Bed Bath & Beyond co-founder Leonard Feinstein and his wife, Susan, are donating $25 million to the Northwell Health medical institute in Manhasset that bears their name to expand research into multiple areas of medicine, including neuroscience and bioelectronics.

The Feinsteins gave an initial $25 million in 2005 to what was then North Shore University-LIJ Health System, and the medical research division was named in their honor.

The new gift will add to The Feinstein Institute for Medical Research’s capacity to conduct clinical trials, study cancer and sepsis and to investigate complex autoimmune conditions, such as lupus and rheumatoid arthritis.

The Bed Bath & Beyond chain has about 1,000 retail stores in the United States, Canada and Mexico.

“I am very proud of the work [the scientists] are doing and so is my wife,” Leonard Feinstein said. “We are just happy to give this support to the research institute and feel very lucky to be able to do it.”

The couple also had personal reasons that drove their desire to help establish the institute.

“Our son had a head injury a number of years earlier and there was nowhere to go,” Feinstein said, noting that nursing home care was the only option then offered for severe head injury. “So we decided that we wanted to get something up and running.”

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Since that injury 35 years ago, the Brookville couple has supported scientific efforts to find treatments — and cures — for neurological and other conditions.

Feinstein said he is intrigued by the institute’s burgeoning emphasis on bioelectronic medicine, in which pulses of electricity are being studied as a breakthrough way to address medical disorders.

The Feinstein Institute’s president and chief executive, Dr. Kevin Tracey, pioneered the field. Last summer, a small study in Europe based on Tracey’s theories showed that an implanted pill-sized, signal-producing device can effectively treat rheumatoid arthritis — without medication.

“These were people who couldn’t button their shirts, or tie their shoes. They couldn’t catch a ball,” Feinstein said. “But in two weeks they could do all of those things and more.”

He said Tracey told him that his indelible legacy probably won’t be Bed Bath & Beyond, but the Feinstein Institute and the discoveries that flow from it.

The institute is one of several Long Island research centers that has received major donations.

In November, Kavita and Lalit Bahl gave Stony Brook University $13.75 million to found a new cancer research center, named in their honor.

In 2014, hedge fund billionaire James Simons and his wife, Marilyn, gave $50 million to Cold Spring Harbor Laboratory to create the Simons Center for Quantitative Biology. That emerging interdisciplinary field utilizes fundamental concepts from physics, mathematics, computer science and chemistry to better analyze biological data.

The Simonses, in other donations to fuel scientific enterprise on Long Island, made gifts to Stony Brook University of $150 million in 2011 and $60 million in 2008.