- The retina projects its information in a map-like manner
- The information stays this way as it passes through different regions of the brain
- Because of this, deficits in visual perception can be determined based on where damage is in the visual pathway or the brain
    - Scotomas are these regions of blindness

Retinotopic mapping

There are two types of photoreceptors in the eye: rods and cones. They are light-sensitive receptors. Rods are most active when there is dim lighting. Cones are most active when there is bright lighting, and can detect color.

Photoreceptors

- The LGN is a part of the thalamus that transmits visual information
- Receives information from the optic tract
- Sends information to the occipital lobe
- Some axons terminate in the primary visual cortex of the occipital lobe-- these are called optic radiations

Lateral geniculate nucleus (LGN)

- Optic nerve transmits signals to the superior colliculus
- Controls quick movements of the eye to look at a specific target 
- Helps control pupil size

Superior colliculus role in vision

The optic nerve is a bundle of nerve fibers formed by the convergence of axons from retinal ganglion cells. It exits through the back of the eye and serves as the primary pathway for transmitting visual information from the retina to the brain.

Optic Nerve

Visual information is processed within the brain through two main parallel pathways. The 'what pathway' is tasked with object recognition and identification. In contrast, the 'where/how pathway' is concerned with an object's location in space and how to interact with it.

"What" vs. "Where/How" Pathways of Vision

- Visual information is first processed by cells in the retina 
    - photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells
- Axons of ganglion cells make up the optic nerve, which transmits this visual information to the lateral geniculate nucleus (LGN) and the superior colliculus of the brain
- Neurons of the LGN synapse on the primary visual cortex, in the occipital lobe

University of Michigan - Ann Arbor

- How the eye functions
- Neural signals to the brain regions
- Receptive fields
- Brain regions involved in sight
- Vision impairment and blindness
- Visual illusions

Topics in Vision

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

As the primary sensory organ for vision, the eye captures and transmits light waves from the environment. These waves initiate the process of sight by entering through the pupil after passing across the cornea.

How the eye functions

Many different conditions can cause visual impairment or blindness. 

Vision impairment and blindness

Neural signals from the eye to the brain

- The visual cortex has many regions that process visual information
- Most visual information passes through the primary visual cortex, or area V1 or Brodmann area 17
- There are many other areas of the visual cortex that have important roles in vision

Brain regions involved in sight

- Sensory stimulus region and features that elicit a neuronal response
- Provides information about the function of a cell
- Neurons at different levels of the visual systems have different receptive fields, and therefore, different functions in vision

Receptive fields of visual system

David Hubel and Torsten Wiesel were neurophysiologists whose groundbreaking research on the visual system earned them the 1981 Nobel Prize in Medicine. Over two decades of collaboration, they made fundamental discoveries about how the brain processes visual information, particularly regarding the neurology of perception.

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