The primary distinction between anterograde and retrograde amnesia lies in the timeline of memory loss relative to a specific causal event. Retrograde amnesia involves the loss of memories from the past, specifically those formed before the event. In contrast, anterograde amnesia is the inability to form new memories moving forward into the present, or after the event has occurred. This relationship can be visualized as a single-line flow diagram with the event at the center, where an arrow for retrograde amnesia extends backward into the past and an arrow for anterograde amnesia extends forward into the present.