It was the annual Labor Day tradition for the Savini family, a makeshift version of The Gong Show performed before the neighborhood on a wooden deck stage at their beach house in Massachusetts. In past years, Nicole Savini’s mom and friends dressed up in nightgowns as the housewives version of The Supremes, singing “Stop in the Name of Love” into wooden spoons.

The theme this year involved a tongue-in-cheek skit on global warming, with the family singing rewritten lyrics to “Don’t Worry Be Happy,” complete with a fake weathercast warning of Sharknado’s arrival, as well as the Lobster-pocolypse and Clamageddon. Nicole’s dad, John, dressed up as a shark from Jamaica.

But one person was emotionally absent from the production, though physically present: Nicole’s mom, Kathy.

For most of Nicole’s life, her mother would get into the spirit of “The Gong Show,” dressing up in costume, practising the choreography and lines. Instead, this year a special seat had been reserved for her among the lawn chairs in the audience, and while everyone else cracked up, Kathy didn’t react.

It took many months, and some Internet research, for the family to get a diagnosis. Her mother’s change in behavior was caused by a little-known disease called frontotemporal dementia, a neurological disorder centered in the frontal lobe of the brain, the part responsible for our behavior and emotions. While Alzheimer’s usually affects older people, and is detected as a person begins to lose memory, frontotemporal dementia causes people to lose their personalities first, and usually hits in the prime of their lives — the 30s, 40s, and 50s.

Over the last decade, new research in patients with frontotemporal dementia and other illnesses, has helped neuroscientists understand more about the roles different parts of the brain play in where our personalities come from.

A study released in October by Dr. Brad Dickerson and colleagues at Harvard Medical School in the Journal of Neurology, Neurosurgery & Psychiatrypinpointed regions in the brain that showed atrophy from frontotemporal dementia and found that those with the most damage to the “perception network” (amygdala, orbitofrontal cortex, superior temporal, and fusiform cortex) also showed the most prominent difficulty responding to social cues, facial expressions, and eye gaze, and had the most trouble interpreting gestures and body language—the kind of cues that sarcasm relies on.

Frontotemporal dementia patients with the greatest deterioration in the “affiliation network,” (involved in motivating a person to connect with others and generating rewarding feelings during social interactions) exhibited the most severe social and emotional detachment, and patients with the greatest damage to the “aversion network” (involved in detecting and avoiding untrustworthy or threatening individuals) became more willing to trust strangers, and in some cases gave away private personal information despite negative consequences.

On the surface people with frontotemporal dementia might still seem normal, able to hold a job, and talk to people about the weather. But those traits that family and friends know and love—such as empathy, shyness, shame, pride, or wittiness—begin to disappear.

As the disease invades parts of the brain, patients’ altered behaviors have helped researchers understand how embarrassment comes from the pregenual anterior cingulate cortex. Or how recognizing sarcasm can be traced to structures in the temporal lobes, according to UC San Francisco researcher Kate Rankin, who has studied frontotemporal dementia patients.

Nicole’s mom’s diagnosis was especially ironic, given their close-knit, funny family in Marshfield, Massachusetts. Sarcasm had always been a central element of Nicole’s life, leading her to produce satirical segments for Stephen Colbert’s show, like this one on Maine’s missing scallop gonads, which, today, would go right over her mom’s head.

There are moments now when all Nicole can do is laugh at how simultaneously tragic and hilarious her mother’s illness is. She sees absurdity in situations that her mother can no longer grasp. Lately, Kathy has been obsessed with opening people’s mailboxes. “We keep telling her it’s a federal offense,” said Nicole.

Then, Kathy will open another.

“Mom what is that?”

“Federal offense,” she will reply in a monotone. “Federal offense.”

“People say all the time that comedy comes from tragedy,” Nicole said. “If you can’t laugh, you’re just going to be crying all the time. But it’s an overwhelming disease. You are really helpless. There is no medication, no road map, no end in sight.”

* * *

An estimated 50,000 to 60,000 people in the U.S. are diagnosed with frontotemporal dementia, although experts estimate that many more suffer from the condition but have not yet received a correct diagnosis, according to The Association for Frontotemporal Dementias.

The symptoms are often wrongly blamed on alcoholism, depression, menopause, mid-life crises, stress, or schizophrenia, and patients can go through years of negative tests for other ailments like cancer, strokes, and syphilis before learning the truth about what is actually wrong. People living with frontotemporal dementia, are unaware that they have even changed. But for loved ones, sometimes it’s like living with a stranger.

