Siri Leknes

• Chiron, Aimie; Fernandez, Aurore; Schmidt, Léa; Plaza-Wüthrich, Sonia; Suter, Marc R. & Leknes, Siri Graff [Vis alle 7 forfattere av denne artikkelen] (2026). Justify your disability! A simulated medical evaluation as a novel stress induction model in chronic pain. Comprehensive Psychoneuroendocrinology. 27, s. 1–11. doi: 10.1016/j.cpnec.2026.100378. Fulltekst i vitenarkiv
• Spisak, Tamas; Hartmann, Helena; Zunhammer, Matthias; Kincses, Balint; Wiech, Katja & Wager, Tor D. [Vis alle 29 forfattere av denne artikkelen] (2026). Meta-analytic evidence for distinct neural correlates of conditioned versus verbally induced placebo analgesia. Nature Communications. 17(1). doi: 10.1038/s41467-026-74743-0. Fulltekst i vitenarkiv Vis sammendrag

  Placebo analgesia demonstrates that belief and expectation can significantly alter pain, even without active treatment. Placebo analgesia can be induced through verbal suggestion, classical conditioning, or their combination, though the role of conditioned neural responses above and beyond effects of verbal instructions remains unclear. We conduct a systematic meta-analysis of individual participant data from 16 within-participant placebo neuroimaging studies (n = 409), employing univariate and multivariate analyses to identify shared and distinct mechanisms of placebo analgesia induced by suggestions alone versus suggestions combined with conditioning. Both techniques increase activity during pain in the dorsolateral prefrontal and inferior parietal cortices and decrease activation in the insula, putamen, and primary sensory areas. Adding conditioning enhances engagement of regions associated with context representation and pain modulation (e.g., dorsolateral/dorsomedial prefrontal cortices) and decreases in nociceptive regions (e.g., primary sensory and insular areas). Conditioning also strengthens the negative association between analgesia and nociceptive activity, as quantified by the Neurologic Pain Signature. Combining conditioning with instructions yields greater placebo analgesia, mediated by increased ventromedial prefrontal and dorsal caudate activity, alongside decreased sensory-nociceptive and cerebellar activity. These findings suggest the two strategies rely on partially distinct mechanisms in the brain.

• Eikemo, Marie; Løseth, Guro Engvig; Carlyle, Molly; Trøstheim, Martin Ostenfeldt; Ernst, Gernot Walter & Pazmandi, Claudia [Vis alle 14 forfattere av denne artikkelen] (2026). Effects of psychosocial stress on opioid self-administration in healthy participants: a randomized, placebo-controlled crossover trial. Nature Mental Health. doi: 10.1038/s44220-026-00700-x. Fulltekst i vitenarkiv
• Trøstheim, Martin Ostenfeldt; Pedersen, Mads Lund; Leknes, Siri; Hama, Lennja Majid; Roland, Mathias Nikolai & Lobmaier, Philipp Paul [Vis alle 10 forfattere av denne artikkelen] (2025). Reward Sensitivity in Patients Receiving Opioid Agonist and Antagonist Treatment for Opioid Use Disorder: An Observational Study. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. ISSN 2451-9022. 10(11), s. 1166–1176. doi: 10.1016/j.bpsc.2025.04.013. Fulltekst i vitenarkiv Vis sammendrag

  Background Disrupted reward processing is a core component in neurobiological theories of addictions, including opioid use disorder (OUD). While acute opioid agonist and antagonist administration can modulate reward behavior and experiences, it remains unclear how typical long-term OUD treatment with these medications impacts patients’ sensitivity to substance-free rewards. Therefore, we conducted a cross-sectional study of reward sensitivity in opioid agonist– and antagonist–treated patients with OUD and healthy volunteers. Methods Ninety-six patients with OUD on extended-release naltrexone (n = 45) or opioid agonists (n = 51) and 50 healthy volunteers completed a probabilistic reward task (PRT) and self-report measures of anhedonia, depression, preoccupation with immediate consequences, substance craving, and life satisfaction in a single session. We used signal detection analysis and drift diffusion modeling to derive behavioral reward bias measures from PRT performance. Group differences were modeled with beta and linear regression. Results Patients reported significantly greater anhedonia (Cohen’s ds ≥ 0.64), depression (ds ≥ 0.53), and preoccupation with immediate consequences (ds ≥ 0.54) than healthy volunteers, but differences between naltrexone- and opioid agonist–treated patients were nonsignificant (ds ≤ 0.26). Group differences in behavioral reward bias were small and nonsignificant (ps = 1, Bayes factor [BF]01s ≥ 84.13). Anhedonia was significantly associated with lower life satisfaction (odds ratio [95% CI], 1.10 [1.04 to 1.17]). There were no other significant associations between reward sensitivity measures and life satisfaction or craving (ps ≥ .31, BF01s ≥ 2.58). Conclusions These data support an association between OUD and reduced well-being irrespective of opioid agonist or antagonist treatment, highlighting patients’ need for psychosocial support and/or adjunct interventions. Major detrimental effects of naltrexone treatment on well-being seem unlikely from these and previous results.

