NESC 3227 Lecture Notes - Adult Stem Cell, Cerebral Cortex, Medulloblastoma

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Published on 17 Apr 2013
School
Dalhousie University
Department
Neuroscience
Course
NESC 3227
Professor
Page:
of 3
March 12th, 2013
March-12-13
1:08 PM
Scoring for ANT
Alerting: No cue - double cue
Orienting: Spatially uninformative cue - spatially informative cue
Executive: Congruent - incongruent
Rehabilitation of unilateral visual neglect
48% of right hemisphere stroke patients have neglect
Severity of neglect predicted functional disability and family burden more accurately than did
extent of brain damage
Anchor technique
Told to focus on marking line on the left side of the page, helping them focus more on left
hemisphere
It works for the task you're working on, but generality is very poor
Spatio-motor cuing
Multiple representations of space in different senses and in motor control
So if you change the sensory inputs to the areas that are damaged, we may be able to use that to
help patients orient to area of space they neglect to orient to
Unilateral neglect and spatio-motor cuing
Used only for persons who do not have hemiplegia
Told to passively or actively move contralateral arm in response to hearing a buzz
o If left neglect, move left hand
o Active is when they're asked to move it themselves
o In passive and electrode on arm causes muscle stimulation to move hand
Unilateral neglect and prism adaption
Displace visual field by small amount (10%) to the right
o So some left visual field items are shifted over
Individual asked to make pointing gestures to stimuli in their left visual field
Pointing to midline improved when wearing prisms
When removed, the improvement was still observed
Update on prisms and neglect
Patients asked to wear prism glasses at home for 2 weeks for this treatment
Over the treatment, peoples contralateral neglect improved
Although there was improvement on the task, activities of daily learning showed no form of
improvement
Possibly because to use prisms maximally, the patient needs to be able to see their hand as a form
of visual feedback
Eye movements tell only half the story
3 patients 12 months after right hemisphere stroke adapted to prisms
Pointing, cancellation tasks, and emotional expression on chimeric faces
Results showed eye movements improved, moving towards both visual fields
However did not have any effect on peoples perception of chimeric faces
o So it may have improved eye movement neglect, but did not affect perceptional neglect
***Start Chapter 23***
Cell birth or neurogenesis
The ectoderm is where cells begin being made in the neural tube
Neurogenesis lasts about 4.5 months in humans
Brain lesions during this period are much less devastating than they would be after neurogenesis
Neural migration
In radial migration, cells in the neural tube move toward the cortex by following radial glial
processes
Cell layers in the cerebral cortex
Layers develop from the inside out
o Layer 6 laid down first
Incomplete migration:
Ectopic neurons, heterotopias
o Clumps of neurons in the white or grey matter that did not make it to their final destination
o Brain warts or ectopic neurons
These ectopic neurons lead to heterotopias
Cell differentiation
Once neurons reach their location, they differentiate into what they'll need to be
Lesions during the differentiation period are more devastating to later function
Neural maturation
Growth of dendrites and axons
Axonal growth faster because they usually have to travel farther
o Once connected to target, it helps direct the growth and connections made by the dendrites
Dendritic branching increases significantly over the first two years of life
Synapse formation
Many more synapses are produced than actually needed
o Peaks at around 2 years
o After that the numbers begin declining (as much as 50% in puberty)
Pruning
Cutting of unneeded connections
More cell death occurs in the primary somatosensory than in the frontal lobes
Myelinogenesis
Occurs until 18+ years of age in humans
Increase speed of neural connections
Adult neurogenesis and cell differentiation
Stem cells produce new neurons in two regions
o Olfactory bulbs
o Hippocampal dentate gyrus
Important to note that olfactory neurons are in contact with external environment, and may be
killed by external toxins. So as long as there is scaffolding in place, these neurons can regenerate
o So when sheared from brain trauma, don't regenerate
Do adult stem cells function
Very likely do
Researchers had patients who were about to have brain resections done
Dissected out areas of dentate gyrus and cultured those stem cell neurons
o About half of them had high proliferation
Of those, about half differentiated into neurons
o The other half had a very low proliferation
Patients with a high rate of stem cell proliferation scored normally on the sodium amorbital
memory test
Patients with low proliferation scored quite poorly
o Correlation is extremely high
Gliogenesis gone wild
In tumors, signal that tells cells to stop proliferating gets lost
Creating very dense ball of cells occupying some space
Tumors in the posterior fossa
Type of tumor called the medulloblastoma
o Embryonic tumors have a likelihood of being discovered peaking at 10 years
o Glial tumors usually peak after 18 years in adulthood
Shoves all the soft tissue of the brain sideways
o Causing a shift in the midline
Can cause tonsillar herniation
o Cerebellar tonsils are forced down hole in base of brain, compressing brain stem
Effects of early diffuse brain injury
Whole brain radiation in childhood seems to impair further development
Progressing in the past 20 years
Quality of living decreased in 70% of children treated with whole brain radiation
Less radioactive therapy lead to better outcomes

Document Summary

Orienting: spatially uninformative cue - spatially informative cue. 48% of right hemisphere stroke patients have neglect. Severity of neglect predicted functional disability and family burden more accurately than did extent of brain damage. Told to focus on marking line on the left side of the page, helping them focus more on left hemisphere. It works for the task you"re working on, but generality is very poor. Multiple representations of space in different senses and in motor control. So if you change the sensory inputs to the areas that are damaged, we may be able to use that to help patients orient to area of space they neglect to orient to. Used only for persons who do not have hemiplegia. Told to passively or actively move contralateral arm in response to hearing a buzz. If left neglect, move left hand: active is when they"re asked to move it themselves. In passive and electrode on arm causes muscle stimulation to move hand.