OPT 404

• What is the primary focus of OPT404?

  Visual perception
• What is the function of photoreceptors in the retina?

  They contain pigments sensitive to light
• What are the components of the visual pathway mentioned?

  Retina, LGN, colliculi, pretectal area

  
• What types of vision do rods and cones provide?

  Rods: scotopic; Cones: photopic
• What is the ratio of L, M, and S cones in the retina?

  1. M:S = 8:4:1
• How do combinations of cone responses lead to color perception?

  They create a spectrum of color perception
• What is a visual receptive field?

  • Portion of sensory space
  • Elicits neuronal responses when stimulated
  • Example: skin surface, visual tuning properties
• Who defined the receptive field of a single unit?

  Sir Charles Scott Sherrington
• What did Hartline study in relation to receptive fields?

  Physiological characteristics of optic nerve fibers
• Who first described the center-surround architecture of visual receptive fields?

  Stephen William Kuffler
• What are the characteristics of center-surround receptive fields?

  • Approximately circular shape
  • Central area excites or inhibits response
  • Surrounding area acts antagonistically
• What is the Difference of Gaussians (DOG) model?

  It describes ON-centre and OFF-surround responses
• How do ON-centre and OFF-surround responses differ in RGCs?

  ON-centre excites; OFF-surround inhibits
• What is the role of lateral inhibition in visual processing?

  It enhances contrast by inhibiting adjacent cells
• What happens when light shines on a bipolar cell with adjacent photoreceptors illuminated?

  It experiences lateral inhibition

  
• What is the early explanation for the grid illusion?

  • More lateral inhibition reduces activity at intersections
  • Less lateral inhibition increases response at intersections
  • Perception of darker or brighter spots
• Which statement about RGC receptive fields is INCORRECT?

  ON-centre fields show excitation when fully illuminated
• What is the effect of more lateral inhibition on the perception of the intersection in the Hermann grid illusion?

  It reduces activity, making it appear darker
• What happens when there is less lateral inhibition at the intersection?

  It results in a stronger response, appearing brighter
• What occurs when looking directly at the intersections of the Hermann grid?

  The dark spots disappear
• How does the receptive field (RF) size at the fovea affect activity?

  Smaller RFs are fully illuminated, returning to baseline
• Who conducted research on the Hermann grid illusion?

  Geier et al. (2008)
• Which statement about RGC receptive fields is INCORRECT?

  ON-centre RGCs show inhibition when fully illuminated
• What is the visual field quadrant associated with the superior temporal region?

  Superior temporal quadrant
• What happens to the image when it falls on the retina?

  It is inverted and laterally reversed
• What is a retinotopic map?

  A distorted map of the retina in the optic nerve
• What occurs at the optic chiasm regarding nasal retinal fibers?

  They undergo decussation
• How does each visual hemifield project in the visual pathway?

  To the contralateral hemisphere

  
• What type of visual field defect is caused by lesioning the optic chiasm?

  Bitemporal hemianopia
• What is the visual field defect associated with a central scotoma?

  Loss of central vision
• What visual field defect results from contralateral homonymous hemianopia?

  Loss of vision in one visual field
• What is the primary function of the magnocellular pathway?

  Motion and luminance information processing
• What type of information does the parvocellular pathway convey?

  Color information and luminance fine details
• What is the role of the koniocellular pathway?

  1. cone color and brightness information
• Which retinal ganglion cells are primarily involved in the magnocellular pathway?

  Parasol RGCs
• What percentage of RGCs feeding signals into the LGN are midget, parasol, and bistratified RGCs?

  90%
• What chromatic property characterizes midget RGCs?

  Red-green color-opponent
• What is the contrast sensitivity of parasol RGCs?

  High
• What type of spatial frequency are midget RGCs sensitive to?

  High spatial frequency
• What is the temporal frequency sensitivity of parasol RGCs?

  Sensitive to high temporal frequency