Effects of oxytocin administration and conditioned oxytocin on brain activity: An fMRI study

Salivary oxytocin and amygdalar alterations in functional neurological disorders

Individuals diagnosed with functional neurological disorder experience abnormal movement, gait, sensory processing or functional seizures, for which research into the pathophysiology identified psychosocial contributing factors as well as promising biomarkers. Recent pilot studies suggested that (epi-)genetic variants may act as vulnerability factors, for example, on the oxytocin pathway. This study set out to explore endogenous oxytocin hormone levels in saliva in a cohort of 59 functional neurological disorder patients and 65 healthy controls comparable in sex and age. First, we examined the association between salivary oxytocin levels with the genetic allelic variant (rs53576) of the oxytocin receptor gene (OXTR), its epigenetic changes indicated by methylation rates, and clinical variables-including childhood trauma. Second, due to previously reported effects of oxytocin changing the volume and functional connectivity of the amygdala, as well as the known involvement of the amygdala in the pathophysiology of functional neurological disorders, we further looked at both structural and functional imaging of the amygdala. While patients did not significantly differ from healthy control in their peripheral oxytocin levels, there was a specific interaction of OXTR methylation and peripheral oxytocin dependent on group: higher methylation rates correlated with higher salivary oxytocin in patients only, while this was not the case in healthy control [F(1109) = 8.92, P = 0.003, d = 0.541]. Moreover, patients with the AA-genotype (minor allele) of the rs53576 genetic variant of the OXTR gene presented with higher OXTR methylation levels [F(2106) = 10.25, P < 0.0001, d = 0.58]. Lastly, amygdalar connectivity to the hippocampus, the posterior cingulate cortex, the inferior parietal cortex and the inferior temporal cortex as well as smaller amygdalar volume were correlated to peripheral oxytocin levels in patients only [F(2,38) = 5.36, P  = 0.025,  d = 0.431], but not in healthy control. No significant interactions with childhood trauma were identified. Our study revealed a significant interplay between peripheral oxytocin and OXTR methylation in patients only, potentially influenced by genotype. One could hypothesize that higher peripheral oxytocin denotes a compensatory mechanisms for the increased methylation of the OXTR, which might affect amygdalar functional connectivity. These findings help to further understand underlying pathophysiological mechanisms, considering oxytocin's involvement in functional patients and could offer a potential site of treatment for future studies.

The effects of oxytocin and vasopressin administration on fathers' neural responses to infant crying: A randomized controlled within-subject study

In a randomized double-blind within-subject control study we investigated the effects of oxytocin and vasopressin administration on neural reactivity to infant cry sounds in 70 first-time fathers in the first year of fatherhood. Additionally, we examined whether effects of oxytocin and vasopressin administration on neural reactivity were moderated by fathers' early childhood experiences. Neural reactivity to infant cry sounds (versus control sounds) was measured using functional magnetic resonance imaging (fMRI). Furthermore, participants reported on their childhood experiences of parental harsh discipline and parental love withdrawal. Whole brain analyses revealed no significant effect of vasopressin or oxytocin administration on neural activation in response to infant cry sounds. Region of interest analyses showed decreased amygdala activation in both the oxytocin condition and the vasopressin condition as compared to placebo. We found no moderating effects of fathers' early childhood experiences. Our findings suggest that oxytocin administration may decrease feelings of anxiety or aversion to a crying infant. Whether decreased amygdala activation after vasopressin administration might be explained by contextual factors (e.g., absence of high levels of threat, unfamiliarity of the infant) or represents an affiliative response to infant distress warrants further investigation. Findings of the present study showed that oxytocin and vasopressin are important hormones implicated in neural models of infant cry perception in fatherhood.

A Systematic Review of the Role of Oxytocin, Cortisol, and Testosterone in Facial Emotional Processing

A topic of interest is the way decoding and interpreting facial emotional expressions can lead to mutual understanding. Facial emotional expression is a basic source of information that guarantees the functioning of other higher cognitive processes (e.g., empathy, cooperativity, prosociality, or decision-making, among others). In this regard, hormones such as oxytocin, cortisol, and/or testosterone have been found to be important in modifying facial emotion processing. In fact, brain structures that participate in facial emotion processing have been shown to be rich in receptors for these hormones. Nonetheless, much of this research has been based on correlational designs. In recent years, a growing number of researchers have tried to carry out controlled laboratory manipulation of these hormones by administering synthetic forms of these hormones. The main objective of this study was to carry out a systematic review of studies that assess whether manipulation of these three hormones effectively promotes significant alterations in facial emotional processing. To carry out this review, PRISMA quality criteria for reviews were followed, using the following digital databases: PsycINFO, PubMed, Dialnet, Psicodoc, Web of Knowledge, and the Cochrane Library, and focusing on manuscripts with a robust research design (e.g., randomized, single- or double-blind, and/or placebo-controlled) to increase the value of this systematic review. An initial identification of 6340 abstracts and retrieval of 910 full texts led to the final inclusion of 101 papers that met all the inclusion criteria. Only about 18% of the manuscripts included reported a direct effect of hormone manipulation. In fact, emotional accuracy seemed to be enhanced after oxytocin increases, but it diminished when cortisol and/or testosterone increased. Nonetheless, when emotional valence and participants' gender were included, hormonal manipulation reached significance (in around 53% of the articles). In fact, these studies offered a heterogeneous pattern in the way these hormones altered speed processing, attention, and memory. This study reinforces the idea that these hormones are important, but not the main modulators of facial emotion processing. As our comprehension of hormonal effects on emotional processing improves, the potential to design good treatments to improve this ability will be greater.

