week 1

• What is the main focus of visual neurophysiology?


  Processing signals in the visual system
• Why is it important to study visual neurophysiology?

  To learn about visual deficits beyond optical factors
• What are the two main reasons for studying visual neurophysiology?

  Clinical reasons and intellectual motivation
• What methods are used to study the visual system?

  • Neuroanatomy: Structure of visual components
  • Neurophysiology: Interaction of components
  • Psychophysics: Human interaction with stimuli
  • Psychology: Higher order processing impacts
• What is the role of Optical Coherence Tomography (OCT)?

  To visualize the structure of the retina
• What does an Electroretinogram (ERG) measure?

  Electrical output from the retina
• What are the main components of the visual pathway?

  Eyes, sub-cortical structures, cortex
• How many nerve fibers are in the retina?

  1 million nerve fibers
• What does the distorted topographical representation of the retina imply?

  Processing occurs to compensate for distortion
• What is the purpose of the retrolental illumination method?

  To illuminate the eye from behind the lens
• What does the term "phototransduction" refer to?

  Conversion of light into neural signals
• What is the main task of the retina?

  To gather and transform light information
• What are the two types of summation in retinal processing?

  Spatial summation and temporal summation
• What are the types of retinal ganglion cells?

  • Scotopic and photopic systems
  • Foveal and peripheral vision
  • On and off centre cells
  • Magnocellular and parvocellular systems
• What is the simplest pathway for signal transmission in the retina?

  Cone > Bipolar cell > Ganglion cell
• What role do amacrine cells play in the retina?

  They mediate signals between bipolar and ganglion cells
• What is the significance of lateral inhibition in vision?

  It increases visual acuity by suppressing signals
• How do bipolar cells respond to light?

  They can hyperpolarize or depolarize
• What is a receptive field?

  Area affecting a neuron's activity
• How do receptive fields change in complexity?

  They become more complex higher in processing
• What distinguishes ON-centre cells from OFF-centre cells?

  ON-centre cells depolarize with center light
• What are the stages in visual perception?

  1. Light reflected from objects
  2. Image formation
  3. Sampling of image
  4. Transduction to neural activity
• What is the role of horizontal cells in the retina?

  To inhibit other cells and enhance contrast
• How do ganglion cells' receptive fields differ from bipolar cells'?

  Ganglion cells have concentric receptive fields
• What is the term for the area that modifies neuron activity?

  Receptive field
• How is the receptive field of a single photoreceptor cell defined?

  It corresponds to a tiny spot of light
• How do receptive fields change in complexity through the retina?

  They become increasingly complex in layers
• What shape do the receptive fields of bipolar cells have?

  Circular
• What is the effect of light on the centre and surround of bipolar cell receptive fields?

  They work in opposite ways
• What are the two types of bipolar cells?

  ON-centre and OFF-centre cells
• What happens when light strikes the centre of an ON-centre bipolar cell's receptive field?

  It causes depolarization of the cell
• What is the response of OFF-centre cells to light in their centre?

  It inhibits (hyperpolarizes) the cell
• How do ganglion cells' receptive fields compare to bipolar cells'?

  They also have centre-surround antagonism
• How do ON-centre and OFF-centre ganglion cells respond to stimulation?

  By increasing or decreasing action potential frequency
• What inhibits the response to stimulation of the centre of a ganglion cell's receptive field?

  Stimulation of the surround
• What do rods and cones project to in the retina?

  Bipolar cells
• What do midget bipolar and ganglion cells provide the brain?

  High spatial resolution
• What distinguishes ON-bipolar cells from OFF-bipolar cells?

  ON-bipolars are turned on by light
• How do OFF-bipolar cells respond to light?

  They are excited by darkness
• What do the two sets of cone bipolar cells synapse with?

  Separate sets of ON and OFF ganglion cells