MEMORY WITHOUT CONTEXT - AMNESIA WITH CONFABULATIONS AFTER INFARCTIONOF THE RIGHT CAPSULAR GENU

Objective-To explore the mechanism of an amnesia marked by confabulati ons and lack of insight in a patient with an infarct of the right infe rior capsular genu. The confabulations could mostly be traced back to earlier events, indicating that the memory disorder ensued from an ina bility to store the temporal and spatial context of information acquis ition rather than a failure to store new information. Methods-To test the patient's ability to store the context of information acquisition, two experiments were composed in which she was asked to decide when o r where she had learned the words from two word lists presented at dif ferent points in time or in different rooms. To test her ability to st ore new information, two continuous recognition tests with novel non-w ords and nonsense designs were used. Recognition of these stimuli was assumed to be independent of the context of acquisition because the pa tient could not have an a priori sense of familiarity with them. Resul ts-The patient performed at chance in the experiments probing knowledg e of the context of information acquisition, although she recognised t he presented words almost as well as the controls. By contrast, her pe rformance was normal in the recognition tests with non-words and nonse nse designs. Conclusion-These findings indicate that the patient's amn esia was based on an inability to store the context of information acq uisition rather than the information itself. Based on an analysis of h er lesion, which disconnected the thalamus from the orbitofrontal cort ex and the amygdala, and considering the similarities between her diso rder, Wernicke-Korsakoff syndrome, and the amnesia after orbitofrontal lesions, it is proposed that contextual amnesia results from interrup tion of the loop connecting the amygdala, the dorsomedial nucleus, and the orbitofrontal cortex.