40 Hz studies

Aging and Cholinergic Modulation of the Transient Magnetic 40-Hz Auditory Response

Jyrki Ahveninen, Iiro P. Jääskeläinene, Seppo Kaakkola, Hannu Tiitinen, and Eero Pekkonen

Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, P.O. Box 13, FIN-00014, Helsinki, Finland

Apperception & Cortical Dynamics Research Team, Department of Psychology, University of Helsinki, P.O. Box 13, FIN-00014, Helsinki, Finland

Department of Psychology, Department of Neurology, University of Helsinki, P.O. Box 13, FIN-00014, Helsinki, Finland

BioMag Laboratory, Medical Engineering Centre, Helsinki University Central Hospital, Helsinki, Finland

Massachusetts General Hospital–NMR Center, Harvard Medical School, Charlestown, Massachusetts

Abstract

Cholinergic blockade by scopolamine, a central muscarinic receptor antagonist, may produce transient memory impairment in healthy subjects, and it has been used as a neurochemical model of cognitive degeneration in aged individuals. To observe the muscarinic modulation of memory and cortical auditory processing, nine cognitively intact elderly subjects (59–80 years) were studied using neuropsychological tests and 122-channel magnetoencephalography (MEG) after an administration of scopolamine hydrobromide (0.3 mg, iv) or glycopyrrolate (0.2 mg, iv), a peripheral muscarinic antagonist. A double-blind randomized crossover design was used in two sessions separated by at least 1 week. Scopolamine, but not glycopyrrolate, produced a transient impairment of verbal memory performance in the elderly subjects. MEG indicated that the auditory-evoked 40-Hz magnetic response was significantly larger after scopolamine than after glycopyrrolate administration. Furthermore, reanalysis of our earlier results in younger subjects (20–31 years), basically supporting the present MEG findings, tentatively suggests that the scopolamine effects on the 40-Hz response may be slightly pronounced with aging. In sum, the transient magnetic 40-Hz auditory response may be useful in studies on brain cholinergic deficits in elderly subjects.

To whom correspondence should be addressed at the Cognitive Brain Res. Unit, Department of Psychology, P.O. Box 13, FIN-00014 University of Helsinki, Finland. Fax: +358 9 191 22924. E-mail: jyrki.ahveninen@helsinki.fi.

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