Lecture 7: 309
– Cortical Streams of Processing:
+ ventral stream travels to the temporal lobe
+ dorsal stream goes to the parietal lobe
– theories of object recognition:
+ view-dependent frame of reference:
- template theory – recognize it
- to recognize an object, we have to have representations of it in multiple different frames
- depends on the viewpoint that we've seen it – angles
- can call upon the template to recognize the object
+ view-invariant frame of reference:
- geon theory
- when looking at an object... look at the geons that make it up
- see the geons and recognize the object at this angle, etc
– Dependent vs. Invariant?
+ repetition suppression
- see a object and brain activity occurs ... few seconds later, see it again and have less brain
activity relative to the first time – idea of repetition suppression activity
+ task: show people objects with same orientation or different orientation... shows different parts
of brain that shows sensitivity
- see a new object, have a high brain activity... same view, less brain activity... but different view,
there's high amount of brain activity again (treating it like a completely different object) in the
right fusiform area (bottom part of temporal lobe) – dependent. More template-like
- new object emits high brain activity, but same view and same object in a different view has
lower brain activity – invariant. Left fusiform area, more geon-theory like.
+ each hemisphere processes information in slightly different ways
– Representing complex objects at the neural level:
+ Gnostic hypothesis: “grandmother cells”
+ when looking at a person, one neuron corresponds and activates .. → recognize the person
- idea that you have one cell when activated, corresponds to perception of grandmother. When see
grandmother, activate all sorts of feature about her (ie: face shape/hair) and this constellation of
brain activity, all of these features that corresponds to grandma... when activated together, they
activate the grandmother self, the cells that corresponds to grandma.
- thinking about grandma...
- seeing different features of an object, activate agnostic cell, and when the single cell is activated,
perceive the given stimulus
+ ensemble coding hypothesis:
- instead of having a grandmother cell, you have lots of features that activate together
- to recognize grandma, picking up same features an agnostic cell would but there isn't some cell
- perceiving all these features that make up grandma & this constellation of activity leads you to
say it's grandma
– Category-specific loss of knowledge?
+ herpes virus coming into the brain... demolishes the temporal lobes;; selective to both sides
+ show objects to people with the damage and ask to describe it → not specific, general. + damage to temporal lobes...
- temporal lobes linked to concept knowledge... different categories of knowledge spread across
different parts of the temporal lobe
- knowledge of the people is stored in the front part of the lobe
- knowledge of animals is stored a little bit further back
- knowledge of tools is even further back.
+ see how it lines up to impairments... if you damage the front and the back, you're more likely to
have damaged the middle as well.
– Object recognition is an incredibly important process that relies on high-quality visual input and
the ability to link this input to stored conceptual knowledge
– How is knowledge stored? Evidence seems to be favoring ensemble coding but lesion studies
might tempt us into thinking there is a “Ryan Reynolds” cell in our brain..
– The Corpus Callosum:
+ left and right hemispheres don't do exactly the same thing – modest specialization exists (ie:
+ right side of body controlled by left frontal lobe
+ attention more specialized in right hemisphere; language in left
+ separation difficult to probe
+ purpose: connects the two hemispheres together – whatever the right side of brain knows, left
knows quite transfer = information transfer done at light speed
+ epilepsy... seizures that don't have current underlying cause
- grand mal seizures... involves involuntary motor movements – body shakes. Person loses
consequences, cease for a certain amount of time and wake up confused. Can have multiple
seizures per day depending on severity. There's anti-epileptic medication that reduce excitability
of brain, works well on some people.
+ can cut out part of a brain that's responsible for generating seizures... problem: many seizures
come from medial temporal lobe (involves hippocampus – hotspot for seizures).
- taking it out is really undesirable... fix one problem, create another.
+ callosotomy: cut the corpus callosum, the bridge between the two hemispheres.
- reduce the spread of seizure... contain it to one side of the brain
- people more likely to respond to medication, seizures reduced
– Surgical resection of the corpus callosum
+ front, back or middle of it can be cut
+ have to cut part of the skull and brain to reach the corpus callosum
– Functional subdivisions of corpus callosum:
+ divided by types of information it transfers
+ frontal part of the corpus callosum transfer motor information – corresponds to frontal lobes
(have motor corticies)
+ somatosensory area that corresponds to the parietal lobe (Posterior midbody)
+ auditory for temporal lobe (Isthmus)
+ Splenium is for occipital lobe
+ Rostrum – higher cognitive?
+ Nowadays, just cut the front of corupus callosum. If you cut the anterior midbody, clinical
results are just as the same as cutting the whole brain → cut little as possible and get maximum results
+ when cutting the corpus callosum, each side of the brain is going to try and do their own thing –
difference in processing, specialization between the two hemispheres → “Split brain patients”
+ Tachistoscopic Presentation: split brain patient sits and stares at a screen. Information presented
on the screen so quickly that you can't even move your eyes – whatever's on the right visual field
is going to the left side of the brain …. Left side of brain knows something that the right doesn't
know;; vice versa. Can isolate knowledge information to one hemisphere or both.
- key and ring presented;; key on left, ring on right. Can recall the object seen on the right visual
field that goes to the left hemisphere. Never says key – right hemisphere cannot talk.
- when asked to grab the object he had seen with his right hand, grabs the ring – whatever he can
say, he can grab it with his right hand.
- when asked to grab the object he had seen with his left hand, grabs the key – right hemisphere
controls knowledge by moving the left hand. When asked why he grabbed the key, he's not
sure/tries to make up a story that explains his behavior.
- when right hemisphere does something and left hemisphere doesn’t know why, left tries to make
sense of it – reason.
+ when seeing a horse on LVF, draws a saddle instead with the left hand – semantically related.
Right hemisphere controls the left hand to draw.
– Looking at faces composed of fruits/vegetables:
+ right hemisphere better at holistic whole-processing of faces.
– Degree of information transfer in the corpus callosum:
+ Normal brain: receive the stimulus on the left side to the right hemisphere. But the information
crosses over to the left so you can say what it is.
+ Complete split: information contained in right he