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 Fearful, timid and withdrawn: a monkey who was reared in isolation from its mother is incapable of normal social and exploratory behaviour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 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 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
