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- 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. |
- Ahmed, B, et al.
(författare)
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Cortical dynamics subserving visual apparent motion
- 2008
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Ingår i: Cerebral cortex (New York, N.Y. : 1991). - : Oxford University Press (OUP). - 1460-2199 .- 1047-3211. ; 18:12, s. 2796-2810
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Bazov, Igor, 1973-, et al.
(författare)
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Neuronal Expression of Opioid Gene is Controlled by Dual Epigenetic and Transcriptional Mechanism in Human Brain
- 2018
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 28:9, s. 3129-3142
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Tidskriftsartikel (refereegranskat)abstract
- Molecular mechanisms that define patterns of neuropeptide expression are essential for the formation and rewiring of neural circuits. The prodynorphin gene (PDYN) gives rise to dynorphin opioid peptides mediating depression and substance dependence. We here demonstrated that PDYN is expressed in neurons in human dorsolateral prefrontal cortex (dlPFC), and identified neuronal differentially methylated region in PDYN locus framed by CCCTC-binding factor binding sites. A short, nucleosome size human-specific promoter CpG island (CGI), a core of this region may serve as a regulatory module, which is hypomethylated in neurons, enriched in 5-hydroxymethylcytosine, and targeted by USF2, a methylation-sensitive E-box transcription factor (TF). USF2 activates PDYN transcription in model systems, and binds to nonmethylated CGI in dlPFC. USF2 and PDYN expression is correlated, and USF2 and PDYN proteins are co-localized in dlPFC. Segregation of activatory TF and repressive CGI methylation may ensure contrasting PDYN expression in neurons and glia in human brain.
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| 10. |
- Boyle, Julie A., et al.
(författare)
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The Human Brain Distinguishes between Single Odorants and Binary Mixtures
- 2009
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 19:1, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- Single odors are processed differently from odor mixtures in the cortex of rodents. We investigated whether single and binary odor mixtures activate different regions also in the human brain. We analyzed data from positron emission tomography scans using pyridine, citral, and 5 mixtures of pyridine and citral in proportions varying from 10/90 to 90/10, with 50/50 being the most impure. Comparing mixtures with single odorants gave activation in the left cingulate and right parietal and superior frontal cortices and bilateral activation in the anterior and lateral orbitofrontal cortices. We also found that brain activity in the lateral orbitofrontal cortex (OFC) increased with odorant impurity, whereas the anterior OFC was activated for binary odor mixtures and deactivated for single components. We conclude that binary odor mixtures and their individual components are processed differently by the human brain. The lateral portion of the OFC responds to mixture impurity in a graded fashion, whereas the anterior portion acts like an on-off detector of odor mixtures.
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