Ylva Østby

• Tamnes, Christian Krog & Østby, Ylva (2018). Morphometry and development: Changes in brain structure from birth to adult age, In Gianfranco Spalletta; Fabrizio Piras & Tommaso Gili (ed.),  Brain Morphometry.  Springer.  ISBN 978-1-4939-7647-8.  10.  s 143 - 164 Fulltekst i vitenarkiv.
• Ivanovic, Jugoslav; Larsson, Pål Gunnar; Østby, Ylva; Hald, John K; Krossnes, Bård Kronen; Fjeld, Jan Gunnar; Pripp, Are Hugo; Alfstad, Kristin Åshild; Egge, Arild & Stanisic, Milo (2017). Seizure outcomes of temporal lobe epilepsy surgery in patients with normal MRI and without specific histopathology. Acta Neurochirurgica.  ISSN 0001-6268.  159(5), s 757- 766 . doi: 10.1007/s00701-017-3127-y
• Tuft, Mia; Østby, Ylva; Nakken, Karl Otto & Lund, Caroline (2017). Aicardi syndrome and cognitive abilities: A report of five cases. Epilepsy & Behavior.  ISSN 1525-5050.  73, s 161- 165 . doi: 10.1016/j.yebeh.2017.05.002
• Tamnes, Christian Krog; Walhovd, Kristine B; Engvig, Andreas; Grydeland, Håkon; Krogsrud, Stine Kleppe; Østby, Ylva; Holland, Dominic; Dale, Anders & Fjell, Anders Martin (2014). Regional hippocampal volumes and development predict learning and memory. Developmental Neuroscience.  ISSN 0378-5866.  36(3-4), s 161- 174 . doi: 10.1159/000362445 Fulltekst i vitenarkiv.
• Tamnes, Christian Krog; Walhovd, Kristine B; Dale, Anders M.; Østby, Ylva; Grydeland, Håkon; Richardson, George; Westlye, Lars Tjelta; Roddey, J Cooper; Hagler, Donald J.; Due-Tønnessen, Paulina; Holland, Dominic; Fjell, Anders Martin & Database, ADNI (2013). Brain development and aging: Overlapping and unique patterns of change. NeuroImage.  ISSN 1053-8119.  68, s 63- 74 . doi: 10.1016/j.neuroimage.2012.11.039
• Tamnes, Christian Krog; Walhovd, Kristine B; Grydeland, Håkon; Holland, Dominic; Østby, Ylva; Dale, Anders M. & Fjell, Anders Martin (2013). Longitudinal Working Memory Development Is Related to Structural Maturation of Frontal and Parietal Cortices. Journal of Cognitive Neuroscience.  ISSN 0898-929X.  25(10), s 1611- 1623 . doi: 10.1162/jocn_a_00434 Fulltekst i vitenarkiv.
• Tamnes, Christian Krog; Fjell, Anders Martin; Westlye, Lars Tjelta; Østby, Ylva & Walhovd, Kristine B (2012). Becoming Consistent: Developmental Reductions in Intraindividual Variability in Reaction Time Are Related to White Matter Integrity. Journal of Neuroscience.  ISSN 0270-6474.  32(3), s 972- 982 . doi: 10.1523/JNEUROSCI.4779-11.2012
• Walhovd, Kristine B; Tamnes, Christian Krog; Østby, Ylva; Due-Tønnessen, Paulina & Fjell, Anders Martin (2012). Normal variation in behavioral adjustment relates to regional differences in cortical thickness in children. European Child and Adolescent Psychiatry.  ISSN 1018-8827.  21(3), s 133- 140 . doi: 10.1007/s00787-012-0241-5
• Østby, Ylva; Tamnes, Christian Krog; Fjell, Anders Martin & Walhovd, Kristine B (2012). Dissociating memory processes in the developing brain: The role of hippocampal volume and cortical thickness in recall after minutes versus days. Cerebral Cortex.  ISSN 1047-3211.  22(2), s 381- 390 . doi: 10.1093/cercor/bhr116
• Østby, Ylva; Walhovd, Kristine B; Tamnes, Christian Krog; Grydeland, Håkon; Westlye, Lars Tjelta & Fjell, Anders Martin (2012). Mental time travel and default-mode network functional connectivity in the developing brain. Proceedings of the National Academy of Sciences of the United States of America.  ISSN 0027-8424.  109(42), s 16800- 16804 . doi: 10.1073/pnas.1210627109 Vis sammendrag

