Chapter 4 - Lectures Flashcards
What is Function Architecture?
How neurons are organized based on their physiological properties
What is binocular overlap?
When two eyes are observing a stimulus, the region of binocular overlap is depending on where different points are along the visual field, where the stimulus will fall on different points of your retina
What is the Nasal Retina?
When a stimulus falls on the Retina near the nose
An image on to your 10-11 o’clock would fall where on your right eye?
The Temporal Retina
Objects in the Left Visual Field will fall onto the ___ of the left eye, and ___of the right eye
nasal retina // temporal retina
Objects in the Right Visual Field will fall onto the ___ of the left eye, and ___ of the right eye
temporal retina // nasal retina
What direction does the Nasal Retina send its information?
Across the midline of the brain, this is called Decussation
What direction does the Temporal Retina send its information?
Keeps it on the same side, Ipsilateral
What type of projection does the Temporal Retina have?
Ipsilateral projection, meaning it’s projecting to the same side of the brain.
What is Ipsilateral Projection?
Projection to the same side of the brain.
What type of projection does the Nasal Retina have?
Contralateral Projection, where it crosses over and projects to the opposite side of the brain.
What is Contralateral Projection?
Projection that crosses over and projects to the opposite side of the brain
Objects that are in the left visual field will project to the ___ side of the brain
Right
There is a ___ representation of the visual field, that is to say, what is present in the outside world and the visual field, is represented in the ___ side of the brain.
Contralateral // Opposite
Where is the Lateral Geniculate Nucleus (LGN) located?
The Thalamus
How many layers are there in the Lateral Geniculate Nucleus (LGN)?
6
Which layers of the LGN contain BIG cells/neurons?
Layers 1 & 2, called Magnocellular layers
Which layers of the LGN contain SMALL cells?
Layers 3, 4, 5 & 6, Parvocellular
What are the Interlaminary Zones of the LGN?
Pale stripe zones separating the layers
What cells are in the Interlaminary Zones of the LGN?
Koniocellular (very small cells)
Why do we know very little about Koniocellular neurons?
Because they are so tiny that they are hard to record from using microelectrodes
Which layers of the LGN receive input from the Ipsilateral Eye?
Layers 2, 3 & 5
Which layers of the LGN receive input from the Contralateral Eye?
Layers 1, 4 & 6
What is Retinotopic Organization/Retinotopy?
Means that neurons that are neighbours on the retina (photoreceptors that are beside each other, or ganglion cells that are beside each other) maintain this spatial organization
What does “neighbours on the retina are neighbours in the brain” refer to?
Neighbours on the retina are represented by neighbouring neurons in the LGN and other areas in the cortex
What does Retinotopic mean?
Retintopic essentially means retinal mapping, so it’s using the same frame of reference as the retina
How many Retinotopic maps are there in the LGN?
6, one for each layer
What are features of the 6 Retinotopic maps in the LGN?
Each map corresponds to input from a distinct eye, and has either magnocellular neuroanatomy or parvocellular neuroanatomy.
What is a consequence of Retinotopic organization?
Tiling
Is there Retinotopic organization in the Primary Visual Cortex?
Yes
What neurons are recorded in the Primary Visual Cortex?
Simple, Complex, and End-Stop cells
What is the organization of Simple, Complex, and End-Stop cells in the Primary Visual Cortex?
These cells are not scattered randomly throughout the cortex, they are organized neuroanatomically based on their physiological characteristics, so neighbouring cells are physiologically similar, such that they create ordered maps across the cortex
How many cortical layers are there between the white matter (Pia) and surface of the brain?
6
What are Cortical Columns?
Stacks of cells extending through all 6 layers, these columns contain cells that do a similar job
Columnar Organization depends on what ___ you’re discussing
Job
The size of the column depends on which ___ we are measuring.
Visual characteristic
Retinotopic maps form ___
Location Columns
How wide is each cortical column?
1mm wide
In Location Columns, receptive fields are generally ___ in space and represent the ___ area.
overlapping // same
For Location Columns located near the Fovea, the receptive fields are ___
Smaller
For retinotopic columns that are located in the periphery, the receptive fields are ___
Larger
If you were using an electrode to record across multiple location columns, what might you find?
The receptive field slowly changes in position over time
What is the second type of organization in the visual cortex?
The Magnification Factor
The signals from the ___ in the visual cortex account for 8% to 10% of the area
Fovea
The ___ is over-represented in the cortex
Fovea
The over-representation of the Fovea in the cortex is thought to provide extra processing for ___
High-acuity tasks
What part of the brain surrounds the Fovea?
The Macula
The ___ takes up a very large portion of the visual cortex, whereas going towards the ___ as you go paler in colour, it takes up a very small region
macula // periphery
What is the relationship between the density of photoreceptors at the level of the fovea and receptive fields for a given area of space?
There is this very dense packing of photoreceptors at the level of the fovea and those create very small receptive fields for a given area of space
What is the third type of organization in the visual cortex?
Orientation Columns
What are Orientation Columns?
