2007 Sensory Physiology

• sensory information passes from the rods and cones to the bipolar cells, which also generate graded potentials

  • bipolar cells receive input from rods or cones (but not both)
  • the degree of convergence between photoreceptors and bipolar cells varies throughout the retina (less convergence in the fovea, more on the periphery --- i.e., greater acuity in the fovea)
  • photoreceptors can release either excitatory or inhibitory neurotransmitter
• bipolar cells subsequently stimulate ganglion cells, which generate action potentials
• horizontal and amacrine cells modulate activity in the bipolar and ganglion cells; in particular, they produce lateral inhibition, and they contribute to the complexity of ganglion cell receptive field properties

S&G Figure 10.29

• the retina consists of 3 nuclear layers (described along the light path from front to back) which contain:

  1. INNER - the ganglion cell bodies whose axons form the optic nerve
  2. MIDDLE - bipolar cells
  3. OUTER - the photoreceptors (rods and cones)
• in between the primary cell layers are two plexiform layers (also called inner and outer), which contain the amacrine and horizontal cells, respectively