• Løseth, Guro Engvig; Eikemo, Marie & Leknes, Siri (2025). Opioid Regulation of Social Homeostasis: Connecting Loneliness to Addiction. Biological Psychiatry. ISSN 0006-3223. 97(10), s. 971–981. doi: 10.1016/j.biopsych.2024.11.011. Fulltekst i vitenarkiv
• Baranski, Erica; Gardiner, Gwendolyn; Shaman, Nicholas; Shagan, Jennah; Lee, Daniel & Funder, David [Vis alle 140 forfattere av denne artikkelen] (2024). Personality and conceptions of religiosity across the world's religions. Journal of Research in Personality. ISSN 0092-6566. 110. doi: 10.1016/j.jrp.2024.104496. Fulltekst i vitenarkiv
• Løseth, Guro Engvig; Trøstheim, Martin Ostenfeldt & Leknes, Siri (2024). Endogenous mu-opioid modulation of social connection in humans: a systematic review and meta-analysis. Translational Psychiatry. 14(1). doi: 10.1038/s41398-024-03088-3. Fulltekst i vitenarkiv
• Carlyle, Molly; Wit, Harriet de & Leknes, Siri (2024). Impact of childhood adversity on acute subjective effects of stimulant and opioid drugs: Evidence from placebo-controlled studies in healthy volunteers. Journal of Psychopharmacology. ISSN 0269-8811. 38(11), s. 986–997. doi: 10.1177/02698811241268892. Fulltekst i vitenarkiv
• Gardiner, Gwendolyn; Lee, Daniel I.; Baranski, Erica; Funder, David C.; Beramendi, Maite & Bastian, Brock [Vis alle 50 forfattere av denne artikkelen] (2023). The economic well-being of nations is associated with positive daily situational experiences. Current Research in Ecological and Social Psychology (CRESP). 4. Fulltekst i vitenarkiv
• Carlyle, Molly; Kvande, Malin; Meier, Isabell M.; Trøstheim, Martin Ostenfeldt; Buen, Kaja & Jensen, Eira Nordeng [Vis alle 9 forfattere av denne artikkelen] (2023). Does childhood adversity alter opioid drug reward? A conceptual replication in outpatients before surgery. Addiction Research and Theory. ISSN 1606-6359. doi: 10.1080/16066359.2023.2211348. Fulltekst i vitenarkiv
• Scarth, Morgan; Hauger, Lisa Evju; Thorsby, Per Medbøe; Leknes, Siri; Hullstein, Ingunn Riise & Westlye, Lars Tjelta [Vis alle 7 forfattere av denne artikkelen] (2023). Supraphysiological testosterone levels from anabolic steroid use and reduced sensitivity to negative facial expressions in men. Psychopharmacology. ISSN 0033-3158. doi: 10.1007/s00213-023-06497-2. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Rationale Anabolic-androgenic steroids (AAS) are used to improve physical performance and appearance, but have been associated with deficits in social cognitive functioning. Approximately 30% of people who use AAS develop a dependence, increasing the risk for undesired effects. Objectives To assess the relationship between AAS use (current/previous), AAS dependence, and the ability to recognize emotional facial expressions, and investigate the potential mediating role of hormone levels. Methods In total 156 male weightlifters, including those with current ( n = 45) or previous ( n = 34) AAS use and never-using controls ( n = 77), completed a facial Emotion Recognition Task (ERT). Participants were presented with faces expressing one out of six emotions (sadness, happiness, fear, anger, disgust, and surprise) and were instructed to indicate which of the six emotions each face displayed. ERT accuracy and response time were recorded and evaluated for association with AAS use status, AAS dependence, and serum reproductive hormone levels. Mediation models were used to evaluate the mediating role of androgens in the relationship between AAS use and ERT performance. Results Compared to never-using controls, men currently using AAS exhibited lower recognition accuracy for facial emotional expressions, particularly anger ( Cohen’s d = −0.57, p FDR = 0.03) and disgust ( d = −0.51, p FDR = 0.05). Those with AAS dependence ( n = 47) demonstrated worse recognition of fear relative to men without dependence ( d = 0.58, p = 0.03). Recognition of disgust was negatively correlated with serum free testosterone index (FTI); however, FTI did not significantly mediate the association between AAS use and recognition of disgust. Conclusions Our findings demonstrate impaired facial emotion recognition among men currently using AAS compared to controls. While further studies are needed to investigate potential mechanisms, our analysis did not support a simple mediation effect of serum FTI.

• Eikemo, Marie; Meier, Isabell M.; Løseth, Guro Engvig; Trøstheim, Martin Ostenfeldt; Ørstavik, Nikoline & Jensen, Eira Nordeng [Vis alle 10 forfattere av denne artikkelen] (2023). Opioid analgesic effects on subjective well-being in the operating theatre*. Anaesthesia. ISSN 0003-2409. 78(9), s. 1102–1111. doi: 10.1111/anae.16069. Fulltekst i vitenarkiv
• Meier, Isabell M.; Eikemo, Marie; Trøstheim, Martin Ostenfeldt; Buen, Kaja; Jensen, Eira Nordeng & Karlsen, Siri Gurandsrud [Vis alle 10 forfattere av denne artikkelen] (2023). Factors associated with use of opioid rescue medication after surgery. Regional anesthesia and pain medicine. ISSN 1098-7339. doi: 10.1136/rapm-2023-104412. Fulltekst i vitenarkiv
• Trøstheim, Martin; Eikemo, Marie; Haaker, Jan; Frost, J. James & Leknes, Siri (2022). Opioid antagonism in humans: a primer on optimal dose and timing for central mu-opioid receptor blockade. Neuropsychopharmacology. ISSN 0893-133X. s. 1–9. doi: 10.1038/s41386-022-01416-z. Fulltekst i vitenarkiv
• Sailer, Uta & Leknes, Siri (2022). Meaning makes touch affective. Current Opinion in Behavioral Sciences. ISSN 2352-1546. 44. doi: 10.1016/j.cobeha.2021.101099. Fulltekst i vitenarkiv Vis sammendrag

  The pleasantness of gentle stroking (CT-targeted touch) varies highly between individuals and studies, indicating that relevant factors may not be accounted for. We propose that the affective value of a touch event is determined by how well its perceived purpose matches the goals of the touch receiver. The perceived purpose or meaning of touch is in turn informed by the sensory characteristics together with the setting, person factors, and the touchee’s expectations. Affective touch is often a sign of affection, intended to soothe or show support. In a typical lab study however, the toucher is a stranger and its purpose is research. The purpose of laboratory touch is nevertheless compatible with the goal of participants, namely to contribute to research. To fully understand how the perception of affective touch emerges, more studies should directly manipulate participants’ beliefs about the purpose of touch.

• Løseth, Guro Engvig; Eikemo, Marie; Trøstheim, Martin; Meier, Isabell M.; Bjørnstad, Herman & Asratian, Anna [Vis alle 10 forfattere av denne artikkelen] (2022). Stress recovery with social support: A dyadic stress and support task. Psychoneuroendocrinology. ISSN 0306-4530. 146. doi: 10.1016/j.psyneuen.2022.105949. Fulltekst i vitenarkiv Vis sammendrag

  How does social support bolster resilience? Here, we present a new dyadic paradigm to study causal mechanisms of acute and ecologically valid social support in the laboratory. The Dyadic Stress and Support Task (DSST) consists of a psychosocial stress phase and a recovery phase. During DSST stress, a pair of participants take turns to perform public speaking and mental arithmetic in front of a panel. Unable to see or touch each other, they witness each other’s performance and feedback. During DSST recovery, the pair either interact freely with each other for 5 min (social support condition) or interact separately with an experimenter (non-support condition). To establish the validity of the DSST, we tested 21 pairs of long-term close friends in a pilot study. Primary outcome measures were ratings of affective state and bodily arousal (VAS scales 0–100). Secondary outcome measures were heart rate and salivary cortisol. DSST stress successfully induced subjective Stress Activation, increased Negative Affect and decreased Positive Affect. We also observed increased heart rate and salivary cortisol. After DSST recovery, Stress Activation and Negative Affect ratings were reduced in both groups. Positive Affect was completely restored to pre-stress baseline levels in the Social support group, while remaining significantly lower in the Non-support group. The DSST successfully induced stress and negative affect and captured stress recovery in both groups. Free-form interaction with the friend enhanced recovery of affective state, supporting the validity of spontaneous interaction between friends as a model of social support.

