I'm going to remove one light fixture and stick my camcorder up there, same as when I was trying (unsuccessfully) to capture on camera the source of the roof leak (this one for real, it was like having a little indoor waterfall during Ida) on the right side of the same ceiling.
One of the many projects I'm trying to revving up for is the replacement of the t&g boards on the ceiling with sheetrock...
Might be worth looking into the NJ program. Sounds like you have a pretty classic air sealing/insulation problem with your attic. Depending on the work you could wind up having it done nearly for free. I went through this last summer and it worked out really well.
Home Performance with ENERGY STAR | NJ OCE Web Site
www.njcleanenergy.com