Term Test 1 Vedran’s office hours: Thursday, Nov. 4 (10-12) and Tuesday, Nov. 9 (2-3).
Lecture Outline What is parental behaviour? Rat model Hormones Experience Reward Neural circuitry of maternal behaviour Ontogeny and maternal behaviour Human maternal behaviour Sensory changes in new mothers Hormones Ontogeny
What is Parental Behavior and Why are Interested in It? Parental Behavior - any behavior toward a reproductively immature organism that increases the likelihood that the immature individual will survive to maturity. Evidence suggests that early life environment (parental care) is important for development 30% of mothers who were abused, abuse their own babies 5% who were not abused, abuse their own babies (Knutson, 1995) Sensitive mother - securely-attached infant (Goldberg) Securely-attached infant--- relationally -secure adult (Waters et al., 2000)
Why are animals parental? Ultimate reasons: passing on genes Proximal reasons: protection nutrition temperature regulation shelter learning (instincts)
Maternal vs. Paternal vs. Biparental Environmental demands have played a role in determining parental styles Maternal Behavior – mothers Paternal Behavior – fathers Biparental – both parents Alloparenting - parenting given by individuals that are not the biological mother or father
PATERNAL BEHAVIOUR reversed roles: highly advanced paternal care examples: pipefish seahorse stickleback fish
BI-PARENTAL CARE both parents contribute to raising the offspring examples: penguins ring doves California mice voles Marmoset monkeys Humans
Differences Between Species in the Amount of Care Provided
Three Different Types of Maternal Care in Eutheriean Mammals (based on the type of offspring) Precocial Born at an advanced stage of development Little or no help is required for survival ex. lambs, other ungluates Hider-type vs. follower-type Altricial Born at an early stage of development. Helpless require substantial parental care to survive ex. Dogs, rats, rabbits Third type - can also be semi-precocial/semi-altricial; ex. Humans and other primates.
Description of Rat Maternal Behaviour Nest building Pup retrieval Pup licking Nursing postures Normally these behaviors are evident soon after parturition Rats that have never given birth (nulliparious or virgins) do not show these behaviors
The Onset of Maternal Behavior HIGH LOW Virgin / onset of pregnancy Day 16 parturition
Parabiotic Preparation preparation where blood is exchanged between a rat that was maternal and a rat that was not maternal Soon after virgin rat will show maternal behavior Conclusion: blood- borne factor is important in the induction of maternal behavior in rats
Other Hormones – Glucocorticoids (Corticosterone) Corticosterone (moderate levels) facilitates maternal pup licking in rats
Maternal Responsiveness HIGH LOW Virgin / onset pregnancy Day 16 parturition P E CORT OXY PRL
Postpartum Experience Soon after the parturition the hormones that initiated the onset of maternal behavior begin to decrease So what maintains the maternal responsiveness? Can experience with pups maintain maternal responsiveness? Non-partum multiparous female rats are responsive to young pups How much experience is necessary so that rats are maternal responsive in the absence of hormones?
PARADIGM TO ASSESS MATERNAL EXPERIENCE EXPOSURE PHASE Experience or No experience separation TESTING PHASE retention testing Latency to respond maternally to pups Parturition 0.5h, 1h, 2h, 24h 10 days
Learning to Maternal – Maternal Memory (Rats need about 30 min of interaction with pups to acquire the experience) Orpen & Fleming, 1987
Maternal Experience Effect Maternal Experience Effect: A brief interactive experience with pups post-partum sustains maternal responsiveness throughout lactation and beyond (at least 30 min). Mother has to be interacting with pups in order to acquire this experience. Seeing, smelling and hearing the pups is not enough (if pups are placed in perforated Plexiglas box) Cyclohexemide (protein synthesis inhibitors) injections soon after maternal experience block the maternal experience effect (prevents cosolidation)(Li & Fleming, 2004) Lesions of nucleus accumbens will also prevent consolidation (Li & Fleming, 2004)
Pups Are Rewarding to New Mothers Mothers will bar press for pups, whereas virgin rats will not Rewarding properties of pups can be blocked with administration of dopamine antagonists
Like other motivated behavior, maternal behavior is dependent on the hypothalamus Specifically, medial preoptic area (MPOA) of the hypothalamus is the most important nucleus for maternal behavior Lesions of MPOA will abolish maternal behavior Neural Circuitry of Maternal Behavior
Cortical lesions do not significantly impact maternal behavior Amygdala inhibits the activity/behavior produced by the MPOA Multiple sources of evidence: electrolytic lesions destroy all the tissue (cell bodies and axons) What could a problem with concluding that MPOA is the brain area for maternal behavior? The excitotoxic lesions – N-methyl-DL-aspartic acid (NMA)
Further Evidence for Involvement of MPOA in Maternal Behavior Looking at activation of brain areas (cells) associated with maternal behavior Looking at activation looking at expression of proteins produced by immediate early genes (IEG) (e.g., c-fos gene produces protein called Fos) Fos protein peaks 1-2 after cells have been active Immunohistochemisty (IHC) – labeling Fos protein using antibodies
Typical Fos Study 1. Let the animal engage in a particular behavior 2. 90 min later sacrifice the animal 3. Perform IHC and look for expression of Fos 4. Control conditions involve control animals being exposed to all the same conditions except the behavior of interest 5. Use subtractive technique (activation in experimental brain – activation in control brain = brain activation associated with behavior of interest).
