2007 Sensory Physiology

• the receptive field properties of ganglion cells are complex, as might be expected based on the interactions of bipolar, horizontal and amacrine cells
  • i.e., photoreceptors detect the frequency, amplitude and location of a light source, but ganglion cells extract more complicated features of the stimulus
  • ganglion cells are more like CNS neurons than primary afferents, even though they are the first cells in the visual pathway to transmit action potentials
• the wavelength information encoded by the photoreceptors is passed on to the ganglion cells, as predicted by labelled line theory
• the effects of lateral inhibition are evident even within the response to a simple light stimulus shown on the left: blue light stimulates this ganglion cell, but white light inhibits it

• lateral inhibition increases contrast, therefore ganglion cells are wired to detect point-to-point differences in colour/intensity
• the receptive fields of ganglion cells are divided into the centre and the surround
• ganglion cells are divided into two categories:

  1. ON CELLS: stimulated by a stimulus to the centre, and inhibited by a stimulus in the surround
     • diffuse light will cause a weak excitation
  2. OFF CELLS: inhibited by a stimulus to the centre, and stimulated by a stimulus in the surround
     • diffuse light will cause weak inhibition

S&G Figure 10.35