Monocular Sensory Perception Exam 1

Front 1

what is the range of sensitivity for the visual system

Back 1

~14 log units change in ambient luminance

Front 2

what is the dynamic range of an individual neuron

Back 2

~2 log units

Front 3

what is a key feature of the Maxwellian View Presentation

Back 3

retinal illuminance of the stimulus was NOT affected by pupil diameter

Front 4

what type of relationship is seen when a flash of light is delivered

Back 4

POISSON DISTRIBUTION

quantal fluctuation

Front 5

what findings were presented in the HS&P experiment

Back 5

1. 90 quanta at the cornea
2. 8-10 quanta within the retinal critical duration for temporal summation and critical area for spatial summation
3. only 1 quantum to each of the above 8-10 photoreceptors

Front 6

how is the eye described under optimum testing condition

Back 6

IDEAL DETECTOR

Front 7

describe dark adaptation

Back 7

the change in visual sensitivity that occurs in the dark, brought about by physical and chemical processes in the eye to enable visual function in the presence of the minimal number of photon

Front 8

the changes during dark adaptation that give the observer visual function include...

Back 8

1. dilation of the pupil
2. increased sensitivity of photoreceptors
3. increasing dominance of rod activity (purkinje shift)

Front 9

what factors must be taken into account when measuring dark adaptation

Back 9

1. size of stimulus
2. wavelength (spectral sensitivity of rods vs cones)
3. duration
4. retinal position

Front 10

dark adaptation testing procedure

Back 10

1. bleaching for 5min
2. total darkness
3. measure light detection threshold over the next 40-45min using ascending method of limits

Front 11

what is the result of reducing the INTENSITY of the adapting light

Back 11

shifting the dark adaptation function DOWN and LEFT

Front 12

what is the result of reducing the DURATION of the adapting light

Back 12

more rapid decrease in the visual threshold during dark adaptation (steeper slope)

Front 13

what is the influence of the spot size of the stimulus

Back 13

1. the larger the size the more rods will be activated
2. rod/cone breaks will be sooner
3. final threshold even lower (reflects spatial summation of rod pathway)

Front 14

bleaching 50% of the retinal rhodopsin raises the increment threshold by a factor of...

Back 14

~10 log units
(10 billion times)

Front 15

what is the half life of bleached rhodopsin

Back 15

approx. 5min

Front 16

what is the S2 component

Back 16

1. OPSIN
2. related to the recovery of rods
3. reveals that opsin is removed with first order kinetics

Front 17

linear S2 of threshold recovery is analogous to...

Back 17

exponential phase of Rhodopsin regeneration

Front 18

explain Fundus Albipunctatus

Back 18

1. problem storing vitamin A
2. does not transform from cis ROL to cis RAL properly due to inability to store vitamin A
3. dysfunctional at the enzymatic limit

Front 19

Fundus Albipunctatus in respect to dark adaption time

Back 19

can dark adapt...it just takes a long time

Front 20

what is the first symptom of vitamin A deficiency

Back 20

nyctalopia: night blindness

Front 21

how does the S2 slope of a patient with VAD compare with a normal patient

Back 21

S2 slope in a patient with VAD FLATTER than a normal patient

Front 22

what are the two explanations for the rate-limited delivery of 11-cis RAL

Back 22

1. physical resistance
2. enzyme kinetics

Front 23

what accounts for the slowness of recovery of human dark adaptation

Back 23

rate-limited delivery of 11-cis RAL to opsin

Front 24

what accounts for the raised thresholds during the S2 phase

Back 24

opsin activation of the cascade

Front 25

how do you test for a luminance efficiency

Back 25

1. method of adjustment
2. direct brightness matching
3. white "standard" test spot of radiance=1100 watts/sr/m^2

under photopic conditions
then normalize the plot

Front 26

what is in the x and y axis of the luminous efficiency function

Back 26

y: RELATIVE spectral efficiency
x: wavelength

peak at 555nm

Front 27

what effects the luminous efficiency function measurements

Back 27

1. ADAPTATION is most important
2. how they are measured
3. retinal eccentricity and stimulus size

Front 28

what is the Purkinje Shift

Back 28

change in wavelength of maximum sensitivity as one adapts to light or darkness

Front 29

what is the photochromatic interval

Back 29

change in sensitivity to light of a specific wavelength as one adapts to light or darkness

Front 30

what is the difference between radiometry and photometry

Back 30

R: the measurement of electro-magnetic energy
P: "corrects" radiometry for the influence of wavelength upon human brightness preception

Front 31

when does abney's law WORK BEST

Back 31

1. lights in the mixture are SIMILAR in wavelength
2. brightness comparison used: heterochromatic flicker photometry and minimally distinct border criterion

Front 32

when does abney's law FAIL

Back 32

1. lights in the mixture are DIFFERENT in wavelength
2. brightness comparison used: heterochromatic brightness matching

Front 33

why is a red fixation light used to test absolute threshold

Back 33

to minimize light adaptation

Front 34

why is a red fixation light used to test absolute threshold

Back 34

to minimize light adaptation