Sure, a neurologist might seem the natural approach, but psychiatrists are more accessible without a referral (and could refer you to a neurologist of need be) and might be able to help you troubleshoot the brain fog - just because it's caused by an implant, doesn't mean that more conventional treatments can't help.
On the off chance that your brain is misfiring all on its own (which I assume you acknowledge is something it's possible for things as complicated and sophisticated as a brain to do, considering even the lost primitive electronics can fail in unpredictable ways), they'd likely be able to help with that, too.