Neuroscience: Visual Processing Cells
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Neuroscience: Visual Processing Cells

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Questions and Answers

Which bipolar cell is likely to exhibit the lowest activity level when light covers both the center and the surround?

  • Parasol bipolar cell
  • Midget bipolar cell
  • OFF center bipolar cell (correct)
  • ON center bipolar cell

    • What type of ganglion cells have the smallest receptive fields and are color sensitive?

  • Rod cells
  • Parasol neurons
  • Midget neurons (correct)
  • Bipolar neurons

    • What happens to ON center cells when light shines in both the center and the surround of their receptive field?

  • Exhibit basal level of activity
  • Exhibit decreased level of activity (correct)
  • Exhibit no change in activity
  • Exhibit maximum level of activity

    • What type of input do midget neurons primarily receive?

    <p>Cones</p> Signup and view all the answers

    Which feature is characteristic of parasol neurons in the retina?

    <p>Broad outlines of shapes detection</p> Signup and view all the answers

    What is the primary function of concentric receptive fields?

    <p>Helps in border detection of objects</p> Signup and view all the answers

    Where does visual information go after it has been transduced in the retina?

    <p>To the visual cortex</p> Signup and view all the answers

    Which type of bipolar cell decreases activity when light is present in the center of its receptive field?

    <p>OFF center cell</p> Signup and view all the answers

    What color perception indicates decreased neuronal activity?

    <p>Green</p> Signup and view all the answers

    Which theory explains recognizing colors despite changes in lighting?

    <p>Retinex Theory</p> Signup and view all the answers

    What is the main feature of the opponent process theory?

    <p>It interprets activity as specific colors (red or green).</p> Signup and view all the answers

    Which of the following is NOT a monocular depth cue?

    <p>Retinal disparity</p> Signup and view all the answers

    Which part of the visual pathway includes both the retina and cortical processing?

    <p>Retinex</p> Signup and view all the answers

    What does lateral inhibition in the eye contribute to?

    <p>Contrast enhancement</p> Signup and view all the answers

    Which of the following is a component of binocular depth cues?

    <p>Retinal disparity</p> Signup and view all the answers

    In the context of color vision, what does the term 'concentric receptive fields' refer to?

    <p>Neural organization in the visual cortex</p> Signup and view all the answers

    What occurs at the optic chiasm?

    <p>Half of the axons from each eye cross over to the other side of the brain.</p> Signup and view all the answers

    What is the primary function of the lateral geniculate nucleus (LGN)?

    <p>Process movement and contrast.</p> Signup and view all the answers

    Which visual cortex layer primarily receives input from the LGN?

    <p>Layer IV</p> Signup and view all the answers

    What type of cells in V1 are specifically responsive to bars or edges with fixed excitatory and inhibitory zones?

    <p>Simple cells</p> Signup and view all the answers

    Which pathway is involved in identifying objects and shapes?

    <p>Ventral stream</p> Signup and view all the answers

    What is meant by ocular dominance in the visual cortex?

    <p>Preference of one eye over the other.</p> Signup and view all the answers

    Which type of cell has a large receptive field and responds uniformly across its entire area?

    <p>Complex cells</p> Signup and view all the answers

    What happens if there is damage to the optic disk?

    <p>Creation of a blind spot.</p> Signup and view all the answers

    What type of receptive field do end-stopped cells have?

    <p>Same as complex, with a strong inhibitory zone at one end</p> Signup and view all the answers

    What structure exits the eye alongside the optic nerve?

    <p>Optic disk</p> Signup and view all the answers

    What is the primary function of the Dorsal stream in visual processing?

    <p>Guiding movements based on visual input</p> Signup and view all the answers

    What condition might result from damage to the MT and MST regions of the brain?

    <p>Motion blindness (akinetopsia)</p> Signup and view all the answers

    What is a characteristic response of neurons in the MT area?

