, Volume 110, Issue 5, pp 537-543

Preserved memory traces within diencephalic amnesia

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Summary.

A male patient with bilateral thalamic lesions (medio-ventral nuclei) was investigated. Despite explicit memory impairments his lexical ability was normal. We recorded magnetic field changes (magnetoencephalography, MEG) during the performance of an animate/inanimate discrimination task in which some words where repeated after long delays. Normally, repeated items are classified significantly faster than their first presentations which is accomplished by an unconscious process called priming. The patient did not show any behavioural evidence of priming but the physiological data indicated preservation of this robust form of memory. Brain activation associated with repetitions was attenuated at early stages. The activity difference was posteriorly distributed which is consistent with previous reports about repetition priming. The present study indicated that the bilateral thalamic lesions of our patient disconnected the information processing stream between the primed information and the behavioural response.

Received August 1, 2002; accepted December 3, 2002 Published online February 19, 2003
Acknowledgements The authors want to thank the Austrian Science Fund, the Austrian National Bank and the Human Frontier Science Program for financial support. Many thanks also go to Prof. Imhof for providing the MR-images of the patient.
Authors' address: Dr. P. Walla, Department of Clinical Neurology (Ebene 6), AKH Wien, Währinger Gürtel 18-20, A-1090 Wien, Austria, e-mail: peter.walla@akh-wien.ac.at