Within days, two of the most famous names in the world of European art house filmmaking have passed away: Ingmar Bergman and Michelangelo Antonioni.
Both men were known for making unique, highly personal, ambitious, symbolic, even confusing films with a reputation for appealing to sophisticated audiences and critics (although both of them occasionally met with derision from the intelligensia for going too far).
What I want to add to the conversation is to point out that, despite their reputation for rarified high-brow intellectualism, both Bergman and Antonioni made entertaining films that in various ways influenced the horror genre.
Bergman's three contributions of interest are THE MAGICIAN, PESONA, and HOUR OF THE WOLF. The first, set in mideval times, contains a wonderfully unsettling sequence near the end, when the titular magician apparently returns from the dead to frighten the wits out of a skeptical doctor. It's a wonderful example of using simple elements (an eyeball in an inkwell, for example) to create a powerful illusion of the supernatural.
PERSONA is an ambitious experiment, a two-person drama in which a nurse and her patient seem to merge personalities. The film is probably most remembered for its then-radical technique of reminding viewers that they are watching a film (it begins with a close-up of a projector lamp flaring to life and contains a later scene where the film seems to catch and burn in the projector), but underneath the art house veneer, PERSONA comes close to being a horror film. It is essentially a vampire story in which a mentally ill actress (who has stopped speaking for no apparent reason) feeds psychologically on the non-stop stream of words pouring out of her nurse. In case you miss the point, Bergman makes it literal near the end, when the actress bites the nurse on the arm and sucks her blood.
HOUR OF THE WOLF is perhaps the most genre-oriented of Bergman's works, a tale of a tortured artist on a deserted island who sees characters from his paintings come to life. One can read the film as a metaphor (the artist tortured by his internal demons), but Bergman presents the nightmarish action more or less as a straight-out horror film, with brief glimpses of men walking on walls and birds of prey transforming into men.
Antonioni's influence on the genre is more cimcuspect. His English-language mystery-thriller BLOW-UP served as inspiration for both Dario Argento's giallo horror film DEEP RED (which borrowed BLOW UP's star David Hemmings) and Brian DePalma's BLOW OUT.
Antonioini was also cited as a major influence by William Friedkin, director of THE EXORCIST. I remember hearing Friedkin say that Antonioini's films "moved laterally," by which Friedkin meant that Antonioni's camera movements and cutting followed the action as it progressed, seldom if ever returning to repeat a camera angle. Friedkin didn't take this stylistic approach quite as far as Antonioni did, but you can definitely see it in his work, which avoids the standard "master shot, medium shot, close up" coverage seen in more traditional filmmaking.
I doubt that either Bergman or Antonioni would want to be regarded as a seminal figure in the horror genre, but it is important to recall that despite their high-flown reputations, neither one necessarily felt above such considerations as simply entertaining an audience.
UPDATE: Can't believe I forgot to mention Bergman's THE VIRGIN SPRING, which Roger Ebert cited as the inspiration for Wes Craven's debut feature, LAST HOUSE ON THE LEFT.