In 2000 Baddeley added a fourth component to the model, called the 'episodic buffer'. This component is a third slave system, dedicated to linking information across domains to form integrated units of visual, spatial, and verbal information with time sequencing (or chronological ordering), such as the memory of a story or a movie scene. The episodic buffer is also assumed to have links to long-term memory and semantic meaning.
The main motivation for introducing this component was the observation that some (in particular, highly intelligent) patients with amnesia, who presumably have no ability to encode new information in long-term memory, nevertheless have good short-term recall of stories, recalling much more information than could be held in the phonological loop.
Other articles related to "episodic buffer":
... In 2000 this model was expanded with the multimodal episodic buffer ... the three component processes the phonological loop, the visuo-spatial sketchpad, and the episodic buffer ... The episodic buffer is dedicated to linking information across domains to form integrated units of visual, spatial, and verbal information and ...