Lecture 2 Flashcards
An article was covered in class and showed brain tissue growth-red and decrease-blue over time. What were the key takeaways from this? (4)
- see that brain is growing and increases in size until teen years
- also occurs in animals (but smaller volume)
- indicates that brain is growing and that this developmental process is ongoing
- the developmental processes are very susceptible to environmnetal stimuli
what is neurogenesis?
formation of new neurons in the brain
what article was provided in class as evidence for adult neurogenesis?
hippocampus and olfactory bulb in adult rodents
- controversy: is there really adult neurogenesis in adult humans?
what were the conclusions of the article covered on learning and brain plasticity? (3)
- evidence that suggests that representation of hand digits can be modified by training
- comparing dipole strength of regions representating finger position and can be stored in string players
- if you use a finger more, its representation strengthens/increases
how does allosteric load relate to the impact of chronic stress on our bodies?
- bc chronic stress can lead to long term increase of cortisol, this can induce changes in the brain that have pathological changes
- NE is responsible for acute stress responses (like flight or fight response) -> cortisol helps bring aroused state back to baseline
- if you have high level of cortisol due to stress, can have adaptation changes (that used to be healthy) that are maladaptive
what is allostatic?
low allostatic load (also involved in brain plasticity)
what results were shown to explain the relationship btw life events and mood disorders?
Negative life events near the onset of depressive episode
Negative life events associate with the severity of cognitive impairment of depression
Levels of cortisol in plasma and CRH in aCSF are increased in patients with depression
When you compare the number of negative life events in months before an episode of depression, the trend is ____ for the general population while ____ for those with depression and suicide attempters
steady; increased
explain the results of the following study (4):
Injected cortisol in rats to induce stress and compared the dendritic representations of CA3 in the hippocampus
- see more changes after chronic injections of cortisol –> see shrinking of dendrites in ca3
- these changes also found in aging –> suggests that chronic stress might make you age faster
- when they quantify the dendrites from the cell body, dendrites away from the cell body are shortened (reduce in length, size)
- if you remove cortisol/stress, the dendrites grow back (in rats) –> dynamic process
what might stress induce for it to be a risk factor for mood disorders?
- using scans to measure brain volume in people with diff mental dx (ie dep)
- meta analysis supports findings of animal studies that theres a decrease in hippocampal volume in people with depression
who were the subjects in the study on the impact of traumatic events (PTSD) on brain health?
- ExP+ : combat exposed subjects WITH ptsd
- UxP+ : co-twins of ExP+ with NO ptsd
- ExP- : combat-exposed subjects with NO ptsd
- UxP- : co-twins of ExP- with NO ptsd
who were the 3 possible scenarios in the study on the impact of traumatic events (PTSD) on brain health?
1: ptsd is related to stress on hippocampus – expect those with ptsd to have smaller hippocampal volume
2: some genetic makeup causes smaller hippocampus to begin with – expect both twins (co-twin WITH and WITHOUT) to have smaller hippocampus
3: whether u have combat experience (independent of ptsd or not) you will have smaller volume
what were the results of the study on the impact of traumatic events (PTSD) on brain health?
found similar relationship: even without experience of combat, size of hippocampus of twin can predict your vulnerability to ptsd
- second scenario is supported by findings
lower hippocampal volumes for twins with ptsd
the presence of _____ factors –> more biological factors that could explain our vulnerability to stress
vulnerability
what are characteristics of stress resilient mice?
- lower HPA axis activity
- higher exploration
- lower anxiety
- lower submissive behavior
what are characteristics of stress resilient mice?
- greater HPA axis activity
- lower exploration
- greater anxiety
- greater submissive behavior
what is early life stress?
Encompasses early traumatic experiences during childhood and adolescence
what are the subtypes of ELS? (5)
emotional abuse, physical abuse, sexual abuse, emotional neglect, and physical neglect
what are the symptoms of those who experienced ELS?
internalizing symptoms (e.g. anxiety, avoidance), externalizing symptoms (e.g. aggression, hyperactivity), and social impairment
ELS ____ the risk of psychiatric disorders
increases
what were the results of the study on ELS on depression?
individual with short form SERT has high risk but ONLY when they experience child maltreatment
indicates that while genetic factors can make you more susceptible, it also has to do with their environmnent
how did they study ELS on brain development?
study individual differences in how moms care for their pups and see if changes in maternal behaviours impact the expression of behaviour in the pups (related to mental dx)
individual diff: some moms spend less time grooming/licking
what were the maternal effects on the HPA-axis?
