Depending on your mood and bias, "Altered States" may be relished or dismissed as an ostentatious freak-out.

At once agitated and half-baked, portentous and banal, the movie appears to owe most of its confusion and sentimentality to screenwriter Paddy Chayefsky, vainly trying to exalt a monster-thriller premise through the force of intellectual bombast.

Opening today at the Uptown and Springfield Mall, "Altered States" is sort of "I Was a Teenage Frankenstein" upgraded into "I was a Faculty Naked Ape." It depicts the obsession odyssey of Eddie Jessup, a young psychological researcher whose experiments in sensory deprivation and drug-induced hallucination trigger a reversion to a primitive state of being -- anatomical as well as behavorial.

In his breakthrough experiment, Eddie emerges from the coffin-like seclusion of a sensory-deprivation tank so closely linked to a primeval genetic heritage that he is changed from the tall, pale, ascetic WASP scholar embodied by William Hurt to the short, furry, savage apeman embodied by Miguel Godreau.

But let's hear Eddie describe the transfiguration in his own words, to savor a bit of the distinctive Paddy Chayefsky idiom. Recapping events from his estranged yet devoted wife Emily (Blair Brown), an anthropologist who has just bailed him out of a Boston jail, Eddie says: "I turned into a protohuman creature. A pack of wild dogs attacked me and chased me to the zoo. That's how I got there. In the zoo, I hunted down, killed and ate a small gazelle. I was utterly primal. I consisted of nothing more than the will to survive, to live through the night, to eat, to drink, to sleep. It was the most supremely satisfying time of my life."

Even in a normal state, Eddie's body has begun to show primordial yearnings, the limbs spontaneously swelling and warping into simian configurations. But the brilliant, destructive self-explorer intends to repeat the regression. The question becomes whether he can survive a final experimental dip in the tank, anxiously monitored by Emily and colleagues Rosenberg and Parrish (respectively, Bob Balaban and Charles Haid -- the latter a bearded, pontifical spitting image of Chayefsky).

For those reluctant to suspend disbelief, the naked-ape episode may prove an insurmountable hurdle. Even if his loved ones dummied up and the police were too dense to connect Eddie with that wild creature -- who also assaulted two guards at the lab -- he was still apprehended in his own naked form sleeping next to the gazelle he slaughtered. Brushing off this detail invites viewers to suspect that a Harvard man will be forgiven any outrage, assuming he commits it in Boston.

This whopper calls attention to the smelliest red herring in the plot: The union of Eddie and Emily seems an absurd misalliance from the outset. Nevertheless, one is obliged to play along for the sake of melodramatic convenience: The story hinges on the power of true love to overcome powers of darkness.

Eddie first jeopardizes his marriage by trekking to Mexico to sample "sacred" mushrooms with a remote Indian tribe. During his visionary conk-out, he associates the image of Emily, naked and squatting on all fours, with a lizard. After sobering up, he finds the eviscerated remains of a lizard within arm's reach.

The gutted gazelle naturally recalls the lizard, and both suggest that Eddie's savage benders will eventually prove a threat to his wife and token pair of kiddies. But having planted these hints, Chayefsky declines to follow through on their logic.

Eddie's transformations are accompanied by visionary interludes which appear to have been farmed out to optical specialists who could come up with nothing fresher than surreal landscapes in homage to Dali and abstrat lightshows in homage to every psychedelic milestone from "The Trip" to "2001." A latecomer to the jamboree, director Ken Russell hasn't left his stamp on these derivative hallucinations.

Orignially begun as a collaborative project with Arthur Penn, "Altered States" ended up as a belated directing assignment for Russell, whose career had been on hold since the unprofitable excesses of "Lisztomania" and "Valentino." Notorious as a directing exhbitionist (the flashiest of the '70s in fact) Russell was nevertheless an incongruous choice for this material. His characteristic fondness for pictorial and emotional delirium ("The Devils," "Tommy") produced a form of self-assertive, wacky claptrap quite different from the kind imposed by Chayefsky's hyperbolic preachiness.

The surprising revelation of "Altered States" is that Russell emerges as the more astute partner.The smartest thing he has done is encourage the actors to talk as fast as they can, and more or less simultaneously. The rapid-fire, overlapping delivery has a lightening effect on Chayefsky's insistence on camouflaging his screenwriting credit with a pseydonym, Sidney Aaron, may have been inspired by annoyance at the lickety-split line readings.

Haid and Balaban easily reaffirm their credentials as two of the best young character actors on the screen; but Hurt and Brown get off to shaky debuts in the leading roles, thanks to Chayefsky. Physicaly and temperamentally ideal for the roles of young scholars, they still fail to achieve a romantic rapport that might save the denouement from happy absurdity. aIn addition, they can't transcend the grotesque and ludicrous postures that the story often obliges them to assume. Many scenes leave them looking defensless, naked in the least expressive or flattering senses of the term.

The events in "Altered Stars" begin in 1967 and end about a decade later; and the movie is caught in a disillusioning time warp. The influence of vintage chiller prototypes is evident, but so the saccharine mysticism of '60s relics like "The Magus and "The Trip." If anything, it's the '60s dippiness that predominates.

Chayefdky may have waited too long to add his flatulent notes of humanitarian alarm and affirmation to the exploitable gimmick of perilous scientific inquiry. Moreover, people who find the search for primitive states of consciousness fascinting (I'm inclined to believe that these recesses can be reactivated all too easily) ought to feel a little sold out by Chayefsky's priorities. When Eddie conjures up a literal primoridial ooze or begins to decompose into so much radiant energy, isn't it a bit of a letdown to think that Emily's love can make everything hunky-dory again?