Self-representation in Kleine-Levin syndrome: a single case fMRI study.

Kleine-Levin syndrome (KLS) is characterized by recurrent episodes of hypersomnia, compulsive hyperphagia, disinhibition, hypersexuality and self modifications. To investigate the Self, we used afunctional magnetic resonance imaging paradigm evaluating Self-reference processing (SRP) and Self-reference effect (SRE) in a17-year-old male adolescent at the end of an episode. We observed enhanced activations in right hemisphere and posterior areas- associated with physical Self representations- during the SRP condition, while during the SRE condition, enhanced activations in bilateral but prevailing left frontal areas- associated with the conceptual Self. These results suggest amodified Self during aKLS episode being more physically grounded.

[Knowing without remembering: the contribution of developmental amnesia]. / Savoir sans se souvenir : les révélations de l'amnésie développementale.

The organization of episodic and semantic memory is currently debated, and especially the rule of the hippocampus in the functioning of these two systems. Since theories derived from the observation of the famous patient HM, that highlighted the involvement of this structure in these two systems, numerous studies questioned the implication of the hippocampus in learning a new semantic knowledge. Among these studies, we found Vargha-Kadem's cases of developmental amnesia. In spite of their clear hippocampal atrophy and a massive impairment of episodic memory, these children were able to acquire de novo new semantic knowledge. In the present paper, we describe a new case of developmental amnesia characteristic of this syndrome. In conclusion, the whole published data question the implication of the hippocampus in every semantic learning and suggest the existence of a neocortical network, slower and that needs more exposures to semantic stimuli than the hippocampal one, which can supply a massive hippocampal impairment.

Long-term memory following transient global amnesia: an investigation of episodic and semantic memory.

BACKGROUND: Several studies noted persistence of memory impairment following an episode of transient global amnesia (TGA) with standard tests. AIM: To specify long-term memory impairments in a group of patients selected with stringent criteria. METHODS: Both retrograde and anterograde memory were investigated in 32 patients 13-67 months after a TGA episode with original tasks encompassing retrograde semantic memory (academic, public and personal knowledge), retrograde episodic memory (autobiographical events) and anterograde episodic memory. RESULTS: Patients had preserved academic and public knowledge. Pathological scores were obtained in personal verbal fluency for the two most recent periods, and patients produced less autobiographical events than controls. However, when they were provided time to detail, memories were as episodic as in controls regardless of their remoteness. Anterograde episodic tasks revealed a mild but significant impairment of the capacity of re-living the condition of encoding, i.e. the moment at which words were presented. CONCLUSIONS: Patients who have suffered from an episode of TGA manifest deficits of memory focused on the retrieval of both recent semantic information and episodic memories and especially the capacity of re-living. These deficits may not result from a deterioration of memory per se but rather from difficulties in accessing memories.

The dynamic time course of memory recovery in transient global amnesia.

AIMS: To investigate the dynamic time course of transient global amnesia (TGA)--that is, the process of recovery and the interindividual variability--by testing four patients during the day of TGA itself (on three occasions) and at follow up (on two occasions). METHODS: A specially designed protocol focusing on semantic (both conceptual and autobiographical knowledge) and episodic (both anterograde and retrograde components) memory. RESULTS: Every patient showed marked impairment of both anterograde and retrograde episodic memory during the acute phase, with a relative preservation of personal and conceptual semantic knowledge. During the following phase, the authors observed similarities and differences among the patients' patterns of recovery. In general, retrograde amnesia recovered before the anterograde amnesia and anterograde episodic memory was recovered gradually in every case. In contrast, shrinkage of retrograde amnesia was more heterogeneous. In two of the patients, this shrinkage followed a chronological gradient and the most remote events were recovered first. In the two other patients, it depended more on the strength of the trace, and there was no temporal gradient. For the latter, an executive deficit could account for difficulties in accessing both conceptual knowledge and autobiographical memories. CONCLUSIONS: This profile of recovery suggests a "neocortical to medial temporal" process in every case, and the possibility of an additional frontal dysfunction in some cases. Hence, the acute phase seems to be characterised by a common episodic impairment. This variability between subjects appears in the recovery phase with two different patterns of impairment.