  A core brain network is engaged in remembering the past and envisioning the future. This network overlaps with the so-called default-mode network, the activity of which increases when demands for focused attention are low. Because of their shared brain substrates, an intriguing hypothesis is that default-mode activity, measured at rest, is related to performance in separate attention-focused recall and imagination tasks. However, we do not know how functional connectivity of the default-mode network is related to individual differences in reconstruction of the past and imagination of the future. Here, we show that functional connectivity of the default-mode network in children and adolescents is related to the quality of past remembering and marginally to future imagination. These results corroborate previous findings of a common neuronal substrate for memory and imagination and provide evidence suggesting that mental time travel is modulated by the task-independent functional architecture of the default-mode network in the developing brain. A further analysis showed that local cortical arealization also contributed to explain recall of the past and imagination of the future, underscoring the benefits of studying both functional and structural properties to understand the brain basis for complex human cognition.

• Tamnes, Christian Krog; Fjell, Anders Martin; Østby, Ylva; Westlye, Lars Tjelta; Due-Tønnessen, Paulina; Bjørnerud, Atle & Walhovd, Kristine B (2011). The brain dynamics of intellectual development: Waxing and waning white and gray matter. Neuropsychologia.  ISSN 0028-3932.  49(13), s 3605- 3611 . doi: 10.1016/j.neuropsychologia.2011.09.012 Vis sammendrag

  Distributed brain areas support intellectual abilities in adults. How structural maturation of these areas in childhood enables development of intelligence is not established. Neuroimaging can be used to monitor brain development, but studies to date have typically considered single imaging modalities. To explore the impact of structural brain maturation on the development of intelligence, we used a combination of cortical thickness, white matter (WM) volume and WM microstructure in 168 healthy participants aged 8-30 years. Principal component analyses (PCAs) were conducted separately for cortical thickness, WM volume, fractional anisotropy (FA) and mean diffusivity (MD) in 64 different brain regions. For all four parameters, the PCAs revealed a general factor explaining between 40% and 53% of the variance across regions. When tested separately, negative age-independent relationships were found between intellectual abilities and cortical thickness and MD, respectively, while WM volume and FA were positively associated with intellectual abilities. The relationships between intellectual abilities and brain structure varied with age, with stronger relationships seen in children and adolescents than in young adults. Multiple regression analysis with the different imaging measures as simultaneous predictors, showed that cortical thickness, WM volume and MD all yielded unique information in explaining intellectual abilities in development. The present study demonstrates that different imaging modalities and measures give complementary information about the neural substrates of intellectual abilities in development, emphasizing the importance of multimodal imaging in investigations of neurocognitive development.

• Østby, Ylva; Tamnes, Christian Krog; Fjell, Anders Martin & Walhovd, Kristine B (2011). Morphometry and connectivity of the fronto-parietal verbal working memory network in development. Neuropsychologia.  ISSN 0028-3932.  49(14), s 3854- 3862 . doi: 10.1016/j.neuropsychologia.2011.10.001
• Fjell, Anders Martin; Walhovd, Kristine B; Westlye, Lars Tjelta; Østby, Ylva; Tamnes, Christian Krog; Jernigan, TL; Gamst, Anthony & Dale, Anders M. (2010). When does brain aging accelerate? Dangers of quadratic fits in cross-sectional studies. NeuroImage.  ISSN 1053-8119.  50(4), s 1376- 1383 . doi: 10.1016/j.neuroimage.2010.01.061
• Westlye, Lars Tjelta; Walhovd, Kristine B; Dale, Anders M.; Bjørnerud, Atle; Due-Tønnessen, Paulina; Engvig, Andreas; Grydeland, Håkon; Tamnes, Christian Krog; Østby, Ylva & Fjell, Anders Martin (2010). Differentiating maturational and aging-related changes of the cerebral cortex by use of thickness and signal intensity. NeuroImage.  ISSN 1053-8119.  52(1), s 172- 185 . doi: 10.1016/j.neuroimage.2010.03.056 Vis sammendrag

