Ch10-Vision

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Questions and Answers

What type of circuits carry input from medium and long wavelength cones?

Bistratified circuits

Parvocellular circuits (correct)

Magnocellular circuits

Koniocellular circuits

Koniocellular circuits are primarily associated with which type of cones?

Long wavelength cones

Medium wavelength cones

Short wavelength cones (correct)

Rod cells

Where do color-sensitive cells in CO blobs of V1 send color information?

To the ventral stream

To thick stripes of V2

To thin stripes of V2 (correct)

To the dorsal stream

Which area is rich in color-sensitive cells and important for color constancy?

V4 Signup and view all the answers

What aspect of visual stimulus does the interblob region of V1 primarily provide information about?

Movement Signup and view all the answers

What occurs to the neurons encountered when an electrode is advanced through an interblob column of cortex?

They show similar response properties. Signup and view all the answers

How do parvocellular circuits differ from koniocellular circuits?

Parvocellular circuits carry input from medium and long wavelengths, while koniocellular circuits exclusively handle short wavelengths. Signup and view all the answers

Which of the following is NOT a function associated with the primary visual cortex?

Facilitating auditory perception Signup and view all the answers

In the primary visual cortex, which aspect of visual stimulus relates to the spatial position of visual input?

Location in the visual field Signup and view all the answers

What type of circuits in the primary visual cortex are responsible for processing information from medium and long wavelength cones?

Parvocellular circuits Signup and view all the answers

Which structure acts as a topographically organized relay station providing input to the primary visual cortex?

Lateral geniculate nucleus Signup and view all the answers

What role do color-sensitive cells in CO blobs of V1 play?

Carry color information to V2 Signup and view all the answers

Which area is identified as being particularly rich in color-sensitive cells and essential for color constancy?

Area V4 Signup and view all the answers

Which form of processing in the primary visual cortex involves the parallel handling of input streams?

Parallel processing Signup and view all the answers

What does the term 'ocular dominance' refer to in the context of visual processing?

The preference for one eye over the other in visual information processing Signup and view all the answers

Receptive fields in the primary visual cortex are characterized by which feature?

All cells within a column share the same retinotopic location Signup and view all the answers

What type of retinal ganglion cells are activated when light shines in the center of their receptive field?

ON-cells Signup and view all the answers

Which type of retinal ganglion cell is inhibited when light shines in the center of its receptive field?

OFF-cells Signup and view all the answers

What role do horizontal cells play in the visual system?

They facilitate lateral inhibition among neighboring cells. Signup and view all the answers

What happens to the release of glutamate from photoreceptors when light turns on?

It decreases significantly. Signup and view all the answers

What is the primary function of ON/OFF retinal ganglion cells?

To respond to changes in light intensity within their receptive field. Signup and view all the answers

What is the significance of contrast enhancement in the visual system?

It sharpens the distinction between light and dark areas. Signup and view all the answers

How do bipolar cells respond to the presence of light?

They can either hyperpolarize or depolarize, depending on their type. Signup and view all the answers

In what way do horizontal cells contribute to temporal contrast?

By providing feedback that helps amplify changes in light. Signup and view all the answers

Which of the following is TRUE about the receptive fields of retinal ganglion cells?

They can have both a center and surrounding area that respond differently to light. Signup and view all the answers

What does the term 'gain control' refer to in the context of visual processing?

Enhancing the contrast of the visual field. Signup and view all the answers

Which type of photopigment is primarily found in the rods?

Rhodopsin Signup and view all the answers

What is the effect of light exposure on the hyperpolarization of retinal ganglion cells?

It leads to a decrease in action potentials. Signup and view all the answers

Which component of visual processing primarily establishes the initial response to light?

Photoreceptors Signup and view all the answers

What happens to cation channels in photoreceptors when they are struck by a photon of light?

They close, leading to hyperpolarization. Signup and view all the answers

What type of signal do retinal ganglion cells (RGCs) produce?

