Lecture 16 ( october 13 2010) Anatomy of the visual pathway (Brain-based visual
-hole in the eye its called the pupil. Size of the pupil can be control; the iris controls the
size of the pupil. When its really bright out the iris makes the pupil smaller. When you
wake into the a dark place, Iris makes your pupil bigger (let as much light in)
-size of the pupil controls by iris
-Light enters to the pupil and it hits the Lens. And go to the retina
-Retina: layer of cells that pick up light information (has Fovea in it)
-Fovea: when you see things really well.
-Optic nerve: connections that carry visual information from eyes to the brain
-then go to optic nerve (no receptor)
-what one eye doesnt see, the other one will see. So theres no blind spot.
The dysfunctional eye
-optometrist (OD): doctor that gives you glasses; check your eyes
-Ophthalmologist (MD): does surgery
-Catarcts : people over 85; lens get burry. (cloudy lens) Treatment: lens replacement
-Glaucoma: check pressures; where there is too much pressure on the eye and it
pushes the “optic nerve” because of this you might be blind.
-Macular degeneration: retina starts to break down. Fovea; where you focus on
-retinal tear: tearing of retina, increase with age.
-papilledema: when the optic nerve is being pushed out because of the brain swell.
-cone-based colorblindess: Red-green (sex linked)
From the eye towards the brain
-the information from the right eye goes to the left, and left side goes into right.
-optic chiasm: when information crosses from one side to another. (information in the
right side of eye will go to the left side; and information in the left side of eye will go to
the right side)
-the left eye doesnt cross
-if you cut the optic chiasm : you can only see in the middle (cannot see outside) tunnel
Blind spots:: scotomas
-damage to the occipital lobe leads to partial or full cortical blindness.
-if your right side is blind, your left occipital lobe is damaged.
-Lens flip image up side down. Blindsight
-if you damage both side of occipital lobe, you are blind.
-10% goes to the brainstem
-90% of vision goes to normal route
-inability to distinguish between colors
-everything is a “gray soup”
-eyes/cones are functioning normally
-this is different from color blindness; this is damage TO THE BRAIN. (the eyes are fine)
-people with this condition, dont want to eat because food looks like shit.
-an issue with perception caused by damage to secondary visual processing areas in the
-its rare; and its possible to lose color in one side but not the other.
-cannot percevie continuous motion
-“strobe light” snapshots of reality
-think about how even basic everyday functions are affected (cannot predict time,
-an issue with perception caused by damage to secondary...
Dorsal and Ventral Streams
-ventral stream: helps us understand what we are looking at (match what you are
seeing in the environment)
-dorsal stream: where everything is (goes to the parietal lobe)
The ventral pathway: temporal lobe
-knowledge representations (match my visual experience with what I see before)/
-Brains inability to link visual perception to known concepts for identification (able to
see things but cannot say what they are) Ex: you can see the cup of a coffee but u dont
know its coffee until you smell it. It can affect faces, tools..etc
-caused by damage to the occipo-temporal region (approximately)
-Described as a disconnection Associative and apperceptive Agnosia
-Associative: can perceive objects ok but cannot assign meaning to objects. I see it but
I just dont know what the object is.
-apperceptive agnoisa: can preceive basic sensory features but cannot form a visual
percept of an object
(cannot see objects correctly)
Category-specific associative agnosias
-can sometimes be limited to single categories, such as people, animals and tools
-damage to anterior temporal lobe
-cannot distinguish between faces but can identify people based on other basic visual
features (or other senses)
-can see different parts of the faces but cannot see whole
-Typically caused by damage to ventral temporal lobe regions, specifically the fusiform
gyrus (right > left) fusiform gyrus: bottom part of the temporal lobe.
-damge to the right its way worse than the left.
Dorsal pathway: parietal lobe
-where things are in the space (like I can see my coffee thats closer to me than my
-map of spatial relations in the environment
-inability to use vision to guide actions
October 27 lecture 22
Language and the brain
-most cases, language is subserved by the Left hemisphere
-usually left side of the brain for right handed, for left handed, 70% language on the
left. Sometimes right or both sides.
-speech: your ability to talk (speech is one aspect of language)
-women recover faster from a stroke in the left because they receive right side more
-this test is important to determine which side of the brain is language. (test for
language lateralization) -anesthetiza one hemisphere and test language abilites. (put one side of your brain
asleep, ex. Put left hemisphere to asleep, if you can answer, your right side is important
for language, if you cannot, left side is important)
-back part of the brain: Fluent but comprehension problems (you may not understand
what people are saying to you anymore)
-usually use fMRI : have you talk to something; see which side is more active
-front part of the brain: understand just fine (good comprehension) but you are not
-first discussed by Paul Broca
-insula is behind the broca's area. All the patients that have broca's aphasia, left insula
is always damaged.
-damaged to the pose frontal inferior gyrus in the left side
Broca's aphasia: symptoms
-non-fluent ouput (someone with broca's aphasia they cannot talk fluently)
-agrammatism: lack grammar; without words that are “the” “and”..etc talk with nouns
and verbs mostly.
-reading and writing: they cannot read (but we can understand what people say but we
cannot say it), they CAN write. Sometimes you cannot write because of the weakness.
Reading is more cognitive, and writing is more motor.
-comprehension intact: (comprehension is usually fine) can understand language, but if
you say things in really complex ways, they wont understand, even have a lot of
information in it.
-impaired prosody: our ability to change the tone of our speech. NOT to change their
tone: impaired prosody.
-right after Broca's discovery
-First discussed by Carl Wernicke
-someone who can TALK but cannot understand.
-damage to superior temporal gyrus, lake ability to understand language.
-poor comprehension: reading and writing also impaired. Cannot read because cannot
translate into meaning
-Fluent output: “fluent” but meaningless (what they say often doesnt make sense at
all), “word salad”
-people with this illness: they think they make sense. -Prosody intact: talk with different tone
-paraphasia: language mistake
-word subtitution (similar meaning)
-Knife for spoon
• “scoon” for “spoon”
-conduction aphasia: (mylinated axon that connects wernicke's to Broca's) links
comprehension to talking/production. If cut, cannot repeat back, cannot translate what
I understand to what I say.
-Stroke is the number 1 that will affect the language.
-watershed infarction: damage by stroke because of low blood pressure. Because blood
cannot get there. 1st place to get damage. Damage to this area: 2 types of aphasia.
Damage to the front (near the frontal lobe) is the transcortical motor aphasia: looks
more like broca's aphasia. You can repeat just fine. Just cannot create words on your
own. (broca's plus repeat). Damage to the back (transcortical sensory aphasia): looks
like Wernicke's aphasia but you can repeat.
-when you have broca's and wernicke's aphasia at the same time. Not fluent and poor
-likelyhoold of recover its small.
-huge stroke to left frontal and temporal lobe.
-inability to read because of brain damage to left posterior occipital lobe is Alexia.
-inability to write is because of brain damage agraphia.
-splenium of the corpus callosum: br