GR are receptors for glucocorticosteroids (low affinity receptors that detect stress levels of cortisol)
in animals with low LG, have higher level of cortisol
increase in GR in the high-LG offspring in the hippocampus
–due to negative feedback system
what was the conclusion of the study of epigenetic programming by maternal behavior?
low LG pups had more methylation and could be reversed if placed in the care of high LG moms
what was the conclusion of the study on epigenetic regulation of GR in humans?
when suicide patients receive childhood abuse, show similar modifications to GR in human brain
els can have impact the particular genes (dna-methylation) that have long term effect on GR
what were the 3 notable conclusions for adult neurogenesis?
1965: used H3-thymidine to label new born neurons in the dentate gyrus(DG)
1998: used bromodeoxyuridine (BrdU) to label new neurons in adult human DG
2013: examined C14 turnover in human hippocampal neurons to reveal adult neurogenesis
2018: used markers of progenitor cells to show undetectable neurogenesis in adult human DG
what did they find in the study on active neurogenesis in adults (nuclear bomb)?
for people born before the event, if they live through the period, the radioactive content of the cells is higher than base since some cells form during the period of high C14
for people born after the rise, see the opposite: as they grow older, they have new neurons formed as the radioactive levels decrease
what is the ongoing debate about adult neurogenesis?
maybe we dont need a lot of neurogenesis, but the process is still there (maybe its just so slow or minimal that its hard to detect)
what is novelty suppressed feeding?
way to study anxiety in the mice
put bright lamp above container – they hate bright light so they avoid going to the center to get the food –> but theyre hungry so creates dillema
latency suggests how anxious the mouse is
how did they use novelty suppressed feeding to study depression?
tx animals with diff antidepressants (including prozac)
found that shock tx does not reduce the latency of anxiety –> only chronic tx helps
suggests that long term antidep tx can reduce anxiety
what were the results of the study on novel suppressed feeding?
X-ray treatment led to a reduction in cell proliferation in the SGZ, with no significant effect on the SVZ
apoptosis was selectively induced in the SGZ following X-ray treatment.
antidepressants reduced latency in sham but not hippocampal-irradiated mice
irradiation of brain regions rostral or caudal to the hippocampus did not prevent the effects of antidepressant treatment on latency in the NSF test
what produced the same effects as antidepressants?
blocking neurogenesis
animals without knock out, increase in social interaction but in those knock out (more new born cells) have less social interaction and increased anxiety
what is the impact of allopregnanolone?
potentiate gaba
gaba relates to brain inhibition –> help you sleep
how does gaba relate to postpartum depression?
15% of women may suffer of post-partum depression after giving birth
shown in animals and humans that it has to do with the impact of steroids on gaba receptors
during preg, you have high levels of progesterone
problem: level of progesterone decreases drastically after birth –> so sudden drop in inhibition
what is chronic social defeat stress in research methods?
natural stressor in rats is dominance/aggression in males
after mice experience the aggression, show depressive behaviour
house them together with a partition afterwards which is supposed to be highly stressful
what is the social interaction test?
later on, some mice will try to avoid the white mouse
animals that were stressed will avoid the white mouse
some mice after being stressed will still go see the white mouse
what pathways might be related to social stress in rats?
NAc in striatum and ventral hipp, mdt and pfc (these three send projections of NAc to control activity)
what were the results of the study that looked at stress and the NAc?
compare nb of activated neurons in the regions that project to the nac
nb of active neurons decreases significantly in stressed animals in the vHIP
also studied activity of cells of these regions that project to nac
- in the vHIP, there are more activated cells in the stressed animals
implies that the vHIP to the NAc (bc of the increase in activity) make the naimal more susceptible to stress
when the VHIP activity is _____, the mice interact more with the aggressive mouse
reduced
how does TMS work?
works for regions close to the skull (ie cortex) –> stimulation to activate or suppress activity
how can you induce neuroplasticity for treating mental disorders?
part of auditory activity has been related to auditory hallucination – try to use tms to reduce these
can do deep brain stimulation by implanting electrodes in the brain – useful for treating PD and dep/alzheimer’s