• Skoglund, Charlotte; Leknes, Siri & Heilig, Markus (2022). The partial µ-opioid agonist buprenorphine in autism spectrum disorder: a case report. Journal of Medical Case Reports. 16(1), s. 1–6. doi: 10.1186/s13256-022-03384-w. Fulltekst i vitenarkiv Vis sammendrag

  Background There are currently no approved medications for impaired social cognition and function, core symptoms of autism spectrum disorder. We describe marked improvement of these symptoms with long-term low-dose administration of the partial µ-opioid agonist buprenorphine. We discuss these observations in the context of a role for endogenous opioid systems in social attachment, and theories integrating those findings mechanistically with autism spectrum disorder. Case presentation M, a 43-year-old Caucasian male, is medically healthy. Despite social difficulties since childhood, he completed high school with better-than-average grades, but failed university education. A psychiatric evaluation in his twenties diagnosed attention deficit hyperactivity disorder but also noted symptoms of coexisting autism spectrum disorder. M accidentally came across buprenorphine in his late twenties and experienced progressively improved social functioning on a low daily dosage (0.5–1.0 mg/day), an effect maintained for 15 years. He lived independently and maintained a part-time occupation. After abrupt discontinuation of treatment, his autistic symptoms returned, and function deteriorated. Following evaluation by our team, buprenorphine was resumed, with gradual return to prior level of functioning. An attempt to formally evaluate M both on and off medication was agreed with him and approved by the Swedish Ethics Authority, but medication had to be resumed when the patient worsened following discontinuation. Conclusions According to the µ-opioid receptor balance model, both excessive and deficient μ-receptor activity may negatively influence social behavior, and accordingly both opioid agonist and opioid antagonist treatment may be able to improve social functioning, depending on an individual’s opioid tone before treatment. Our case report is consistent with these hypotheses, and given the extensive unmet medical needs in individuals with autism spectrum disorders, randomized controlled trial appears warranted.

• Meier, Isabell M.; Eikemo, Marie & Leknes, Siri (2021). The Role of Mu-Opioids for Reward and Threat Processing in Humans: Bridging the Gap from Preclinical to Clinical Opioid Drug Studies. Current Addiction Reports. s. 1–13. doi: 10.1007/s40429-021-00366-8. Fulltekst i vitenarkiv
• Zunhammer, Matthias; Spisák, Tamás; Wager, Tor D.; Bingel, Ulrike; Atlas, Lauren & Benedetti, Fabrizio [Vis alle 30 forfattere av denne artikkelen] (2021). Meta-analysis of neural systems underlying placebo analgesia from individual participant fMRI data. Nature Communications. 12(1). doi: 10.1038/s41467-021-21179-3. Fulltekst i vitenarkiv
• Sulutvedt, Unni; Zavagno, Daniele; Lubell, Jamie; Leknes, Siri; Benavent, Sigrid Aune de Rodez & Laeng, Bruno (2021). Brightness perception changes related to pupil size. Vision Research. ISSN 0042-6989. 178, s. 41–41. doi: 10.1016/j.visres.2020.09.004. Fulltekst i vitenarkiv
• Henningsson, Susanne; Leknes, Siri; Asperholm, Martin; Eikemo, Marie & Westberg, Lars (2021). A randomized placebo-controlled intranasal oxytocin study on first impressions and reactions to social rejection. Biological Psychology. ISSN 0301-0511. doi: 10.1016/j.biopsycho.2021.108164. Fulltekst i vitenarkiv
• Laeng, Bruno; Garvija, Lara; Løseth, Guro Engvig; Eikemo, Marie; Ernst, Gernot & Leknes, Siri (2021). ‘Defrosting’ music chills with naltrexone: The role of endogenous opioids for the intensity of musical pleasure. Consciousness and Cognition. ISSN 1053-8100. 90. doi: 10.1016/j.concog.2021.103105. Fulltekst i vitenarkiv
• Baranski, E.; Gardiner, G.; Lee, D.; Funder, D. C.; Tamnes, Christian Krog & Leknes, Siri [Vis alle 9 forfattere av denne artikkelen] (2021). Who in the World Is Trying to Change Their Personality Traits? Volitional Personality Change Among College Students in Six Continents. Journal of Personality and Social Psychology. ISSN 0022-3514. 121(5), s. 1140–1156. doi: 10.1037/pspp0000389. Fulltekst i vitenarkiv
• Baranski, E; Sweeny, K; Gardiner, G; Leknes, Siri; Holen, Vera Waldal & Hansen, Ingelin [Vis alle 9 forfattere av denne artikkelen] (2020). International Optimism: Correlates and Consequences of Dispositional Optimism across 61 Countries. Journal of Personality. ISSN 0022-3506. 89, s. 288–304. doi: 10.1111/jopy.12582. Fulltekst i vitenarkiv
• Lee, Daniel I.; Gardiner, Gwendolyn; Baranski, Erica; Leknes, Siri; Holen, Vera Waldal & Hansen, Ingelin [Vis alle 9 forfattere av denne artikkelen] (2020). Situational experiences around the world: A replication and extension in 62 countries. Journal of Personality. ISSN 0022-3506. 88(6), s. 1091–1110. doi: 10.1111/jopy.12558. Fulltekst i vitenarkiv
• Hovey, Daniel; Martens, Louise; Laeng, Bruno; Leknes, Siri & Westberg, Lars (2020). The effect of intranasal oxytocin on visual processing and salience of human faces. Translational Psychiatry. 10(318), s. 1–9. doi: 10.1038/s41398-020-00991-3. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The mechanisms underlying the role of oxytocin (OT) as a regulator of social behavior in mammals are only partly understood. Recently, it has been proposed that OT increases the salience of social stimuli. We carried out a randomized, double-blind, cross-over study of the effects of OT on binocular rivalry, a visual phenomenon underpinned by the interplay of excitation and inhibition in the cortex. A final sample of 45 participants viewed images of social stimuli (faces with different emotional expressions) and non-social stimuli (houses and Gabor patches). We demonstrate a robust effect that intranasal OT increases the salience of human faces in binocular rivalry, such that dominance durations of faces are longer—this effect is not modulated by the facial expression. We tentatively show that OT treatment increases dominance durations for non-social stimuli. Our results lend support to the social salience hypothesis of OT, and in addition offer provisional support for the role of OT in influencing excitation-inhibition balance in the brain.

• Trøstheim, Martin; Eikemo, Marie; Meir, Remy; Hansen, Ingelin; Paul, Elisabeth & Kroll, Sara Liane [Vis alle 8 forfattere av denne artikkelen] (2020). Assessment of Anhedonia in Adults With and Without Mental Illness A Systematic Review and Meta-analysis. JAMA Network Open. 3(8). doi: 10.1001/jamanetworkopen.2020.13233. Fulltekst i vitenarkiv Vis sammendrag