Action potentials Signup and view all the answers

Study Notes

The Visual Stimulus

Visible light is a small part of the electromagnetic spectrum (380-760 nm).
Humans are not sensitive to electromagnetic radiation outside this range, while some animals, like honeybees, can detect ultraviolet radiation.
Light acts as both a particle and a wave, with wavelength determining color.
Longer wavelengths correspond to lower frequency and appear as red, shorter to higher frequency, and are perceived as violet.
The intensity of the light wave corresponds to brightness, a constant speed of 186,000 miles/second.

The Visual Stimulus: Color, Purity, and Brightness

A mixture of all wavelengths creates white light.
Light with only one wavelength is called saturated light.
Variations in saturation and wavelengths lead to different hues.
Brightness is determined by the magnitude of the light wave.

The Human Eye: Anatomy

Light travels in straight lines; the iris controls pupil size (dilation = sympathetic, contraction = parasympathetic).
The lens focuses light on the retina.
The image on the retina is inverted.
The fovea is optimized for high acuity and color vision.
The rods, located outside the fovea, are responsible for scotopic and mesopic vision (low light).
Cones, located mostly in the fovea, are responsible for mesopic and photopic vision (bright light).
Photoreceptors at the back of the retina consist of 120 million rods and 6 million cones.
Vergence movements involve both eyes focusing on a single target.
Saccadic movements are quick eye shifts from one point to another.
Pursuit movements smoothly track moving objects.

The Retinal Ganglion Cells

Bipolar cells and photoreceptors are not action potential generating cells.
Retinal Ganglion Cells generate action potentials. -There are 4 types of retinal ganglion cells: parvocellular, magnocellular, bistratified, and photosensitive.
Parvocellular - high sensitivity to color and detail.
Magnocellular - high sensitivity to movement and brightness, also involved in depth perception.
Bistratified - inputs from rods, cones, and amacrine cells.
Photosensitive - contribute to synchronizing daily rhythms and pupillary constriction.

The Visual Pathway

Information from the left visual field travels to the right side of the brain, and vice versa.
The optic nerves join at the optic chiasm.
Signals are relayed to the dorsal lateral geniculate nucleus (LGN) in the thalamus.
Finally, information is processed by the primary visual cortex (V1).

Coding of Light & Dark

Visual information processing involves reception, transduction, and coding.
Receptors contain photopigments (opsin and retinal) that change their structure upon receiving light.
Transduction involves the conversion of light to an electrical signal. In the presence of light the photoreceptors hyperpolarize.
Coding involves the communication of that signal to the brain, producing graded potentials in photoreceptors and bipolar cells, and action potentials in retinal ganglion cells. Lateral inhibition from horizontal and amacrine cells contributes to contrast enhancement.

Coding of Color

Humans have three types of cones, each sensitive to different wavelengths of light (short, medium, and long).
The Trichromatic theory says cone responses combine to perceive all colors.
The Opponent-process theory explains afterimages and color vision by explaining how specific neurons respond to opposing pairs of colors (red/green, blue/yellow).

The Primary Visual Cortex

The Primary visual cortex processes information about location, color, ocular dominance, and orientation.
Magno- and parvocellular pathways provide parallel processing.
Ocular dominance columns show a dominance for input from one eye.
Orientation columns in the cortex respond to different orientations of lines.

Perception of Visual Information

Spatial frequency relates to contrast differences in the visual field.
Visual processing involves two major pathways, the dorsal "where" and the ventral "what" pathways.
Depth perception uses monocular and binocular cues.
The Dorsal stream processes information about spatial location and movement.
The Ventral stream processes information about object recognition and color.

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Description

Explore the fascinating concepts of visible light, color perception, and the anatomy of the human eye. This quiz covers the properties of light, the electromagnetic spectrum, and how we perceive brightness and hues. Test your knowledge on these essential topics in vision science.