Stephen Heywood, whose fight against Lou Gehrig's disease was chronicled in the documentary film "So Much So Fast," died Sunday after an eight-year struggle with the degenerative nerve disorder. He was 37.

He died at his home in Newton, said his brother James Allen Heywood, who attributed the death to an accidental disconnection of a circuit on a ventilator that had helped keep Stephen Heywood alive.

The two brothers created the ALS Therapy Development Foundation in 1999, after Stephen Heywood was diagnosed with ALS in December 1998. The foundation is devoted to treating the disease, formally known as amyotrophic lateral sclerosis, which gradually destroys the ability to control movement. Patients lose their ability to move or speak, but their minds remain unaffected.

Heywood gave his body to science by testing experimental treatments, allowing stem cells to be injected into his spinal column. He also took part in genetic studies and clinical trials for new drugs, and received a brain implant to test how ALS patients' thoughts could be used to control a wheelchair and other robotic objects.

Heywood was born in Newton, and graduated from Colgate University in Hamilton, N.Y., in 1992. He went on to design and build homes in California, and returned to Newton after his ALS diagnosis.