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.