The between neurons are important for long-term memory because they allow neurons to communicate. Each instance of communication strengthens the connections between the neurons, which strengthens memories.

They synapse between neurons are important for long-term memory.

Explanation:

The synapse is the process by which a neuron passes an electrical or chemical signal to another neuron, in order to pass a message and form connections.

This communication between neurons allows the strengthening of long-term memory which is encoded through this process.