Week 6 Flashcards
(40 cards)
1
Q
What were some of the major findings regarding Harry Harlowe’s experiments on attachment?
A
- Regardless of food being present on the wire mother, the baby monkeys still sought out the comfort provided by the cloth mom instead
- This suggests that food is not sufficient to induce attachment
- Also studied impacts of social isolation on long-term behaviour and discovered extreme deficits
- Also found that monkeys who depended on cloth mom still had developmental deficits and exhibited self-soothing behaviours
2
Q
Considering the deficits uncovered from the cloth mom monkeys, what are 2 key components to help promote normal brain development in these monekys?
A
- Required touch AND motion from maternal figure to encourage normal brain development
3
Q
What was the result in cognitive development of the Romanian orphans that were adopted after 6 months?
A
- There were significant drops in IQ compared to those adopted before 6 months
- Illustrates the critical periods of development and the importance of caregiving behaviours
4
Q
What were the major impacts of Romanian institutionalization on the development of the orphans?
A
- Increases in anxiety, depression, ADHD, and attachment disorders
- Overall reduction in grey and white matter
- Reduction in frontal cortex thickness
- Reductions in structural connectivity (DTI)
- Growth stunting (also compounded by poor nutrition)
5
Q
What are some important attributes regarding maternal care in rats?
A
- It’s normally distributed
- Includes specific activities such as arch back nursing (allows pups access to mom’s tummy) and licking and grooming (helps eliminate wastes from pups and promotes development)
- A heritable trait
6
Q
What does it mean to say that maternal care is a heritable trait in rats?
A
- Moms high for LG-ABN have daughters (and granddaughters) who are also high for LG-ABN
- Moms low for LG-ABN have daughters (and granddaughters) who are also low for LG-ABN.
7
Q
What is discovered when we compare the outcomes in stress response between moms with high and low LG-ABN?
A
- Stress response to restraint is lower in LG-ABN moms
- Inverse correlation between amount of care and plasma corticosterone levels (found in blood) (i.e., as LG-ABN increases, the CORT levels decrease)
- Pups from high LG-ABN moms perform better in the Morris Water Task, even at 24 months of age (old)
- Also correlated with greater synaptic density in the hippocampus.
- High LG-ABN pups able to spend more time in teh quadrant where they know the platform should be once the platform has been removed
8
Q
What’s the cross-fostering design in rats?
A
- A way to determine how postnatal environments impact the development of rats
- Moving pups around and to and from moms with either high or low LG-ABN behaviours and assessing the outcomes
- Then measure the time spent by offspring in the centre of an open field
9
Q
What was one of the major outcomes of the cross-fostering design when looking at varying levels of LG-ABN behaviours in moms?
A
- When high LG-ABN pup was given to a low LG-ABN dam, the pup still spends limited time in open field. Not the case for a low LG-ABN pup given to a high LG-ABN dam
- Illustrates how there are more than just genetics at play
- Also further evidence for how a change in behaviour indicates a change in brain
10
Q
What are epigenetics?
A
- The study of heritable changes in phenotype or gene expression caused by mechanisms other than changes in the underlying DNA sequence
- Not changing the genome, only modifying gene expression
11
Q
What are the three major mechanisms of epigenetics?
A
1) Histone modification - methyl groups added to tails of histones, which may block/restrict DNA from being transcribed
2) DNA modification - methyl groups bind to CG base pairs to block transcription
3) mRNA modification - ncRNA binds to mRNA, preventing translation from occurring
12
Q
What should be noted about methylated cytosine nucleotides in the 5 prime promoter regions of DNA?
A
- The promoter regions now unavailable for transcription factors
- Methylated genes are less active than unmethylated ones
13
Q
What are the relevant genes that must be considered when considering epigenetics?
A
- Estrogen and oxytocin receptors in mPOA - Moms behaviour increases the female pup’s sensitivity to estrogen and oxytocin
- Glucocorticoid receptors in the hippocampus
- BDNF and NMDA receptor subunits
14
Q
Which major system in the body is responsible for mediating the stress response?
A
- HPA axis
15
Q
How does the HPA axis work?
A
- In the presence of a stressful event, the hypothalamus releases cortico-releasing hormone to the pituitary gland, which in turn releases adreno-corticotropic hormone to the adrenal gland, which in turn produces cortisol.
- The hypothalamus then monitors the levels of cortisol to control if more should be produced
16
Q
What is the significance of the hippocampus in the HPA axis?
A
- The HPC acts as the hard breaks to the HPA axis to shut down the stress response if needed
- The HPC has the highest density of glucocorticoid receptors in the brain, so is very sensitive to changes in cortisol levels and can intervene if needed.
- Decreased gCr = hyperactivity in the HPA axis
17
Q
What’s the significance in the changes in methylation found between high and low LG-ABN mothers?
A
- The degree of methylation can be indicative of the density of glucocorticoid receptors found in the brain
- These receptors play an important role in mediating the stress response when monitoring the activity in the HPA axis, courtesy of the hippocampus.
18
Q
How can different types of housing impact the stress responses of offspring from high and low LG-ABN mothers?
