RGC Axon Segregation into Ipsilateral Vs

Question

RGC axon segregation into ipsilateral vs. contralateral layers in the LGN:
A) is genetically determined prior to neuronal activity.
B) is disrupted by asynchronous activity in the two eyes.
C) requires cholinergic input from amacrine cells.
D) b and c
E) All of the above

Accepted Answer

RGCs from the two eyes initially project to a common zone in the LGN. Asynchronous activity promotes their segregation into distinct layers, while experimentally controlled synchronous activation disrupts it. Desensitizing nicotinic cholinergic receptors via injection of epibatidine also prevents segregation, indicating that cholinergic input is required.