  Importance Anhedonia, a reduced capacity for pleasure, is described for many psychiatric and neurologic conditions. However, a decade after the Research Domain Criteria launch, whether anhedonia severity differs between diagnoses is still unclear. Reference values for hedonic capacity in healthy humans are also needed. Objective To generate and compare reference values for anhedonia levels in adults with and without mental illness. Data Sources Web of Science, Scopus, PubMed, and Google Scholar were used to list all articles from January 1, 1995 to July 2, 2019, citing the scale development report of a widely used anhedonia questionnaire, the Snaith-Hamilton Pleasure Scale (SHAPS). Searches were conducted from April 5 to 11, 2018, and on July 2, 2019. Study Selection Studies including healthy patients and those with a verified diagnosis, assessed at baseline or in a no-treatment condition with the complete 14-item SHAPS, were included in this preregistered meta-analysis. Data Extraction and Synthesis Random-effects models were used to calculate mean SHAPS scores and 95% CIs separately for healthy participants and patients with current major depressive disorder (MDD), past/remitted MDD, bipolar disorder, schizophrenia, substance use disorders, Parkinson disease, and chronic pain. SHAPS scores were compared between groups using meta-regression, and traditional effect size meta-analyses were conducted to estimate differences in SHAPS scores between healthy and patient samples. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Main Outcomes and Measures Self-reported anhedonia as measured by 2 different formats of the SHAPS (possible ranges, 0-14 and 14-56 points), with higher values on both scales indicating greater anhedonia symptoms. Results In the available literature (168 articles; 16 494 participants; 8058 [49%] female participants; aged 13-72 years), patients with current MDD, schizophrenia, substance use disorder, Parkinson disease, and chronic pain scored higher on the SHAPS than healthy participants. Within the patient groups, those with current MDD scored considerably higher than all other groups. Patients with remitted MDD scored within the healthy range (g = 0.1). This pattern replicated across SHAPS scoring methods and was consistent across point estimate and effect size analyses. Conclusions and Relevance The findings of this meta-analysis indicate that the severity of anhedonia may differ across disorders associated with anhedonia. Whereas anhedonia in MDD affects multiple pleasure domains, patients with other conditions may experience decreased enjoyment of only a minority of life’s many rewards. These findings have implications for psychiatric taxonomy development, where dimensional approaches are gaining attention. Moreover, the SHAPS reference values presented herein may be useful for researchers and clinicians assessing the efficacy of anhedonia treatments.

• Gardiner, Gwendolyn; Lee, Daniel; Baranski, Erica; Funder, David; Leknes, Siri & Holen, Vera Waldal [Vis alle 9 forfattere av denne artikkelen] (2020). Happiness around the World: A Combined Etic-Emic Approach across 63 Countries. PLOS ONE. 15(12). doi: 10.1371/journal.pone.0242718. Fulltekst i vitenarkiv Vis sammendrag

  What does it mean to be happy? The vast majority of cross-cultural studies on happiness have employed a Western-origin, or “WEIRD” measure of happiness that conceptualizes it as a self-centered (or “independent”), high-arousal emotion. However, research from Eastern cultures, particularly Japan, conceptualizes happiness as including an interpersonal aspect emphasizing harmony and connectedness to others. Following a combined emic-etic approach (Cheung, van de Vijver & Leong, 2011), we assessed the cross-cultural applicability of a measure of independent happiness developed in the US (Subjective Happiness Scale; Lyubomirsky & Lepper, 1999) and a measure of interdependent happiness developed in Japan (Interdependent Happiness Scale; Hitokoto & Uchida, 2015), with data from 63 countries representing 7 sociocultural regions. Results indicate that the schema of independent happiness was more coherent in more WEIRD countries. In contrast, the coherence of interdependent happiness was unrelated to a country’s “WEIRD-ness.” Reliabilities of both happiness measures were lowest in African and Middle Eastern countries, suggesting these two conceptualizations of happiness may not be globally comprehensive. Overall, while the two measures had many similar correlates and properties, the self-focused concept of independent happiness is “WEIRD-er” than interdependent happiness, suggesting cross-cultural researchers should attend to both conceptualizations.

• Eikemo, Marie; Lobmaier, Philipp Paul; Pedersen, Mads Lund; Kunøe, Nikolaj; Matziorinis, Anna Maria & Leknes, Siri [Vis alle 7 forfattere av denne artikkelen] (2019). Intact responses to non-drug rewards in long-term opioid maintenance treatment. Neuropsychopharmacology. ISSN 0893-133X. 44(8), s. 1456–1463. doi: 10.1038/s41386-019-0377-9. Fulltekst i vitenarkiv Vis sammendrag

  Disruption of non-drug reward processing in addiction could stem from long-term drug use, addiction-related psychosocial stress, or a combination of these. It remains unclear whether long-term opioid maintenance treatment (OMT) disrupts reward processing. Here, we measured subjective and objective reward responsiveness in 26 previously heroin-addicted mothers in >7 years stable OMT with minimal psychosocial stress and illicit drug use. The comparison group was 30 healthy age-matched mothers (COMP). Objective reward responsiveness was assessed in a two-alternative forced-choice task with skewed rewards. Results were also compared to performance from an additional 968 healthy volunteers (meta-analytic approach). We further compared subprocesses of reward-based decisions across groups using computational modelling with a Bayesian drift diffusion model of decision making. Self-reported responsiveness to non-drug rewards was high for both groups (means: OMT = 6.59, COMP = 6.67, p = 0.84, BF10 = 0.29), yielding moderate evidence against subjective anhedonia in this OMT group. Importantly, the mothers in OMT also displayed robust reward responsiveness in the behavioral task (t19 = 2.72, p = 0.013, BF10 = 3.98; d = 0.61). Monetary reward changed their task behavior to the same extent as the local comparison group (reward bias OMT = 0.12, COMP = 0.12, p = 0.96, BF10 = 0.18) and in line with data from 968 healthy controls previously tested. Computational modelling revealed that long-term OMT did not even change decision subprocesses underpinning reward behavior. We conclude that reduced sensitivity to rewards and anhedonia are not necessary consequences of prolonged opioid use.

• Garland, Eric; Trøstheim, Martin; Eikemo, Marie; Ernst, Gernot & Leknes, Siri (2019). Anhedonia in chronic pain and prescription opioid misuse. Psychological Medicine. ISSN 0033-2917. s. 1–12. doi: 10.1017/S0033291719002010. Fulltekst i vitenarkiv
• Løseth, Guro Engvig; Eikemo, Marie & Leknes, Siri (2019). Effects of opioid receptor stimulation and blockade on touch pleasantness: a double-blind randomised trial. Social Cognitive & Affective Neuroscience. ISSN 1749-5016. 14(4), s. 411–422. doi: 10.1093/scan/nsz022. Fulltekst i vitenarkiv Vis sammendrag

  The μ-opioid receptor (MOR) system has long been thought to underpin the rewarding properties of pleasant touch. Numerous non-human animal studies implicate MORs in social behaviours involving touch, but little is currently known about MOR involvement in human touch reward. Here, we employed a bi-directional pharmacological double-blind crossover design to assess the role of the human MOR system for touch pleasantness and motivation. Forty-nine male volunteers received 10 mg per-oral morphine, 50 mg per-oral naltrexone and placebo before being brushed on their forearm at three different velocities (0.3, 3 and 30 cm/s). In a touch liking task, pleasantness ratings were recorded after each 15 s brushing trial. In a touch wanting task, participants actively manipulated trial duration through key presses. As expected, 3 cm/s was the preferred velocity, producing significantly higher pleasantness ratings and wanting scores than the other stimuli. Contrary to our hypothesis, MOR drug manipulations did not significantly affect either touch pleasantness or wanting. The null effects were supported by post hoc Bayesian analyses indicating that the models with no drug effect were more than 25 times more likely than the alternative models given the data. We conclude that μ-opioid signalling is unlikely to underpin non-affiliative touch reward in humans.

