It’s always interesting to learn what a rich, acquisitive institution like the Museum of Modern Art has added to its collection. The latest report is the exhibition “Transmissions: Art in Eastern Europe and Latin America, 1960-1980,” which opens on September 5 and will present some 300 artworks in numerous mediums, many on view for the first time. Nearly all date from around 1968, a period when art radically diversified, sometimes dematerializing altogether. These works represent artists from distant regions whose efforts ran parallel in terms of strategies (largely Conceptual, frequently performance-oriented), political contexts (often oppressive) and interests (protest, mass media, popular art). Some names — Valie Export, Ana Mendieta, Edward Krasinski, Juan Downey, Fernando Botero — will be familiar; others will be much less so. The show will surely reflect the MoMA’s desire for a broad global reach, but perhaps also the aesthetic narrowness of its relentless elevation of Conceptual-oriented work.