T2 PC9: Physiology of vision T2 PC9: Physiology of vision

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Questions and Answers

What is the term used to describe the process carried out by the receptive field structure of an on-centre off-surround retinal ganglion cell?

Lateral inhibition (correct)

Peripheral suppression

Excitatory inhibition

Central activation

In the model of computation of light intensity by retinal ganglion cells, what is the output at location a?

-2

-3

2 (correct)

What type of retinal ganglion cell enhances information at visual boundaries?

On-centre off-surround (correct)

Off-centre off-surround

Off-centre on-surround

On-centre on-surround

What does the mosaic in Figure 5 represent?

Photoreceptors contributing to excitation and inhibition of retinal ganglion cells Signup and view all the answers

What is another term for the receptive field structure of an on-centre off-surround retinal ganglion cell?

'Lateral inhibition' Signup and view all the answers

What is the equation for predicting the response level of a retinal ganglion cell to the Mach bands?

$Output = ∑(Intensity x weight)$ Signup and view all the answers

What type of stimulus would decrease the activity in the circular region surrounding the central region of an on-centre, off-surround retinal ganglion cell?

Inhibitory stimulus Signup and view all the answers

In Figure 7, what is the output at location h?

5 Signup and view all the answers

What does an on-centre off-surround retinal ganglion cell do to information at visual boundaries?

Enhances it Signup and view all the answers

What is the formula to calculate the angle between two cones in the fovea of the eye?

$s/f$ radians Signup and view all the answers

What is the relationship between radians and degrees?

$1$ radian = $57.3$ degrees Signup and view all the answers

How many minutes of arc are there in $1$ degree?

$60$ minutes of arc Signup and view all the answers

What is the definition of a radian?

The angle made by an arc of a circle whose length is equal to the circle’s radius Signup and view all the answers

How many radians are there in a full circle (360 degrees)?

$2\text{π}$ radians Signup and view all the answers

What is the formula to convert radians to degrees?

Multiply by $180/\text{π}$ Signup and view all the answers

If the actual separation ($s$) between two cones in the fovea of the eye is $0.1$ mm and the focal length ($f$) of the eye is $22$ mm, what is the angle between them in degrees?

Approximately $0.254^\text{o}$ Signup and view all the answers

What is the method used to estimate visual acuity in the text?

Using the Landolt C test chart at a fixed distance of 6 meters Signup and view all the answers

How can the separation between adjacent cones in the fovea be calculated?

From the distribution of cones in the human fovea and assuming a focal length of 17 mm Signup and view all the answers

What experiment involves viewing a pattern on a computer screen for 30 seconds and observing subsequent color perceptions?

Color adaptation and color opponency experiment Signup and view all the answers

What is used to identify people with color deficiencies in the text?

Ishihara test cards Signup and view all the answers

What can be concluded about optic disc's relative position to the fovea based on an experiment involving finding the blind spot?

The blind spot's position on the retina can be determined, allowing conclusions about the optic disc's relative position to the fovea Signup and view all the answers

Which condition results from the loss of specific cone pigments?

Protanopia Signup and view all the answers

Study Notes

Human Vision Experiments and Observations

Figure 2 shows the distribution of cones in the human fovea, allowing estimation of the separation between neighboring cones.
The separation between adjacent cones in the fovea can be calculated from the given data, assuming a focal length of 17 mm.
Visual acuity, tested using the Landolt C test chart, measures the ability to resolve gaps in circles or letters at a fixed distance of typically 6 meters.
Visual acuity can be estimated by self-evaluating the ability to see gap positions in C-like characters on a computer screen.
The angle between two cones in the fovea can be measured in minutes of arc to estimate visual acuity.
Color adaptation and color opponency experiment involves viewing a pattern on a computer screen for 30 seconds and observing the subsequent color perceptions.
The Ishihara test cards are used to identify people with color deficiencies, and participants are asked to identify the numbers on the cards.
Congenital color vision disorders, such as protanopia, deuteranopia, and tritanopia, result from the loss of specific cone pigments.
A peculiar aspect of vision is that the retinal blood vessels are not normally seen, and an experiment involving illuminating the sclera can reveal their appearance.
The experiment to find the blind spot involves observing a cross and a smiley face at a specific distance and measuring the distance between them.
The blind spot's position on the retina can be determined, and conclusions can be drawn about the optic disc's relative position to the fovea based on this experiment.
The color vision and visual perception experiments provide valuable insights into the functioning of the human eye and its limitations.

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Description

Prepare for the BSMS Module 202 (2021) Human Vision Lab by understanding the recommended books and instructions for the practical class. The class focuses on exploring the performance of the human visual system through observations and note-taking in pairs.