Spatial Vision

Question 1

Visual Acuity

Answer 1

A measure of the finest detail that can be resolved by the eyes

Question 2

Cycle

Answer 2

A repetition of black and white stripe

Question 3

Amblyopia

Answer 3

Disorder characterised by reduced spatial vision in an otherwise healthy eye even with proper correction for refractive error (lazy eye)

Question 4

Why is central vision slower than a peripheral vision?

Answer 4

Foveal cones have longer axons than peripheral cones in order to allow dense packing in the central fovea, the longer axons transmit slow signals better than fast one

Question 5

Spatial Frequnecy

Answer 5

Refers to the number of times, a pattern such as a sine wave grating repeats (a cycle) given unit of space (degree of visual angle)

Question 6

How is spatial frequency measured?

Answer 6

It is measured as the number of cycles per degree of visual angle

Question 7

Contrast Sensitivity Function

Answer 7

The ability to perceive sharp and clear outlines of very small objects. CS helps detect objects without a clear outline and distinguish them from their background contrast.

Question 8

Factors Affecting CFS

Answer 8

1)Adaptation level of the eye
2) Temporal modulation of targets (how it varies over time)
3) Age
- Reduces contrast sensitivity because of the reduction in rods, which are eye structures responsible for vision in low-lit areas
4) Refractive State

Question 9

Why does the visual system break down real world images into?

Answer 9

A vast number of components, each of which is essentially a sine wave grating with a particular spatial frequency

Question 10

Fourier analysis

Answer 10

A mathematical procedure by which any signal can be separated into component sine waves at different frequencies.

Question 11

Phase

Answer 11

The position of a grating relative to a fixed position measured in degrees, where one complete cycle is 360 degrees

Question 12

How does a ganglion cell respond when the spatial frequency of the grating is too low?

Answer 12

The ganglion cell responds quickly because part of the fat, bright bar of the grating lands in the inhibitory surround, damping the cell’s response.

Question 13

How does a ganglion cell respond when the spatial frequency of the grating is too high?

Answer 13

When the spatial frequency is too high, the ganglion cell responds weakly because both the dark and bright stripes fall within the centre receptive field centre, washing out the response

Question 14

How does the cell respond when the spatial frequency is just right?

Answer 14

When the spatial frequency is just right, the bright bar filling the centre with dark bars filling the surround, the cell responds vigorously

Question 15

How is each retinal ganglion cell “tuned” to spatial frequency?

Answer 15

Each cell acts like a filter responding best to a specific spatial frequency that matches its receptive field size and responding less to both higher and lower spatial frequencies

Question 16

Responses of retinal ganglion cells also dependent on the ________ of the grating-its position within the receptive field

Answer 16

Phase ; When the grating size and phase are optimal (light bar fills the receptive field center and dark bars fill the surround), the ON center ganglion cell responds vigorously

Question 17

The ______ LGN receives input projects from the left side of the retina in both eyes and the right LGN receives projections from the ____ side of both retinas

Answer 17

left ; right

Question 18

Layers 1, 4, 6 of the right LGN receive input from:

Answer 18

The left contralateral eye

Question 19

Layers 2, 3, 5 get input from

Answer 19

The right ipsilateral eye

Question 20

Topographical Mapping

Answer 20

Orderly mapping go the world in the LGN and the visual cortex and provides us with a neural basis for knowing where things are in space