"According to materialistic science, any memory requires a material substrate, such as the neuronal network in the brain or the DNA molecules of the genes"

This quote by Stanislav Grof is describing the materialistic view of science, which states that memories are stored in physical form. According to this view, memories are kept in the neuronal network of the brain, or in the DNA molecules of the genes. This means that memories are not simply abstract ideas, however are instead physical entities that can be stored and retrieved. This view of memory remains in contrast to the more spiritual view, which specifies that memories are not physical, but rather are spiritual or metaphysical in nature. The materialistic view of science is the dominant view in contemporary science, and it is the view that is most commonly accepted. This quote by Stanislav Grof is a pointer that memories are not simply abstract ideas, however are instead physical entities that can be saved and retrieved.