  Cortical thickness decreases from childhood throughout life, as estimated by magnetic resonance imaging (MRI). This monotone trajectory does not reflect the fundamentally different neurobiological processes underlying morphometric changes in development versus aging. We hypothesized that intracortical gray matter (GM) and subjacent white matter (WM) T1-weighted signal intensity would distinguish developmental and age-related changes in the cortex better than thickness. Intracortical GM and subjacent WM signal intensity and cortical thickness was measured across the brain surface in a healthy life span sample (n = 429, 8–85 years). We also computed the relaxation rate of T2* (R2*) from multiecho sequences and mapped intracortical GM and subjacent WM values to the surface to delineate age-related variability in R2* and to adjust the T1 signal intensity for possible confounds of accumulated iron. While monotone age-related reductions in thickness were found, both intracortical GM and subcortical WM signal intensity showed inverted U patterns with peaks from eight to approximately 30 years of age. The spatial pattern of intracortical neurodevelopment followed a posterior–anterior gradient, with earliest maturation of occipital visual cortices and most protracted in superior frontal regions. From 50 s and 60 s, substantial signal reductions were observed in several regions, including the insula, cingulate, and inferior temporal gyrus. R2* showed similar patterns but peaked much later than the T1-weighted signal intensity measures. The results are presented as animations yielding detailed depictions of the dynamic regional variability in cortical neurodevelopment and aging and demonstrate that cortical thickness and T1-weighted signal intensity are sensitive to different cortical maturational and aging-related processes.

• Westlye, Lars Tjelta; Walhovd, Kristine B; Dale, Anders M; Bjørnerud, Atle; Due-Tønnessen, Paulina; Engvig, Andreas; Grydeland, Håkon; Tamnes, Christian Krog; Østby, Ylva & Fjell, Anders Martin (2010). Life-Span Changes of the Human Brain White Matter: Diffusion Tensor Imaging (DTI) and Volumetry. Cerebral Cortex.  ISSN 1047-3211.  20(9), s 2055- 2068 . doi: 10.1093/cercor/bhp280 Vis sammendrag

  Magnetic resonance imaging volumetry studies report inverted U-patterns with increasing white-matter (WM) volume into middle age suggesting protracted WM maturation compared with the cortical gray matter. Diffusion tensor imaging (DTI) is sensitive to degree and direction of water permeability in biological tissues, providing in vivo indices of WM microstructure. The aim of this cross-sectional study was to delineate age trajectories of WM volume and DTI indices in 430 healthy subjects ranging 8–85 years of age. We used automated regional brain volume segmentation and tract-based statistics of fractional anisotropy, mean, and radial diffusivity as markers of WM integrity. Nonparametric regressions were used to fit the age trajectories and to estimate the timing of maximum development and deterioration in aging. Although the volumetric data supported protracted growth into the sixth decade, DTI indices plateaued early in the fourth decade across all tested regions and then declined slowly into late adulthood followed by an accelerating decrease in senescence. Tractwise and voxel-based analyses yielded regional differences in development and aging but did not provide ample evidence in support of a simple last-in-first-out hypothesis of life-span changes.

• Tamnes, Christian Krog; Østby, Ylva; Fjell, Anders Martin; Westlye, Lars Tjelta; Due-Tønnessen, Paulina & Walhovd, Kristine B (2010). Brain Maturation in Adolescence and Young Adulthood: Regional Age-Related Changes in Cortical Thickness and White Matter Volume and Microstructure. Cerebral Cortex.  ISSN 1047-3211.  20(3), s 534- 548 . doi: 10.1093/cercor/bhp118
• Tamnes, Christian Krog; Østby, Ylva; Walhovd, Kristine B; Westlye, Lars Tjelta; Due-Tønnessen, Paulina & Fjell, Anders Martin (2010). Intellectual Abilities and White Matter Microstructure in Development: A Diffusion Tensor Imaging Study. Human Brain Mapping.  ISSN 1065-9471.  31(10), s 1609- 1625 . doi: 10.1002/hbm.20962 Vis sammendrag

