Centre-Surround Antagonism

This application is designed to visualize and teach the concept of Centre-Surround Antagonism in retinal ganglion cells.

By running this simulator, you can observe how light stimuli mapped to different spatial areas of a receptive field dictate the firing rate (action potentials) of the optic nerve.

🎮 How to Use the Simulator

The interface is divided into two distinct neural pathways:

• Left Panel: The OFF-Centre / ON-Surround Pathway.
• Right Panel: The ON-Centre / OFF-Surround Pathway.

Each panel acts independently. Use the four buttons at the top of each panel to shine light on specific parts of the receptive field:

1. Baseline (Dark): No light is present. Notice that ganglion cells are never truly silent; they maintain a steady, moderate "baseline" firing rate.
2. Light on Centre: A spotlight shines only on the central area of the receptive field.
   • Observe: In the ON-Centre pathway, this triggers a rapid volley of action potentials (excited). In the OFF-Centre pathway, the firing stops entirely (inhibited).
3. Light on Surround: A ring of light hits only the outer portion of the receptive field.
   • Observe: The behavior flips entirely due to lateral inhibition from the horizontal cells.
4. Diffuse Light: Light covers both the centre and the surround.
   • Observe: The excitatory and inhibitory signals cancel each other out, returning the ganglion cell to its baseline firing rate. This demonstrates that the retina detects contrast and edges, not absolute light intensity.

🧠 Biological Diagram Key

The simulation uses standard neurobiology color coding to map the layers of the retina:

• 🟨 Yellow (Photoreceptors): Rods and Cones. These detect the photons (indicated by a glowing animation when light hits them).
• 🟦 Blue (Horizontal/Amacrine Cells): These interneurons provide lateral inhibition. 
• 🟥 Red (Bipolar Cells): The middle layer that relays signals from photoreceptors to ganglion cells. 
• 🟩 Green (Ganglion Cells): The output neurons of the retina. Their long axons form the optic nerve. The green horizontal lines travelling downwards represent electrical action potentials (spikes) heading to the brain.