The group of "meme" stocks, led by videogame retailer GameStop Corp. /zigman2/quotes/203755179/composite GME -6.99% that have been volatile in recent weeks as investors on a Reddit subgroup have egged each other on, were active again in premarket trade Monday. GameStop shares were up 5% premarket, while shares of AMC Entertainment Holdings Inc. /zigman2/quotes/200235402/composite AMC -3.78% , the world's biggest cinema chain, were up 12%. BlackBerry Ltd /zigman2/quotes/202784246/composite BB -3.28% was up 3.8%, and Naked Brand Group Ltd. /zigman2/quotes/204285810/composite NAKD +2.18% was up 9.5%. Koss Corp. /zigman2/quotes/207340503/composite KOSS -5.72% , a maker of headphones, was up 2.9%. GameStop shares have gained 440% in the year to date, as investors on Reddit's WallStreetBets platform sought to punish short sellers who had driven short interest in the stock to 140% by buying the stock and creating a short squeeze.