Following Data 's defeat at a game of Strategema in " Peak Performance " , Pulaski and Councillor Deanna Troi ( Marina Sirtis ) attempt to console him , but it is left to Captain Picard to convince Data that he is not malfunctioning . Pulaski 's final appearance on The Next Generation was in the episode " Shades of Gray " . When Commander Riker fall ill to a dangerous virus during an away team mission , Pulaski drive out the virus with a device that stimulate his memory centre . After she discover that negative memories are more effective in removing the virus , she use memories of fear and survival to save Riker 's life .