Nicholas Sparks Says Gena Rowlands ‘Understood What Was at Stake’ with Her Role in “The Notebook” (Exclusive)

Following Gena Rowlands' death in August, the author fondly recalls working with the actress on the film adaptation of his bestselling novel

Nicholas Sparks is remembering Gena Rowlands’ incredible performance in The Notebook.

Speaking exclusively with PEOPLE about the adaptation of his bestselling novel, the North Carolina-based author, 58, shared his favorite memory of working with the late actress, who died at 94 in August after being diagnosed with Alzheimer's disease five years prior.

In the 2004 film, Rowlands plays an older version of Rachel McAdams’ character, Allie, who is living with Alzheimer's disease.

Many years before her own diagnosis, Sparks recalls that Rowlands was especially adamant about portraying the character and her illness accurately.

Related: The Sweetest Photos of Gena Rowlands with Her Children — and Grandchildren

“What was the neatest thing was that, even 20 years ago, she understood what was at stake with her role, that, for the families who are dealing with this, this can be very difficult,” Sparks tells PEOPLE.

“It can be very painful, it can be weary, frustrating,” he continues. “There's a lot of different emotions. I think she was really clear on the fact that, ‘Hey, I don't want this to be a fantasy. I want it to be like it might be, which is full of heartache and fright and fear and sudden confusion,' and all of those elements that really brought the performance up to a very high level.”

Sparks adds that it "was fun" getting to watch Rowlands work with her son Nick Cassavetes, who served as the film's director after a lengthy search that Sparks says included everyone from Steven Spielberg to Tom Shadyac.

Related: Gena Rowlands' Life and Career in Pictures

For the film’s 20th anniversary in June, Cassavetes spoke with Entertainment Weekly, which is when he revealed that his mother had dementia like her character.

"I got my mom to play older Allie, and we spent a lot of time talking about Alzheimer's and wanting to be authentic with it, and now, for the last five years, she's had Alzheimer's," he told the publication of his mother. "She's in full dementia. And it's so crazy — we lived it, she acted it, and now it's on us."

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During a 2004 interview with O magazine, Rowlands opened up about how her own mother’s struggle with the disease influenced her to take on the role.

"The Notebook, based on the novel by Nicholas Sparks, was particularly hard because I play a character who has Alzheimer's," she told the publication at the time. "I went through that with my mother, and if Nick hadn't directed the film, I don't think I would have gone for it — it's just too hard. It was a tough but wonderful movie."

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