This will only be available if you have purchased the Committee Filter module.

Use this module to determine the categories that the committee members will be able to see when they log onto the committee screen.  With a standard setup all the committee members can see all of the abstracts.  This is fine for small to medium sized conferences where there are a few hundred abstracts.  However if you are expecting to receive several thousand abstracts, it is a good idea to use the committee filter.  This allows the conference administrator to filter the categories available to the various committee members. 

Simply click on the Committee function on the Abstract screen.  Then select the committee member from the drop down list and tick the categories that that particular committee member should be able to see.