NEW YORK — None of the 2,300 words tumbling at a rate of about 200 per minute from the disembodied mouth at the center of Samuel Beckett’s “Not I” is “biscuit.”

Not in the script, anyway.

But as performed by Jess Thom in a production at BRIC House in Brooklyn through Sunday, “Not I” is full of biscuits, usually accompanied by a hard thump to the sternum. The word pops up, singly or in long loops, in Thom’s version of the anguished 12-minute monologue. So do “sausage” and “hedgehog” and other unauthorized, sometimes unprintable interpolations.

That’s because Thom has Tourette syndrome, a neurological condition characterized by verbal and motor tics. But far from masking Beckett’s brilliance or diluting the play’s power, Thom’s speech patterns make uncanny sense of “Not I,” in the process making it more overwhelming.

Nor is Thom the only “neurodiverse” performer now expanding the idea of great acting in great texts on New York stages. The Public Theater’s Under the Radar Festival this month also features members of Australia’s Back to Back Theater, who have various neurological conditions, in an extraordinary play called “The Shadow Whose Prey the Hunter Becomes.”

Following the lead of New York performers like Russell Harvard, who is deaf, Ali Stroker, who uses a wheelchair, and Gregg Mozgala, who has cerebral palsy, these artists are not just making theater that affirms their life experience. They are showing the rest of us how their life experience affirms, and enhances, the theater.

But when it comes to acting, neurodiversity — a term embraced by many people with intellectual, social and other disabilities arising in the brain and nervous system — involves more barriers and engages more prejudice than even physical challenges do. Having seen the 1972 premiere starring Jessica Tandy, I admit I went to see Thom’s “Not I” expecting to be gladder for the actor than for the play.

I even wondered why Thom would want to take on a role, known only as Mouth, that is notorious for its physical, vocal and emotional demands, and why, given her condition, the director Matthew Pountney would want to stage it. “Not I,” in which everything but the actor’s mouth is masked, is already difficult enough to put across, without the added biscuits.

Yet that difficulty in some ways makes Thom an ideal interpreter. Who would know better what it means to live, as Mouth does, between silence and uncontrolled speech? Who would know better what it feels like to have a “mouth on fire” and “something begging in the brain,” than someone with Tourette? In her genial welcome to the performance, which is also signed for the deaf and “relaxed” for those on the autism spectrum, Thom says that in working on the play she came to feel that Beckett was writing about a woman like herself.

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All actors must reach that conclusion in order to play a part well, and the greater the part, the greater the number of actors theoretically able to do so. I say “theoretically” because, in practice, producers do not generally hire people who might suddenly interrupt soliloquies with vulgarities.

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Thom, who has a terrific stage voice and manner, leaves no question as to the theater’s loss in limiting her range of roles. Her performance of Mouth is as terrifying as any and yet, in its vulnerability to neurological static, more human than most. You understand how the very lonely woman Beckett wrote could have wound up that way.

I would hate to have missed this performance, and yet it might easily never have happened. Feeling for too many years that theater was “not a space I could occupy,” Thom said in a post-show discussion, she almost gave up on it. (As a performer, she would have been deemed uncastable; as an audience member, disruptive.) Only in finding “Not I,” produced by Battersea Arts Center along with Thom’s organization Touretteshero, did she find a way to “occupy the only seat in the house I couldn’t be asked to leave.”

That’s admirable, sure. But the key is that once seated there, Thom uses her position to explore something beyond just Tourette. Shining a light into Beckett from a different angle, she illuminates a different part of the rest of us as well.

A similar idea animates “The Shadow Whose Prey the Hunter Becomes,” running at the Public’s Manhattan mother ship through Sunday. At first, the play seems to be merely a witty piece of documentary theater, recreating a real-life meeting at which the performers (Michael Chan, Simon Laherty, Sarah Mainwaring and Scott Price) bicker over their parliamentary roles and chafe about definitions. Some, we learn, are comfortable calling themselves disabled but others are not; Price thinks of himself as someone who, in addition to a thick Australian accent, has an “autistic dialect.”

The equating of accent and autism, one of which we usually consider trivial and the other hugely portentous, was eye-opening for me. If Price’s autism is a dialect, surely my own neurological makeup is one, too. What are all our habits of thinking, our charming neuroses, our nature and character, if seen uncharitably, but undiagnosed defects? What is so typical about neurotypical minds?

But this line of thinking gets sidetracked as “The Shadow” starts a slow turn away from self-definition and toward the unexpectedly related question of the future of technology. The play uses automatic captioning to make sure the actors’ neurological “dialects” can be understood, and Siri, too, makes a marvelous, if sinister, cameo appearance. Soon we discover that the meeting has been called for the purpose not of justifying the neurodiverse but of warning the rest of us about a future in which the technology we’ve created will one day, like the shadow of the title, render everyone inferior — disabled, in fact.

“You will struggle to be understood,” Laherty informs us. “Others will want to highlight your limits.”

Whether or not you accept that dystopian premise, its sideways development is astonishingly artful. What’s more, like Back to Back’s previous Under the Radar offering, “Ganesh Versus the Third Reich,” it is artful in a way specific to the cognitive profiles of the actors involved, who also co-wrote the script with other members of the company. (The director is Bruce Gladwin.) If it moves in unfamiliar ways and is delivered through unfamiliar means, that is a sign that it is delivering new information.

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Which is what we must keep asking the theater to do. Not every idea gets ideally expressed in the gorgeously smooth voice of Jessica Tandy or delivered on legs like Savion Glover’s. Maybe what we have traditionally considered great in the theater is really just one dialect. How exciting to find that because we are all neurodiverse there are bound to be many others.

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Additional Information:

“The Shadow Whose Prey the Hunter Becomes”Through Sunday at the Public Theater, Manhattan; publictheater.org, 212-967-7555. Running time: 1 hour.

“Not I”Through Sunday at BRIC, Brooklyn; publictheater.org, 212-967-7555. Running time: 1 hour.

This article originally appeared in The New York Times .