PSYCH 1XX3 Final: Neuroscience 2 Module
24 Nov 2018
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Neuroscience 2 Module
Unit 1: The structure of the brain
Terminology of neuraxis
• In humans, the nervous system axis, or ‘neuraxis’, curves.
• Dorsal-always refers to back of the axis.
• Ventral- front of the axis or ‘to the belly’
• Because of the curve in neuraxis,
o At level of the head= dorsal up
o At level of spinal cord= dorsal is
to the back.
• Rostral -towards top of the axis.
• Caudal- towards bottom of the axis.
• Medial- locations in brain that are
more central or towards the midline of
brain.
• Lateral- Regions towards outside of
brain.
• These terms can be combined to locate
a very specific brain region. For ex: the
medulla is a region in the hindbrain
which can be divided into several sub-regions.
• One sub-region: rostral ventral media medulla.
• Break it down: rostral (towards the top), ventral (in front of the neuraxis), and
medial (towards midline of brain)
• Dorsal- locations at top of brain.
• Rostral-locations at front of brain
• Lateral-locations at side of brain
• Caudal-locations at bottom of brain.
Can neuroscience explain sibling’s drastically different behaviors?
• Behaviours may differ according to messages delivered by neurotransmitters.
Unit 2: Studying the brain
Special techniques exist for studying the structure and function of the brain
• Most invasive research in neuroscience is not done with humans, vast majority
known about nervous system comes from work with animals, tissue or more reduces
preparations.
• In this module: investigate lesion studies, single cell stimulation and recording, and
popular neuroimaging techniques.
Brain injury links brain anatomy with behavioural deficits.
• Neuroscientists have been interested in case studies of accidental brain injury which
can link anatomy with associated cognitive and behavioural deficits.
• Phineas Gage was a foreman of a railway construction crew, in charge of using
explosives to remove large sections of rock from path of railroad.
o was athletic, intelligent, full of life and very likeable.
o Became a victim of traffic accident, resulting in the blasting of a 3- foot iron
rod completely through his left cheekbone and through his skull.
o He survived except for some loss of vision and facial disfigurement.
o But after recovery, his friends barely recognized him.
o Once upbeat, polite and caring now prone to selfish behavior and bursts of
profanity. Become erratic and unreliable and had trouble forming and
following plans.
o This case provide support for the view that brain has specialized structures
for complex behaviours.
Lesion studies must be specific to target function of a brain region
• Limitation of this case studies of human brain lesions is that they are rarely isolated
to specific structures. Make more difficult task of assigning impaired functions to
specific brain areas.
• Problem can be overcome by studying specific brain lesions induced in animal
models. In such studies, researcher destroys, removes or inactivates a defined brain
region and observe the result on behavior.
• The accuracy of this emerging understanding of structure and function can depend
on precision of lesion.
• Because brain is so highly interconnected, a variety of behaviours are affected by a
single lesion.
Targeted electrical stimulation can provide insight on brain function
• Another approach is to electrically stimulate an area of the brain and observe the
result on behavior to build an anatomical map related to function.
• This technique used by Dr. Wilder Penfield as he performed brain surgery to treat
patients with severe epileptic seizures.
Single cell stimulation helped map behavior to specific brain regions.
• He revolutionized techniques in brain surgery as he perfected his ‘Montreal
procedure’, to treat patients experiencing severe seizures. In doing so, he had to be
sure that critical areas of the brain were left intact.
• He used a thin wire carrying a small electric charge to stimulate the cortex. This
stimulation lead to individual neurons to fire and Penfield could accurately map
perceptual processes and behaviors to specific brain regions.
• Ex: if area of visual cortex was stimulated, patient reported seeing flashes of light
and if an area of the motor cortex stimulated, patients experiences a muscle twitch.
• His work revealed specific function to previously unmapped regions of the brain.
Single cell recording reveals the function of individual neurons
• Electrodes can be used to record ongoing electrical activity in brain using single cell
recording techniques.
• A small electrode inserted into the nervous tissue of a live animal model with its tip
held just outside cell body of individual neuron.
• From this electrode, neural activity is recorded while animal performs a task or a
stimulus is presented.
• Pattern of firing reveals a particular neuron’s functional role.
• Ex: Hubel and Wiesel presented cats with specific visual stimuli while recording from
single cells in the visual cortex. This way individual cell types were identified that
responded to specific categories of visual stimuli.
Large-scale brain structures are studied using neuroimaging techniques
• Although single cell recording can reveal function linked to firing of a special neuron,
it provides information about only a limited area in the brain.
• To study large-scale structure and function of brain regions, neuroscientists use
structural and functional techniques.
CT scan produce structural slices of the brain
• First structural neuroimaging technique developed was computed tomography (CT).
• During CT scan, a series of X-ray slices of the brain are taken and pieced together to
produce a relatively quick and inexpensive picture of the brain.
• Scans often helpful to diagnose brain injuries.
MRIs provide higher resolution images of brain
• Major limitation of CT scan is its relatively low resolution. It’s very difficult to
examine fine brain anatomy with CT scan and so not often used in neuroscience
research.
• For more detailed structural image of the brain, neuroscientists use MRI or magnetic
resonance imaging. In MRI, powerful magnetic fields are generated, which align
hydrogen atoms found throughout the brain. While these atoms aligned, MRI used
to localize tissues precisely throughout the brain.
PET scans display functional role of brain structures.
• Cognitive neuroscientists use functional imaging techniques such as position
emission tomography (PET scan), to learn how brain function relates to cognitive
tasks such as language and memory.
• In PET scan, a radioactive tracer of glucose of oxygen is injected into the
bloodstream. The radioactive molecules make their way to brain and used in
metabolic processes which are detected by PET scan.
Document Summary
Can neuroscience explain sibling"s drastically different behaviors: behaviours may differ according to messages delivered by neurotransmitters. Special techniques exist for studying the structure and function of the brain: most invasive research in neuroscience is not done with humans, vast majority known about nervous system comes from work with animals, tissue or more reduces preparations. In this module: investigate lesion studies, single cell stimulation and recording, and popular neuroimaging techniques. Become erratic and unreliable and had trouble forming and following plans: this case provide support for the view that brain has specialized structures for complex behaviours. Lesion studies must be specific to target function of a brain region: limitation of this case studies of human brain lesions is that they are rarely isolated to specific structures. Make more difficult task of assigning impaired functions to specific brain areas: problem can be overcome by studying specific brain lesions induced in animal models.
