I responded to another post of yours. The cognitive effects could be due to the perphenazine, as could the weight gain. Looking at your med list, I would guess the perphenazine the most likely cause of weight gain. Propranolol can cause a small amount of weight gain in some people as well, but the first gen antipsychotics are pretty well known for doing so. The rest of your meds are weight neutral or weight negative.
I think it's more likely the cognitive effects are due to the Topamax. That's a pretty good dose and it's very well known to cause cognitive dulling, memory issues, it's most common cognitive effect is issues with word recall.
I would only mess with one at a time, though. Is there any way you could up your Geodon? I don't know how well it's working for you, but it's definitely weight neutral, weight negative in a lot of pts and maybe upping it would provide the stability you need, while allowing you to at least reduce either the perphenazine or the Topamax.
Propranolol can also kind of slow down your thinking, but I would think that less likely than the perphenazine or Topamax.
If I had to put my money on the cognitive effects, I'd definitely guess Topamax. If I had to put money on cause of weight gain, I'd go with perphenazine. I guess you have to decide which side effect is worse to live with. Although in all honesty, 6 mg is a really low dose, you may be able to stop it without much difficulty and Geodon does basically the same thing, just with less side effects.
Good luck.