Load-Bearing Wall? Parallel to Joists, single story, but has attic supports
Since your front section at one time was a garage the there was a need to provide a fire break wall between the garage and the living portion of the house. Since the garage undoubtedly had an open ceiling all the way up into the rafter area the fire break wall had to extend way  up to the roof line. To support the heavy drywall used as sheathing on the fire break wall studding was added from the top plate of the lower wall up to the rafters. 

The drywall used on such walls is often 5/8" thick or two layers of 1/2" thick material. 

If going by your picture is accurate it is doubtful if this is a load bearing wall in the conventional sense. However depending on the construction of the top plate it may not be providing the necessary strong tie behavior to prevent rafter sagging in that area if the lower wall was to be removed.