Titre du document / Document title

Effects of a benzodiazepine, lorazepam, on motion integration and segmentation : an effect on the processing of line-ends?

Auteur(s) / Author(s)

GIERSCH A. ⁽¹⁾ ; LORENCEAU J. ⁽²⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Unité INSERM 405, Départment de Psychiatrie, Hôpitaux Universitaires de Strasbourg, 1 place de l'hôpital, 67091 Strasbourg, FRANCE
⁽²⁾ Laboratoire de Physiologie de la Perception et de l'Action, Collège de France, 11 place M. Berthelot, 75005 Paris, FRANCE

Résumé / Abstract

Previous studies have shown that the perceptual integration of component motions distributed across space is inhibited whenever segmentation cues, such as line-ends, are salient. Herein, we investigate to what extent enhanced inhibition induced by lorazepam, a benzodiazepine facilitating the fixation of GABA on GABA_A receptors, modifies the balance between motion integration and motion segmentation at the behavioural level. Motion integration was tested in 16 healthy volunteers taking a single and oral dose of either placebo or lorazepam (0.038 mg kg ¹). The stimulus consisted of an outlined diamond presented behind four, otherwise invisible, apertures and translating along a circular trajectory (Lorenceau & Shiffrar (1992). Vision Research, 32, 263-273). Under these conditions, recovering the global diamond direction requires the integration of the component motions available within each aperture. The observers were asked to discriminate the global, clockwise or counter-clockwise, diamond direction under difficult-at high luminance contrasts-or easy-at low luminance contrasts-conditions. Overall, reaction times and error rates increased in the lorazepam group as compared to the placebo group, suggesting strong non-specific effects. However, the changes in performance in the lorazepam group are not homogeneous across conditions, suggesting that lorazepam also induces specific effects that modulate the integration segmentation balance. Additional experiments performed with visible apertures or visible diamond vertices indicate that the effects of lorazepam are unlikely to reflect a deficit of motion processing or motion integration mechanisms since performance is only slightly impaired in the lorazepam as compared to the placebo group under these conditions. These results suggest that lorazepam might specifically modulate the saliency of line-ends, presumably because processing these features involves inhibitory mechanisms using GABA as a neuromediator, and in turn modify the balance between motion integration and segmentation.

Revue / Journal Title

Vision research   ISSN 0042-6989   CODEN VISRAM 

Source / Source

1999, vol. 39, n^o11, pp. 2017-2025 (50 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier Science, Oxford, ROYAUME-UNI  (1961) (Revue)

Mots-clés anglais / English Keywords

Vision ; Visual stimulus ; Stimulus movement ; Information processing ; Lorazepam ; GABA ; Gabaergic receptor A ; Aperture ; Human ; Perception ; Benzodiazepine derivatives ; Neurotransmitter ;

Mots-clés français / French Keywords

Vision ; Stimulus visuel ; Mouvement stimulus ; Traitement information ; Lorazépam ; GABA ; Récepteur gabaergique A ; Ouverture optique ; Homme ; Perception ; Benzodiazépine dérivé ; Neurotransmetteur ;

Mots-clés espagnols / Spanish Keywords

Visión ; Estimulo visual ; Movimiento estímulo ; Procesamiento información ; Lorazepam ; GABA ; Receptor gabaminérgico A ; Abertura óptica ; Hombre ; Percepción ; Benzodiazepina derivado ; Neurotransmisor ;

Localisation / Location

INIST-CNRS, Cote INIST : 1684, 35400008338221.0070