• Hauger, Lisa Evju; Sagoe, Dominic; Vaskinn, Anja; Arnevik, Espen Kristian Ajo; Leknes, Siri & Jørstad, Marie Lindvik [Vis alle 7 forfattere av denne artikkelen] (2019). Anabolic-androgenic steroid dependence is associated with impaired emotion recognition. Psychopharmacology. ISSN 0033-3158. 236(9), s. 2667–2676. doi: 10.1007/s00213-019-05239-7. Fulltekst i vitenarkiv
• Bastian, Brock; Vauclair, Christin-Melanie; Loughnan, Steve; Bain, Paul; Ashokkumar, Ashwini & Becker, Maja [Vis alle 33 forfattere av denne artikkelen] (2019). Explaining illness with evil: Pathogen prevalence fosters moral vitalism. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 286:20191576(1914), s. 1–10. doi: 10.1098/rspb.2019.1576. Fulltekst i vitenarkiv
• Steenbergen, Henk van; Eikemo, Marie & Leknes, Siri (2019). The role of the opioid system in decision making and cognitive control: A review. Cognitive, Affective, & Behavioral Neuroscience. ISSN 1530-7026. 19(3), s. 435–458. doi: 10.3758/s13415-019-00710-6. Fulltekst i vitenarkiv Vis sammendrag

  The opioid system regulates affective processing, including pain, pleasure, and reward. Restricting the role of this system to hedonic modulation may be an underestimation, however. Opioid receptors are distributed widely in the human brain, including the more “cognitive” regions in the frontal and parietal lobes. Nonhuman animal research points to opioid modulation of cognitive and decision-making processes. We review emerging evidence on whether acute opioid drug modulation in healthy humans can influence cognitive function, such as how we choose between actions of different values and how we control our behavior in the face of distracting information. Specifically, we review studies employing opioid agonists or antagonists together with experimental paradigms of reward-based decision making, impulsivity, executive functioning, attention, inhibition, and effort. Although this field is still in its infancy, the emerging picture suggests that the mu-opioid system can influence higher-level cognitive function via modulation of valuation, motivation, and control circuits dense in mu-opioid receptors, including orbitofrontal cortex, basal ganglia, amygdalae, anterior cingulate cortex, and prefrontal cortex. The framework that we put forward proposes that opioids influence decision making and cognitive control by increasing the subjective value of reward and reducing aversive arousal. We highlight potential mechanisms that might underlie the effects of mu-opioid signaling on decision making and cognitive control and provide directions for future research.

• Løseth, Guro Engvig; Eikemo, Marie Helene; Isager, Peder Mortvedt; Holmgren, Jostein; Laeng, Bruno & Vindenes, Vigdis [Vis alle 8 forfattere av denne artikkelen] (2018). Morphine reduced perceived anger from neutral and implicit emotional expressions. Psychoneuroendocrinology. ISSN 0306-4530. 91, s. 123–131. doi: 10.1016/j.psyneuen.2018.02.035. Fulltekst i vitenarkiv Vis sammendrag

  The μ-opioid system modulates responses to pain and psychosocial stress and mediates non-social and social reward. In humans, the μ-opioid agonist morphine can increase overt attention to the eye-region and visual exploration of faces with neutral expressions. However, little is known about how the human μ-opioid system influences sensitivity to and appraisal of subtle and explicit cues of social threats and reward. Here, we examined the effects of selective μ-opioid stimulation on perception of anger and happiness in faces with explicit, neutral or implicit emotion expressions. Sixty-three healthy adults (32 females) attended two sessions where they received either placebo or 10 mg per oral morphine in randomised order under double-blind conditions. Based on the known μ-opioid reduction of pain and discomfort, as well as reports suggesting that the non-specific partial agonist buprenorphine or the non-specific antagonist naltrexone affect appraisal of social emotional stimuli, we hypothesised that morphine would reduce threat sensitivity and enhance perception of happy facial expressions. While overall perception of others’ happiness was unaffected by morphine treatment, morphine reduced perception of anger in stimuli with neutral and implicit expressions without affecting perception of explicit anger. This effect was statistically unrelated to gender, subjective drug effects, mood and autism trait measures. The finding that a low dose of μ-agonist reduced the propensity to perceive anger in photos with subtle facial expressions is consistent with the notion that μ-opioids mediate social confidence and reduce sensitivity to threat cues.

• Zunhammer, M; Bingel, U.; Wager, T.; Atlas, L.; Benedetti, F. & Büchel, Christian [Vis alle 30 forfattere av denne artikkelen] (2018). Placebo Effects on the Neurologic Pain Signature: A Meta-analysis of Individual Participant Functional Magnetic Resonance Imaging Data. JAMA Neurology. ISSN 2168-6149. 75(11), s. 1321–1330. doi: 10.1001/jamaneurol.2018.2017. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael; Kringelbach, Morten & Leknes, Siri (2018). A neuroscience perspective on pleasure and pain. I Bain, D.; Brady, Michael & Corns, J. (Red.), Philosophy of Pain: Unpleasantness, Emotion, and Deviance. Routledge. ISSN 9780815361640. s. 70–88. Fulltekst i vitenarkiv
• Berna, Chantal; Leknes, Siri; Ahmad, Asma H; Mhuircheartaigh, Roisin N; Goodwin, Guy M. & Tracey, Irene (2018). Opioid-independent and opioid-mediated modes of pain modulation. Journal of Neuroscience. ISSN 0270-6474. 38(42), s. 9047–9058. doi: 10.1523/JNEUROSCI.0854-18.2018. Fulltekst i vitenarkiv Vis sammendrag

  Pain is regulated endogenously through both opioid and non-opioid mechanisms. We hypothesized that two novel pain modulation tasks, one drawing on context/expectations and one using voluntary reappraisal, would show differing levels of opioid dependence. Specifically, we expected that naloxone would block context-related analgesia, whereas mental imagery-based pain reappraisal would be opioid-independent. A double-blind, placebo-controlled intravenous naloxone versus saline crossover design was used. Twenty healthy volunteers completed the two modulation tasks with acute heat stimuli calibrated to induce moderate pain. In the mental imagery task, participants imagined either a “pleasant” or a “comparison” scenario during painful heat. In the relative relief task, moderate heat stimuli coincided with visual cues eliciting relief from the expectation of intense pain, and were compared with moderate heat stimuli delivered under the expectation of non-painful warmth. Both “pleasant imagery” and “relative relief” conditions significantly improved ratings of pain intensity and pleasantness during saline treatment. Indeed, the target stimuli in both tasks, which had been calibrated to induce moderate pain, were rated as mildly pleasant. Furthermore, consistently with the main hypothesis, blocking endogenous opioid signaling with naloxone did not significantly affect imagery-induced regulation of pain intensity or pleasantness. In contrast, the relative relief-induced pain regulation (i.e., context/expectation) was blocked by naloxone. We conclude that endogenous opioid signaling is necessary for expectation-related relative relief analgesia, but not for pain reappraisal through mental imagery. These results support mental imagery as a powerful and clinically relevant strategy for regulating pain affect also in patients where endogenous opioid mechanisms might be compromised.

