Psychophysiology Vision Lateral Inhibition o Helps make contrast more clear by since certain cells activate in response to a stimulus and prevent the response of other cells o Example Rods closer toward the center of the eye respond to a light strongly whereas other rods farther from the center are not activated to the light but still register it as darkness Therefore it makes the contrast between light and dark more severe so the light might seem brighter in contrast to the darkness Retinal disparity Optic Chiasm o The difference between what each eye sees o The greater the retinal disparity the better o Images from each eye are transmitted to the opposite side of the brain at the optic o Example An image from the left eye is sent to the right side of the brain to be chiasm processed A lot of individuals who are born blind and receive surgery do not like having the sense of sight after surgery Visual information goes to the thalamus o A specific area in the thalamus is the lateral geniculate nucleus LGN o Information then goes to the primary visual cortex V1 A few neurons branch off to the hypothalamus o These branches are important for sleep wake cycles Every layer of the primary visual cortex gets more specific as visual information goes deeper into the cortex Each visual neuron has its own receptive field o The receptive field of the neuron gets more specific as the visual information goes The visual cortex can actually shut down to prevent you from seeing something you do further into the cortex not need to see 3 kinds of ganglion cells o Parvocellular cells Located in the LGN Located closer to the phobia in the eye Good for color and detail Thus the parvocellular pathway is sensitive to detail o Magnocellular cells Located in the LGN Distributed throughout the retina Not color sensitive Good for movement detection o Koniocellular cells Located in the LGN Distributed throughout retina Some are color sensitive Those that are sensitive to color are better at detail The ventral stream is the what pathway o It is important for object recognition o Thus damage to the ventral stream causes difficulty with object recognition The dorsal stream is the where and how pathway o It is helpful for locating an object in space and moving towards it o Thus damage to the dorsal stream causes difficulty in reaching out and grabbing something Three different cell types o Simple cells o Complex cells o Hyper complex cells o These three types of cells also have different receptive fields and are more sensitive when deeper in cortex V5 temporal lobe o Important for movement o Medial temporal MT area and medial superior temporal MST area are two visual areas in the temporal lobe that are important for movement o A lot of information goes from the MT to the MST Development o Infants have adult sized eyes at birth o Infants prefer to look at complex patterns Example Other people s faces o The fusiform gyrus is responsible for facial recognition o Infants are able to tell the difference between correct faces and faces that have some type of defect o In infants the phobia is immature but their peripheral vision is better o Infants have difficulty shifting attention o The critical period for visual development lasts about two months If one eye is closed for the first few weeks of life then the cortical area that corresponds to visual input becomes unresponsive You can fix this issue by wearing an eye patch over your good eye This forces the bad eye to focus This technique is used for amblyopia or lazy eye If not treated the eye may eventually go completely blind o Therefore visual experience is critical for proper development If neurons become inactive experience can possibly make them active again Disorders Astigmatism is an abnormal curvature of the eye o Around 70 of kids are born with this condition Strabismus cross eyed is when people lack binocular vision o These people lack depth perception Visual Agnosia is the inability to recognize patterns or objects o Example Cannot identify a soccer ball by its pattern or shape Prosopagnosia is a problem with recognizing complex patterns o Example You cannot identify faces Achromatopsia is true color blindness because people with this condition see the world in shades of grey o Other color blind people can see color they just cannot see color as easily cannot tell the difference between different shades of color etc Akinetopsia is where you visually cannot detect motion o This is a problem related to the MT middle temporal cortex Cortical blindness is when an individual loses all or almost all vision but is still able to detect motion actually see it o Related to damage to the V1 area Blindsight is the ability to respond to something visual although the person does not o People who are cortically blind can have this ability Capgras delusion is where a person can recognize faces but they do not believe that the person they are seeing is the person they know They believe the person is a look alike phony o This delusion is attributed to having problems with the fusiform gyrus