1. ¹UMR CNRS 5020, Laboratoire Neurosciences et Systèmes Sensoriels, Lyon, Cedex, France
2. ²Laboratoire de Pharmacologie, Hôpital Edouard Herriot, Lyon, France
3. ³Unité clinique de Psychiatrie Biologique, Le Vinatier, Bron, France
4. ⁴Pharmacie du CHS le Vinatier, Bron, France

Correspondence: Dr N Morand-Villeneuve, Laboratoire de Neurosciences, Université de Franche-Comté, 1, place Leclerc, 25030 Besancon Cedex, France. Tel: +33 381 665 728; Fax: +33 381 665 754; E-mail: nadege.morand-villeneuve@univ-fcomte.fr

Received 12 February 2002; Revised 22 August 2002; Accepted 19 September 2002.

Abstract

The aim of this study was to test for an influence of benzodiazepine (BZD) on various perceptual and/or cognitive auditory processes. Loudness, auditory selective attention, and the ability of subjects to form perceptual streams out of alternating tone sequences were tested. Nine subjects were tested before, 1, 3, 7, and 24 h after a single-dose oxazepam vs placebo administration in a crossover design. A sample of blood allows us to measure plasma oxazepam concentration. The results revealed a significant reduction in stream segregation expressed as d' scores 1 h after oxazepam intake in the test subjects. No significant change occurred across time in the same subjects when they were administrated a placebo in another session. Furthermore, oxazepam had no substantial and systematic influence either on auditory selective attention or on loudness perception. Altogether, these results suggest that the perceptual organization of sound sequences involves inhibitory neural mechanisms, which can be affected by BZDs. This outcome is consistent with existing models of auditory stream segregation and may be paralleled with earlier findings on the effect of BZDs on perceptual binding in the visual modality.