• Ree, Anbjørn; Mayo, Leah M; Leknes, Siri & Sailer, Uta (2018). Touch targeting C-tactile afferent fibers has a unique physiological pattern: A combined electrodermal and facial electromyography study. Biological Psychology. ISSN 0301-0511. 140, s. 55–63. doi: 10.1016/j.biopsycho.2018.11.006. Fulltekst i vitenarkiv
• Eikemo, Marie Helene; Biele, Guido; Willoch, Frode; Thomsen, Lotte & Leknes, Siri (2017). Opioid modulation of value-based decision-making in healthy humans. Neuropsychopharmacology. ISSN 0893-133X. 42(9), s. 1833–1840. doi: 10.1038/npp.2017.58. Fulltekst i vitenarkiv
• Liljencrantz, Jaquette; Strigo, Irina A.; Ellingsen, Dan Mikael; Krämer, Heidrun H.; Lundblad, Linda C. & Nagi, Saad Saulat [Vis alle 8 forfattere av denne artikkelen] (2017). Slow brushing reduces heat pain in humans. European Journal of Pain. ISSN 1090-3801. 21(7), s. 1173–1185. doi: 10.1002/ejp.1018. Fulltekst i vitenarkiv
• Brandtzaeg, Ole Kristian; Johnsen, Elin Follaug; Røberg-Larsen, Hanne; Seip, Knut Fredrik; MacLean, Evan L. & Gesquiere, Laurence R. [Vis alle 9 forfattere av denne artikkelen] (2016). Proteomics tools reveal startlingly high amounts of oxytocin in plasma and serum. Scientific Reports. 6:31693. doi: 10.1038/srep31693. Fulltekst i vitenarkiv Vis sammendrag

  The neuropeptide oxytocin (OT) is associated with a plethora of social behaviors, and is a key topic at the intersection of psychology and biology. However, tools for measuring OT are still not fully developed. We describe a robust nano liquid chromatography-mass spectrometry (nanoLC-MS) platform for measuring the total amount of OT in human plasma/serum. OT binds strongly to plasma proteins, but a reduction/alkylation (R/A) procedure breaks this bond, enabling ample detection of total OT. The method (R/A + robust nanoLC-MS) was used to determine total OT plasma/serum levels to startlingly high concentrations (high pg/mL-ng/mL). Similar results were obtained when combining R/A and ELISA. Compared to measuring free OT, measuring total OT can have advantages in e.g. biomarker studies.

• Nilsen, Andre Sevenius; Blix, Ines; Leknes, Siri; Ekeberg, Øivind; Skogstad, Laila & Endestad, Tor [Vis alle 8 forfattere av denne artikkelen] (2016). Brain activity in response to trauma-specific, negative, and neutral stimuli. A fMRI study of recent road traffic accident survivors. Frontiers in Psychology. 7:1173. doi: 10.3389/fpsyg.2016.01173. Fulltekst i vitenarkiv
• Løseth, Guro Engvig; Leknes, Siri & Ellingsen, Dan Mikael (2016). The neurochemical basis of motivation for affiliative touch. I Olausson, Håkan; Wessberg, Johan; morrison, India & McGlone, Francis (Red.), Affective Touch and the Neurophysiology of CT Afferents. Springer. ISSN 9781493964185. s. 239–264. doi: 10.1007/978-1-4939-6418-5_15. Fulltekst i vitenarkiv
• Chelnokova, Olga V; Laeng, Bruno; Løseth, Guro Engvig; Eikemo, Marie Helene; Willoch, Frode & Leknes, Siri (2016). The µ-Opioid System Promotes Visual Attention to Faces and Eyes. Social Cognitive & Affective Neuroscience. ISSN 1749-5016. 11(12), s. 1902–1909. doi: 10.1093/scan/nsw116. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael; Leknes, Siri; Løseth, Guro Engvig; Wessberg, Johan & Olausson, Håkan (2016). The neurobiology shaping affective touch: Expectation, motivation, and meaning in the multisensory context. Frontiers in Psychology. 6. doi: 10.3389/fpsyg.2015.01986. Fulltekst i vitenarkiv Vis sammendrag

  Inter-individual touch can be a desirable reward that can both relieve negative affect and evoke strong feelings of pleasure. However, if other sensory cues indicate it is undesirable to interact with the toucher, the affective experience of the same touch may be flipped to disgust. While a broad literature has addressed, on one hand the neurophysiological basis of ascending touch pathways, and on the other hand the central neurochemistry involved in touch behaviors, investigations of how external context and internal state shapes the hedonic value of touch have only recently emerged. Here, we review the psychological and neurobiological mechanisms responsible for the integration of tactile “bottom–up” stimuli and “top–down” information into affective touch experiences. We highlight the reciprocal influences between gentle touch and contextual information, and consider how, and at which levels of neural processing, top-down influences may modulate ascending touch signals. Finally, we discuss the central neurochemistry, specifically the μ-opioids and oxytocin systems, involved in affective touch processing, and how the functions of these neurotransmitters largely depend on the context and motivational state of the individual.

• Eikemo, Marie Helene; Løseth, Guro Engvig; Johnstone, Tom; Gjerstad, Johannes; Willoch, Frode & Leknes, Siri (2016). Sweet taste pleasantness is modulated by morphine and naltrexone. Psychopharmacology. ISSN 0033-3158. 233(21), s. 13711–3723. doi: 10.1007/s00213-016-4403-x. Fulltekst i vitenarkiv Vis sammendrag

  Background: Rodent models highlight the key role of μ-opioid receptor (MOR) signaling in palatable food consumption. In humans, however, the effects of MOR stimulation on eating and food liking remain unclear. Objectives Here, we tested sweet pleasantness experience in humans following MOR drug manipulations. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism and decreased by antagonism. In line with rodent findings, we expected the strongest drug effects for the sweetest (high-calorie) sucrose stimuli. As very sweet stimuli are considered aversive by many people (called sweet dislikers), we also assessed whether MOR manipulations affect pleasantness ratings of sucrose-water stimuli differently depending on subjective and objective value. Methods: In a bidirectional psychopharmacological cross-over study, 49 healthy men underwent a sweet taste paradigm following double-blind administration of the MOR agonist morphine, placebo, and the opioid antagonist naltrexone. Results: As hypothesized, MOR stimulation with morphine increased pleasantness of the sweetest of five sucrose solutions, without enhancing pleasantness of the lower-sucrose solutions. For opioid antagonism, an opposite pattern was observed for the sweetest drink only. The observed drug effects on pleasantness of the sweetest drink did not differ between sweet likers and dislikers. Conclusions: The bidirectional effect of agonist and antagonist treatment aligns with rodent findings showing that MOR manipulations most strongly affect the highest-calorie foods. We speculate that the MOR system promotes survival in part by increasing concordance between the objective (caloric) and subjective (hedonic) value of food stimuli, so that feeding behavior becomes more focused on the richest food available.