Many smaller columns found within a Retinotopic/Location Column
Each orientation column contains neurons that only like a single orientation.
What types of neurons/cells are found in Orientation Columns?
You can have simple, complex, or end-stopped cells, but they all prefer the same orientation
If you were to use an electrode to record across many Location Columns and Orientation Columns, what would you expect to find?
The location of the receptive field would gradually change and the preferred orientation of the neuron recorded would also change
Where is the first stage where information from the left and right eye combine?
The Primary Visual Cortex
True or False: Either the left or right eye has control over the activity/firing of a cell
True
What is Ipsilateral Dominant Response?
The eye that is on the same side of the brain that you’re recording on has a strong response.
What is a Hypercolumn?
A column made up of columns
For every region of retinotopic space there is a representation with a ___
Hypercolumn
The ___ contains more of these Hypercolumns because the receptive fields are ___, and there are fewer of these hypercolumns to represent the ___ visual field, however the receptive fields are ___
fovea // smaller // peripheral // larger
What is another name for the Primary Visual Cortex?
The Striate Cortex, named after the stripe in layer 4B, referred to the line of gennari
What is the name of the region outside of the Primary Visual Cortex/Striate Cortex?
The Extrastriate Cortex
There is a split in information processing outside of ___
V1
True or False: There are many cortical visual areas outside of the primary visual cortex
True
Who uncovered this split in information processing outside of V1?
Underlyger and Mishken
What tasks did Underlyger and Mishken train monkeys in?
Object discrimination and Landmark discrimination
When monkeys had part of their temporal lobe removed, what happened?
They could no longer judge what objects were. They could no longer perform the object discrimination task, but they could still perform the landmark discrimination task
When monkeys had part of their parietal lobe removed, what happened?
They could no longer judge where objects were. They failed the landmark discrimination tasks, but they were still able to perform the object discrimination task.
What is Double-Discrimination?
Where lesioning one area alters one task, but leaves the other task spared, and lesioning a complimentary area has the converse behavioural affects
The Parietal/Dorsal Stream is important for object ___
Location
The Parietal/Dorsal Stream is the ___ pathway
“Where”/”How” (new)
The Temporal/Ventral Stream is important for object ___
Identification
The Temporal/Ventral Stream is the ___ pathway
“What”
Patient “D.F.” has damage to the ventral stream, what symptoms might he have?
Cannot recognize objects (i.e. visual agnosia), but can interact with them
Patient “V.K” has damage to the parietal stream, what symptoms might he have?
Can identify the objects, but cannot interact with them appropriately
What did Milner and Goodale change the Parietal/Dorsal pathway to?
From “Where” to “How”
When asking patient D.F, who has damage to the Ventral/Temporal stream, to match the orientation of his hand to a card slot, what may happen?
He will not be able to do it
When asking patient D.F, who has damage to the Ventral/Temporal stream, to insert a card into a slot, what might happen?
He will be able to do it
How well would patient D.F, who has damage to the Ventral/Temporal/What stream, perform a perceptual orientation matching task? (i.e, match hand orientation to card-slot orientation)
He would not be able to do it
How well would patient D.F, who has damage to the Ventral/Temporal/What stream, perform a visuomotor posting task?
He would be able to do it with extreme accuracy
What is the card-posting task an example of?
Visuomotor posting
What is visuomotor posting doing?
Using vision for ACTION
There is discrimination between visual processing for object identification or features of an object, ___ pathway, and then vision for action, the ___ pathway
“What” // “How”
What is the neuroanatomy name for the pathways?
Parietal and Temporal pathway
What is the functional name of the pathways?
Dorsal/Parietal = ”Where” and “How” pathway, and the Ventral/Temporal = “What” pathway
What is the neuroanatomical terminology for the two pathways?
Dorsal = near the top, and Ventral = near the bottom.
What is a good pneumonic device for remembering which pathway is which?
Using a nonsense word “whatemporal”, all you need to remember that the temporal stream is down, and whtemporal means it is the “What” stream in the temporal lobe.
Is it possible to dissociate the two visual streams in people without brain damage?
Yes
How do you dissociate the two visual streams in people without brain damage?
Using the Ponzo Illusion
In the first task of the Ponzo Illusion, where participants are asked to estimate the size of lines 1 & 2, what pathway is that using?
The “What” pathway, which measures distance in a relative sense, it’s fooled by the Ponzo
In the second task of the Ponzo Illusion, where participants are asked to pinch either or line, what pathway is that using?
The “How” pathway, is measuring vision for action, which measures objects within personal space, within arms reach, fairly accurately because you have to grab these objects very precisely regardless of what kind of visual illusions might be happening, it’s not fooled by the Ponzo
In the first task of the Ponzo Illusion, where participants are asked to estimate the size of lines 1 & 2, what is the reality?
Line 2 looks longer than Line 1, but the reality is is that Line 1 is longer than line 2
What is a Module?
A brain structure specialized to process information about a specific type of stimulus
Particular cortical nuclei seem to have ___ functions
specific/special
What does the number of modules the visual system depend on?
