Love 1: Intro, Oxytocin, Vasopressin, Romantic Love

13 important questions on Love 1: Intro, Oxytocin, Vasopressin, Romantic Love

What is the importance of animal models in investigating adult pair bonding?

They give us insight into biological mechanisms in humans

Who measured sexual/ romantic relationships in humans?

Walum et al., 2008 - studied genetic variation in the vasopressin receptor 1a gene and its association with pair-bonding behaviour in humans
Results - if both your copies of the vasopressin gene are a particular variant allele…your marriage is of poorer quality

(slide 3, p. 1 lecture notes)

Who used a neuroimaging technique to study romantic and paternal love?

Bartels & Semir, 2004 - fMRI studies in humans, UCL

Used neuroimaging subraction technique - tested activation specifically relating to task (i.e. core brain activities underlying romantic & paternal love) - see slide 4 & 5, p. 1 lecture notes) 

RESULTS:
---> both types of attachment activated regions specific in each, as well as overlapping regions in the brain's reward system that coincide with areas rich in oxytocin & vasopressin receptors

(we know so much about brain’s reward system and areas rich in oxytocin and vasopressin receptors mainly from animal work, see slide 1, p. 2 lecture notes)
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Is biparental care necessary for pair bonding? i.e. is there a link between pair bonding and biparental care?

---> There are many successful mammalian species without biparental care
---> Bur for humans, especially, a lot of time/ resources needs to be devoted by the parents to the young - male and female (parents) team up as economic unit?

Example

Praire vole vs meadow voles
  • Praire voles = exhibit a monogamous social structure (i.e the male sticks around and is involved in parenting the offspring)
  • Meadow voles = solidarity & polygamous


Implies:
- Lasting pair bond between adult mates
- Both male and female care for offspring     

What is oxytocin and vasopressin involved in? What is the difference between males and females?

Oxytocin and vasopressin = prosocial neuropeptides
---> Involved in pair bonding and parental behaviour

In both sexes, but rough but useful generalisation:
- Oxytocin more important in females ♀
- Vasopressin more important in males ♂

Oxytocin and Vasopressin work in part with reward systems in forebrain regions such as the ventral pallidum, caudate, putamen, and nucleus accumbens

Oxytocin can be summarised as ‘prosocial', what does it promote?

  • Maternal and paternal behaviour
  • Attachment in young
  • Social recognition
  • Sexual behaviour
  • Pair bonding and social bonding (i.e. adult affiliation)
  • Empathy and Theory of mind (humans)
  • Interpersonal warmth & Trust (humans)
  • Reduces anxiety (cautious social distance?)



(Read about links between the evolution of maternal behaviour and adult sexual behaviour.)

What study shows that oxytocin promotes pair bonding?

Ross & Young, 2009

---> oxytocin receptor density is increased in monogamous vole
Oxytocin receptor density in Nucleus Accumbens (Nacc) and Caudate and Putamen and prefrontal cortex is clearly very much higher (black staining) in the prairie vole compared to the rat and mouse (which are NOT monogamous)

Another, better comparison by Ross & Young, 2009

Some brain regions where oxytocin receptors are expressed:
PFC = prefrontal cortex

CP = caudate and putamen
NAcc = Nucleus Accumbens
---> Oxytocin receptor density is clearly much higher in the prairie vole, the monogamous species, than the non-monogamous montane vole       - Thus more oxytocin receptors may predispose to pair bonding?

How can we get a direct test of the influence of oxytocin-related systems in pair bonding?

By blocking oxytocin receptor activity in the receiving neurons in oxytocin-receptor-rich brain regions
Laboratory test of pair-bonding - the Partner Preference Test

Describe Ross & Young's partner preference test?


Subjects: female prairie voles doing partner preference test (Thus partners or strangers are males)

Time in contact - more with partner than with stranger
Oxytocin receptor ANTAGONIST (i.e. blocks oxytocin) infused into 3 different oxytocin-receptor-rich regions

Results:

Infusion of the OXT-R antagonist into the Nucleus Accumbens OR Prefrontal Ctx was sufficient to BLOCK preference for the mating partner over a stranger.

(see slide 2, p. 4 for graph)

Conclusion: Oxytocin receptors in the Nucleus Accumbens and Prefrontal Ctx are required for normal pair bonding

What are 3 examples of situations where oxytocin is released?

- Prairie vole mating
- In rats & sheep during vaginocervical stimulation
- In human sexual behaviour (not much studied)

Some evidence in ♀ for positive relationship between:
subjectivity intensity of orgasm & oxytocin release

What shows that there is different timing of vasopressin and oxytocin peaks?

Vasopressin:
---> peaks during arousal/ before ejaculation
--->  Appetitive
---> Like Dopaminergic
---> Signal in nucleus accumbens

Oxytocin:
---> peaks at ejaculation (& still quite high afterwards ('afterglow')
---> more towards ‘satisfaction’, more like Opoidergic signal
---> Naloxone blocks the release of OXT after orgasm (and the Subjective pleasure)

(slide 5, p. 4 lecture notes)

Oxytocin interacts with other neurotransmitter systems and brain regions, what are 2 examples of these?

Dopamine and Opioids in ventral forebrain

(Try to consider in your reading the idea of the relationship between attachment and reward ---> attaching is rewarding)

What experiment studied oxytocin in human couples?

Ditzen et al., 2009

Gave participants either oxytocin or a placebo

RESULTS:
--->  Subjects given oxytocin show more positive than negative behaviour (has more of an effect on males)
---> Subjects given oxytocin show lower cortisol levels after couple conflict i.e. oxytocin reduces stress (social buffering) (around the same effects in males and females)

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