It depends what the message is.
That would be an interneuron otherwise known as an associative neuron.
Your afferent neurons send a message to your brain.
Retina
When you want to move a muscle, your brain sends a message out to the muscle you want to move, and the muscle sends a message back to your brain that your moving it and where.
Afferent
It sends the message to your brain of what your seeing
Your eyes send a message to your brain and then your brain sends a message back telling you what your seeing.
It sends the message to your brain of what your seeing
It sends the message to your brain of what your seeing
It sends the message to your brain of what your seeing
It sends the message to your brain of what your seeing
The brain sends them a message.