    <p>Respond to absolute speed and direction of movement</p> Signup and view all the answers

    What does the Fusiform Face Area primarily contribute to?

    <p>Facial recognition and detailed visual expertise</p> Signup and view all the answers

    Which motion-related phenomenon is described as a brief decrease in visual cortex activity during eye movements?

    <p>Saccades</p> Signup and view all the answers

    What might be an evolutionary benefit of newborns being wired to pay more attention to faces?

    <p>To bond with caregivers and recognize social cues</p> Signup and view all the answers

    What is prosopagnosia primarily associated with?

    <p>Impaired ability to recognize faces</p> Signup and view all the answers

    Which type of visual information do neurons in the MST specifically respond to?

    <p>Complex motion stimuli such as rotation</p> Signup and view all the answers

    What primarily causes red-green color deficiency in color blindness?

    <p>Both long and medium cones developing the same photopigment</p> Signup and view all the answers

    What is the main explanation for negative color afterimages according to the opponent process theory?

    <p>Decreased activity in neurons corresponding to the color viewed</p> Signup and view all the answers

    Which color opposites are represented in the opponent process theory?

    <p>Red and green, yellow and blue, black and white</p> Signup and view all the answers

    How do neurons behave after the stimulus is removed in the context of negative afterimages?

    <p>Increased activity in the neurons that were previously fatigued</p> Signup and view all the answers

    Why does trichromatic theory fail to explain negative color afterimages?

    <p>It solely focuses on the initial perception of colors</p> Signup and view all the answers

    What is a distinguishing characteristic of the opponent process theory?

    <p>It involves perceiving colors in pairs of opposites</p> Signup and view all the answers

    Which scenario best illustrates the effect described by opponent process theory?

    <p>Suddenly seeing blue after staring at red for a long time</p> Signup and view all the answers

    What typically happens to cone activity when staring at a color for an extended period?

    <p>The cone activity of that color becomes fatigued</p> Signup and view all the answers

    Study Notes

    Bipolar and Ganglion Cells

    • Bipolar cells receive input from photoreceptors and horizontal cells
    • Ganglion cells receive input from bipolar cells

    Concentric Receptive Fields

    • Receptive field= an area in visual space to which a cell responds
    • Concentric receptive field= 2 circles with different polarities
      • Center and antagonistic surround
      • ON center cells- increase activity when light shines in the center and decrease activity when light shines in the surround
      • OFF center cells- decrease activity when light shines in the center and increase activity when light shines in the surround

    Midget and Parasol Neurons

    • Midget neurons have small cell bodies and receptive fields, are located near the fovea and are color sensitive
    • Parasol neurons have large cell bodies and receptive fields, are located throughout the retina and are not color sensitive

    The Route of Visual Information

    • After being transduced, information goes to cells in the retina
      • Optic disk
      • Optic chiasm
      • Lateral geniculate nucleus (LGN)
      • Primary visual cortex (V1)
      • Further processing in other cortical areas

    The Optic Disk

    • The optic nerve and blood vessels exit the eye here
    • Lack of photoreceptors results in a blind spot

    The Optic Chiasm

    • Half of the axons from each eye cross over to the other side of the brain
    • After the optic chiasm, the nerves are referred to as the optic tract

    The Lateral Geniculate Nucleus (LGN)

    • Midget retinal ganglion neurons → parvocellular neurons in the LGN
      • Visual details, color
    • Parasol retinal ganglion neurons → magnocellular neurons in the LGN
      • Movement, outlines of shapes, contrast between light and dark
    • After the LGN, the nerves are referred to as the optic radiation

    The Primary Visual Cortex (V1)

    • Located in the occipital lobe
    • Layer IV receives input from the LGN and projects to many regions, including the frontal cortex:
      • The frontal cortex also projects back to V1 to modify experience
    • Conscious visual experience

