Seeing red

[emjay]

Based on what I know about neurons, I think the distribution of neurotransmitters in the brain represents at least partly a chaotic system.  Minor vibrations in the skull, the particular timing of the pulse, and almost anything else could affect the trigger timing of an indidual neuron, or possibly a group of neurons.  We often talk about QM unpredictability as adding an essentially random element to all events, but I think the brain is so complex that classical mechanics should make brain function as unpredictable as the weather, especially over long times.

I'd say dreaming is an excellent example.  Maybe you could see the strange and unpredictable content of dreams each night as a series of butterfly effects causing parts of the brain to light up and come into coordination with each other, sometimes in ways that daily sense perceptions would never allow for.

As a general rule, neurotransmitters don't stay 'outside' of neurons that long... they are released into the 'synaptic cleft' - a narrow gap between the axon of the pre-synaptic neuron and the dendrite of the post-synaptic neuron - in order to trigger receptors on the other side. But any that remains in the synaptic cleft - in the extracellular space - is either broken down or recycled by 'reuptake' in normal circumstances. If there's a problem with that process, then there'll be imbalances like you describe, but under normal circumstances it should be pretty ordered. But you're right... neurotransmitters and other substances floating around in the extracellular fluid could have wide scale effects on the whole network, adding yet another level of complexity to it's operation. Unfortunately I don't know enough about such global effectors, but I wouldn't be surprised if 'neurohormones' had exactly this effect, as a way of mobilising the whole network to act in a different way at the level of it's individual neurons. Because neurotransmitters come in different types and cause different reactions in the receiving neurons... for instance at a simple level, excitatory neurons release a different type of neurotransmitter than inhibitory neurons, causing the post-synaptic neuron to react differently at the site of the synapse, producing excitatory current in the first case and inhibitory current in the second. So in a way neurotransmitters allow the type of neuron to be identified at the synaptic level. It's pretty cool really.

As to dreams, I don't know. I think dreams are about consolidating learning... strengthening synaptic connections... but I don't know.