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Description
Flashcards by Greg MacPherson, updated 4 months ago
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Created by Greg MacPherson
almost 3 years ago
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| Question | Answer |
| Unit Three - Module 18 Sensation: Vision | Sensation: Vision |
| wavelength | A wavelength is the distance between successive peaks in a wave. |
| frequency | Frequency is the number of complete wavelengths that can pass a point in a given time. |
| amplitude | The amplitude of a wavelength is its height. |
| hue | Hue is the dimension of colour that we experience - red green blue etc.... The hue is determined by the wavelength of light. The shorter wavelengths gives the purple and blue end of the spectrum. The longer wavelengths give the red end of the spectrum. |
| intensity | Intensity is the amount of energy in a light wave, which influences what is perceived as brightness. The intensity is determined by the wave's amplitude. |
| cornea | The eye's clear, protective outer layer, covering the pupil and iris. |
| pupil | The adjustable opening in the centre of the eye through which light enters. |
| iris | A ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening. |
| lens | The transparent structure behind the pupil that changes shape to help focus images on the retina. |
| retina | The light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the process of visual information. |
| fovea centralis | A small depression in the retina of the eye where visual acuity is highest. The centre of the field of vision is focused in this region, where retinal cones are particularly concentrated. |
| optic nerve | It carries sensory nerve impulses from the more than one million ganglion cells of the retina toward the visual centres in the brain. |
| blind spot | A spot where there are no receptor cells because this is where the optic nerve is leaving the eye. However, we don't see a black hole created by this blind spot because our brain automatically fills it in. |
| accommodation | The process of the lens changing its curvature and thickness in order for the lens to focus the light rays. |
| myopia | if the lens focusses the image on a point in front of the retina, one sees near objects but not distant objects. This is also known as nearsightedness. |
| rods | A type of retinal receptor cell that detects black, white, and grey, and is sensitive to movement. They are necessary for peripheral and twilight vision, when cones don't respond. A human retina has about 120 million rods. |
| cones | A type of retinal receptor cell that are concentrated near the centre of the retina and function in daylight or well-lit conditions. They detect fine detail and give rise to colour sensations. A human retina has about 6 million cones. |
| bipolar cells | Bipolar cells are interneurons in the retina that transfer neural impulses from rods and cones to ganglion cells. |
| ganglion cells | Ganglion cells receive neural impulses in the retina from the bipolar cells. The axons of the ganglion cells bundle together to form the optic nerve. |
| visual acuity | The degree of clarity, or sharpness, of visual perception. It is greatest when the visual image projects directly onto the fovea centralis. |
| Young-Helmholtz Trichromatic Theory | A theory of how humans perceive colour. According to this theory, the human retina contains three different receptors for colour (meaning each one is most sensitive to one color): one is most sensitive to red, one is most sensitive to green, and one is most sensitive to blue. These colour receptors combine the colours to produce the perception of virtually any color. You notice that there are no receptors specific to orange, but by stimulating the right cones in the right way, orange color is produced. |
| Thomas Young | A nineteenth century English scientist who contributed to our knowledge of vision. His work led in part to the Young-Helmholtz Trichromatic Theory. |
| Hermann von Helmholtz | A nineteenth century German scientist whose work led in part to the Young-Helmholtz Trichromatic Theory. |
| colour vision deficiency (colour blindness) | Colour vision deficiency is the inability to distinguish certain shades of colour. |
| afterimage | Visual illusions in which retinal impressions persist after the removal of a stimulus. |
| Opponent-Process Theory | This theory suggests that the way humans perceive colours is controlled by three opposing systems. We need four unique colours to characterize perception of colour: blue, yellow, red, and green. According to this theory, there are three opposing channels in our vision. |
| Ewald Hering | A German physiologist whose work led to the Opponent-Process Theory of colour vision. |
| feature detector cells | Groups of nerve cells in the brain's primary visual cortex that respond to specific features of a stimulus, such as colour, form (shape, edges, lines), and movement. |
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David Hubel
Image:
Dhubel (binary/octet-stream)
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Canadian neurophysiologist who won a Nobel prize for his co-discovery of feature detector cells in the brain. |
| Torsten Wiesel | Swedish neurophysiologist who won a Nobel prize for his co-discovery of feature detector cells in the brain. |
| supercell clusters | Supercell clusters are clusters of cells that respond to more complex patterns of visual information. |
| fusiform face area | Located in the temporal lobe, it is believed to specialize in face recognition. |
| parallel processing | Information processing in which two or more sequences of operations are carried out simultaneously by independent processors. A capacity for parallel processing in the human brain would account for people’s apparent ability to carry on different cognitive functions at the same time. |
| blindsight | A condition in which a person can respond to a visual stimulus without consciously experiencing it. |
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