    Different Types of Cells in the Primary Visual Cortex

    • Simple cells: Small receptive field that is bar or edge shaped with fixed excitatory and inhibitory zones
    • Complex cells: Medium sized receptive field that is bar or edge shaped, but responds equally throughout a large receptive field
    • End-stopped cells: Have the same shape as the complex cell but with a strong inhibitory zone at one end

    Ocular Dominance

    • Each eye's inputs remain separate in the LGN and at the input layer IV of V1
    • Alternating bands/columns of ocular dominance across the cortical surface
      • Ocular dominance= a neuron’s preference for one eye over another

    Orientation Columns

    • Cells have a preferred orientation
    • Cells with the same orientation preference are organized into columns
      • Preference for neighboring columns is not random; Orientation selectivity changes only slightly as you move from column to column

    Further Processing in Other Areas

    • Secondary visual cortex (V2): Receives information from V1, processes it further and sends it on to other areas
    • Two major pathways:
      • Ventral stream: "what pathway"
        • Important for identifying objects; Damage causes deficits in the identification of shapes/orientations of objects, naming objects, recognition, etc.
      • Dorsal stream: "where pathway"
        • Important for visually guided movement; Damage causes deficits in the integration of vision with movements

    MT and MST

    • MT (V5)= middle temporal lobe: Neurons respond selectively when something moves at a particular speed in a particular direction
      • Detect absolute speed, acceleration, and deceleration; Respond to photographs that imply movement
    • MST = medial superior temporal cortex: Respond to more complex stimuli such as the expansion, contraction, and rotation of a scene
      • Occurs when you move your head forward and backward and when you tilt your head

    MT and MST

    • Allow you to distinguish between eye movements and object movements
      • Neurons respond when an object moves relative to its background; No response if both the object and background move in the same direction at the same speed
    • Damage → motion blindness (akinetopsia)= the inability to determine direction, speed, or whether an object is moving
    • Saccades= voluntary eye movement: Brief decrease in the activity of the visual cortex during quick eye movements; Temporary motion blindess

    Fusiform Gyrus/Fusiform Face Area

    • Facial recognition
    • Detailed visual recognition/expertise
    • Newborns are “wired” to pay more attention to faces than to other stationary displays
      • There is an evolutionary benefit for recognizing faces

    Prosopagnosia

    • Impaired ability to recognize faces
    • Occurs after damage to the fusiform gyrus of the inferior temporal cortex (or doesn’t form correctly)

    The Trichromatic Theory

    • Doesn't explain negative color afterimages

    The Opponent Process Theory

    • We perceive color in terms of opposites
      • Continuum from red to green, another from yellow to blue, another from white to black
      • After you stare at one color long enough, you fatigue that response and swing to the opposite
        • ↑ activity = blue, ↓ activity = yellow
        • ↑ activity = red, ↓ activity = green

    The Opponent Process Theory

    • How does this explain negative color afterimages?
      • When the stimulus is removed, the fatigued neuron rebounds
      • The neurons that had been suppressing activity now increase their activity, which the brain interprets as red
      • The neurons that had been increasing their activity now decrease their activity, which the brain interprets as green

    Which Theory is Correct? Both

    • The Trichromatic Theory explains most color perception but the Opponent Process Theory helps explain negative afterimages

    Retinex Theory

    • The Trichromatic theory and opponent process theory can’t explain color consistency
      • Recognizing colors despite changes in lighting
    • Retinex = retina + cortex; Other brain regions (like the PFC) alter functioning of visual cortex (V1/V2)

    Depth Perception

    • Two types of depth cues:
      • Monocular depth cues (relative size, height in plane, interposition, linear perspective)
      • Binocular depth cues (retinal disparity- where the visual cue hits the retina in each eye)

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    Description

    This quiz explores the functions and characteristics of bipolar, ganglion, midget, and parasol neurons in the visual processing system. It also delves into receptive fields and their roles in visual perception. Test your understanding of how these cells contribute to our ability to process visual information.

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