Visual Pathways 1

• What is the primary focus of OPT404?

  Visual perception
• What is the first structure in the visual pathway from the retina?

  LGN (lateral geniculate nucleus)

  
• What are the two types of photoreceptors in the retina?

  Rods and cones

  
• What type of vision do rods provide?

  Scotopic vision
• What type of vision do cones provide?

  Photopic vision
• What is the ratio of L, M, and S cones in the retina?

  1. M:S = 8:4:1
• What is the function of horizontal cells in the retina?

  • Build long-range lateral connections
  • Connect photoreceptors and bipolar cells

  
• What is a visual receptive field?

  Portion of sensory space eliciting responses
• Who first defined the receptive field of a single unit?

  Hartline
• What did Kuffler describe about RGCs' receptive fields?

  Center-surround architecture
• What are the characteristics of ON-centre and OFF-centre receptive fields?

  • ON-centre: Excitation when illuminated
  • OFF-centre: Inhibition when illuminated

  
• What is the Difference of Gaussians (DOG) model?

  Model describing ON-centre and OFF-surround responses
• What is the main response of RGCs to a small light spot?

  Increase in firing activity
• What happens to RGC activity when light shines on the inhibitory surround?

  Decrease in firing activity
• How does lateral inhibition affect bipolar cells?

  • Produces inhibition at bipolar cells
  • Cancels excitation from adjacent photoreceptors

  
• What visual phenomenon is explained by lateral inhibition?

  The grid illusion
• What is the shape of RGC receptive fields?

  Roughly circular
• What occurs when the entire receptive field is illuminated for ON-centre RGCs?

  Excitation occurs

  
• What is the role of edges in visual perception?

  Provide important information about objects
• What are the key studies related to receptive fields in RGCs?

  1. Hartline's studies on optic nerve fibers
  2. Kuffler's center-surround architecture
  3. Enroth-Cugell and Robson's contrast sensitivity
• What is the primary response of RGCs to light and dark bars?

  Varies based on illumination pattern
• What happens to the perception of grey dots at intersections in the grid illusion?

  Dots appear due to lateral inhibition
• What occurs at the fovea regarding receptive fields?

  RFs are smaller and fully illuminated
• Who conducted early studies on the grid illusion?

  Geier et al. (2008)
• What is the incorrect statement about RGC receptive fields?

  Excitation occurs when the entire field is illuminated
• What is the role of the accessory optic system?

  Contributes to visual processing
• What is the function of amacrine cells?

  Interact with bipolar cells and RGCs
• What is the significance of the thalamic pulvinar?

  Involved in visual perception
• How does neural noise affect RGC activity?

  Influences baseline firing rates
• What historical context is important for visual perception studies?

  Development of receptive field theories
• What are the physiological characteristics of receptive fields in different species?

  Varies based on species and environment
• What methods are used to measure contrast sensitivity in RGCs?

  Linear system analysis with gratings
• What are the implications of receptive field organization for visual processing?

  Enhances edge detection and contrast

  
• How are receptive fields related to visual illusions?

  They explain phenomena like the grid illusion
• Why is the visual pathway important for overall perception?

  It integrates visual information for interpretation
• What is the effect of more lateral inhibition on perception?

  It reduces activity and perceives darker
• How does less lateral inhibition affect the response of the center?

  It results in a stronger response and brighter perception
• What happens to the dark spot when looking directly at intersections?

  The dark spot disappears
• Why do receptive fields (RFs) at the fovea return to baseline activity?

  Because they are all illuminated
• What is the shape of receptive fields of retinal ganglion cells (RGCs)?

  Roughly circular in shape