User:Justin Tsay/Sandbox

THOMAS is an acronym for "The Human Oxytocin Mediated Attachment System". It refers to a system in human neurochemistry where oxytocin motivates a desire to interact with other people, and is released in response to a feeling of being trusted.

Oxytocin has traditionally been known for its effects on birth, nursing and maternal behavior. In addition to these effects, oxytocin also plays a role in calmness, stress and social behavior.

Amygdala-Dependent
In a double-blind experiment where patients are shown various facial expressions, oxytocin was shown to play a role in socially reinforced learning. Other studies have shown oxytocin to induce amnesia in patients in stressful experiments, it is thought that oxytocin plays a role in enhancing learning where there is a positive social effect, and help in forgetting stressful, dangerous experiences.

Two twin patients with Urbach-Wiethe disease showed no socially reinforced learning, leading into the importance of a working amygdala. The patients were able to identify positive and negative faces, bypassing the amygdala and possibly using other brain regions, resulting in increased reaction times and a more complicated cognitive process.

Male and female control groups showed identical results in the learning task and cognitive empathy portion. In the emotional empathy portion though, women showed much higher ratings than men. After being treated with oxytocin did men show similar results as untreated women. This difference may be due to women showing enhanced oxytocin release compared to men

Effects of Physical Contact
A study on premenopausal women shows increased oxytocin levels correlate to lower blood pressure and heart rate, achieved by self-reported frequent partner hugs. Increased oxytocin levels are also seen in mothers with more children at home, “consistent with the animal literature linking higher oxytocin activity to greater maternal behavior.”

Increased plasma oxytocin levels are seen in both men and women in relationships, but males did not exhibit the same increased oxytocin levels or decreased sympathetic nervous system activity as seen in women “Because of oxytocin’s role in the initiation of maternal behavior, it is logical in an evolutionary sense that reproductive-age females might have the potential for greater and more broadly influential oxytocin activity

The physiological explanation is still unknown linking oxytocin to cardiovascular effects, but “might be due to decreased central alpha-adrenergic activity, or to direct peripheral effects of circulating oxytocin on the heart and vasculature”. Other possible factors include personality factors, experiential factors, and biological factors.

"Happy" Facial Expression Recognition
Adults who were treated with oxytocin were able to identify “happy expressions” more accurately compared to those given a placebo. The same study suggests that adults given oxytocin also exhibited fewer mistakes in recognizing happiness in comparison to other expressions. However, results are inconclusive with other oxytocin findings: oxytocin has no effect in identifying cartoon line drawings of happy expressions, and having “no effect on facial expression recognition accuracy.” These differing results could be due to a lack of uniform procedures in these experiments.

Oxytocin may also reinforce social behavior by promoting trustworthiness in the individual based on certain expressions. “A smile indicates that the expresser is trustworthy – that he or she seeks affiliation and does not present a threat.” There are also other signs of happiness to look for in inducing trust; and studies have been conducted to show that trustworthy expressions result in a perceived expression of happiness It is believed oxytocin is responsible for trust by increasing sensitivity to identify happiness cues.

Marmosets
Marmosets given an oxytocin treatment showed signs of increased huddling, as well as actively seeking out social contact with their partner. During a 3-week period of being treated with oxytocin, marmosets prefer to approach a new social partner, followed by meeting an opposite-sex stranger, and then venturing into an empty cage; and do so quicker than marmosets treated with an oxytocin antagonist or scientific control. “The OT treatment effects appeared to be specific to social behavior, since neither general activity nor sexual and aggressive behaviors were altered. These results suggest that the oxytocinergic neural circuits underlying social behaviors are influential in pair-bond formation in marmosets.”

“In general, the formation of social relationships is characterized by intense social contact and sexual interactions, and over time, the frequency of these sociosexual behaviors decreases to a level that is maintained throughout the duration of the pairing.”

In the study, oxytocin antagonists showed stronger effects on changing social behavior versus oxytocin treatments. In contrast to other studies, marmosets did not appear to show increased sexual behaviors as seen in rats, mice and prairie voles.

Rats
Frequent pet strokes have been shown to increase oxytocin oxytocin levels and decrease blood pressure.

Mice
Mice genetically bred without oxytocin receptors have been shown to have impaired social behavior. During infancy, these oxytocin gene knockout mice show decreased signs of vocalization, and decreased signs of licking; adult females show fewer maternal traits and the males show increased levels of aggression

Voles
Oxytocin differences in Praire Vole vs. Meadow Vole Hammock, 2007

Variation in OTR expression in brain can contribute to variation in social behavior

Implications
Oxytocin receptor agonists may be beneficial in men to enhance social motivated learning and emotional empathy. Other possible suggested areas of oxytocin treatment include autism spectrum disorders, schizophrenia and psychopathy. For autism spectrum disorders however, it has been shown cognitive empathy is the impairment, and findings have resulted in oxytocin treatments having minimal cognitive empathy effects ;

For future studies, the genetic differences of oxytocin will be investigated. In looking at chemical structures of oxytocin in mammals such as humans, chimps, baboons, and dogs, marmosets stand out in showing a 1 amino acid substitute in their oxytocin. The planned study will test whether the marmoset oxytocin creates a form of oxytocin that binds more firmly with oxytocin receptors or if it is likely to modify neuronal function.