The three major groups of so-called feature detectors in visual cortex include simple cells, complex cells, and hypercomplex cells . Simple cells are the most specific, responding to lines of particular width, orientation, angle, and position within visual field.
What are simple cells in the primary visual cortex?
A simple cell in the primary visual cortex is a cell that responds primarily to oriented edges and gratings (bars of particular orientations) . These cells were discovered by Torsten Wiesel and David Hubel in the late 1950s.
What is in the primary visual cortex?
The primary visual cortex, often called V1, is a structure that is essential to the conscious processing of visual stimuli . ... These different types of neurons preferentially respond to different types of visual stimuli, thus it seems these pathways are each somewhat specialized for specific categories of stimuli.
How many cells make up the visual cortex?
Sublamina 4Cα receives mostly magnocellular input from the LGN, while layer 4Cβ receives input from parvocellular pathways. The average number of neurons in the adult human primary visual cortex in each hemisphere has been estimated at around 140 million .
What type of cells analyze visual information?
The ganglion cells are the last link in the chain of neurons in the retina. This chain begins in each retina’s 125 million photoreceptors, which gather information and channel it, via a small number of synaptic connections, to the retina’s 1 million ganglion cells.
Where is the primary visual cortex located?
The primary visual cortex (Brodmann area 17 ) is also known as the calcarine cortex, striate cortex, or V1. It is the main site of input of signals coming from the retina. It is located on the medial aspect of the occipital lobe , in the gyrus superior and inferior to the calcarine sulcus.
What happens if the primary visual cortex is damaged?
Destruction of the primary visual cortex leads to blindness in the part of the visual field that corresponds to the damaged cortical representation. The area of blindness – known as a scotoma – is in the visual field opposite the damaged hemisphere and can vary from a small area up to the entire hemifield.
What is Retinotopic mapping?
Retinotopy (also known as retinal mapping) is the mapping of visual information from the retina to neurons in the brain . ... The connections between different parts of the brain that deal with visual input are elegantly connected to form a retinotopic map of the visual field.
What are the two kinds of columns in the primary visual cortex and how are they arranged?
In primary visual cortex, two major types of columns have been described: the ocular dominance columns and the orientation columns (see Hubel and Wiesel, 1977).
In what ways are simple and complex cells in the primary visual cortex different?
The difference between the receptive fields and the characteristics of simple and complex cells is the hierarchical convergent nature of visual processing . Complex cells receive inputs from a number of simple cells.
What is a feature detector in the visual system?
any of various hypothetical or actual mechanisms within the human information-processing system that respond selectively to specific distinguishing features. For example, the visual system has feature detectors for lines and angles of different orientations as well as for more complex stimuli, such as faces.
How does the visual cortex create an image?
Vision begins with light passing through the cornea and the lens, which combine to produce a clear image of the visual world on a sheet of photoreceptors called the retina . As in a camera, the image on the retina is reversed: Objects above the center project to the lower part and vice versa.
How much of the cortex is visual?
“ More than 50 percent of the cortex, the surface of the brain, is devoted to processing visual information,” points out Williams, the William G. Allyn Professor of Medical Optics. “Understanding how vision works may be a key to understanding how the brain as a whole works.”
What is the correct pathway of vision?
The visual pathway consists of the retina, optic nerves, optic chiasm, optic tracts, lateral geniculate bodies, optic radiations, and visual cortex . The pathway is, effectively, part of the central nervous system because the retinae have their embryological origins in extensions of the diencephalon.
What is the function of visual system?
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ability to detect and process visible light) as well as enabling the formation ...
How vision works step by step?
- Light enters the eye through the cornea. ...
- From the cornea, the light passes through the pupil. ...
- From there, it then hits the lens. ...
- Next, light passes through the vitreous humor. ...
- Finally, the light reaches the retina.