What your general philosophy is, whether you are a Chunkers and Splitters
What is a Chunker?
A Chunker likes to have as few modules as possible.
What is a Splitter?
Splitters want to find as many super-specialized modules as possible
In the monkey Infratemporal Cortex (IT), there are neurons that code for ___
Faces
Monkeys, when shown different types of stimuli, either whole body, face alone, or body alone, in the Infratemporal cortex subregion, most of them would ___ to faces and they would give ___ to these other objects.
respond // weak responses
Where the Infratemporal Cortex (IT) is in the Macaque brain, and where the Fusiform Face Area in humans are, are both in the ___ pathway.
“What”
What is the face-specific region identified in humans using fMRI?
The Fusiform Face Area (FFA).
What is Prosopagnosia?
Difficulty recognizing faces of individual people. They can still identify a face as a face, they know there’s eyes, nose and mouth, as well they can describe the shape and texture, but they cannot put a name to the face or who it is
What happens if the FFA is “broken”?
Prosopagnosia
What is the Parahippocampal Place Area (PPA) activated by?
Activated by pictures of outdoor and indoor scenes, but not objects or little widgets
What is the Extrastriate Body Area (EBA) activated by?
Activated by pictures of bodies and body-parts, but not face or man-made objects
What have studies shown that can also activate the fusiform face area (FFA)?
Cars (in car experts), and birds (in bird experts)
What does the FFA being able to be activated by cars in car experts show?
The FFA might not just be for faces, it might be for distinguishing individual members of a collective category
We are all humans, we have different faces, and maybe that’s why the FFA is activated by the different configurations of our faces, just like cars all have 4 wheels, a hood, and windshield, but the shape of the car, and all these other attributes may distinguish the different types
What is the challenge of studying neurons?
Neurons just respond to the stimulus, they’re not gonna tell you their job
How do we get a better sense of these modules?
What you find is based on what you ask, and so in order to get a better sense of these modules, we need to approach the correct questions and then we will be able to get better and better answers.
What does it mean to have Distributed Coding within a specific module?
That there are a whole bunch of neurons that are coding for many complex features, and this will increase the ultimate information processing capacity of that region.
Why will a huge portion of cortex will be activated by any particular stimulus?
Different visual stimuli, naturalistic scenes or objects, are inherently multidimensional, meaning that a single stimulus can be characterized in many different ways if we just imagine a face
What part of the brain evaluates attractiveness?
The Frontal Lobe
What part of the brain responds to familiarly and the emotions that are portrayed on the face?
The Amygdala
What part of the brain does Basic face processing and identity?
The FFA
Which part of the brain examines where the person is looking and also as well as mouth and face movements?
The Superior Temporal Sulcus
True or False: A single face and many other objects can be processed along many dimensions
True
Even relatively isolated objects will be represented in a ___
Highly distributed manner
How can we represent that even relatively isolated objects will be represented in a highly distributed manner?
Huth’s map of “Continuous Semantic Space”
How was Huth’s map of “Continuous Semantic Space” created?
Using fmri, and they showed subjects different pictures and asked them to label what they were seeing, whilst they were labelling and viewing the scenes, they had their brains imaged. They created, out of all the labels, a claytogram, which is kind of like a phylogenetic map for semantic meanings around things
What might you notice in Huth’s map of “Continuous Semantic Space”
You’ll notice there are clusters of certain colours from the semantic map, but there is a tremendous scattering of colors everywhere.
- You have this multiple modules processing the different dimensions of a particular stimulus, and then within these modules you have this distributed coding where many neurons are taking part.
- What you essentially get is for a scene of complex stimuli, the visual stream extends over almost the entire cortex, it’s activating huge amounts of cortex.
Where do perception and memory meet?
At the end of the visual stream
Following the visual stream to the end, what do you get?
This is where perception meets memory
If we follow the Temporal/”What” stream all the way down, where does it reach?
It reaches the underside of the cortex where we get into the entorhinal, hippocampal, and parahippocampal region
What are the Entorhinal, Hippocampal, and Parahippocampal regions associated with?
They are traditionally associated with memory
What is the Medial Temporal Lobe (MTL) important for?
Important for memory formation
Patient H.M. had bilateral removal of the hippocampus to treat epilepsy, what happened to him?
He became unable to create new memories, but was able to perceive and recognize objects.
Is the Medial Temporal Lobe (MTL) a sensory or memory area?
It has sensory responses, but its more of a memory area
What is the Mind-Body Problem?
This is relating information in the body or brain, the activity of the brain, with your conscious awareness of the world around you, that is the mind
What are the “Easy” problems of consciousness?
Neural Correlates of Consciousness. Having these neural correlates of things that are related to consciousness.
What is the “Hard” problem of consciousness?
We don’t know how these signals combine to create consciousness, and so we cannot have a causal relationship between neural activity, or the pattern of activation in the brain, with consciousness. We are many, many decades away from solving this problem.
