Test 183  (Ocular physiology)

1. The following are true about critical fusion frequency: 

a. it refers to the rate at which stimuli can be presented 
    and still be perceived as separate stimuli

b. it is dependent on visual acuity

c. it is dependent on the spacing between neighbouring 
    photoreceptors

d. it depends on the time-resolving ability of the eye

e. the frames used in movie are presented at a rate above 
    the critical fusion frequency.
 

Answera.T   b.F  c.F   d.T  e.T
Critical fusion frequency is the at rate at which stimuli 
can be presented and still be perceived as separate stimuli. A rate above the critical fusion frequency will 
make the stimuli appears continuous. Movie uses frames above this rate so that the pictures are perceived as continuos. The frequency depends on the time-resolving ability of the eye.

2. Structures involved in colour vision include:

a. parvocellular pathway

b. superficial layer 4C of visual cortex

c. superior collliculi

d. geniculate layers 1-2

e. cerebellum
 

Answera.T  b.F  c.F  d.F  e.F
Superior colliculi and cerebellum are not involved in colour vision. Deep layer 4C of the visual cortex and the geniculate layers 3-6 as well as the parvocellular pathway are involved in colour vision.

 
 

3. Area(s) in the visual cortex involved in colour vision include:

a. V1

b. V2

c. V3

d. V7

e. V8
 

Answer
a.F   b.F  c.F  d.F  e.T
Only V8 of the visual cortex is involved in colour vision.

 

. 4. Differences between the M cells and P cells include:

a. M cells have larger cell bodies than P cells

b. M cells have slower conduction rate than P cells

c. M cells have larger receptive field than P cells

d. M cells do not synapse in lateral geniculate body 
    whereas P cells do

e. M cells detect motion and P cells colour vision
 

Answer
a.T  b.F  c.T  d.F  e.T
M cells have a more rapid conduction rate than P cells. Both M and P cells synapse in the lateral geniculate body.

5. The superior colliculi:

a. receives P fibres from the retina

b. receives M fibres from the retina

c. regulates saccade movement

d. is the centre for pursuit movement

e. is connected to the cerebellum via the tectopontine tract
 

Answer
a.F   b.T  c.T  d.F e.T
The superior colliculi regulates the saccade movement 
and receives M fibres from the retina. The cerebellum is the centre of pursuit movement.

 

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