Since the optic nerve must pass through the retinal layer, we all have a blind spot devoid of light receptors. This normally goes unnoticed, since the brain attempts to compensate for missing sensory information by filling it in based on surrounding patterns. Which step of the sensory pathway is represented by perceptual filling-in of the physiological blind spot?

Question

A.  interpretation
B.  stimulus
C.  transduction into receptor potential
D.  action potential transmission

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

Gather Content
What do you already know about retinal signaling? What other information is related to the question?

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  interpretation

Clarify Question
What is the key concept addressed by the question?
        · Why do we not notice our blind spot?
What type of thinking is required?
            o This is an analyze question because you have to break sensory (visual) signaling into different stages and understand which aspects would be responsible for the lack of perception of a blind spot.

Gather Content
What do you already know about retinal signaling? What other information is related to the question?
        · You already know that the sensory perception of vision starts with photons of light activating photoreceptors in the back of the retina. Then receptor potentials lead to action potentials transmitted to the optic nerve, and then to the visual cortex of the brain. The part of the retina in which the optic nerve passes through does not have any photoreceptors and is referred to as the blind spot. Thus, any light that hits the blind spot will not be detected since there are no photoreceptors to detect it. The brain will receive no stimulation from that area of the visual field.

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
        · If you were to order the answers in terms of the process of the visual pathway, the order would be first stimulus (which is light), then transduction into receptor potentials, which are then converted to action potentials (if the receptor potentials are great enough), and finally the action potentials are sent to the brain (visual cortex) where they are interpreted. There is nothing wrong with the first step, stimulus, because the light still shines on the back of the retina even if there are no photoreceptors to receive the signal in the blind spot, so the answer is not stimulus. If there are no photoreceptors to receive the light signal in the blind spot, then no transduction of receptor and action potentials will be possible from the blind spot. Thus, the brain will not receive any information from the retina about the area of the blind spot. The brain fills-in the perception of a blind spot based on visual information surrounding the blind spot via higher processing and “interpretation” of the whole visual field.

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o Answering this question correctly depended not only on understanding the steps of the sensory pathway of visual processing , but on your ability to determine which aspects of this pathway is responsible for filling-in the perceptual gap produced by the blind spot. If you got an incorrect answer, did you realize that “interpretation” was referring to higher visual processing in the brain? Did you understand that there would be a lack of receptor and action potentials from the blind spot causing a perceptual hole, not filling in this gap?