PSYC 310 Lecture Notes - Lecture 12: Conditioned Place Preference, Reinforcement Learning, Dorsal Raphe Nucleus
7 May 2018
School
Department
Course
Professor
PSYC 318
Behavioural Neuroscience II
January 10th, 2018
Lecture 2/24: Social Reward I
• Paper: social reward requires coordinated activity of nucleus accumbens ocytocin and
serotonin (Nature: Dolen, Darvishzadeh, Huang, Malenka)
o Nucleus accumbens
▪ The NAc is at ventral part of the basal ganglia structure
▪ Generally involved in motivation processes, reinforcement learning and
reward seeking
▪ NAc tends to show increased activity when animals are doing any
rewarding activity
• Involved in question of whether you enjoy rewarding things, learn
from rewarding experiences?
• In rodents: when manipulated, alters their willingness to pay
attention and put work in to get rewards
▪ Plays a role in prioritizing our goals: what we value, how much effort and
work we put into getting them
o Social reward
▪ Some species of mammals form lifelong pair bonds and raise their
offspring together as a couple
• Ma dot for the
• Research on this topic focuses on two species of prarie voles, one
fors lifelog pair ods ad the other doest
• Whats differet etee the rais of the to speies to eplai
this very different pair-bonding behavior?
▪ Main difference is the amount of oxytocin receptors in the NAc
• Animals who formed lifelong pair-bonds had robust expression of
oxytocin in NAc and those ho didt for the had lo
expression
▪ Took a monogamous species, artificially raised oxytocin expression
• If they did it in females, they tended to form lifelong pair bond
with the next male prarie vole they encountered
▪ Blocking receptors – animals unlikely to form pair bonds
▪ Took non-monogamous prarie vole species without much oxytocin
receptor expression, artificially caused brain to have more oxytocin
receptors
• They suddenly started to form lifelong pair bonds
• People thought oxytocin signaling in this region was critical
mediator of social reward in general
• Oxytocin
o The odig horoe
find more resources at oneclass.com
find more resources at oneclass.com
o Plays role in social bonding, sexual reproduction, childbirth, parental behavior
and lactation
▪ Tends to be there when people are forming connections to other
members of the species
o Is only made by a small collection of neurons in the hypothalamus
▪ Only made in hypothalamic neurons
▪ These neurons send axons out to many areas of brain, release oxytocin as
neuropeptide signaling molecule which influences oxytocin activity
▪ Also released into pituitary -> bloodstream as a hormone
▪ Increases in humans in blood after orgasm, childbirth, nipple stimulation
associated w/ breastfeeding
▪ Evoke feelings of contentment, trust, reductions in anxiety, feelings of
calmness and security when in the company of a mate
o More subtle results in humans
▪ Modulatory role that sets conditions to form more long-term social
bonds
o Genetic differences in oxytocin receptor (OXTR) have been associated with
maladaptive social traits such as aggressive behavior
▪ Another study said a different version of receptor correlates with high
quality of marriage in females
▪ Variations of receptor in humans correlate with different social behaviors
• Levels rise in blood at times we would expect involvement in
social interactions
• Compared to prairie voles, most mammals had very few ocytocin receptors in their NAc
o True for mice, who are not monogamous and have very little if any oxytocin
receptor expression in their NAc
• Paper:
o In mice, does oxytocin play a role in the rewarding properties of social
interactions?
▪ Behavior evidence that mice find social interactions rewarding in the first
place?
• Conditioned place preference assay (CPP)
o Test to measure motivational effects or reinforcing
properties of objects or experiences. Can also be used as
learning or memory test
o Standard protocol:
▪ Put animals in 2-3 room chamber and they are free
to explore, each room highly distinct, little to no
preference for a specific room
▪ Condition by locking mice in each room of the
chamber and there is either something good or bad
in the room: food, noxious smell, sexual partner,
foot shocks
find more resources at oneclass.com
find more resources at oneclass.com
▪ Next day unlock, give preference test for any of the
rooms
o Dependent measure is time spent in each room: do
animals seek out or avoid room where something
good/bad happened due to positive/negative associations
with the cues in that room?
• Social reward measured with a CPP assay
o Mice living in groups, often 3-5 mice per cage and this is
their home environment
o Take mouse out of home, put in two-room chamber, floor
material (bedding) different in the chamber
o After pre-conditioning trial, do two days of conditioning
where mouse is back with his friends but with floor
material associated with one side of this room
o On average, after conditioning days mice spent slightly
more time in side of room that had same bedding as the
room with their friends they previously were in.
▪ Normalized social preference score: post amount
of time / pre amount of time = normalized social
preference score. A score > 1 means preference for
side of room they associate with friends
▪ Post time – pre time = preference score
• Demonstration that mice find social interactions
rewarding/reinforcing
o Whe there ith their frieds, the ues i the roo get
an associated value that animals later choose to seek out
o Is oxytocin receptor activity involved in the forementioned learning?
▪ Get animals used to injections using saline
▪ After adjustment, inject with either saline or with an oxytocin receptor
blocker
▪ So, oxytocin receptors somewhere in animal necessary for social reward
learning
• But where in the brain/what neural circuits are important?
• They assume it is the NAc
• Is oxytocin released in the NAc?
o Question is not easy to prove
o Mie dot hae otoi reeptors i NA
▪ But, drug there usig has some off-target effects (oxytocin receptor
antagonist)
▪ Some propose: drug is doing something unexpected, blocking social
reward by doing something else but might not be related to critical
oxytocin receptor activity (making them sick, for example)
o How to prove that in mice oxytocin is released in the NAc?
find more resources at oneclass.com
find more resources at oneclass.com