Identifying super-feminine, super-masculine and sex-defining connections in the human braingraph

For more than a decade now, we can discover and study thousands of cerebral connections with the application of diffusion magnetic resonance imaging (dMRI) techniques and the accompanying algorithmic workflow. While numerous connectomical results were published enlightening the relation between the braingraph and certain biological, medical, and psychological properties, it is still a great challenge to identify a small number of brain connections closely related to those conditions. In the present contribution, by applying the 1200 Subjects Release of the Human Connectome Project (HCP) and Support Vector Machines, we identify just 102 connections out of the total number of 1950 connections in the 83-vertex graphs of 1064 subjects, which-by a simple linear test-precisely, without any error determine the sex of the subject. Next, we re-scaled the weights of the edges-corresponding to the discovered fibers-to be between 0 and 1, and, very surprisingly, we were able to identify two graph edges out of these 102, such that, if their weights are both 1, then the connectome always belongs to a female subject, independently of the other edges. Similarly, we have identified 3 edges from these 102, whose weights, if two of them are 1 and one is 0, imply that the graph belongs to a male subject-again, independently of the other edges. We call the former 2 edges superfeminine and the first two of the 3 edges supermasculine edges of the human connectome. Even more interestingly, the edge, connecting the right Pars Triangularis and the right Superior Parietal areas, is one of the 2 superfeminine edges, and it is also the third edge, accompanying the two supermasculine connections if its weight is 0; therefore, it is also a "switching" edge. Identifying such edge-sets of distinction is the unprecedented result of this work.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11571-021-09687-w.

Intranasal oxytocin administration but not peripheral oxytocin regulates behaviors of attachment insecurity: A meta-analysis

In light of the roles of oxytocin (OT) in social bonding and interpersonal relationship, studies have examined the roles of OT in human attachment, but by and large previous findings are inconsistent. Here, we conducted - meta-analyses to estimate the associations between peripheral OT level (e.g., blood and salivary OT) and attachment (i.e., attachment dimensions and behaviors of attachment insecurity) and examine the effects of intranasal OT administration on behaviors of attachment insecurity. The analyses indicated that: (1) Peripheral OT level was not significantly associated with attachment dimensions (e.g., attachment anxiety and attachment avoidance) and behaviors of attachment insecurity; (2) intranasal OT administration significantly reduced behaviors of attachment insecurity of neutral contexts, particularly behaviors of attachment avoidance. The findings suggest that intranasal OT administration is an available approach for reducing behaviors of attachment insecurity of interpersonal situations with ambiguous social cues, which implicates suggestions for therapeutic treatments of attachment-related dysfunctions.

Effects of different smoothing on global and regional resting functional connectivity

PURPOSE

Spatial smoothing is an essential pre-processing step in the process of analysing functional magnetic resonance imaging (fMRI) data, both during an experimental task or during resting-state fMRI (rsfMRI). The main benefit of this spatial smoothing step is to artificially increase the signal-to-noise ratio of the fMRI signal. Previous fMRI studies have investigated the impact of spatial smoothing on task fMRI data, while rsfMRI studies usually apply the same analytical process used for the task data. However, this study investigates changes in different rsfMRI analyses, such as ROI-to-ROI, seed-to-voxels and ICA analyses.

METHODS

Nineteen healthy volunteers were scanned using rsfMRI with three applied smoothing kernels: 0 mm, 4 mm and 8 mm. Appropriate statistical comparisons were made.

RESULTS

The findings showed that spatial smoothing has a greater effect on rsfMRI data when analysed using seed-to-voxel-based analysis. The effect was less pronounced when analysing data using ROI-ROI or ICA analyses. The results demonstrated that even when analysing the data without the application of spatial smoothing, the results were significant compared with data analysed using a typical smoothing kernel. However, data analysed with lower-smoothing kernels produced greater negative correlations, particularly with the ICA analysis.

CONCLUSION

The results suggest that a medium smoothing kernel (around 4 mm) may be preferable, as it is comparable with the 8 mm kernel in all of the analyses performed. It is also recommended that the researchers consider analysing the data using two different smoothing kernels, as this will help to confirm the significance of the results and avoid overestimating the findings.