The memory loss was definitely from the meds, for me.
Topamax made me lose 4 months of my life. No memory retention at all. Could not remember anything short term and quite a percent of long term, too.
Gabapentin/Neurontin has 'Neurontin moments'.
Fuzziness and minor forgetfulness
("Now, where are the keys to the car? - Where did I put that shopping list?").
After about 4-6 weeks, it became manageable, altho I still had post-its all around, as reminders for- things to do, appointments, etc. I also keep a daily appointment book to put notes in, as well. After being on it for over 6 years, you get used to it.
Switching to Lyrica did not affect me negatively at all.