What happens when someone's brain has a low level of neurotransmitters?

Neurons aren't able to communicate with each other

and when neurons aren't able to communicate with each other, stroke is just one example of a condition when communication between nerve cells breaks down. Micro-failures in brain functioning also occur in conditions such as depression and dementia ... Neuron networks reconnect during such periods of inactivity and become hypersensitive

Neurons aren't able to communicate with each other.