• Jonassen, Rune; Chelnokova, Olga V; Harmer, Catherine; Leknes, Siri & Landrø, Nils Inge (2015). A single dose of antidepressant alters eye-gaze patterns across face stimuli in healthy women. Psychopharmacology. ISSN 0033-3158. 232(5), s. 953–958. doi: 10.1007/s00213-014-3729-5. Fulltekst i vitenarkiv
• Johnsen, Elin Follaug; Leknes, Siri; Wilson, Steven Ray Haakon & Lundanes, Elsa (2015). Liquid chromatography-mass spectrometry platform for both small neurotransmitters and neuropeptides in blood, with automatic and robust solid phase extraction. Scientific Reports. 5. doi: 10.1038/srep09308. Fulltekst i vitenarkiv Vis sammendrag

  Neurons communicate via chemical signals called neurotransmitters (NTs). The numerous identified NTs can have very different physiochemical properties (solubility, charge, size etc.), so quantification of the various NT classes traditionally requires several analytical platforms/methodologies. We here report that a diverse range of NTs, e.g. peptides oxytocin and vasopressin, monoamines adrenaline and serotonin, and amino acid GABA, can be simultaneously identified/measured in small samples, using an analytical platform based on liquid chromatography and high-resolution mass spectrometry (LC-MS). The automated platform is cost-efficient as manual sample preparation steps and one-time-use equipment are kept to a minimum. Zwitter-ionic HILIC stationary phases were used for both on-line solid phase extraction (SPE) and liquid chromatography (capillary format, cLC). This approach enabled compounds from all NT classes to elute in small volumes producing sharp and symmetric signals, and allowing precise quantifications of small samples, demonstrated with whole blood (100 microliters per sample). An additional robustness-enhancing feature is automatic filtration/filter back-flushing (AFFL), allowing hundreds of samples to be analyzed without any parts needing replacement. The platform can be installed by simple modification of a conventional LC-MS system.

• Ellingsen, Dan Mikael; Leknes, Siri & Kringelbach, Morten (2015). Hedonic Value. I Brosch, T. & Sander, D. (Red.), Handbook of Value: Perspectives from Economics, Neuroscience, Philosophy, Psychology and Sociology. Oxford University Press. ISSN 9780198716600. s. 265–286. Fulltekst i vitenarkiv
• Bastian, Brock; Jetten, Yolanda; Hornsey, Matthew & Leknes, Siri (2014). The Positive Consequences of Pain: A Biopsychosocial Approach. Personality and Social Psychology Review. ISSN 1088-8683. 18(3), s. 256–279. doi: 10.1177/1088868314527831. Fulltekst i vitenarkiv
• Leknes, Siri & Bastian, Brock (2014). How does pain affect eating and food pleasure? Pain. ISSN 0304-3959. 155(4), s. 652–653. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael; Wessberg, Johan; Chelnokova, Olga V; Olausson, Håkan; Laeng, Bruno & Leknes, Siri Graff (2014). In touch with your emotions: Oxytocin and touch change social impressions while others' facial expressions can alter touch. Psychoneuroendocrinology. ISSN 0306-4530. 39(1), s. 11–20. doi: 10.1016/j.psyneuen.2013.09.017. Fulltekst i vitenarkiv
• Leknes, Siri & Bastian, Brock (2014). The Benefits of Pain. Review of Philosophy and Psychology. ISSN 1878-5158. 5(1), s. 57–70. doi: 10.1007/s13164-014-0178-3. Fulltekst i vitenarkiv
• Chelnokova, Olga V; Laeng, Bruno; Eikemo, Marie; Riegels, Jeppe Kjær; Løseth, Guro Engvig & Maurud, Hedda [Vis alle 8 forfattere av denne artikkelen] (2014). Rewards of beauty: the opioid system mediates social motivation in humans. Molecular Psychiatry. ISSN 1359-4184. doi: 10.1038/mp.2014.1. Fulltekst i vitenarkiv
• Løseth, Guro Engvig; Ellingsen, Dan Mikael & Leknes, Siri (2014). State-dependent μ-opioid modulation of social motivation. Frontiers in Behavioral Neuroscience. 8. doi: 10.3389/fnbeh.2014.00430. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael; Wessberg, Johan; Eikemo, Marie Helene; Liljencrantz, Jaquette; Endestad, Tor & Olausson, Håkan [Vis alle 7 forfattere av denne artikkelen] (2013). Placebo improves pleasure and pain through opposite modulation of sensory processing. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 110(44), s. 17993–17998. doi: 10.1073/pnas.1305050110. Fulltekst i vitenarkiv
• Leknes, Siri Graff; Berna, Chantal; Lee, Michael; Snyder, Gregory; Biele, Guido & Tracey, Irene (2013). The importance of context: When relative relief renders pain pleasant. Pain. ISSN 0304-3959. 154(3), s. 402–410. doi: 10.1016/j.pain.2012.11.018. Fulltekst i vitenarkiv
• Leknes, Siri Graff; Wessberg, Johan; Ellingsen, Dan Mikael; Chelnokova, Olga V; Olausson, Håkan & Laeng, Bruno (2013). Oxytocin enhances pupil dilation and sensitivity to hidden emotional expressions. Social Cognitive & Affective Neuroscience. ISSN 1749-5016. 8(7), s. 741–749. doi: 10.1093/scan/nss062. Fulltekst i vitenarkiv
• Wanigasekera, Vishvarani; Lee, Michael; Rogers, Richard; Kong, Yazhuo; Leknes, Siri Graff & Andersson, Jesper [Vis alle 7 forfattere av denne artikkelen] (2012). Baseline reward circuitry activity and trait reward responsiveness predict expression of opioid analgesia in healthy subjects. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 109(43), s. 17705–17710. doi: 10.1073/pnas.1120201109. Fulltekst i vitenarkiv

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• Erga, Aleksander Hagen; Karlsen, Cecilia L.; Hetland, Jens; Hagen, Egon; McKay, James R. & Leknes, Siri (2022). Anhedonia during recovery from polysubstance use. doi: https:/2022.lisbonaddictions.eu/. Fulltekst i vitenarkiv
• Bochynska, Agata; Quintana, Daniel; Mayor, Julien; Leknes, Siri; Roettger, Timo & Mayiwar, Lewend [Vis alle 7 forfattere av denne artikkelen] (2022). Fram for troverdig forskning: Forskningen må være gjennomsiktig og etterprøvbar. 54(4), s. 38–39. Fulltekst i vitenarkiv Vis sammendrag

  Forskere ved Universitetet i Oslo, Handelshøyskolen BI og Høgskolen i Østfold har etablert det nasjonale nettverket Norwegian Reproducibility Network (NORRN). NORRN skal bidra til god forskningspraksis i Norge gjennom å fremme og legge til rette for åpenhet og etterprøvbarhet av forskningsresultater.

