Flashbacks are memories of past traumas.
Many times there is no actual visual or auditory memory.
One may have the sense of panic, being trapped, feeling powerless with no memory stimulating it. These experiences can also happen in dreams. In order to survive, that insulated child remained isolated, unable to express the feelings and thoughts of that time. It is as though we put that part into a time capsule until it comes out full-blown in the present. When that part comes out, the little one is experiencing the past as if it were happening today.