PSY280 - 2. Signal detection theory Flashcards

Question

myopia

Answer 1

object is near, light focussed farther back, so near objects are not a problem for people emmetropia: perfectly converges light to the retina nearsightedness - eyeball is too long, for distant objects, it converges at the front need concave lenses to bend light out a little bit

Answer 2

Brings parallel rays of light into focus at a point in front of the retina to the image that reaches the retina is blurred Refractive myopia: cornea/lens Bends the light too much Axial myopia: eyeball is too long Farpoint: distance at which light becomes focused on the retina Glasses bend incoming light focused as if it were at the far point Laser assisted… (lasik): sculpting cornea

Answer 3

Farsighted: can see distant objects clearly but has trouble seeing nearby objects Focus point for parallel rays of light is located behind retina usually because eyeball is too short short eyeball convex lenses to follow shape

Answer 4

due to an irregularly shaped cornea cornea is not spherical - football shaped intersections look blurry horizontal + vertical lines intersect at diff depths

Answer 5

dendrites listen axons talk cell body integrates all the signals There is some variation in structure, but neurons tend to have a basic “recipe”

Answer 6

pick up information from environment, rather than from other neurons. interact with environ to translate stimuli into electrical signals receptors respond to diff energies touch: mechano energy vision: electromagnetic energy

Answer 7

Ion channels + ion transporters regulate # of ions inside & outside of the cell. ion transporter: selective + require energy to transport ions

Answer 8

sodium more concentrated outside + K inside At rest, there are more positive ions outside than inside. membrane potential is all relative negative membrane potential

Answer 9

sodium (Na+) ion channels open + Na+ rushes into axon, resulting in fewer positive ions outside. more positive inside + flip open allowing sodium to enter + makes membrane more positive which triggers opening of next one shoots up to +40 membrane potential causes Na+ channels to close + potassium (K+) channels to open, letting K+ out.

Answer 10

trade 3 Na+ for 2 K+, so that ions end up in their original concentrations. Na + K+ pumps actively put back ions in original locations

Answer 11

15 mv difference for threshold, diff neurons have diff resting membrane refractory period can’t do anything for this period whole process happens within 2 milliseconds all or none principle

Answer 12

Neurons usually produce & release only one kind of neurotransmitter: •excitatory: (Na+) sodium channels open •inhibitory: (K+) potassium channels open excitatory: easier to get to threshold inhibitory: even more negative - threshold farther reuptake: take up neurotransmitter + stop releasing

Answer 13

Neurons usually have receptors for multiple neurotransmitters can receive both excitatory + inhibitory signals rate of firing dictated by summated signals

Answer 14

Neurons fire in absence of stimuli (spontaneous activity) signals can involve either an increase/decrease in firing rate no change means signals are cancelling each other out = no perception

Answer 15

Transduction occurs in rods + cones Millions of molecules of light-sensitive visual pigment that are contained in the outer segments of the receptors Visual pigments contain a long protein called opsin + a much smaller light-sensitive component called retinal

Answer 16

Retinal is the crucial part of the visual pigment molecule because when combined the resulting molecule absorbency visible light changes its shape from being bent to straight – Isomerization creates a chemical chain reaction that activates thousands of charged molecules to create electrical signals in receptors Chain reaction amplifies effect of isomerization Visual pigments shape specific aspects of our perceptions

Answer 17

light needs to interact with all of these cells before photoreceptors can translate these signals layer of the retinal that is further away from the retina these cells need to be transparent in order to reach the photoreceptors the electrical signals comes forward to the ganglion cells

Answer 18

outer segments are packed with photopigments like rhodopsin, composed of opsin and a retinal molecule. diff receptors have diff photopigments opsin is always a huge chain protein molecule that weaves in + out of the membrane + retinal molecule at the end, but it’s the thing that responds to light

Answer 19

When a photon hits the retinal when light hits it is isomerizes + detaches, it becomes activated unstimulated, on in the dark

Answer 20

current running through photoreceptors in the dark change in membrane potential because ions keep moving across membrane Dark adaptation: increasing sensitivity in dark Rod and cone receptors adapt to the dark at different rates Macular degeneration: destroys Cone rich fovea and a small area that surrounds it Creates a blind region in the central vision

Answer 21

Retinis pigmentosa: degeneration of retina that is passed from one generation to the next Attacks peripheral rod receptors and results in poor vision in the peripheral visual field Blind spot: absence of receptors Blind spots are hard to detect Some mechanism in the brain fills in the place where the image disappears

Answer 22

Na+ ions are flowing inward via cGMP-gated sodiums channels in the outer segment K+ is flowing outward via potassium channels in the inner segment The sodium-potassium pump is working to restore the balance

Answer 23

outer membrane to be more positive in inner segment, K+ channels open + leaving the cell - makes cell more negative pump tries to restore balance -40mv resting potential