Post-partum Maternal Experience is Associated with Fos Expression In Response To Distal Pup Cues or Pup- associated Cues in MPOA Day 1: experienced pp rats were exposed to pups (p) box(b),cage (c) for two hours; inexperienced animals were not Day 10: animals exposed to pups in a box in new cage (pbc), box in cage (bc) or home (h) for 2 hours Animals sacrificed for c-fos icc Fleming & Korsmit, 1996
MPOA has receptors of hormones thought to be involved in maternal behavior Neural Circuitry of Maternal Behavior
Sensory Control of Maternal Behavior Sensory stimuli from pups (touch and smell in particular) are important for maternal behavior Fos studies show activation in somatosensory cortex in maternal rats Removal of olfactory bulbs reduces maternal licking in postpartum rats
Sensitization of Virgin Rats Initially virgin rats avoid pups Might show aggression / cannibalize pups However, if virgin rats are exposed to pups for days they will eventually show maternal behavior (sensitization) Why might this be the case? Neophobia – fear of new things (pups sight, smell) Olfactory bulb removal facilitates sensitization process in virgin rats (or infusion of ZnSO4) Amygdala lesions also facilitate maternal behavior in virgins If virgins are neophobic, does that mean that new mothers are less neophobic? Yes, less fearful of novel envioronments, food etc.
Ontogeny – Early Life Experiences with One’s Own Mother There a positive correlation between the maternal “style” of mother rats and the maternal “style” of their daughters Genetics or experience?
ARTIFICIALLY-REARED (AR) and MOTHER-REARED (MR) GROUPS AR (MIN)- AR, with two AGL strokings (days 4-16) AR (MAX)-AR, 8 dorsal MR (sham)- AR sham surgery MR (intact)-MR
AR PUPS, RAISED WITHOUT MOTHERS, SHOW DEFICITS IN ADULT MATERNAL BEHAVIOR MATERNAL-LIKE LICKING STIMULATION REVERSES THESE EFFECTS *# # * * * * #
Artificial-Rearing Reduces Fos in Response to Pups in MPOA - Replacement ‘stroking’ reverses some of these effects NUMBER OF CELLS * * Gonzalez et al. in prep
Maternal Behavior in Humans Many cultural differences – no clear set of maternal behaviors Affectionate behaviors: patting, cuddling and kissing etc. Instrumental behaviors: changing diapers, changing the clothing and burping the infant etc.
Sensory Changes in New Mothers Compared to non-mothers, new mothers find odors associated with infants more pleasing (or less aversive): general body odor, urine and feces New mothers are good at identifying the odor, cries and tactile features of their infant
Cry Study: Affect (VAS) and Heart-rate Responses to Infant Cries and Control stimuli Heart-rate monitor cry stimuli VAS
Maternal Behavior in Humans – Hormones: Cortisol
Mothers with a positive shift in the ratio of estradiol to progesterone (i.e., the ratio increases) show more positive attachment to their infants than mothers whose pregnancy endocrine profile shows a negative shift (or no change) Maternal Behavior in Humans – Hormones: Estradiol and Progesterone
Mothers Who Received Continuous Care by at Least One Caregiver Prior to Age 12 Show More Affectionate Touching but less Instrumental Touching with their Infants Maternal Behavior in Humans – Ontogeny
Some Questions To Think About: What is the role of hormones in rat maternal behavior? What maintains the maternal behavior in the rat? What is the evidence for the involvement of particular brain structures in maternal behavior? What is the role of early life environment? What is the role of hormones in human maternal behavior? What is the the role of early life environment in human maternal behavior?