Idiom comprehension of 15 patients with mild probable Alzheimer's disease was examined by means of a sentence-to-picture matching task. Patients had to choose between two pictures, one representing the figurative and the other the literal interpretation. They were also submitted to a literal sentence comprehension test and to a pencil-and-paper dual task. Whereas literal comprehension was normal in seven subjects and mildly impaired in the others, idiom comprehension was very poor in all of them and correlated with the performance on the dual task. When the idiom test was repeated using an unrelated situation as an alternative to the picture representing the figurative meaning, performance significantly improved. It was hypothesized that the response in the sentence-to-picture matching task in the case of idioms requires sentence processing followed by the suppression of the literal interpretation. Alzheimer's disease patients proved to be unable to inhibit the literal meaning, although they had not lost the idiomatic meaning. In a second experiment, 15 Alzheimer's disease patients with a comparable level of cognitive impairment were submitted to the same idiom comprehension test, and to a test of verbal explanation of the idioms. The results showed significantly better performance in the oral task than in the sentence-to-picture matching task. In oral explanation, however, Alzheimer's disease patients also produced some literal interpretation whenever this represented a possible situation in the real world. We suggest that, during idiom interpretation, the literal meaning needs to be suppressed in order to activate the figurative meaning, and we stress the fact that both linguistic and extralinguistic factors must be taken into account to explain idiom interpretation.

We report two cases of recovery from retrograde amnesia, which occurred almost suddenly, 1 year and 1 month from onset, respectively. Amnesia followed a left thalamic infarction in one patient and a mild head trauma in the other. Full and permanent recovery occurred within a short time after the spontaneous emergence to consciousness of a single autobiographical event, triggered by the specific experience of a very similar new event. Recovery was limited to retrograde amnesia, leaving unaffected the anterograde deficit present in one of the patients. The nature (psychogenic versus organic) of our patients' memory loss is commented upon in the light of a review of previously reported cases of retrograde amnesia. The transient defect of retrograde memory is discussed in terms of a reversible distortion of the neuronal 'patterned matrices' suggested by Gloor (Brain 1990; 113: 1673-94).

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