• Leknes, Siri Graff & Vittersø, Axel (2022). Hvorfor er vi så glad i rus? Fulltekst i vitenarkiv
• Eikemo, Marie; Løseth, Guro Engvig & Leknes, Siri (2021). Do endogenous opioids mediate or fine-tune human pain relief? Pain. ISSN 0304-3959. 162(12), s. 2789–2791. doi: 10.1097/j.pain.0000000000002286. Fulltekst i vitenarkiv
• Løseth, Guro; Eikemo, Marie & Leknes, Siri Graff (2019). Effects of opioid receptor stimulation and blockade on touch pleasantness: a double-blind randomised trial. Social Cognitive & Affective Neuroscience. ISSN 1749-5016. doi: 10.1093/scan/nsz022. Fulltekst i vitenarkiv
• Brandtzæg, Ole Kristian Merkesvik; Johnsen, Elin Follaug; Røberg-Larsen, Hanne; Leknes, Siri; Lundanes, Elsa & Wilson, Steven Ray Haakon (2016). Robust nano liquid chromatography mass spectrometry system for targeted determination of oxytocin in human serum/plasma. Fulltekst i vitenarkiv
• Johnsen, Elin Follaug; Wilson, Steven Ray Haakon; Leknes, Siri & Lundanes, Elsa (2015). Highly automated platform for simultaneous identification of all classes of neurotransmitters by hydrophilic interaction liquid chromatography-MS. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael & Leknes, Siri (2014). Forbedring av smerte og velbehag ved bruk av placebo. BestPractice nordic. 10, s. 16–17. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael & Leknes, Siri (2014). Kan vi snu smerteopplevelsen fra vond til god? Forventninger, kontekst og lettelse påvirker smerte. BestPractice nordic. 9, s. 6–7. Fulltekst i vitenarkiv
• Jonassen, Rune; Chelnokova, Olga V; Harmer, Catherine; Leknes, Siri & Landrø, Nils Inge (2014). A single dose of antidepressant alters eye-gaze patterns across face stimuli in healthy women. Fulltekst i vitenarkiv
• Chelnokova, Olga V; Laeng, Bruno; Eikemo, Marie Helene; Riegels, Jeppe; Løseth, Guro & Maurud, Hedda [Vis alle 8 forfattere av denne artikkelen] (2014). Rewards of beauty: The opioid system mediates social motivation in humans. Molecular Psychiatry. ISSN 1359-4184. 19(7), s. 746–747. doi: 10.1038/mp.2014.1. Fulltekst i vitenarkiv
• Johnsen, Elin Follaug; Folven, Lars; Leknes, Siri; Greibrokk, Tyge; Wilson, Steven Ray Haakon & Lundanes, Elsa (2014). On-line coupling of various spe phases with HILIC-LC for enrichment and separation of polar neurotransmitters in various biological matrices. Fulltekst i vitenarkiv
• Ellingsen, Dan Mikael & Leknes, Siri (2013). Placebo gav lindrad smärta, men också ökad njutning. Läkartidningen. ISSN 0023-7205. 110(49-50). Fulltekst i vitenarkiv
• Leknes, Siri; Berna, Chantal; Lee, M; Snyder, G.; Biele, Guido & Tracey, Irene (2013). Response to the commentary “Multiple potential mechanisms for context effects on pain”. Pain. ISSN 0304-3959. 154(8), s. 1485–1486. doi: 10.1016/j.pain.2013.04.002. Fulltekst i vitenarkiv
• Ellingsen, Dan-Mikael & Leknes, Siri (2013). Placebo gav lindrad smärta, men också ökad njutning. Läkartidningen. ISSN 0023-7205. 110. Fulltekst i vitenarkiv
• Chelnokova, Olga V; Laeng, Bruno; Riegels, Jeppe; Løseth, Guro Engvig; Eikemo, Marie Helene & Leknes, Siri Graff (2013). THE HUMAN OPIOID SYSTEM MEDIATES ATTENTION TO OTHERS' EYES. Journal of Cognitive Neuroscience. ISSN 0898-929X. s. 216–216. Fulltekst i vitenarkiv
• Leknes, Siri Graff & Laeng, Bruno (2009). Social touch: investigating the role of oxytocin for interactions in the hedonic experience of touch and emotion. SFN Abstract Viewer/Itinerary Planner. Fulltekst i vitenarkiv Vis sammendrag

  Touch is a key means of interpersonal communication. The hormone oxytocin has been closely linked with affectionate touch. In this preliminary study, we investigate how altering the emotional expression and identity of visually perceived human faces may affect the hedonic experience of soft stroking touch. Conversely, the effects of social touch upon face perception are investigated. Finally, this study uses intranasal oxytocin administration (40IU) to elucidate the role of this hormone for social touch. Images of angry, neutral and happy facial expressions were chosen from the Karolinska Directed Emotional Faces database. In addition, two types of “hybrid” faces that showed anger or happiness only in the lowest spatial frequencies (1-6 cycles/image) and a neutral expression in the rest of the bandwidth (7-128 cycles/image) were used. Faces in the five emotion conditions were of the same 20 men and 20 women and were matched for luminance. Images were displayed in a pseudorandomised order for 3 sec and accompanied by touch (soft strokes of 3cm/sec to the forearm) or control stimulation (70Hz vibration presented once/sec to the dorsum of the hand). To avoid bias, the experimenter performing touch and vibration stimuli wore a silk glove and was hidden from view. The outcome measures of this double-blind, placebo-controlled within-subjects study were pupil diameter and subjective ratings of touch and face perception. Three main hypotheses were tested in this preliminary investigation. 1) Socially relevant seen emotion affects perception of social touch. 2) Pupil size reflects the pleasantness and subjective relevance of social touch. 3) Social touch and oxytocin affect perception of human face stimuli. The significance of preliminary findings was assessed with one-tailed, paired t-tests. As hypothesized, pilot data (N=9) showed an effect of socially relevant seen emotion on perception of touch pleasantness (but not touch intensity). When subjects viewed angry faces, touch pleasantness (6.0±0.4, mean±SD) was significantly lower than with neutral (6.2±0.4, p=0.033) or happy face stimuli (6.4±0.4, p=0.028). Overall, soft stroking was significantly more pleasant than the control stimulus (p=0.018) but both were equally intense (p=0.44) during oxytocin and placebo sessions (N=5). As expected, pupil size increased during pleasant, social touch relative to control stimulation (mean diameter difference 0.04±0.02 mm, p=0.032). Finally, there was a trend towards reduced ratings of perceived anger during social touch in the oxytocin session only (p=0.056; placebo session p=0.33), consistent with an anxiety-reducing effect of oxytocin and social touch.

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