It affects each patient’s character differently. A proud CEO and dedicated father could one day start walking around with his pants down, or stealing candy from a convenience store without embarrassment or shame. A devoted girlfriend might nonchalantly tell her partner intricate details of past relationships with other men.

Nurse and medical anthropologist Jill Shapira, who works at the University of California, Los Angeles with frontotemporal dementia patients and their families, recounted the story of a husband who had always been loving and kind. One day, his wife fell on the floor. As she was sprawled on her back, he stood over her and asked, “When’s dinner?”

“That’s often a wake up call,” Shapira said. Spouses tend to think their partner is having an affair, or has lost interest in them. “First you get pissed. Then you say this isn’t him. This isn’t the person I married.”

* * *

Kathy fell in love with John, when they were teens, after he wooed her while playing a comedic role in a high school play, “The Perfect Idiot.”

“I was the star, but I was not the idiot,” Nicole’s dad told her recently, when she asked about their love story. Nicole’s mother had told her that she fell in love with John because “he was such a ham.”

“I don’t remember her saying I was a ham,” John replied. “I think she might have said she was impressed by my talent. I don’t remember the word ham coming up, just talented maybe.”

When prom came around, John wasn’t going to ask Kathy. He planned on asking another girl, because he had asked Kathy out once before in 9th grade, and she said no. She had to work. But after he impressed her with the play, Kathy told him she needed a date. “She decided I was going to ask her,” he said. “I was Project Prom.” After they ended up dating, he asked her about the 9th grade rejection. Kathy said very matter-of-factly that she did, indeed, have to work that day.

Growing up, Nicole’s dad was the biggest joker of all.

He would spend months making up lyrics and skits for “The Gong Show,” which has involved various family members and neighbors dressed as cowboys, Vegas showgirls, or news reporters in ponchos caught in Hurricane Earl, replacing the lyrics to “My Girl,” with them singing, “My Earl.” One year, Nicole’s dad dressed up a rapper, “L.L. Bean.”

One of the first telltale signs of Kathy’s illness was the weight gain. She shoved food into her mouth without restraint. Once, as Nicole prepared a birthday cake with M&Ms, her mom reached in to grab a handful.

“Don’t, they’re for the cake,” Nicole told her.

“Okay,” her mom replied, and then put them in her mouth anyway.

It was clear to Nicole then, her mom clearly had lost control of her behavior. She also became apathetic, and had trouble organizing her shelves or keeping appointments. She gained 100 pounds in a year.

At first, doctors thought it could be sleep apnea. But Nicole’s sister, Catherine, didn’t buy it. “I got kind of pushy with the neurologist,” Catherine said. “I made my mother go back to make another appointment, even though she didn’t want to…I remember crying to my mother, saying, ‘I just think something is wrong and I think you need to go.”

Rankin of UCSF, has conducted tests on patients with frontotemporal dementia and other brain diseases, putting subjects through video tests featuring actors who recite lines in a sitcom style like, “No of course you don’t look fat,” (when he does), or “I’d be happy to do it. I’ve got plenty of time.” (when he doesn’t). The patients had to observe facial expressions, voice patterns, gestures, and posture, to determine the speaker’s intended meaning, from cues like eye rolling and exaggerated voice prosody, and then answer questions about their sincerity or sarcasm.

Rankin’s and others’ research has shown that the underlying neurological layers of sarcasm involve regions of the superior frontal gyrus, which is involved in self-awareness, decision making, and laughter, as well as the medial and anterior temporal lobes, which have been indicated in language processing and integrating information about attitudes, intentions, and emotions. Understanding more complex forms of sarcasm can also require parts of the brain involved in empathy and reading other people’s mental states.

Other scientists have found that 70 percent of frontotemporal dementia patients showed damage to brain cells called von Economo neurons, found in the anterior cingulated cortexes, which are involved in self-awareness and socializing.

“Studies like these shed light on the ways that specific social skills are hardwired into our brains to a greater extent than people previously would have believed,” said Rankin, “which is why a disease like frontotemporal dementia can make someone act like a completely different person.”

