[From an email with a friend]

>How does learning occur within cells ?

That's still a highly speculative area, but the main mechanism is thought to be a concept called LTP (long term potentiation). You can find loads about that on a casual search. However, the theory is kind of obvious on the network level. Just imagine that all the possible paths in a network represent multiple outcomes in terms of memory or learned behavior. The easiest things to achieve are those options accessed by traveling the easiest course(s) in the network. It you want to "learn," you're just trying to change the resistance in specific paths. The paths are gated by synapses between the cells, so you often hear about "synaptic weights."

>Also what is the difference between the two, excitatory and inhibitory?

One makes a neuron more likely to fire, the other makes it less likely. It's just like the gas and the brake in your car.

>what are their process in our learning abilities and the like?

The learning and memory end of it is a little more complicated, but the gist of it is that the more you use a pathway, the more likely it can be accessed again (i.e., "use it or lose it").

>What are their roles in our ability to think, speak, act and comprehend? or do they even have a role in such things?

They definitely have a role in everything in the human (or animal) condition, but the "how?" of it is harder to tease out. A lot of people have worked out circuitry to explain some things, but usually we're talking about motor movements. For example, the knee-jerk reflex takes (I think) four neurons, three excitatory and one inhibitory. Most neuroscience and some physiology texts contain this diagram. On the other hand, no one have figured out where consciousness resides in the brain, nevermind how it works!

[Posted to the neuroscience group on MySpace.com in response to a request for clarification of the following]

Definitions below are lifted from hyperdictionary.com (a great site!), but the elaboration in the parentheses is my own.

neuroscience - the scientific study of the nervous system. (The important distinction is that you're talking about studying something physical. If you aren't talking about neurons in part or in whole -as in neurotransmitters, receptors, etc.-, then it isn't neuroscience.)

neurology - the branch of medicine that deals with the nervous system and its disorders. (A specific application of neuroscience in a medical context. There's a big overlap with psychology as well, but a neurologist is looking for a physical basis of pathology, not a mental one.)

psychology - the science of mental life (Does not require a physical basis to understand mental life. However, psychology increasingly acknowledges that mental life emerges from a physical substrate and this places constraints on the underlying processes.)

cognitive science - the field of science concerned with cognition [Follow-up: cognition - the psychological result of perception and learning and reasoning]. (This is more nebulous and actually finds a good balance between psychology and neuroscience a lot of the time. It borrows from both, but also yields things like computational models that have no clear basis in either neuroscience or psychology. This isn't a criticism, by the way.)

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