equation modeling, we found that inter-individual differences in striatal connectivity had an indirect effect (via fronto-parietal functional connectivity) and a direct effect on a compound EF measure of working memory, inhibition, and set-shifting/flexibility. The effect of fronto-parietal connectivity on cognition did not depend on age: the influence was as strong in older as younger children. In contrast, striatal connectivity was closely related to changes in cognitive ability during childhood development, suggesting a specific role of the striatum in cognitive plasticity. These results support a new principle for striatal functioning, according to which striatum promotes cognitive development by strengthening of cortico-cortical connectivity.
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| 6. |
- Darki, Fahimeh, et al.
(författare)
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T1-Weighted/T2-Weighted Ratio Mapping at 5 Months Captures Individual Differences in Behavioral Development and Differentiates Infants at Familial Risk for Autism from Controls
- 2021
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Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 31:9, s. 4068-4077
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Tidskriftsartikel (refereegranskat)abstract
- Identifying structural measures that capture early brain development and are sensitive to individual differences in behavior is a priority in developmental neuroscience, with potential implications for our understanding of both typical and atypical populations. T1-weighted/T2-weighted (T1w/T2w) ratio mapping, which previously has been linked to myelination, represents an interesting candidate measure in this respect, as an accessible measure from standard magnetic resonance imaging (MRI) sequences. Yet, its value as an early infancy measure remains largely unexplored. Here, we compared T1w/T2w ratio in 5-month-old infants at familial risk (n = 27) for autism spectrum disorder (ASD) to those without elevated autism risk (n =16). We found lower T1w/T2w ratio in infants at high risk for ASD within widely distributed regions, spanning both white and gray matter. In regions differing between groups, higher T1w/T2w ratio was robustly associated with higher age at scan (range: similar to 4-6.5 months), implying sensitivity to maturation at short developmental timescales. Further, higher T1w/T2w ratio within these regions was associated with higher scores on measures of concurrent developmental level. These findings suggest that T1w/T2w ratio is a developmentally sensitive measure that should be explored further in future studies of both typical and atypical infant populations.
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| 7. |
- Davenport, ML, et al.
(författare)
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Altered Brain Structure in Infants with Turner Syndrome
- 2020
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Ingår i: Cerebral cortex (New York, N.Y. : 1991). - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 30:2, s. 587-596
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Tidskriftsartikel (refereegranskat)abstract
- Turner syndrome (TS) is a genetic disorder affecting approximately 1:2000 live-born females. It results from partial or complete X monosomy and is associated with a range of clinical issues including a unique cognitive profile and increased risk for certain behavioral problems. Structural neuroimaging studies in adolescents, adults, and older children with TS have revealed altered neuroanatomy but are unable to identify when in development differences arise. In addition, older children and adults have often been exposed to years of growth hormone and/or exogenous estrogen therapy with potential implications for neurodevelopment. The study presented here is the first to test whether brain structure is altered in infants with TS. Twenty-six infants with TS received high-resolution structural MRI scans of the brain at 1 year of age and were compared to 47 typically developing female and 39 typically developing male infants. Results indicate that the typical neuroanatomical profile seen in older individuals with TS, characterized by decreased gray matter volumes in premotor, somatosensory, and parietal-occipital cortex, is already present at 1 year of age, suggesting a stable phenotype with origins in the prenatal or early postnatal period.
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| 8. |
- de Boer, Lieke, et al.
(författare)
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Corticostriatal White Matter Integrity and Dopamine D1 Receptor Availability Predict Age Differences in Prefrontal Value Signaling during Reward Learning
- 2020
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 30:10, s. 5270-5280
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Tidskriftsartikel (refereegranskat)abstract
- Probabilistic reward learning reflects the ability to adapt choices based on probabilistic feedback. The dopaminergically innervated corticostriatal circuit in the brain plays an important role in supporting successful probabilistic reward learning. Several components of the corticostriatal circuit deteriorate with age, as it does probabilistic reward learning. We showed previously that D1 receptor availability in NAcc predicts the strength of anticipatory value signaling in vmPFC, a neural correlate of probabilistic learning that is attenuated in older participants and predicts probabilistic reward learning performance. We investigated how white matter integrity in the pathway between nucleus accumbens (NAcc) and ventromedial prefrontal cortex (vmPFC) relates to the strength of anticipatory value signaling in vmPFC in younger and older participants. We found that in a sample of 22 old and 23 young participants, fractional anisotropy in the pathway between NAcc and vmPFC predicted the strength of value signaling in vmPFC independently from D1 receptor availability in NAcc. These findings provide tentative evidence that integrity in the dopaminergic and white matter pathways of corticostriatal circuitry supports the expression of value signaling in vmPFC which supports reward learning, however, the limited sample size calls for independent replication. These and future findings could add to the improved understanding of how corticostriatal integrity contributes to reward learning ability.
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| 9. |
- de Manzano, O, et al.
(författare)
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Action-Perception Coupling and Near Transfer: Listening to Melodies after Piano Practice Triggers Sequence-Specific Representations in the Auditory-Motor Network
- 2020
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Ingår i: Cerebral cortex (New York, N.Y. : 1991). - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 30:10, s. 5193-5203
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how perception and action are coupled in the brain has important implications for training, rehabilitation, and brain–machine interfaces. Ideomotor theory postulates that willed actions are represented through previously experienced effects and initiated by the anticipation of those effects. Previous research has accordingly found that sensory events, if previously associated with action outcomes, can induce activity in motor regions. However, it remains unclear whether the motor-related activity induced during perception of more naturalistic sequences of actions actually represents “sequence-specific” information. In the present study, nonmusicians were firstly trained to play two melodies on the piano; secondly, they performed an fMRI experiment while listening to these melodies as well as novel, untrained melodies; thirdly, multivariate pattern analysis was used to test if voxel-wise patterns of brain activity could identify trained, but not novel melodies. The results importantly show that after associative learning, a series of sensory events can trigger sequence-specific representations in both sensory and motor networks. Interestingly, also novel melodies could be classified in multiple regions, including default mode regions. A control experiment confirmed these outcomes to be training-dependent. We discuss how action-perception coupling may enable spontaneous near transfer and action simulation during action observation.
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| 10. |
- Dunås, Tora, et al.
(författare)
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Multimodal Image Analysis of Apparent Brain Age Identifies Physical Fitness as Predictor of Brain Maintenance
- 2021
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Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 31:7, s. 3393-3407
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining a youthful brain structure and function throughout life may be the single most important determinant ofsuccessful cognitive aging. In this study, we addressed heterogeneity in brain aging by making image-based brain agepredictions and relating the brain age prediction gap (BAPG) to cognitive change in aging. Structural, functional, anddiffusion MRI scans from 351 participants were used to train and evaluate 5 single-modal and 4 multimodal predictionmodels, based on 7 regression methods. The models were compared on mean absolute error and whether they were relatedto physical fitness and cognitive ability, measured both currently and longitudinally, as well as study attrition and years ofeducation. Multimodal prediction models performed at a similar level as single-modal models, and the choice of regressionmethod did not significantly affect the results. Correlation with the BAPG was found for current physical fitness, currentcognitive ability, and study attrition. Correlations were also found for retrospective physical fitness, measured 10 years priorto imaging, and slope for cognitive ability during a period of 15 years. The results suggest that maintaining a high physicalfitness throughout life contributes to brain maintenance and preserved cognitive ability.
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