  Higher-order cognitive functions are supported by distributed networks of multiple interconnected cortical and subcortical regions. Efficient cognitive processing depends on fast communication between these regions, so the integrity of the connections between them is of great importance. It is known that white matter (WM) development is a slow process, continuing into adulthood. While the significance of cortical maturation for intellectual development is described, less is known about the relationships between cognitive functions and maturation of WM connectivity. In this cross-sectional study, we investigated the associations between intellectual abilities and development of diffusion tensor imaging (DTI) derived measures of WM microstructure in 168 right-handed participants aged 8-30 years. Independently of age and sex, both verbal and performance abilities were positively related to fractional anisotropy (FA) and negatively related to mean diffusivity (MD) and radial diffusivity (RD), predominantly in the left hemisphere. Further, verbal, but not performance abilities, were associated with developmental differences in DTI indices in widespread regions in both hemispheres. Regional analyses showed relations with both FA and RD bilaterally in the anterior thalamic radiation and the cortico-spinal tract and in the right superior longitudinal fasciculus. In these regions, our results suggest that participants with high verbal abilities may show accelerated WM development in late childhood and a subsequent earlier developmental plateau, in contrast to a steadier and prolonged development in participants with average verbal abilities. Longitudinal data are needed to validate these interpretations. The results provide insight into the neurobiological underpinnings of intellectual development.

• Tamnes, Christian Krog; Østby, Ylva; Walhovd, Kristine B; Westlye, Lars Tjelta; Due-Tønnessen, Paulina & Fjell, Anders Martin (2010). Neuroanatomical correlates of executive functions in children and adolescents: A magnetic resonance imaging (MRI) study of cortical thickness. Neuropsychologia.  ISSN 0028-3932.  48(9), s 2496- 2508 . doi: 10.1016/j.neuropsychologia.2010.04.024
• Østby, Ylva; Tamnes, Christian Krog; Fjell, Anders Martin; Westlye, Lars Tjelta; Due-Tønnessen, Paulina & Walhovd, Kristine B (2009). Heterogeneity in Subcortical Brain Development: A Structural Magnetic Resonance Imaging Study of Brain Maturation from 8 to 30 Years. Journal of Neuroscience.  ISSN 0270-6474.  29(38), s 11772- 11782 . doi: 10.1523/JNEUROSCI.1242-09.2009
• Fjell, Anders Martin; Østby, Ylva & Walhovd, Kristine B (2007). Intraindividual variability in cognitive performance and its neural foundation an important approach in studying the developing and aging mind, In Marta A Lange (ed.),  Leading-Edge Psychological Tests and Testing Research.  Nova Science Publishers, Inc..  ISBN 1-60021-571-8.  Chapter 12.  s 193 - 200

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• Østby, Hilde & Østby, Ylva (2018). Adventures in memory. The science and secrets of remembering and forgetting.. Greystone Books.  ISBN 978-1-77164-347-4.  302 s.
• Østby, Hilde & Østby, Ylva (2016). Å dykke etter sjøhester. En bok om hukommelse. Capellen Damm.  ISBN 978-82-02-52256-8.  280 s.

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• Østby, Ylva (2018). Kroppen, kunsten og maskinene. Tidsskrift for Den norske legeforening.  ISSN 0029-2001.  138(17) . doi: 10.4045/tidsskr.18.0520
• Kukkonen, Karin & Østby, Ylva (2016). Literature and Cognition. A Conversation..
• Østby, Ylva (2016). Memory and the brain in temporal lobe epilepsy - integrating basic science and clinical perspectives in epilepsy surgery. Vis sammendrag

  Patients With temporal lobe epilepsy who are offered neurosurgery to achieve relief from seizures risk memory problems. However, Research on memory problems have traditionally been confined to the use of standard list Learning tasks. In this talk, I draw on modern memory theory like constructive memory theories, and propose New ways of measuring memory as outcome after surgery. Also, New ways of considering memory Networks in the brain are reviewed.

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