Dr. Bruce Miller, who heads the University of California, San Francisco Memory and Aging Center, believes these discoveries in the brains of frontotemporal dementia patients will also one day influence how psychiatric disorders are treated, like depression, bipolar disorder, or ADHD. “If you don’t develop these fine-grained assessments of emotional deficits in psychiatric patients, you’ll never understand them.” Brain research is important for frontotemporal dementia patients. “It’s even more exciting for the psychiatric diseases, which are more common.”

“Oh, hon, I didn’t realize you were so hungry,” John joked.

Everyone was surprised that Kathy laughed.

Another time, Nicole tried to get her mom to put on her pants by singing the hokey pokey. Her mom cracked a smile.

“I see her wake up, it’s almost like I can see the neuro-whatever-you-call-thems firing in her brain,” Nicole wrote in an essay. “She’s back and she’s with me. And, for a moment, I am with my old mom, the one with a sharp wit, who can clearly see that, frankly, I look ridiculous.”

Occasionally, Kathy still made jokes. Once, she wore a fake leopard skin coat and announced, “No animals were harmed in the making of this coat.” She went out to dinner and with her daughters, who ordered mussels. Kathy said, “I don’t like mussels unless they’re on dad.”

Kathy’s deterioration took longer for John to accept. At first, he continued going on vacations with her, as if life was normal. They went to Niagara Falls, and John made an appointment for Kathy at the spa, while he went golfing. Kathy went for a walk instead, stopping at an ice cream cart, where she started to eat without paying the vendor, who got so upset he called the police.

When officers arrived, Kathy told them, “Well, I don’t have $4. Are you going to arrest me for eating ice cream?”

The next day John tracked down the ice cream man to give him the $4. That was when he learned he could no longer leave her alone.

Another day, Nicole and her dad opened the door on Kathy and saw that in an attempt to wash her face, she had actually covered her arms and face with shaving cream. Nicole and John burst out laughing. They looked at each other for approval like, “Can we laugh about this or not?”

Humor has helped guide Nicole and her family through the challenges of dealing with her mother’s personality changes. In the beginning, John told Kathy, “We’ve laughed every day up to this point, so why don’t we just laugh our way through the rest of the way?”

In New York, Nicole joined a support group for families whose loved ones have the disease. As soon as Nicole arrived, she said, “Just so everyone knows, I’m not interested in being here.”

At one point, the social worker asked everyone to say something unexpectedly good about what had happened since the diagnosis. When her turn came, Nicole said, “There’s nothing. I’m not going to make something up. I don’t think there’s a thing.”

Her family was no longer the same. She used to look forward to going home, and now it only made her stressed out. Her old mom was gone.

Other people were more positive. They talked about their families becoming closer, about recognizing what most others take for granted, and of learning to take care of themselves first, even before sacrificing for their loved ones.

Bullshit, Nicole thought.

But she kept attending the meetings, making friends with people like Deanna Angello, whose father also suffered from frontotemporal dementia. Together, they commiserated. Deanna’s father had been a music aficionado, with a vast collection, but he lost interest in listening to his albums. He was also a huge fan of “Seinfeld.” At every chance he could, Deanna’s father would go into the minute details of the last episode he saw, referring to George, Kramer, Elaine, and Jerry like old friends.

“He could recite any episode ever made,” Deanna said.

One day, about nine months after the diagnosis, Deanna went home and noticed that he had lost interest in “Seinfeld” too. He didn’t find the show funny anymore and would stare apathetically at cartoons, never changing the channel.

“How do you move forward with your life?” Deanna would say to Nicole. They would talk about feeling guilt for living their own lives, when their parents’ lives seemed to be withering away.

Nicole took a month off work to help care for her mother. “I went into Stephen’s office and started crying.” Colbert hugged her and said, “Calm down, whatever it is.” When Nicole went home, she realized her mother was losing her ability to carry on a conversation.

The prognosis only seemed to get darker. The Savinis learned that frontotemproal dementia can be passed down hereditarily. Nicole found out that there was a chance she may have inherited the protein that causes it. But she refuses to take the test to determine whether or not that could actually be the case. She does not want to know. Neither does her sister.

Five years after the diagnosis, Kathy doesn’t make jokes or laugh at them anymore, not even in a knee-jerk reaction kind of way.

“But there are moments,” Nicole said. “They are fewer and farther between, but sometimes they still exist. They come out even when you think all is lost.”

Something about Kathy’s grandson brings out a softer side. Kathy no longer hugs her adult daughters, Nicole said. But she lets her grandson sit on her lap. He smiles at her. And every once in a while, she smiles back.