A
- Regardless of the pups being from high and low LG-ABN mothers, enriched housing developed pups to exhibit similar behaviours, such as the time spent in the inner field. The enriched housing mediated the stress response
- Regardless of the pups being from high and low LG-ABN mothers, impoverished housing developed pups to have a heightened stress response regardless of what genetics indicate
19
Q
What’s the take-home message from environmental impacts on stress response?
A
- Regardless of what behaviours genetics indicate, these behaviours can be mediated and levelled by the factors found in the environment
- Ideally, environmental programming helps prepare the animal to survive the environment they were raised in (ex. maybe beneficial to have a heightened stress response in an impoverished environment)
20
Q
What’s the impact of promoting methylation in high LG-ABN mothers?
A
- Use methionine to increase methylation
- Would observe a drop in glucocorticoid receptors in high LG-ABN offspring
- Would then observe an increase in stress behaviours, such as freezing
21
Q
What’s the impact of removing epigenetic marks in low LG-ABN mothers?
A
- Inject a histone deacetylase inhibitor (TSA)
- Would see a decrease in methylation (able to transcribe more in the genome)
- Therefore would see an increase in GR density
- This would lead to a lowered stress response
22
Q
What are the main functions of oxytocin in reproductive and parental behaviour?
A
- Causes uterine contractions (released during orgasm)
- Can be used to induce labour
- Regulates the milk letdown response (triggered by nipple stimulation)
23
Q
Where is oxytocin produced?
A
- In the mPOA and the ventral bed nucleus of the stria terminalis (vBNST)
24
Q
What may occur is oxytocin levels in a mother rat if changed?
A
- Maternal behaviour is potentiated if oxytocin is given centrally (onset of behaviour is accelerated)
- Oxytocin antagonist disrupts maternal behaviour onset
- Blocking oxytocin doesn’t totally eliminate maternal behaviour, but some are impaired
25
What behavioural outcomes were observed when an oxytocin receptor knockout was performed in mice?
- Pup retrieval impaired (takes a lot longer)
- Nursing behaviour intact but no milk ejection
26
What guides moms to perform pup retrieval?
- Guided by olfactory and auditory cues from pups
- Pups perform ultrasonic cries when cold and outside the nest
- Retrieval behaviour is dependent upon sensory input from vibrassae
27
What is unique about the vibrassae?
- It's a sense organ
- Representation in somatosensory cortex where there is a one to one connection of whisker to barrel cells in the olfactory bulb
- "Whisking" movements allow exploration of objects and the environment (how they feel their way around the space)
28
What would happen if one of the whiskers were plucked?
- The activity in the corresponding barrel cell would decrease until the whisker in that region to grow back
- Evidence of neuroplasticity
29
What did the whisker-dependent texture discrimination study illustrate?
- A version of novel object performance
- Rats were able to identify differences in sandpaper texture based on their whisking behaviours alone
- Further demonstrates that whiskers are important and active systems
30
What happens when lidocaine (local anaesthetic) is injected into the masseter muscles versus the vibrissal pads?
- In masseter muscles (near jaw) = Retrieval behaviour is unimpaired
- In vibrissal pads = There's a behavioural impairment (can't retrieve pups)
31
Over time, how do virgin rats react to pups?
- Given enough time (3-4 days) they will tolerate proximity
- 7 days - retrieves, builds nests, licks, grooms, and huddles over pups
- We see a suppression of initial aversion and promotion of approach behaviour (sensitization has occurred)
32
What inhibits maternal behaviour in virgin females?
- Olfaction
- Also seen in human mothers. Able to quickly identify the smell of their own babies after a short period of time
33
How can we test to ensure that olfaction inhibits mediating maternal behaviours
- Remove fluctuating hormones by operating a hysterectomy and ovariectomize the rat
- Inject zinc sulfate destroys the olfactory epithelium
- Doing so removes an olfactory aversion that virgin rats initially have
34
What does inhibiting olfaction tell us about it's role in maternal behaviour?
- Illustrates that it is not necessary for maternal behaviour
- Anosmic moms will care for pups, although there are some deficits in doing so (shows that there are many systems at play)
35
What are the two main brain regions involved in mediating maternal behaviour?
- The medial preoptic area and the vBNST
- Responsible for relaying info from both hormones and sensory systems
36
What does lesions to the mPOA and the vBNST cause?
- Disrupts all maternal behaviours.
- Although other behaviours remain intact (ex. food hoarding)
- mPOA and vBNST likely a part of a common pathway
37
What does implantation of estrogen in a lesioned mPOA in a virgin lead to?
- Implantation of estrogen facilitates maternal behaviour
38
Why would lesioning the medial amygdala impact increase maternal behaviour in virgin rats?
- The medial amygdala feeds into the mPOA
- lesioning this connection would allow maternal behaviour to occur since the odour of pups isn't being monitored by top-down processing (i.e., can't inform virgins of their aversion to pups)
39
Why is the ventral tegmental area important in maternal behaviour?
- Lesions disrupt maternal behaviour. Can do so by turning off VTA with a GABA agonist
- This disrupts retrieval behaviour
- Does not disrupt nursing
- Don't know what exact role it plays in maternal behaviour, but know it is important
40
How is the VTA involved in circuit connectivity in maternal behaviour?
1) mPOA projects through the VTA to motor areas
2) Sensory information passes close to the VTA
3) Part of the reward pathway (DA neurotoxic lesion disrupts behaviour)
