Increasing brightness in only part of the image

I would do similar to what has been mentioned, but would do this on an Adjustment Layer. Probably the best way to do this would be to make your adjustment, probably with Levels, Curves, or less control, but easier Brightness/Contrast.

Then, create that Selection, possibly a heavily Feathered Circle in the middle of the image. When you think you're close to where you want the Selection to take place, Save Selection as a Layer Mask for your Adjustment Layer. It will now all the Adjustment Layer to have its effect, and will restrict it in the outer areas of the image. If necessary, you can use Quick Mask Mode to do things like expand that Mask (Ctrl+T - Free Transform), or maybe add a bit of Gaussian Blur to "feather" it a bit more.

This allows for totally non-destructive editing of your image. Do a Save for the PSD with the Adjustment Layer and Masks.

Good luck,

Hunt

PS - you can create your Selection, that will be the Layer Mask first, and with it active, just add the Adjustment Layer, and the Selection will be the Mask for it.

There are a few ways to go about it...

1.  If it's just minor brightening of the parts you want people to focus on, I'd probably select the Dodge tool, set for Midtones, a large fuzzy brush, and a small pressure.  Then brush over the image to lighten the parts you want.

2.  You could select the parts you want to increase brightness in then use Brightness/Contrast.  Use a lot of feathering in the selection if you want the effect to fade out gradually.

3.  You could brighten the whole thing, then select the History Brush, and return the parts you don't want changed by painting over them.

4.  There are ways to do it with layers, masks, etc. as well.

These are just some ideas.

-Noel