Different patterns of confabulation.

In this study we investigated the amnesic-confabulatory condition of two patients, M.B. and S.D., exhibiting different patterns of confabulation. Neuropsychological examination showed in M.B. a normal intellectual efficiency and a selective deficit of episodic memory, whereas S.D. was impaired in tests of intellectual efficiency, episodic memory, semantic knowledge and frontal functions. The relation of confabulation to retrieval conditions and the degree of impairment of the semantic memory system was investigated with a set of questions involving the retrieval of various kinds of information. In M.B. confabulation was restricted to episodic memory tasks, whereas in S.D. it also affected the retrieval of semantic information. S.D.'s confabulatory reports were 'semantically anomalous', whereas the semantic structure of M.B.'s confabulations was appropriate. Further investigation using the encoding specificity paradigm showed an interaction of encoding/retrieval conditions in M.B. but not in S.D. This pattern of results is discussed in terms of a different level of disruption of processes that normally monitor the retrieval of information. It is further argued that the confabulation content must be considered in terms of its semantic structure and relies on the level of integrity of semantic knowledge.