Amacrine cell

Amacrine cells are interneurons in the human retina that interact with retinal ganglion cells and/or bipolar cells.

  • Amacrine cells interact with bipolar cells and/or ganglion cells. They are another type of interneuron which in this case monitor and augment the stream of data through bipolar cells and then control and refines the response of ganglion cell subtypes.
  • Amacrine cells are located in a central but inaccessible region of the retinal circuitry. Most are without tale-like axons. Whilst they clearly have multiple connections to other neurons around them their precise inputs and outputs are difficult to find. They are driven by and feedback to the bipolar cells but also synapse on ganglion cells, and with each other.
  • Amacrine cells are known to serve narrowly task-specific visual functions including:
    • Efficient transmission of high fidelity visual information with a good signal-to-noise ratio.
    • Maintaining the circadian rhythm which keeps our lives tuned to the cycles of day and night and so helps to govern our lives throughout the year.
    • Measuring the difference between the response of specific photoreceptors compared with surrounding cells (centre-surround antagonism) which enables edge detection and contrast enhancement.
    • Object motion detection which provides an ability to distinguish between the true motion of an object across the field of view and our own eye movements.
  • Centre-surround antagonism refers to the way retinal neurons organize their receptive fields.  The centre component is primed to measure the sum-total of signals received from a small number of cones directly connected to a bipolar cell. The surround component is primed to measure the sum of signals received from a much larger number of cones around the centre point. The two signals are then compared to find the degree to which they disagree.