Exam 1: Sensation and Perception

organization of an image into distinct objects/groups

perceptual organization

optic chiasm

point at which optic nerve fibers cross in the brain

nasal half of retina

visual field that is closer to the midline (nose)

temporal half of retina

visual field that is further away from the midline, close to the temple

ipsilateral visual cortex

half of the cortex that aligns with the same eye (L eye L cortex/ R eye R cortex)

contralateral visual cortex

half of the cortex that aligns with the opposite visual field (ex. L field R cortex)

primary visual cortex/ area V1

located in the occipital lobe, represents visual information

part of the eye that has the largest dedicated PVC area

the fovea

contralateral organization

each brain hemisphere represents the opposite visual field

degree of visual angle

measures distal stimulus in angular terms, accounting for size and distance from the viewer

cortical magnification- foveal information

foveal information is higher resolution because it takes up more dedicated V1 area

cortical magnification- peripheral information

peripheral information is blurry and de-magnified

Hubel and Wiesel's cat experiment

measured cat's neural responses via microelectrodes to determine orientation selectivity

orientation selectivity

property of cells which only fire in response to stimuli at a certain angle

simple cells

-respond to edges and bars

-elongated receptive fields

-clear ON and OFF regions

-stimulus must fall exactly within ON region

complex cells

-no distinct ON or OFF regions

-respond to stimulus anywhere within the receptive field

-selective to direction of motion

ocular dominance

cortical columns of neurons that respond to the left or right eye only

cortical column

vertical row of cells that is orientation selective

hypercolumn

horizontal row of cells that is either left or right receptive field selective

spatial vision

the ability to detect patterns of light

relationship between size of receptive field and level of detail

inverse- the larger the receptive field, the poorer the detail

lateral geniculate nucleus

area in the thalamus that receives retinal information via the optic nerve and transmits it to area V1

multi-channel model

the visual system analyzes information in distinct spatial scales

spatial frequency

scale of visual information from coarse to fine- cycles per unit distance

sine grating

measure of visual information by light intensity

amplitude

intensity of contrast between light and dark values

Fourier's theorem

every image can be constructed by adding sine gratings and spatial frequency

contrast sensitivity function (CSF)

minimum contrast level within a sine grating that can be detected (absolute threshold)

CSF formula

1/threshold= sensitivity