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Brain Disorders Quiz 2

Terms in this set (68)

What are 4 ways of diagnosing a patient?
clinical history of symptoms + neurological exam + neuropsychiatric testing + neuroimaging
What is the Mini Mental State Exam (MMSE)?
An example of neuropsychiatric testing to test for cognitive impairment (0-30)
A doctor suspects that a solider has a bullet lodged in his head. What is the first neuroimaging technique that he should try?
X-ray (cheap, fast, good for penetrating foreign object)
What is the biggest difference between MRI and CT scan?
MRI does not use X-rays
If a doctor suspected a patient to have a swelling or edema, what neuroimaging technique should he employ?
Structural MRI (water/fluid will appear bright) with Diffusion-weighted images
If a doctor scanned a patient's brain who has multiple sclerosis (MS), what can he expect to see?
scars in white matter because immune system destroys myelin
In what direction does water diffuse more quickly along a white matter tract?
Along (not across)
What neuroimaging is most commonly used to diagnose epilepsy?
EEG
What is encephalopathy?
disease that affects brain function/structure (typically decreases signal transmission)
A patient is suspected of suffering from dementia. What neuroimaging should the doctor do?
PET (metabolic activity will show which regions have neurodegenerated)
Which neuroimaging technique detects changes associated with blood flow to measure brain activity? What signal is measured?
fMRI, BOLD signal
What are the 2 descriptions of the visual field?
vertical and horizontal meridian?
A hemifield typically refers to what visual fields?
left and right halves (not top/bottom)
What part of the eye has no light-detecting photoreceptor cells and is on the optic disc of the retina?
blind spot
What part of the eye is specialized for high acuity vision, color vision, and only contains only cone photoreceptors?
fovea
What does the principle of univariance state?
1 photoreceptor can be excited by different combinations of wavelength + intensity so the brain can't determine color of certain point of image w/o info from other photoreceptors
How do photoreceptors absorb light?
through photopigments called opsin
If eyes are stabilized, why does an image sometimes end up blurring/disappearing? (i.e Troxler Effect)
photoreceptors and RGCs become desensitized to current stimulus because once an opsin absorbs light, it takes time to return to functional state (underwent conformational change)
What is the importance of saccades?
prevent local rods, cones, and RGCs from adapting so they don't get worn out
True/False: Cone types are stable across individuals and between eyes
False, varies between eyes AND across individuals
What does the opponent processing theory state?
color is processed in 2 different opponency channels:
1. red-green
2. blue-yellow
What explains color illusions?
opponent processing effect (photoreceptors become desensitized and eventually stop responding. If you look somewhere else, surrounding OPPOSITE photoreceptors that aren't desensitized send out strong signal)
What is the relationship between RGC's dendritic field size and eccentricity?
higher eccentricity = bigger dendritic field size (explains acuity differences in diff parts of the eye)
How are different RGC types classified?
1. size and shape
2. light responses
What are the 3 different pathways that RGC project into the cortex? (remember they are parallel visual processing streams)
1. Magnocellular = parasol
2. Parvocellular = midget
3. Koniocellular = small bistratified
Which parallel visual processing stream takes on S-cone input?
Koniocellular pathway (small bistratified RGC)
Which parallel visual processing stream is primarily consisted of parasol RGC?
Magnocellular pathway ("m" for motion, parasol = big)
What are ipRGCs?
intrinsically photosensitive retinal ganglion cells
- respond sluggishly
- signal presence of long-term light
- regulate circadium rhythm + melatonin release
- possible conscious vision role
What are cataracts and what are they commonly caused by?
lens clouding that prevents light from hitting retina
- age + UV rays
A man has complete colorblindness (even at night)and has low visual acuity. He also suffers from nystagmus. What type of color blindness does he have?
Rod monochromacy
A man is fully colorblind but his central vision is still functional. What type of color blindness does he have?
L/M cone monochromacy
If a person have Protanopia dichromacy, why kind of colorblindness does he exhibit?
red-green colorblind because he has a problem with his L cones
A loss of S cones will cause what kind of colorblindness?
blue-yellow colorblindness (Tritanope dichromacy)
What is the most common type of colorblindness?
anomalous trichromacy (all 3 cones still functioning but shift in sensitivity)
What type of colorblindness is sex-linked?
red-green (blue-yellow is autosomal)
How do you test for red-green color blindness?
