They are "collar ties" which are traditionally placed in the upper third of the rafter height at every third rafter. They generally reinforce the rafters and keep them from pulling apart at the ridge in high winds. How important they are depends on the whole roof structure which I can't see from the photo.

To help you I would need to know if the tops of the exterior walls are tied to one another with floor joists and how big the rafters are, their spacing and what the code loading requirements are (snow), or at least where you live and what code applies.

Depending on the answers you might be able to raise the ties to just below the ridge board or get rid of them altogether.

Who would I talk to to determine what I can do? A regular contractor? Thanks for your help!!!

Any experienced carpenter should be able to figure this out but if you give me all the dimensions and a full view photograph or a sketch and what code (if any) applies and the snow loads, I can tell you what you can do; it's not a difficult thing to do.

Collar ties exist to keep the walls from spreading apart where there are no ceiling joists. Collar ties are placed in the middle third of the rafter length. Any lower than that, they are "ceiling joists". Any higher than that, they have no value in preventing the walls from spreding apart from the outward thrust of the rafters. Their placement, fastening, sizing, and the sizing of the rafters themselves can only be specified by a structural engineer. Other than that, you are relying on the "old carpenter's rule of thumb".
Since you already have your wall plates tied together with joists, these members are probably just nailers for the drywall/plaster. If you decide to remove them, it probably wouldn't hurt (may be a good idea) to add plywood gussets to the peak to tie the rafters to each other. Use construction adhesive and screws. But this is just rule o' thumb stuff, too.
Casey

Rafter and collar ties are often confused for each other. They are not intended to provide the same structural benefit although there is a point where they come close so the difference in definition must be arbitrary.

"Collar ties" are located in the upper third of the rafter height in order to prevent the rafter tops from separating from the ridge although they do add some strength to the rafters in bending when uniformly loaded by snow. They are not intended to prevent walls from spreading because they are too high to serve this puppose effectively. In fact, for them to be effective the rafters would have to be much larger and nails would not be sufficient to provide the necessary tie connections. This is possible but would require the services of a structrual engineer.

Ties that are placed in the lower 2/3 of the rafter height are intended to prevent the wall top plates from spreading and are called "rafter ties". When they are placed at the wall top plates they are called ceiling joists or attic floor joists rather than ties.

The IRC provides rafter span modification formulas for designing rafters with "rafter ties" above the top plates and below the 2/3 rafter height level.

The requirement for "collar ties" in the upper 1/3 of the rafter height gets added and removed from codes from time to time. It is absent from the 2003 IRC but is back in the 2006 edition.