Lecture 8 olfaction, social recognition and social memory Flashcards
what does bonding require?
olfaction, social recognition and social memory
describe imprinting
Imprinting is phase-dependent and non-associative learning
Influences behaviour, bonding and mate selection…
how do mice recognise socially?
very dependent on olfaction and pheromones.
Strange males are attacked and commonly killed by resident.
what is the role of the main olfactory system in rodents?
Detects volatile compounds
Pathways project from olfactory bulb to Amygdala
Responds to wide range of social and non-social cues
what is the accessory olfactory system?
Vomeronasal organ (VNO)
Detects non-volatile compounds
Pathways project to Amygdala
Detects socially relevant non-volatile cues
VNO is a sexually dimorphic structure, ie rat and mice male>female due to testosterone.
what is a pheromone?
“Substances secreted to the outside of an individual and received by a second individual of the same species in which they release a specific reaction, for example, a definite behaviour or developmental process”
Substances secreted by one individual which elicit specific behaviour in another of the same species
Where is the VMO located?
roof of mouth, behind main olfactory bulb.
VMO lesion leads to?
Male/Maternal aggression towards intruder male is strongly dependent on a functional VNO.
also reduces sexual behaviours, mounting.
VNO pathways?
different structures and outputs, but eventually both converge downstream on amygdala.
anterior/posterior AOB
VNO receptors?
Vomeronasal sensory neurons (VSN), GPCR
V1R & V2R
Detect pheromones - very sensitive mammalian chemoreceptors.
V1R very specific
V2R more general
V1R - anterior AOB
2R - posterior AOB
both converge downstream at amygdala
Complex with MHC class 1b and B2-microglobulin
what is a releaser pheromone?
Many examples of single or few molecules which elicit dramatic behavioural effects
What is a primer pheromone?
Chemical signal which cause longer term effects on neuroendocrine or developmental pathways
examples of rabbit pheromones?
nipple searching pheromone in rabbits, as babies blind.
boar releaser pheromones?
2 androgen derived, brings sow into oestrous and can see if ready to mate.
why are VNO GPCRs weird?
dont use cyclic nucleotides as second messengers.
Instead use member of transient receptor potential (TRP) superfamily, ion channels.
TRPC2 ion channel particularly.
TRP2 knockout mice
can’t detect males over females.
male aggression eliminated, also sexual behaviour towards male increases.
V1Rab knockout mice
maternal protective behaviour attenuated (latency to attack, time attacking, number of attacks), but not pup directed behaviours (retrieval).
sexual behaviour attenuated but not male male aggression.
ESP-1?
secreted by male mice in tears, detected by females.
increase in sexual behaviour for females when detected.
requires TRPC2.
both male and female amygdala responded, MPA high male response, VMH strong female response.
VMH goes on to produce sexual behaviour response.
ESP1 is not effective in female TRPC2 deficient mice
ESP22
pheromone produced by females in tear fluid.
produced early 2-3 weeks old.
if put onto females, male sexual behaviour towards the female is reduced.
cue to indicate sexual immaturity.
TRP2 knockout don’t show response.
Male mice do not exhibit sexual behaviour to juvenile females (but Trp2-/- do!)
sweaty t shirt study
worse t shirt 2 days, women smelt, reported attraction.
women were most attracted to men with an MHC most dissimilar from their own.
reports were reversed when women were taking oral contraceptives.
smells reminded the women of their own/former mates were more likely to be
MHC dissimilar than MHC similar.
we are driven to have diversity in immune system
where does the neural framework for bonding usually come from?
most forms of bonding are likely built upon the neural framework evolved for infant-mother bonding
oxytocin pseudofunction
trust/love hormone
oxytocin and vasopressin functions?
They act as hormones – secreted from posterior pituitary.
Oxytocin: Labour, uterine contractions, and milk let down
Vasopressin: Water balance
They act as neurotransmitters within the brain.
Oxytocin: Mate and offspring recognition, feeding
Vasopressin: circadian system, sex drive, learning memory
both very old hormones.
oxytocin pathways?
post pituitary to PVN and SCN
oxytocin knockout
social recognition impaired in both sexes.
main olfactory system not impaired
normally male mice get bored of same female if put repeatedly into cage, KO treat her as if new everyday.
can’t recognise her. vice versa.
if test non social olfactory cues, ie scent, they show same acclimitisation to stimuant and get bored.
role of amygdala?
involved in enforcive or affiliative behaviours.
modified by oxytocin
VNO projects where?
AOB accessory olfactory bulb, projects to amygdala
PVN projects where?
amygdala via oxytocin.
amygdala and testosterone/oestrogen?
check out some paper Sano et al 2016
sex steroids priming oxytocin signal?
oestrogen increases oxytocin production, also production of receptors in amygdala.
oestrogen receptor KO mice?
social defects
VNO structure?
sexually dimorphic.
Hormonal cascade from GnRH neurones initiates perinatal testosterone surge in males which masculinises the pathway
Allows sex specific response to pheromones
(male pheromones elicit gene activation in these structures in female mice).
