Endogenous oxytocin levels in children with autism: Associations with cortisol levels and oxytocin receptor gene methylation

Chronic oxytocin improves neural decoupling at rest in children with autism: an exploratory RCT

BACKGROUND

Shifts in peak frequencies of oscillatory neural rhythms are put forward as a principal mechanism by which cross-frequency coupling/decoupling is implemented in the brain. During active neural processing, functional integration is facilitated through transitory formations of "harmonic" cross-frequency couplings, whereas "nonharmonic" decoupling among neural oscillatory rhythms is postulated to characterize the resting, default state of the brain, minimizing the occurrence of spurious, noisy, background couplings.

METHODS

Within this exploratory, randomized, placebo-controlled trial, we assessed whether the transient occurrence of nonharmonic and harmonic relationships between peak-frequencies in the alpha (8-14 Hz) and theta (4-8 Hz) bands is impacted by intranasal administration of oxytocin, a neuromodulator implicated in improving homeostasis and reducing stress/anxiety. To do so, resting-state electroencephalography was acquired before and after 4 weeks of oxytocin administration (12 IU twice-daily) in children with autism spectrum disorder (8-12 years, n = 33 oxytocin; n = 34 placebo). At the baseline, neural assessments of children with autism were compared with those of a matched cohort of children without autism (n = 40).

RESULTS

Compared to nonautistic peers, autistic children displayed a lower incidence of nonharmonic alpha-theta cross-frequency decoupling, indicating a higher incidence of spurious "noisy" coupling in their resting brain (p = .001). Dimensionally, increased neural coupling was associated with more social difficulties (p = .002) and lower activity of the parasympathetic "rest & digest" branch of the autonomic nervous system (p = .018), indexed with high-frequency heart-rate-variability. Notably, after oxytocin administration, the transient formation of nonharmonic cross-frequency configurations was increased in the cohort of autistic children (p < .001), indicating a beneficial effect of oxytocin on reducing spurious cross-frequency-interactions. Furthermore, parallel epigenetics changes of the oxytocin receptor gene indicated that the neural effects were likely mediated by changes in endogenous oxytocinergic signaling (p = .006).

CONCLUSIONS

Chronic oxytocin induced important homeostatic changes in the resting-state intrinsic neural frequency architecture, reflective of reduced noisy oscillatory couplings and improved signal-to-noise properties.

Chronic oxytocin administration stimulates the oxytocinergic system in children with autism

Clinical efficacy of intranasal administration of oxytocin is increasingly explored in autism spectrum disorder, but to date, the biological effects of chronic administration regimes on endogenous oxytocinergic function are largely unknown. Here exploratory biological assessments from a completed randomized, placebo-controlled trial showed that children with autism (n = 79, 16 females) receiving intranasal oxytocin for four weeks (12 IU, twice daily) displayed significantly higher salivary oxytocin levels 24 hours after the last oxytocin nasal spray administration, but no longer at a four-week follow up session. Regarding salivary oxytocin receptor gene (OXTR) epigenetics (DNA-methylation), oxytocin-induced reductions in OXTR DNA-methylation were observed, suggesting a facilitation of oxytocin receptor expression in the oxytocin compared to the placebo group. Notably, heightened oxytocin levels post-treatment were significantly associated with reduced OXTR DNA-methylation and improved feelings of secure attachment. These findings indicate that four weeks of chronic oxytocin administration stimulated the endogenous oxytocinergic system in children with autism.