Answer 24

Activated rhodopsin activates a G-protein, which activates an enzyme - converts cGMP to GMP, closing the sodium channels no more cgmp, sodium channels slam shut

Answer 25

photoreceptors releasing excitatory neurotransmitter (glutamate) action potentials don’t start until the ganglion cells, photoreceptor responses are graded in dark -40mv, releasing a lot of glutamate with isomarization - becomes more negative

Answer 26

with isomarization - becomes more negative photoreceptors are hyperpolarized & release less glutamate just about how much neurotransmitter is being released

Answer 27

Rods work in the low lighting conditions, but not sensitive to detail. Cones work in bright lighting conditions + process color & detail. 120 million rods to 6 million cones -most in the fovea, most sensitive rods photoreceptors under dim light - hard to see stuff cones need a lot of light to do their jobs blind spot bundles ganglion nerves to take it to the back of the eye

Answer 28

measure rate of dark adaptation how long does it take to see effectively in the dark constantly reevaluating threshold 2 stages of adaptation photopigments of rods + cones regenerate at different rates

Answer 29

Dark adaptation curve: junction relating sensitivity to light to time in the dark, beginning when lights are extinguished Look at small fixation point while paying attention to a flashing test light that is off to the side minimum amount of energy necessarily to just barely see the light is converted to sensitivity

Answer 30

Sensitivity equals 1/threshold, high threshold corresponds to low sensitivity Light adopted sensitivity: sensitivity measured in the light, measured while the eyes adapted to the light Once in the dark observer continues adjusting the intensity of the flashing light so it can just barely be seen, tracking the increase in sensitivity that occurs in the dark As observer becomes more sensitive to light she must decrease the light intensity to keep it just barely visible

Answer 31

Dark adaptation curve shows that as adaptation proceeds, observer becomes more sensitive to the light Dark adopted sensitivity: sensitivity at the end of dark adaptation, 100,000 times greater than the light adopted sensitivity measured before dark adaptation begin

Answer 32

time it takes to adapt to dark reflects how long it takes for visual pigment to regenerate. regenerate: takes longer for rods than cones

Answer 33

Image of the test light falls only on the cones by having observer look directly at the test light so the image will fall on the all cone fovea cones maxes out in the dark rods continue to regenerate + become more sensitive overtime rod cone break

Answer 34

Rod monochromats: people who have no cones due to a rare genetic defect Once dark adaptation begins, rods increase sensitivity + reach final dark adopted level in about 25 minutes Rod – Cone break: place where the rod to begin to determine the dark adaptation curve

Answer 35

relative sensitivity to light as a function of it’s wavelength. for short wavelengths it needs to be intense to detect it how bright something appears at the the same intensity yellowish green is brightest colour of the day

Answer 36

Visual pigment bleaching: after retinal part of the visual pigment changes its shape retinal separate from the opsin part of the molecule causes the molecule to become lighter in color retinal needs to return to its bent shape + become reattached to the opsin Sensitivity to light depends on the concentration of chemical – Visual pigment

Answer 37

speed at which our sensitivity increases in the dark depend on chemical reaction – regeneration of the visual pigment Detached retina: bleach pigment separated right now and opsin can no longer be recombined in the person becomes blind in the area of the visual field serve by the separate area of the retina

Answer 38

Measuring spectral sensitivity curve We present one wavelength at a time + measured observers sensitivity Life of a single wavelength – mono chromatic light – created using special filters called a spectrometer Ability to see what wavelengths is plotted in terms of sensitivity versus wavelength

Answer 39

stimulates only the cones Measure rod spectral sensitivity curve by measuring sensitivity after the eye is dark adopted Rods are more sensitive to short wavelength of light then cones Purkinje shift: shift from cone vision to rod vision occurs at dusk because you’re eye begins dark adopting in low light levels so the rods begin to influence vision

Answer 40

Absorption spectrum: plot of amount of light absorbed versus the wavelength of the light

Answer 41

Short wavelength pigment absorbs light best at about 419 nano meters, medium wavelength pigment absorbs light at about 530 190 m and long wave length pigment absorbs light at 558 nm fewer short wavelength receptors + much less of the short wavelength pigment Sensitivity in the dark and sensitivity to different wavelengths are determined by the properties of the rod and cone visual pigment

Answer 42

Signals are transmitted out of back of the eye in optic nerve to a group of neurons called the lateral geniculate nucleus and then to the visual receiving area of the cortex

Answer 43

Electrodes are connected to a meter that records the difference in charge between the tips of the two electrodes Difference in potential between the tips when an axon is at rest is -70 mV Resting potential: inside the neuron is 70 mV more negative than the outside Action potential last about one millisecond

Answer 44

Propagated response: once the response is triggered it travels all the way down axon without decreasing in size Changing stimulus intensity affect the rate of firing Refractory period: interval between the time A nerve impulse occurs in the next one can be generated by the axon – 1ms Spontaneous activity: establish as a baseline level of firing for the neuron