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| -To detect physical energy ( a stimulus) from the environment and convert it into neural signals |
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To select, organize and interpret our sensations
-Complex process |
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- Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
-incoming data |
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-Info processing guided by higher level mental processes as we construct perceptions, drawing on our experience and expectations.
-Existing knowledge
-sensory info can be ambiguous |
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- "old" view
-perception involves adding up sensations |
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-"new" view
- Mind groups patterns according to law of perceptual organziation |
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| -Reality is organized or reduced to the simplest form posible |
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| -Specialized neurons that detect a variety of physical events |
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| -Process by which stimuli impinge on the sensory receptor thereby altering its membrane potential. |
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-Electrical changes in the cell's membrane potential in response to stimuli
-affect the release of neurotransmitters and thereby modify firing in neurons |
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-Suspended in orbits in the front of the skull
-held in place and moved by 6 exraocular muscles attached to the sclera |
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| Transparent outer layer at the front of the eye |
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| -Pigmented ring of muscles behind the cornea |
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Opening in the iris
-Regulates the amount of light that enters the eye |
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| Clear geltainous substance |
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| -neural tissue that contains photoreceptors that is located on the inner surface of the posterior portion of the eye |
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| - The receptor cells in the retina that transduce light photic(light) energy into electrical potentials |
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Definition
- types of photoreceptor that is sensitive to low intensity light
-vision in low light conditions
-Peripheral vision and lots of convergence |
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-type of photoreceptor that is sensitive to different wavelengths of light
-In the fovea
- Hight acuity and little convergence |
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-Central region of the retina
-Mediates most acute vision
-contains only cones |
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| -Location of the exit point from the retina for the fibers of the ganglion cells that form the optic nerve |
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Definition
| Photoreceptors form synapses with them and they in turn synapse on the ganglion cells |
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| Axons are the optic nerve that travels back to the brain |
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Definition
| -Transmit info in a parallel direction and combine info from adjacent photorecptors |
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| -Transmit info in a parallel direction and combine info from adjacent bipolar and ganglion cells. |
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Definition
-Optic nerve travels back and undergoes a partial decussation at the optic chiasm
-called optic tract
-Optic tract trabels back and synapses in the lateral geniculate nucleus of the thalamus (LGN)
-Neurons in the LGN project up to the primary visual cortex |
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Definition
| -Layer of membrane containing photopigments located in the outer segment |
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Special molecules imbedded in the membrane that are responsible for transduction of visual info
- 2 parts: Opsin(protein dye) bonded to retinal
-Exposed to light breaks the opsin and retinal
-causes changed in membrane potential and rate of glutamate release |
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| Conduction of visual signal |
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Definition
-Light hyperpolarizes the photoreceptor
-Reduces release of transmitter by the photoreceptor
-Leads to bipolar cell depolarization
-Depolarization causes depolarization of ganglion cell
- Deporlarization of ganglion cells leads to APs and firing rate is altered |
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Definition
-Any color could be reproduced by mixing various quantities of 3 colors
- founded by Young |
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- Yellow, blue, red and green are primary colors but some blend while others dont
-Founded by Hering |
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| usually dont have the opsin for one the 3 cones |
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| -Red light excites whereas green light inhibits the ganglion cell or vice versa |
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| -yellow light excites whereas blue light inhibits the ganglion cells or vice versa. |
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| -Orientation sensitive cell that has a receptive field organized in an opponent fashion |
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-Orientation sensitive in that it responds best to a line of particular orientation but responds more if the line is moved.
-Motion |
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| -location of ends of lines |
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-Involved in the formation of mental images
-Sends projections to many other regions of visual cortex
-Sends info to the extrastriate cortex
-Organized as a hierarchy so info is analyzed and then can be passed on for further analysis |
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-Processing of several aspects of the stimulus simultaneously
-Brain divides a visual scene into subdivisions such as color, depth, form, movement, etc. |
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-Region of visual association cortex that surrounds V1
-V5 is involved in perception of visual motion
-V2,V4 and inferior temporal (IT) area are involved in perception of form |
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| Inferior temporal (IT) area |
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Definition
-Involved in perception of form
-Show receptive field for complex objects
- Activated by faces and prospagnosia |
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-Visual association cortex involved in color perception
- used in color constancy |
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| -The relatively constant appearance of the colors of objects viewed under differing illumination conditions. |
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Definition
| -Lesions restricted to V8 in humans result in the loss of color perception without a loss in visual acuity |
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