This is not what I experience. For a couple of years I studied really hard and all I did was eat, sleep and study. During these times I definitely recognize what you have experienced. It's a form of narrowing down your world because you focus.

After studying hardcore, I slowly opened up again (read: I did less and less). This partially had to do with a mild depression (self-diagnosed, take it with a grain of salt). I noticed that during this period, I simply reflected more. I asked questions about other things.

And that's how I felt smarter and more intellectual again. simply because I had the time.

I wonder how you would experience a gap year. It may be the case that your 'original intelligence' comes back.