PSYCO275 Chapter Notes - Chapter 5: Photographic Emulsion, Intraperitoneal Injection, Immunocytochemistry
6 Jun 2018
School
Department
Course
Professor
PSYCO 275 - Chapter 5
Part One: Methods of Studying the Nervous System
●Methods of Visualizing or Stimulating the Living Human Brain
○X-Ray-Based Techniques
■Only the unabsorbed portions of the beam reach the photographic plate
■X-ray photography is effective in characterizing internal structures that
differ greatly from their surroundings (ex. Revolver in a suitcase full of
clothes)
■Contrast X-Rays
●Involve the injecting into one compartment of the body a substance
that absorbs x-rays either less than or more than the surrounding
tissue.
●The injected substance then heightens the contrast between the
compartment and the surrounding tissue during x-ray photography
●Cerebral Angiography: uses infusion of a radio-opaque dye into a
cerebral artery to visualize the cerebral circulatory system during
x-ray photography
○Useful for localizing vascular damage but the displacement
of blood vessels could also indicate the location of a tumor
■Computed Tomography
●A computer-assisted x-ray procedure that can be used to visualize
the brain and other internal structures of the living body
●Scans of eight or nine horizontal brain sections are typically
obtained from a patient and make a 3D structure when combined
○Radioactivity-Based Technique
■Positron Emission Tomography
●PET scans
●Functional brain images
●Radioactive FDG (fluorodeoxyglucose) is injected into the
patient’s carotid artery (the artery that feeds the ipsilateral cerebral
hemisphere)
●Each PET scan is an image of the levels of radioactivity (indicated
by color coding) in various parts of the horizontal level of the brain
●This doesn’t really show the structures of the brain, only a map of
the radioactivity
●PET + MRI addresses the PET scans’ shortcomings (functional
images + structures)
○Magnetic-Field-Based Techniques
■Magnetic Resonance Imaging (MRI)
●Structural brain-imaging procedure in which high-resolution
images are constructed from the measurement of radio-frequency
waves that H-atoms emit as they align with a powerful magnetic
field (brain is made up of water)
●Provides clearer images than a CT
●Can produces images in 3D: in order to provide relatively high
spatial resolution
(the ability to detect and represent differences in
spatial location)
■Functional MRI (fMRI)
●Widely used for medical diagnosis
●Produces images representing the increase of oxygen flow in the
blood to active areas of the brain
●Active areas in the brain take up more oxygenated blood
●Oxygenated blood had magnetic properties that influence the
radio-frequency waves emitted by H-atoms in an MRI
●BOLD signal (blood-oxygen-level-dependent): the signal recorded
by the fMRI
●4 advantages over the PET:
○Nothing has to be injected into the volunteer
○Provides both structural and functional information in the
same image
○Its spatial resolution is better
○It can be used to produce 3D images of activity over the
entire brain
●BUT fMRI has poor temporal resolution, that is, it is poor at
specifying the timing of neural events (it takes 2 to 3 seconds to
measure the BOLD signal when these events, such as APs occur in
the millisecond range)
■Diffusion Tensor Imaging
●Identifying the pathways along which water molecules rapidly
diffuse
●Tracts (bundles of axons) are the major routes for rapid water
diffusion in the brain, diffusion tensor imaging provides an image
of major tracts
●Connectome
: connections of the brain’s structure
○Transcranial Stimulation
■Transcranial Magnetic Stimulation (TMS)
●Technique that can be used to turn off an area of human cortex by
creating a magnetic field under a coil positioned next to the skull
●The magnetic stimulation temporarily turns off part of the brain
while the effects of the disruption on cognition and behavior are
assessed
●Can also be used to “turn on” an area of cortex
■Transcranial Direct Current Stimulation (tDCS)
Document Summary
Part one: methods of studying the nervous system. Methods of visualizing or stimulating the living human brain. Only the unabsorbed portions of the beam reach the photographic plate. X-ray photography is effective in characterizing internal structures that differ greatly from their surroundings (ex. Involve the injecting into one compartment of the body a substance that absorbs x-rays either less than or more than the surrounding tissue. The injected substance then heightens the contrast between the compartment and the surrounding tissue during x-ray photography. Cerebral angiography: uses infusion of a radio-opaque dye into a cerebral artery to visualize the cerebral circulatory system during x-ray photography. Useful for localizing vascular damage but the displacement of blood vessels could also indicate the location of a tumor. A computer-assisted x-ray procedure that can be used to visualize the brain and other internal structures of the living body.
