Ah - right to the heart of the issue. After the initial "shock" of discontinuing my meds, I noticed a number of things that concerned me. The first was that I was emotionally volatile - I had no way of predicting my mood. That prompted me to research the drug a little (Trileptal), and I found that it is indeed used to treat bi-polar disorder. The second thing I noticed was that I was incredibly euphoric. I was remembering all sorts of things from my childhood, and making all sorts of mental connections (thinking much more rapidly, it seemed).
I've heard that this drug in particular works by inhibiting sodium channels in nerve cells - in effect that would inhibit brain activity in general. What I was experiencing, I assume, was my brain reacting to the sudden ease of accessing my memory. I see no possible mechanism for managing relative levels of the drug within the brain, so this effect would carry on to other brain functions as well. Since being off the medication I notice that I can better concentrate. I don't think it's unreasonable to assume that this would affect the learning process as well.
From what I've read, dilantin works in a similar manner. If you're using this drug solely to stabalize your moods, I would look into switching to something that works through the inhibition of seratonin reuptake into the presynaptic terminals. Again, I am not an expert, but I see no issues with this method. What it does, essentially, is increase the amount of seratonin absorbed in post-synaptic neurons. Seratonin plays a part in neural plasticity...I see no harm in increasing the efficiency of absorption.
Not to preach - I just prefer to err on the side of caution when it comes to cognition!