Ishihara Plates
What are tetrachromats?
women (2-3%) who have 4 cone types and can see 100 million colors
Where are the 1st binocular cells created?
V1
List 3 types of specialized tuning of V1 cells
1. receive inputs from monocular or binocular cells
2. responds best to oriented lines
3. increase response to contrast
4. preferred spatial frequency
5. preferred direction and depth
Scotoma is caused by damage to what part of the eye?
retina
What happens if you have a lesion on the right optic nerve?
total blindness of right eye
What happens if you have a lesion at the optic chiasm?
Bitemporal Hemianopsia (can only see inner halves)
What happens if you have a lesion in the left optic tract?
Right Homonymous Hemianopsia (can only see left VF of each hemifield)
Describe the normal visual pathway at a high level from retina to V1:
retina --> optic nerve --> optic chiasm --> optic tract --> thalamus --> optic radiations --> V1
Calcification of carotid arteries and hydrocephalus are common causes of what type of scotoma?
Binasal Hemianopsia (damage to uncrossed fibers --> CANNOT see inner 1/2 of each CF bcs nasal retina sees contralaterally)
A patient has a tumor on his optic chiasm. What type of scotoma would this cause?
Bitemporal hemianopsia (only see inner 1/2 of each VF)
A patient suffered a stroke that damaged his left V1. What type of scotoma does he have?
homonymous hemianopsia (cannot see right 1/2 of each VF)
How much of the human brain does the visual cortex compose of?
20%
Which visual stream is known as "perception for recognition"?
Ventral Visual Stream
What is important about visual field maps/retinotopic maps?
The organization of the maps follows the organization of the retina so retinotopic maps are cortical regions where nearby neurons analyzing nearby points of an image on the retina
What explains why the cortical representation of the fovea is much larger than that for the periphery, giving it higher acuity?
Cortical magnification
What is the first stage that starts with information at the peripheral sensory receptors? What parts of the eye would consist of this?
sensation (photoreceptors + ganglion cells)
What is the process of recognizing, organizing, and interpreting information from sensory receptors?
perception
How does camouflage work?
confuses V1 neurons that typically detect edges in a scene so that the ventral stream cannot identify which objects are being formed by these edges
What does the hollow mask illusion show?
Our depth perception can be overridden by our higher order expectations of 3D faces
What is blindsight?
A patient with a damaged V1 has no conscious knowledge/perceptually blind but responds appropriately to visual stimuli (possibly due to part of visual pathway that bypasses V1 to go straight into MT)
Where does object perception occur?
lateral and ventral occipital cortex
Mr. Sacks can perceive everything he sees and can even describe each item in geometrical terms. But he is unable to identify what anything is. For example, he cannot tell his wife apart from a coat rack but he can tell that it is his wife when she speaks. What does he suffer from?
Visual Object Agnosia (memory of object still in tact by other senses)
Given a picture of a key, a man is able to almost perfectly copy it but he does not know that he is drawing a key. What is he suffering from?
Associative Object Agnosia
Given a picture of his mother, John can tell that it is a woman but can't tell who she is. What is he suffering from?
Associative prosopagnosia
Katie is lying in bed when her mother comes in to visit her. She tells her mother to get out because she believes that an imposter has taken her mother's identity. What is Katie suffering from?
Capgras Syndrome
Name 2 delusional misidentification syndromes
Capgras + Fregoli Syndrome
Chris is paranoid that all the people that come visit his hospital room are all actually one person in disguise secretly plotting to kill him. What is he suffering from?
Fregoli Syndrome
Looking at a picture, Mary knows that there are multiple objects but can only recognize 1 at a time. Given a book, she cannot read the words or sentences. What is Mary suffering from?
Ventral Simultagnosia
Describe the color pathway (3 steps)
1. cone photoreceptors
2. Parvocellular pathway (midget RGC)
3. visual cortex (ventral)
Bob suffered a TIA and has mostly recovered but he came to suddenly lose his vision for 3 hours. His eyes were not damaged. His color vision eventually came back but what did he suffer from?
Transient Achromatopsia
Describe the motion pathway (3 steps)
1. Rods and cones
2. magnocellular pathway (parasol RGC)
3. V1 and MT (medial temporal)
Jen has been on antidepressants for a couple of years and noticed that she is beginning to be unable to perceive motion. What is she suffering from?
Akinetopsia
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