Neuroplasticity is an area of research I'm very interested in and already have taken a few research-based courses in but I feel like I've only just scratched the surface of it. The brain can, "re-wire" but only in certain areas. The hippocampus functions in consolidating short-term memory and working memory to long-term memory, retrieving long-term memory storage and spatial navigation. It does not re-wire (or if it does to no great extent) partly due to the fact it uses pyramidial neurons, whereas many other brain areas do not. Likewise, the amygdala also uses pyramidial neurons.

Some of the research I focused on in other courses dealt with analyzing the structural differences at the level of the synapse. In other words, analyzing changes in interneuron communication. The issue with neuro-imaging studies, such as fMRI, is they indicate changes in structural size and activation, however, they cannot indicate whether the activation is inhibitory or excitatory. Normally this can be determined based on known information of the brain region but when a completely different brain area activates that did not prior to psychotherapeutic treatment, it can be difficult to determine whether it is inhibitory or excitatory.

I'm not a doctor so I may not be able to give a clear answer. Using the computer model of the brain, there are several sites at which information stored in long-term memory can be lost or disrupted. First, it cannot be retrieved because the memory has degraded. Second, the memory is indeed retrieved but it is drastically altered, so your expectations of the memory do not coincide with the content of the memory. Third, the memory is retrieved and fully intact, however, other brain areas are affected preventing the memory from being "read". Fourth, there are several very similar memories that have been integrated into one, so key details that you may want have been omitted. This fourth possible cause occurs in everyone. A great example is when you went to school, you learned math (just to keep things simple I'm only picking 1 academic subject). You learned how to add, subtract, multiply and divide, as well as geometry, calculus, algebra, etc... . The problem is, you are very unlikely to remember in which grade you learned each of these topics because that fine detail has been omitted. All four of these are normally attributed to the memory degraded as a result of time, however, in your case I would say the medications. As for why and how, that becomes a complex biochemical discussion that probably is not yet fully uncovered by research. Why your memory has been drastically affected whereas others who took the same medication were not isn't something that can be answered in any great detail. It would partially come down to genetics, although that answer has to wait until the Human Genome Project is fully complete.

I don't want to sound too ghoulish but your doctor probably isn't the person to turn to for your answers. Clinicians are rarely taught or know the in-depth mechanisms of how medications work in the body and brain. Obviously he/she can tell you the medication crosses the blood-brain barrier via receptor-mediated transport and is designed to target ___ receptors. Beyond that, you probably would get more detailed answers from a researcher in pharmacology specializing in pharmacodynamics. Clinicians are limited by what they're told the medication does in a summarized and simplified form. When talking to their patients, they further summarize and simplify the information.