Impaired mental simulation of specific past and future personal events in non-depressed multiple sclerosis patients

The aims of the present study were (i) to explore autobiographical memory and episodic future thought in multiple sclerosis (MS), using Levine's Autobiographical Interview; (ii) to investigate the influence of the Interview's high retrieval support condition (the specific probe phase) on MS patients' past and future simulations and (iii) to obtain the patients' estimations of their own difficulties, during the test, and in everyday life. To that end, we examined 39 non-depressed relapsing-remitting MS patients and 34 healthy subjects matched for gender, age and education level. The 73 participants underwent an adapted version of the Autobiographical Interview in two conditions: remembering and imagining personal events. The group of patients also underwent an extended neuropsychological baseline, including particularly, anterograde memory and executive functions. The results showed that the MS patients' scores on the baseline were mildly or not impaired. On the contrary, the Autobiographical Interview measure, i.e., the mean number of internal details, for each of the two phases of the test - free recall and specific probe - was significantly lower in simulated past and future events in comparison with the healthy controls. Within each group, autobiographical memory performance was superior to episodic future thought performance. A strong positive correlation was observed between past and future mental simulation scores in both groups. In conclusion, our results showed, for the first time, the co-occurrence of deficit of remembering the past and imagining the future in MS patients. They also showed more difficulty in imagining future events than remembering past events for both patients and normal controls. MS being a neurological condition very frequent in the young adult population, the clinical considerations of our study might be of interest. Indeed, they give rise to new insights on MS patients' daily life difficulties related to impaired mental simulation of personal events despite general abilities, including anterograde memory, only mildly or not impaired.