Lecture 29- Disorders of the nervous system II Flashcards
What is known about abuse induced trauma?
-have to provide nurturing environment during development otherwise= permanent defects -orphanage kids, sexual abuse in church -Harlow replicated it in monkey= socially maladjusted
What are the 3 pieces of evidence for the abuse induced trauma in children?
- Time spent in orphanages with conditions of social deprivation correlates with incidence of neurological impairment 2. MRI tractography showing abnormally sparse connections with prefrontal cortex in a healthy child and deprived child (much less) 3. Fearful, timid and withdrawn: a monkey who was reared in isolation from its mother is incapable of normal social and exploratory behaviour
When is the criticial period for normal adult behaviour?
-not when these behaviours are taught or modeled or even seen -much earlier in life -requires tactile-based attachment and nurturing experiences
How is the visual system an example of a learned system?
-visual perception requires experience or learning -it is the learnt present
How do we know that the input from each eye is separated in the LGN and the visual cortex?
-form layers in Visual cortex as well (separated left and right eye) -white= the contralateral black= the non injected eye -need input from both eyes to get depth percetion
Why is depth perception important? (stereopsis)
-get perception of depth up to the length of your arm= helpful with treading needle and other fine visual motor tasks, relies on the inputs going to the right place (still separated etc.) -stereopsis= the ability to detect depth
What was the experiment with a healthy cat and eyes?
- how we get the depth perception
- what if you do not allow info to the visual cortex
- would you get depth perception?
- record activity from cells in V1, looking at lot of neurons, put light on one eye or the other= to see if it is innervated from one eye or both
- 1: only contralateral eye input 25 neurons only
- 7 the opposite
- most neurons responded to both to a degree
—this is what you need to have stereoptic vision
What was the cat eye experiment when one eye was shut for 2.5 months after birth?
- now one eye closed off for 2.5 months
- then open and see how the neurons respond= all the neurons you find only respond to the ipsilateral eye (the one open the entire time) and never from the other
- requirement to have both open
- NR= some were unresponsive
What was the cat eye experiment when the eye was closed in a mature cat?
- if you clos ethe eye when mature 12-38 months
- almost the same as normal
- have streeoptosis
What was the cat eye experiment when the eye was closed for 3 and for 6 days shortly after birth?
- case B:- 6 days only= and still the entire visual cortex was inactive for one eye
- A: 3 days= some input from one and the other but none from both
- must have input from both eyes to have the system working normally
- so it can compare retinal images and gives us sense of depth
What does this picture show?
A: white input= one eye -black input= the other, equal distribution
B:here animal with one eye closed off= unequal dedication of the visual cortex
What is the difference in neuronal appearance in short term and long term monocular deprivation?
- the deprived= bad, open= fine
- same when long and short term
- weird looking to the normal
What were the experimental results with a starbismic cat?
- strabismic= lazy eye
- their visual cortex also weird, very few cells driven by both eyes
- the same pattern as when closed almost
- we only use both inputs as much when something really close range and fine task
What is strabismus?
-lazy eye, eyes misaligned
What does MRI tractography show?
-white matter tracts
What happened to the frog with an extra eye?
-competition for the visual cortex
What is the idea of neural competition in the visual cortex?
- competing in the visual cortex
- there is a period where it really matters, if lot of input then you will outcompete the weak input
- when right eye= lot of input, left eye= weak= the right will outcompete
- here not only LTP, they have many synapses, grow larger!
- the opposite= reduce in size and number
What are the chemical things involved in the V1 neural competition?
- strong input when cell is sensitive to it then
- critical period involve transcription of factros that cause the cell to have more synaptic terminals
- CREB= gene expression
What are the critical periods for some neural systems?
- there are critical periods for many things
- competing inputs and neurons
- perfect pitch, before 7 years
- language, 0-12 months
What causes the behaviour in abused people?
–plasticity in stress response
- amygdala is at the center of this, can learn to associate things via this
- amygdala has potent activation in hypothalamus and pituitary= endocrine activation HPA activation
- amygdala gets sensory input, then goes from basolateral nuclei to central nuclei and from there to the targets associated with stress response
What is the HPA?
-hypothalamus-pituitary axis -input from amygdala
What is part of the stress response? (4)
- HPA activation (via hypothalamus)
- Activation of sympathetic nervous system (via hypothalamus)
- Avoidance behaviour (via periaqueductal gray matter)
- Increased vigilance (via diffuse modulatory systems)
What is he stress HPA axis and its feedback modulation control like?
- cortisol= regulates its release, when lot of cortisol = activates hippocampus= actiavets inhibitory neurons that decrease the cortisol release
- the opposite with amgdala= encourages release
- there is a point where this breaks down, the system
- excesses levels of cortisol= get hippocampus overexcitation= undergo overexcitation neural death= so then cortisol is not controlled, cannot reduce the activity of the stres axis (HPA) hypothalamal pituitary axis
What is the HPA in abused people?
-HPA overactivity is a common finding in depressed patients -it breaks down, too much cortisol in the system -the hippocampal control is not working
What are the 3 pieces of evidence for that abuse impacts the HPA?
- Childhood maltreatment is associated with reduced volume in the hippocampal subfields 2. Reduced medial prefrontal cortex volume in adults reporting childhood emotional maltreatment 3. Interaction of childhood stress with hippocampus and prefrontal volume reduction in major depression
