Evidence of neonatal memory of odor configuration
Résumé
The perception of some mixtures of odorants engages configural abilities, i.e. the perception of these mixtures as single odor objects. For instance, data in human adults demonstrated that a mixture of two odorants (AB), one smelling like strawberry and the other like caramel, generates the configural perception of the odor of pineapple (Le Berre et al., 2008; Barkat et al., 2012). Configural processing may be adaptive also for young organisms, to which rapid extraction of chemical information from the maternal environment, highly complex, is a prerequisite to survival. Thus, results in newborn rabbits suggest the perception of a unique odor in the AB mixture (smelling like configural pineapple in humans) and different from the odors of the elements (Coureaud et al., 2008, 2009a). To clearly demonstrate that the configural AB perception does not directly depend on A and B perception, we investigated here whether rabbit neonates recognize the AB mixture even in the absence of A and B recognition. To that goal, rabbit pups were conditioned to AB on day 1. On day 2, recall of A and recall of B were followed by intraperitoneal injection of either saline or a pharmacological amnesic agent (see Coureaud et al., 2009b, 2011). Testing for behavioral responsiveness to A, B and AB occurred on day 3. Control pups responded behaviorally to AB but also to A and B. As expected, the pups injected with the amnesic agent did not respond to A and to B. However, they responded to AB, indicating an AB perception independent of A and B representations. In summary, the present results confirm the perception by rabbit neonates of a configuration in the AB mixture, and demonstrate for the first time the neonatal ability to memorize odor mixtures as configurations independent of the memory of their elements.